water systems automation - state of the art
TRANSCRIPT
WATER SYSTEMS
WATER SYSTEMS
Current information on automation of Reclamation wder systems,
A State of the Art report by the Water Systems Automation Team.
JULY 1973
UNITED STATES DEPARTMENT OF THE INTERIOR Rogers C. 0. Morton, Secretary
-BUREAU OF RECLAMATION Gilbert G. Stamm, Commissioner
ACKNOWLEDGMENT
The Water Systems Automation Team composed of Lloyd F. Weide,Hydraulic Structures Branch; Rudy S. Hogg, Electrical Branch;Joseph L. Johnson, Mechanical Branch;-all Division of Design; JackC. Schuster, Hydraulics Branch, Division of General Research; andCharles A. Calhoun, Team Leader, Operations Branch, Division ofWater O&M appreciates the help of other Reclamation employees inpreparing this report. Particular acknowledgment is given toBenjamin A. Prichard of the Operations Branch, Division of WaterO&M; Clark P. Buyalski, Hydraulics Branch, Division of GeneralResearch; Edward A. Serfozo, Electrical Branch, Division of Design;Joseph M. Lord, Jr., Hydrology Branch, Division of PlanningCoordination; and to Robert E. Haefele and Genevieve S. Thomas ofTechnical Services Branch, Division of Engineering Support.
Regional Automation Coordinators who have furnished input to thisreport are: R. W. Slater, Region MP; J. A. Rawlings, Region UM; andW. L. Jamison, Region LM. John G. Hoffman of Rio Grande Projectwrote the bulk of the mathematical model description.
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PREFACE
In June 1971 the Water Systems Automation Team was fonned atthe Bureau of Reclamation's Engineering and Research Center. ThatTeam has the dual responsibility of managing research anddevelopment of water systems automation equipment and conceptsand coordinating water systems automation activities at the E&RCenter. Regional Automation Coordinators were selected to provideliaison with the Team on automation activities within each region.
By letter dated April 17, 1972, Commissioner of Reclamation EllisL. Armstrong assigned the Team the task of writing a"state-of-the-art" report on water systems automation.
This report describes the current state of development of automaticequipment and concepts used on or planned for Reclamationprojects. Emphasis is placed on open-channel conveyance systems.The need for automating, remotely controlling, and/or monitoringstorage dam outlet works and spillway gates; diversion dams;pumping plants; canal checks, wasteways, and turnouts; and pipesystems is discussed. Types of automation having potentialapplication to water systems are described.
A Research and Development Program is currently under way toexplore the application of various types of automation to watersystems. The interface between the water systems automation effortand the irrigation management effort is also discussed. A descriptionof planned applications of automation to individual canals and majorprojects follows. Cost considerations related to automation concludethe report. The appendices include definitions, a tabulation ofexisting automation installations on Reclamation projects, and adescription of the parameters of downstream control.
Advances in technology now make automatic control feasible foralmost any water system. Equipment is now becoming availablewhich can be used to monitor and control even the most complexinstallation. However, the application of these new tools oftechnology to water projects is limited by their cost.
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CONTENTS
Preface . . . . . . . . . . . . . . . .
Summary. . . . . . . . . . . . . . . . . . . . . .Automation Needs. . . . . . . . . . . . . . . . . .
Storage Works . . . . . . . . . . . . . . . . . . .
Outlet works . . . . . . . . . . . .Spillways. . . . . . . . . . . . . . . . . . .
Diversion Works . . . . . . . . .
Diversion dams and structures . . . . . . . . .Pumping plants. . . . . . . . . . . . . . . . .
Conveyance and Distribution Systems . . . . . . . . . .
Canal checks . . . . . . . . . .Pipe systems . . . . . . . . . . . . . . . . . .Turnouts. . . . . . . . . . . . . . . . .Wasteways . . . . . . . . . . . . . . . . . . .
Operation and Automation . . . . . . . . . . . .
Concepts of Operation . . . . . . . . . . . . . . . . . . .
General. . . . . . . . . . . . . . . . .Upstream control. . . . . . . . . . . . . .Downstream control ,.
Controlled volume operation . . . . .
Types of Water Systems Automation . . . . . . . .
General . . . . . . . . . . . . . .Feedback control. . . . . . . . . . . . . . . . .
General. . . .Two position controlFloating controlProportional controlProportional plus reset control
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Remote Control . . . . . . . . . . . . . . . . .
Manual operation . . . . . . . . . . . . . . .Automatic operation. . . . . . . . . . . . . . . . .Equipment . . . . . . . . . . . . . . . . . .
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General Applications . . . . . . . . . . . . . . . . . . .
Open channel systems. . . . . . . . . . . . . . .Pipe systems. . . . . . . . . . . . . . . . . . . . .
Research and Development . . . . . . . . . . . . . . . . . .
General. . . . . . . . . . . . . . . . . . . . . . . .Mathematical Modeling. . . . . . . . . . . . . . . .Laboratory Models . . . . . . . . . . . . . . . . .Control Development. . . . . . . . . . . . . . . . . . .
Laboratory simulations. . . . . . . . . . .Equipment operating environment . . . . . . . . . .Floating control . . . . . . . . . . . . . .Proportional control. . . . . . . . . . . . . . .
EL-FLO controllerSmith controller
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Proportional plus reset control . . . . . . . . . . . .Proportional plus reset plus rate control . . . . . . . . .Computer-operated supervisory controls. . . . . . . . . . .
Irrigation Scheduling-Management Interface . . . . . . . . . . .
Planned Installations. . . . . . . . . . . . . . . . . .
Coalinga Canal. . . . . . . . . . . . . . . . . . . . . .Corning Canal. . . . . . . . . . . . . . . .South Gila Canal. . . . . . . . . . . . . . .Garrison Diversion Unit. . . . . . . . . . . . . . . . . .Central Arizona Project. . . . . . . . . . . . . . . . . .
Cost Considerations . . . . . . . . . . . . . . .
General . . . . . . . . . . . . . . . . . . . . .Communications Systems. . . . . . . . . . . .Automatic Equipment . . . . . . . . . .Other Items. . . . . . . . . . . . . . . . .
Appendix I. Definitions . . . . . . . . . . . . .Appendix II. Partial Inventory of Types of
Automation on Reclamation Projects. . . . . . . . . . . . . .
1. Carriage Facilities-Canals. . . . . . . . . . . . . . .2. Carriage Facilities-Pipelines. . . . . . . . . . . .3. Diversion Dams. . . . . . . . . . . . . . . .4. Major Pumping Plants. . . . . . . . . . . . . .5. Storage Reservoirs-Outlet Works . . . . . . . . . .
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Figure Page
1 Upstream control-Supply operation 102 Traditional concept of canal operation 103 Downstream control-Demand operation 114 Constant volume concept of canal operation 125 Two-position control 146 Floating control 157 Proportional speed floating control 168 Two-stage floating control 169 SOT/VRT floating control 16
10 Proportional control 1711 Characteristic results of control by proportional
and proportional plus reset modes orientedfor downstream control 18
12 Schematic diagram of equipment for ColumbiaBasin little man controller 20
13 Schematic diagram of equipment for Friant-Kernlittle man controller 20
14 Schematic diagram of equipment for proportionalupstream control of electrically powered gate 21
15 Schematic diagram of equipment for upstreamcontrol of hydraulically powered gate 22
16 Typical cathode-ray-tube plot of output datafrom mathematical model studies 25
17 Laboratory evaluation of control components 2718 Schematic of downstream control by the
HyFLO method 2819 Coalinga Canal 3120 Coming Canal 3221 South Gila Canal 3422 Garrison Diversion Unit 3523 Central Arizona Project 3624 Schematic of downstream control by the
HyFLO method 56
Appendix III. Parameters of Downstream Control . . . .References. . . . . . . . . . . . . . . . . . . . . . . .
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LIST OF FIGURES
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T he purpose of this report is to provideoperators, planners, and designers with
currelLt information on automation of watersystems. In the report the term "automation" isused in a broad sense to include all remotecontrol and automatic control equipment whichaids or replaces man in the operation of watersystems. The Bureau of Reclamation hasincorporated varying degrees of automation inthe design of water systems for many years.
The scope of this report is limited to theapplication of automation to Reclamation watersystems. Emphasis is placed on open-channelinstallations because in most cases todayopen-channel conveyance systems are operatedunder less than optimal conditions. Subjectscovered include automation needs, types ofautomation, research and development, plannedinstallations, and cost considerations.
Water deliveries from Federal Reclamationprojects totaled nearly 27.0 million acre-feetduring 1971. Water service was provided tonearly 16 million people. Deliveries were madeto over 147,000 farms comprising over 10million acres of i"igable lands and to 249municipalities or other entities for municipal,industrial, and miscellaneous uses. Some 47,000miles of canals and laterals, 305 storagereservoirs, and 316 diversion dams were inoperation on Bureau of Reclamation projects toprovide this service. Considering these varied andextensive facilities and current and projectedwater needs, the best practical methods of watermanagement should be developed and institutedto assure efficient use and conservation ofexisting developed water supplies. Thesemethods, including use of automation, should beadopted for planning new water projects.
Water systems are automated to improveservice to' water users, to increase efficiency of
operation, and to reduce cost of operation.Automation of water systems is a product of aninterdisciplinary effort to develop devices toimprove operation of these systems. Tools suchas analog electronic circuitry, computers,mathematical models, and self-containedmechanical controllers are required. The type ofautomation installed on a particular projectdepends on the type of operation desired andthe complexity of that system. Factors such ascost of labor, value of water, and reliability ofequipment, require consideration. Withincreasing water system complexity, automationis more often justified now that it was in thepast. Most new water systems should bedesigned with some degree of automation.
Less than optimal operation of anopen-channel conveyance system is frequentlydue to the difficulty of matching the inflow andoutflow of the system. Mismatches betweendiversions and deUveries can occur as a resul t ofinaccurate regulation, unexpected changes ininflow or outflow, lack of adequate storage, andthe long time lag inherent in conventional canaloperation. For instance, many conventionallyoperated canal systems require a full day ormore of travel time for a change in flow to getthrough the conveyance system. The ability toaccommodate increases or decreases in demandat the turnouts due to unexpected rainfall,critical temperature changes, or other reasons isdependent upon the time lag of the system.Automation can greatly decrease the effect ofthis time lag, compensate for inaccurateregulation, and generally provide better serviceto the water users at less cost and with less wasteof water.
Pressure pipe systems are the best means ofproviding automatic control of discharge to aturnout where delivery is based on demand.However, pipe systems are usually more
expensive to construct than open-channelsystems and some water conveyance systems arenot intended to be operated to meet a demand.Proper automation of a water system requires ananalysis of what the system is intended to doand an economic comparison of the alternativesto maximize the benefits.
Advances in technology now make sometypes of automation possible for almost anywater system. Equipment is now becomingavailable which can be used to monitor andcontrol even the most complex installation.However, the application of these new tools of
technology to water projects is often limited byeconomic considerations.
A partial inventory of types of automation inuse on Reclamation projects is included as anappendix to this report. The inventory includesinstallations on carriage facilities-canals, carriagefacilities-pipelines, diversion dams, majorpumping plants, and storage reservoirs-outletworks. Information on the type of equipmentand mode of control is included where known.Also included in the appendix is a list ofdefinitions of commonly used automation termsand a description of the basic parameters W[]of downstream control. S rl
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Automatic and remote controls are neededfor water storage and conveyance
systems to improve service to water users,increase efficiency of operation, and reduce costof operation.
Recent Bureau of Reclamation water-usestudies have shown that an average of only 44percent of the water delivered to irrigators'fields on Reclamation projects is stored in theroot zone for beneficial comsumptive use bycrops. Seepage from canals and laterals accountsfor 20 percent of the total water diverted forirrigation in the United States. Thesepercentages do not represent real losses becausemuch of this water returns to streams orreplenishes ground-water aquifers that providethe water source for wells or springs. However,there is a real need for improvement ofmanagement and utilization of water inirrigation operations. Factors responsible forinefficient management and utilization ofirrigation water are many and often interrelated.Application of modern technology in programsof research and development for automation ofwater systems will improve the efficiency ofproject and farm irrigation systems andmanagement of conveyance and distributionsystems. More efficient use and bettermanagement of irrigation can make more wateravailable for municipal, industrial, andrecreational use to help meet today 's and futureneeds.
No absolute rule can be made to include oromit automatic or remote controlling andmonitoring devices on specific features ofBureau projects. Planners, designers, andoperators together face the tasks of analysis andsynthesis to arrive at solutions for each featureand/or project. Comprehensive studies of costs,safety, and reliability along with the service tobe provided by each feature and the overall type
of operation desired should be assembled priorto final decisions. Listed below are some of theitems which should be considered in thesestudies:
1. Water conservation measures.
2. Water rights-downstream requirements.
3. Operator attendance.
4. Accessibility of water system features.
5. Communication channels.
6. Degree of control desired.
7. Maintenance of automation system.
8. Reliability of forecasting.
9. Rapidity of inflow and time availablefor operation.
10. Consequences of overtopping storageor conveyance features.
11. Reliability of power source.
12. Reliabilityequipment.
of automatic control
13. Shutdown time for power generatingstations or pumping plants.
14. Economic comparisons.
The water users' need for water is not alwayspredetermined sufficiently in advance to assureexpeditious delivery or permit rapid shutoffs.Such uncontrolled situations as unexpectedrainfall or the need for protective spray toprevent frost are often not readily
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accommodated. Control systems which makewater more quickly available greatly enhance themargin of profit for water users, and thosewhich accommodate quick shutoffs can improvesystem efficiency.
Automation of water systems is needed toreduce labor cost to the water user. Simpleautomatic devices have been used for manyyears to operate single water control structures.Although these devices are limited in the degreeof control they can provide, they are provenlabor-saving devices. In the past most suchdevices have been for control of individualstructures. A real need now exists for equipmentand concepts which will provide efficientoperation of complete conveyance and/ordistribution systems. This requires a systemsapproach to fit the concepts and equipment tothe operational needs. The end product will gobeyond automation per se and will includeoperations research techniques to optimize thecontrols and operations. Further sophisticationof automation devices will not only reduce laborcosts but help conserve water through betteroperation of water control structures.
The facilities of a typical water system can beclassified generally. as storage works, diversionworks, conveyance system, and distributionsystem. The storage works consist usually of oneor more storage reservoirs, generally havingoutlet works for regulation of water releasestherefrom, and a spillway for protection of thedam. The diversion works may consist of atypical diversion dam with headworks forcontrolling releases into the conveyance system,and with a sluice gate and spillway for streamregulation and protection of the structure. Itmay also consist only of a head works or apumping plant discharging into the conveyancechannel. The conveyance system generally is anopen-channel system with structures for controlof flow in the system and for delivery into thedistribution system. It may also be a pipe oraqueduct with control and delivery structures.The distribution system is a series of openditches or pipe laterals with a control structureand a delivery structure to the water user. Oftenthe same control concepts can be applied to theconveyance and distribution systems.
Automation has been applied in varyingdegrees to all types of water control structuresfrom the storage works through the distributionsystems. Each water control structure serves aspecific function in a water system. Generallyspeaking, all of the control structures controleither a water surface elevation by regulation ofa control gate or pumping plant, or control thequantity of water being discharged through orinto a particular structure. The type ofautomation selected to accomplish a particularcontrol structure function or to operate a totalwater system depends upon the requirement forand economics of the particular situation. Thediscussion of the need for automation in thefollowing sections includes descriptions of thefunctions of various water control structures asthey apply to the segments of the total system.The concepts of operation of the control devicesand the applications of these devices arediscussed in the next chapter-Operation andAutomation.
STORAGE WORKS
Outlet Works
Perhaps more than any other water controlstructure, outlet works of dams are operated ona scheduled basis. At present, changes for systemdemands are seldom made automatically at thestorage reservoir. Consequently, most outletworks are either manually or remotely operated.Operation of water systems in a manner whichautomatically meets the demands of the waterusers will require automatic operation of outletworks. In many systems, remote control of adistant storage dam outlet works can result in acost savings due to the elimination of the needfor a full-time dam tender.
Spillways
In contrast to the routine operating purposesserved by other automatic applications discussedin this report, spillway gate automation servesprimarily as an emergency protective device.Spillways pass flood inflows in excess of outletworks discharge and available reservoir storagecapacities. The use of gated spillways introduces
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the possibility of overtopping and failure of thedam if the gates are not properly operatedduring critical flood periods. Concrete damsprovide greater safety against failure due toovertopping; therefore, automatic operation ofthose spillway gates is not usually required.Automatic spillway gate operation is providedon some Reclamation earth dams to insureproper gate operation.
DIVERSION WORKS
Diversion Dams and Structures
While diversion dams and canal headworks areoften self-contained and isolated, they can bethe focal point for demands of the distributionsystem. The control operation must not onlymeet downstream demands in the river anddiversion demands, but also must dampenhydraulic transients to provide smoothoperation of the entire system. Operation can bevery complicated and often requires a hierarchyof control features. For example, a minimumdownstream release to the river may be requiredto meet water rights and/or fish and wildlifecommitments. Additional available supply maybe diverted. Diversion discharge is, of course,limited to diverison demand and systemcapacity. Excess supply is usually wasted orbypassed downstream. The discharges involvedare often defined legally and very stringentmeasurements, monitoring, and controlling arerequired. Automatic controls can be designed tonot only provide the control functions requiredat these installations, but also to perform thelogic required for hierarchical decisions.
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Red Bluff Diversion Dam, a feature of the Central ValleyProject in California. This structure illustrates thecomplicated operations often encountered at irrigationheadworks. The facility includes fish diverters and ladders, asedimentation basin and spawning bed, and the diversionworks for the Tehama-Colusa Canal, all of which require wellcoordinated operation. Photo P-602-200-5667 NA
Helena Valley Pumping Plant and Canyon Ferry Dam,Montana. The two pumps in the foreground lift water to bedischarged into the Helena Valley Canal for delivery toirrigators and municipal users. Photo P296-600-97IA
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Pumping Plants
Pumping plants are required to raise waterfrom a water supply to an elevation wheregravity flow can deliver the water to the user.Pumping plants are usually designed with severalpumping units of various sizes so that thedischarge from several combinations of units canclosely approximate the water demand at anyparticular time. Water conveyance systems thatoperate with manually con,trolled gate structurescan satisfactorily be supplied by a pumping
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plant that has pumping units with manualON-OFF control. However, when the waterconveyance system is operated automatically ona demand basis. the supply pumping plant mustalso include automatic downstream control.Thus, the degree of pumping plant automationand the number and sizing of pumping units aredefmed by the degree of automation providedfor the downstream water system.
CONVEYANCEAND
DISTRIBUTION SYSTEMS -Prototype installation of automatic controls above a canalcheck. Photo P801-D-73319
Canal Checks
decisions to operate the control gates for theentire system.
Canal check gates should be automated toimprove the operation of a canal, to isolatereaches of a canal in the event of a break, and toeliminate repetitive operator attendance. Pipe Systems
Full pressure pipe systems provide the bestsystem of automatic control of discharge. Fordemand systems, water delivery to turnouts, aswith household faucets, can vary from no flowto full flow or vice versa automatically with noprior scheduling by the user. Full pressure pipesystems meet this demand. Because of thisinherent capability, a higher state of automationhas been achieved for full pressure pipe systemsthan for open systems. However, these pipesystems are sometimes prohibitively expensive;thus low head pipe systems or open channelsystems are used. Also, demand systems do nothave universal application.
To provide full turnout discharge or deliveryfrom a canal, a specific minimum depth of wateris required. Automatic controls will sensedeviations of water surfaces on the canal andoperate adjacent checks upstream ordownstream to provide a nearly constant waterlevel. Interference or interplay between' canalchecks in series may cause hydraulic transientsto build up and create undesirable conditions.Optimum operation will result only from propercontrol of the entire canal system. A controlscheme which takes this interplay into accountcan result in operation as efficient as that of aclosed pipe system .
Canal breaks can flood the surroundingcountryside. Checks can be operated in such anemergency to isolate reaches of a canal so thatthe entire canal is not drained. To provide thedesired checking action, the check gates may beoperated manually, remotely, or automatically.
Low head pipe systems present special controlproblems due to their tendency to amplifyharmonic surges. The cost of such a system isusually between that of a comparableopen-channel and a full pressure pipe system .Many miles of low head pipe have been installedon Reclamation projects. Generally, suchsystems do not have the rapid response of fullpressure systems and prior scheduling foroperation is required. Special needs do exist forthe automatic operation of both full pressureand low head pipe systems. On Reclamationprojects, common control problems include
Manual operation requires manual openingand closing of the gate at the canal check.Remote monitoring and control has theadvantage of bringing water level and gateposition information to a central point. Fromthis control center man or computer can make
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limiting head to economic ranges, limitingdischarge, and limiting water-hammer transients.
Operators of manually controlled canals andlaterals often find it difficult to maintainuniform water surfaces while making thechanges necessary for operation. This difficultyis increased by the occurrence of unexpectedstorms. The automation of control structureswill increase the stability of water surfaces oncanals and laterals where such automation isinstalled. However, different concepts ofautomation provide different degrees ofstability, some of which are not compatible withgravity-flow turnouts. Automation of theturnou t structures can eliminate thisincompatibility, thereby increasing the overallflexibility of operating concepts. Improvedoperation resulting from automated turnoutstructures will not only benefit irrigators byminimizing problems associated with
Turnouts
'-"'Automation of gravity flow turnouts is
needed to provide uniform deliveries fromdistribution systems. A changed water surface ina canal or a changed pressure in a pipelinechange the rates of flow through turnouts fromthe canal or pipeline. Turnout flows thatincrease or decrease unexpectedly are difficultto accommodate and often create costly andtime-consuming problems for irrigators usingsurface irrigation. Automation can e/iminatethese prob/ems with equipment that adjusts aturnout to maintain uniform de/ivery in spite offluctuating water surfaces or pressures.
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Aerial view of the intake channel to the Pleasant Valley Pumping Plant, a major turnout on the San Luis Canal a few miles fromCoalinga, California. Photo P80S-200-S87 NA
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nonuniform delivery, but will also permit theoperators of distribution systems to be moreaccurate in scheduling operations. Accuratescheduling promotes the conservation of waterresources by eliminating the need for operationwaste.
Wasteways
Wasteways are the traditional safety valves ofcanal operation. They remove excess water andprevent overtopping the canal. Scheduled excessor operation waste is caused by inability toadjust turnout flows to exactly equal flow intothe canal. Unscheduled excess occurs as the
result of unscheduled reduction in delivery flowsor inflow resulting from storm runoff.Wasteways require automation to assure thateither scheduled or unscheduled excess water isremoved from the canal without attendance byan operator.
Wasteways have been automated in the pastwhenever canals are designed to accept storminflow or where large amounts of unscheduledexcess water can be expected from othersources. Future installations should include suchprovisions. Operational waste should beeliminated or greatly reduced where a highdegree of automation is provided for W[]other structures within a system. Srl
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CONCEPTS OF OPERATION
General
I f a sufficient supply of water exists andthe conveyance system is capable of
transporting the appropriate flows, then a watersystem can be operated to meet the needs of theusers. Such a demand-type system is notfeasible, however, if the supply or theconveyance of water is limited to lesser amountsthan required. Where the use of water must belimited because of less than adequate storage orconveyance capacities, a supply-type system isnecessary. For instance, a domestic water supplyusually operates to meet the demands of theusers whenever a faucet is turned on. However,in times of water shortages, water use is limitedand water is available only on a rationed orprorated basis. Conversely, in any water system,if water is available in plentiful supply and theconveyances are adequate, the system can beoperated to meet the demands. Otherwise, watermay be only available to users with the highestpriorities or all users may have available only afraction of their full demand.
The two most common methods of operatinga water system utilize either upstream ordownstream control. With upstream control thesensor is located upstream from the structurebeing controlled and with downstream controlthe sensor is located downstream from thestructure being controlled. Upstream control isassociated with a supply-type operation anddownstream control is associated with ademand-type operation. Also, open-channelsystems have predominantly been operated withunstream control while pressure conduit systemshave for the most part been operated withdownstream control.
Each of the structures described previouslycan be operated with either of these methodsbut upstream control has been the traditionalmethod of operation on open-channel systems.Whether upstream or downstream the method ofoperation can be independent of the automationincorporated therein. However, downstreamcontrol of open-channel systems has beenachieved largely through the use of automaticdevices.
The operation of storage dam outlet works isusually based on meeting the needs of the waterusers consistent with providing storage reserves.Thus, releases from storage during periods ofadequate supply serve to meet the full demandsof the users. During periods of limited supply,however, the releases are restricted and a systemof priorities or across-the-board reductions isimposed. The flow of water can be tracedthrough the system from source to user and thecontrol structures described previously can beoperated to meet the demand on the system orto deliver a restricted supply to the users.
Upstream Control
Equipment that is operated to regulate awater surface immediately upstream from thecontrolling element provides upstream control,Figure 1. When more water is supplied than isrequired to satisfy deliveries, the excess is passeddownstream to the end of the conveyance whereit must be wasted or stored. When the supply isless than the demand, deficiencies will firstaffect deliveries at the lower end of the system.Satisfactory operation depends upon theamount of water supplied to the system. Thistype of operation is called a supply system. Toassure that all deliveries are satisfied, operatorsof supply systems usually introduce a little
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Figure I.-Upstream control-Supply operation.
excess water into the system, which results inoperational waste.
Traditional operation of a water system i:,complex, requiring numerous visits to controlstructures for adjustment when changes aremade. Water is introduced into the systemaccording to schedules developed from ordersplaced by users. As the water reaches eachcontrol structure in the system, that structuremust be adjusted to pass the desired flow. Whenchanges are large, adjustment at individualstructures may require several hours.Satisfactory operation requires schedulingsufficiently in advance to allow water to travelfrom the source to arrive at the point of deliveryat the desired time.
Automation of upstream control is mostappropriate for structures where inflow cannotbe scheduled, such as spillway control gates ondams, and wasteway gates that remove storminflow from a canal. Automation of upstreamcontrol is also generally appropriate forstructures in conveyances that are operated inthe traditional manner. Traditional operationbecomes more appropriate as the distancebetween control structures becomes greater.Other situations which are compatible withtraditional operation are long lengths ofconveyances with insig-nificant turnoutrequirements and conveyances where travel timeis not critical such as a channel which transportswater from a large storage source to a largestorage sump.
On traditionally operated canals, watersurfaces upstream from control structures arenormally maintained at a constant elevation for
all flow conditions, Figure 2. The achievementof uniform flow through each check reach isdelayed by the need to either build up or drawdown storage within the reach. Extensivesystems that require considerable time betweenthe introduction of water into the system anddelivery often use regulating reselVoirs to speedup response.
Automation can minimize the need fordeveloping schedules for the operation ofupstream controlled structures. In all otherrespects, the requirements for operating anautomated upstream controlled conveyance arethe same as for local manual operation in that:
1. Deliveries may be controlled manuallyor by some other automatic equipment.
2. Operators must develop schedules forintroducing water into the conveyance basedon desired delivery rates, desired deliverytimes, and the time required for water travelto the delivery locations.
These similarities permit the installation ofupstream controls on individual structures
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I Normal water surface - full flow
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hecked water surface - no flowAdditional storage required to increase flow
from" NO FLOW" to "FUll FLOW".
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Figure 2.- Traditional concept of canal operation.
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without requiring automation of the entireconveyance. Rate-of-flow controllers are oftenutilized at headworks or inlet structures toassure that inflow into the conveyance remainsuniform.
Downstream Control
Equipment that is operated to regulate awater surface downstream from the controllingelement provides downstream control. Thesensor location is selected at a point thatprovides the best intelligence to relatedownstream demands to upstream inflow, toprovide stability of control, and to maximize thechannel capacity. Generally, this means that thesensor should be at the downstream end of thereach, Figure 3. Such location reduces the needfor considering variations of friction factors, butusually increases the effect of time lag.
Where downstream controls are used tomaintain uniform flow through a Parshall flumeor over a weir they become rate-of-flowcontrollers. The control water surface should belocated appropriately for measuring depth offlow through the structure. The measuringstructure should be installed as near as practicalto the controlling element to reduce lag.Commercial rate-of-flow controllers are alsoavailable to suit nearly all types of commercialmeasuring devices.
Downstream control provides a demand-typeoperation in which overall operation iscontrolled by the amount of water beingwithdrawn from the conveyance. As water iswithdrawn, controlling elements are adjusted tointroduce water into the system. Operationalwaste is minimized because the amount of water
DOWNSTREAMCONTROLLER DOWNSTREAM
CONTROLLER
(-
- FLOW-
being supplied to the system at any time isdetermined by the amount of water beingwithdrawn.
Downstream control eliminates the need fordeveloping schedules for either the operation ofindividual structures or for introducing waterinto the system. Except for control of deliveries,no manual input is required as long as sufficientwater is available at the inlet or head worksstructure. When the supply of water is notsufficient to meet the demand, deficiencies firstaffect deliveries at the upper end of the system.
Pressure pipe conveyances inherently providea demand-type operation. However, severalfactors make demand-type operation moredifficult to achieve on open-channel systems.Gravity flow with a free water surface is moresluggish and more sensitive to relative variationsin head than is flow through pipe underpressure. The dead time or time required for achange of flow to move through the system ismuch greater for an open system than for a pipesystem. Water surfaces must be controlled moreclosely because the physical facilities required tocontain wide fluctuations are much moreextensive and costly.
Because pressure pipe conveyances inherentlyprovide a demand type of operation, theoperators of pipe systems readily recognize theconcept of downstream control. Conversely, theconcept is difficult for many operators ofopen-channel systems to understand because it iscontrary to their traditional method ofoperation. Upstream controls are not normallyintermingled with downstream controls on aconveyance except downstream controlledrate-of-flow controllers are sometimes used at
DOWNSTREAMCONTROLLER
Figure 3.-Downstream control-Demand operation.
II
the headworks of upstream controlled canals.However, different conveyances within a systemmay be appropriate to either method of controldepending upon operational requirements.
Downstream control is most appropriate forautomating structures where deliveries cannot bescheduled, such as in a municipal or industrialwater supply system. The appropriateness ofdownstream control increases with increasingdifficulty in preparing accurate schedules forboth introducing water into the conveyance anddetailed operation of control structures. Anincreasing trend towards demand-type operationby irrigators also increases the appropriatenessof downstream control for all conveyances thathave appreciable delivery requirements.
Controlled Volume Operation. During theformulat~on of plans for operating the CaliforniaAqueduct, the California Department of WaterResources developed a new concept of canaloperation. Operation by this method, calledcontrolled volume operation, virtually eliminatesthe need for regulating reservoirs whileincreasing operational flexibility. Response timeis reduced to the time required to achieve stableflo w within a check reach. Howeveradjustments at control structures must b~scheduled and well coordinated. This method ofoperation is included in operational studies thatare underway for the Granite Reef Aqueduct onthe Central Arizona Project.
This new concept was originally calledconstant volume operation because it appearedthat the volume of water within each checkreach would be maintained at a nearly uniformvalue for all flow conditions, Figure 4. However,hydraulic analysis shows that this is not alwaysthe case. Controlled volume operation doesreduce the need to build up or draw downstorage required for traditional operation.
By controlling water surfaces upstream fromcontrol structures at elevations that are higherthan required for f70w at design capacity,controlled volume operation provides capabilityto pass design flow through each structure atany time. Simultaneous adjustment at allstructures makes it possible to adjust canal
operation at any time to any desired condition.Remote adjustment of these control structures isneeded to provide the coordination required.Detailed schedules of flow requirements at eachstructure are also needed. Computer-assistedoperation is desirable where numerousadjustments must be made simultaneously.
TYPES OF WATER SYSTEMSAUTOMATION
General
The trend in recent years has been towardincreased automation of water systems, asdescribed previously in this report. Not only areaut 0 mat i c con troIs desired for existinginstallations but automatic operation is alsobeing included for features that are either underconstruction, in the design stage, or beingplanned for future construction. This trendincreases the importance of understanding boththe concepts that are available for operatingwater systems and the present capabilities ofautomation to conform to these concepts.
The application of automation to watersystems has been in the form of local automatic(feedback) control or remote control. Thesecategories are somewhat overlapping, however,in that remote automatic operation can usefeedback control. Nevertheless, the followingdiscussion of feedback control, remote control,and applications serves to describe the currentstate-of-the-art for automation of water systems.
w61~~,tzp
81~I'"~---,
-.Jr~01::>~Ig
Normal water surface-FULL FLOW 81~I'"Checkedwater surface- NOFLOW) I
,~~Nearly balanced areaS require na additional
I-- - -storage when Increasing flowfrom "NOFLOW Ita FULLFLOW' I
IIII
/'lo/PE'O\ \\
IIII
I////'III~'~/// ~Bottom grade
Figure 4.-Constant volume concept of canal operation.
12
A completely automatic system requires noinput from operators for normal operation.Arrangements of equipment sense physicalconditions and make the decisions andadjustments necessary for operation. Municipalwater systems often provide highly automatedoperation in which overall operation of thesystem is controlled by individual users as theywithdraw water from the system. Operators donot enter the decisionmaking process until theconveyance becomes relatively large. Irrigatorsalso desire this type of demand operation.
Because of difficulties in estimating realisticfriction factors for conveyances and dischargecoefficients for gates, operators of waterconveyance systems normally utilize watersurfaces at selected locations within the systemas indicators of desirable conditions. It thusbecomes appropriate for automatic controlequipment to utilize water levels to controloperation. Flow is normally measured whererequired for accounting purposes or to assureproper operation of the system. The alternativemethod of controlling operation by estimatingflows at all control structures presents additionalcomplications.
The automation of industrial processes ishighly developed. Knowledge of thecharacteristic results of different controlfunctions and appropriate application of thesefunctions has developed into a specialty. Wheresimilarities exist this knowledge and much of theequipment developed for industrial automationhas application to Bureau requirements forautomatic operation of water conveyancesystems. Much of the equipment needed forautomatic operation of Reclamation pipeconveyances is available commercially. However,while present technology now makes it possible,there is very little commercial equipment thathas been developed specifically for, or can beappropriately applied to, automatic operation ofopen-channel conveyances.
Feedback Control
General. Basic feedback control systems aredesigned to return a portion of the output signalto the input of a controller to maintain a
prescribed relationship between input andoutput signals. This feature provides a means todamp out oscillations and produce minimumovershoot for a more stable and responsivecontrol system.
Feedback controls for the automaticoperation of water conveyance systems cancontrol either rate-of-flow or water surfaces. Thefollowing discussion is directed primarilytowards controllers that control water surfacesalthough the principles involved also apply torate-of-flow controllers. Feedback controls thatoperate equipment to control water surfaces donot require the difficult field calibrations ofgates and valves that are associated withrate-of-flow controllers.
The characteristic manner in which feedbackcontrols perform control fWlctions, or react todeviatiolls, of the controlled variable, is calledthe mode of control. The five common modes ofcontrol are two-position control, floatingcontrol, proportional control, reset action, andrate action.
Two-position, floating, and proportionalcontrols provide three different controlfunctions, and all three of these modes ofcontrol are in common use on Reclamationprojects. Equipment installed for each of thesetypes of control varies widely because some ofthe automation on Reclamation projects hasbeen developed independently by operatingpersonnel. Limitations imposed by mechanicalequipment and differing local conditions havealso required modification of the controlfunction in many instances.
Reset action is generally used withproportional control to eliminate the offset thatis inherent in this mode of control. Rate actionnever exists alone, but is always combined withproportional or proportional plus reset actionsto increase the speed of response and reduceovershoot of the con trolling element.Equipment for accomplishing proportional plusreset control of water systems is underdevelopment. Future studies are planned toinclude proportional plus rate control andproportional plus reset plus rate control.
13
Mathematical representation of these controlfunctions becomes desirable when feedbackcontrol is to be programed into a computer forreal-time control or study. Feedback control canbe represented mathematically by the.generalized process control algorithm
N
Output =Kl (e) +K:f
e (dt) + K3 (de/dt)
~Proportion Reset Rate
where output =position of the con-trolling element
Kl , K2 , and K3 = real numbers repre-senting gain factorsof proportion, reset,and rate, respectively
e = deviation of the controlled variable(error)de and dt = increments of deviation andtime, respectivelyN = period of time for reset action
Two-position control is a special case of theproportional portion of this algorithm in whichOutput = ON or OFF and e = 0 or 1. Floatingcontrol is a special case of the reset portion ofthis algorithm where e = I, 0, or -1.
Two-position Control. Two-position controlis the simplest mode of automatic control. Thecontrol function moves the controlling elementto one of two extreme positions as determinedby the controlled water surface. When these twoextreme positions become fully opened or fullyclosed, the controller becomes an ON-OFFcontroller, and can be an electrical switch forthe operation of pumps, Figure 5.
Water surfaces controlled by two-positioncontrols will cycle continuously from one sideof the operating range to the other. Excessivecycling can be reduced by increasing storage inthe operating range. Corrective action should beslightly larger than the maximum requirement.Two-position controls are most appropriate forinstallations where storage is large as compared
to the rate of corrective action. If storage is largeand corrective action occurs at a suitable rate,lag becomes immaterial.
Floating Control. Floating control is moreproperly called single speed floating control. Incontrast to two-position control, which changesthe position of the controlling element from oneextreme position to the other (ON-OFF),floating control changes the position of thecontrolling element at a constant speedwhenever the controlled water surface deviatesfrom its target depth by a predeterminedamount. The direction of gate movement isdetermined by the direction of the deviation.The controlling gate makes no mqvement as longas the controlled water surface is within thedead band (the desired range of operation).When the controlled water surface is outside thedead band, the controlling gate will continue tomove until either the water surface returns tothe dead band or the gate reaches a fully openedor fully closed position. The control functionand its common modifications are shown inFigure 6.
The speed at which the controlling elementmoves is critical for floating controls. Movementis at a much slower rate than for two-positioncontrol because intermediate positioning isdesired. Controlled water surfaces have aninherent tendency to cycle, which can beminimized and often limited to the width of thedead band by a proper speed of correctiveaction. Significant lag in the system, or rapidload changes even though small, will aggravatethese cycling tendencies. Floating control ismost appropriate for installations with no
TIME-;z0
~ : S fo~e~~n~r~n:-------.J Over shoot caused by log.ui-- - - --- -- ----;;
a. CONTROLLINGWATER SURFACE(CONTROLLED WATER SURFACE SIMILAR)
Pump on I
IPump an
Pump off
b. CONTROL FUNCTION IN PUMP OPERATION(ORIENTED FOR DOWNSTREAM CONTROL)
Figure 5.-Two-position control.
14
- -n
- _l--=t: - - -U
-U
j 2o~g~t- d~!h---- -
n-
-- f-! -1-----
--:-De~d-b~nd-u- _n- !_nnn_U---tU-
o. CONTROLLING WATER SURFACE(RESULTS OF CONTROLNOT SHOWN)
copenlng~ f CIOSlng:l
b. CONTROL FUNCTION IN GATE OPERATION(ORIENTEDFOR UPSTREAM CONTROL)
[Openi ng--+-Ant,- Hunt.j f- CIOSingjAntl-Huntl
c. CONTROL FUNCTION MODIFIED BY ANTI-HUNT
Open f-Anti-HunH I Close
I L J r-Anti-Hunt-j
I L SOT /SRT Cycles ~ >1
e. CONTROL FUNCTION MODIFIED BY SOT/SRT AND ANTI-HUNT
Figure 6.-Floating control.
appreciable lag and where load changes can becounteracted by gradual changes in gateposition. Corrective action should be slightlyfaster than needed to accommodate the mostrapid load changes that can occur.
When the controlling gate moves too rapidlyit behaves like two-position control withcharacteristic cycling of the controlled watersurface and frequent reversal in direction of gatemovement (hunting). Because the mechanizationprovided on most Reclamation gates is intendedto permit manual adjustment as rapidly aspracticable, the resulting speed of movement isusually much faster than desired for single speedfloating control. In order to achieve the slowermovements required for their installations, mostoperators have incorporated timers into thecontrol equipment to provideset-operate-time/set-rest-time (SOT/SRT) cyclesof operation for gate motors. Adjustability inthe timer settings provides flexibility to selectthe appropriate average speed of gate movementfor each structure. A completely stable gateposition for uniform flow is seldom achieved bythis modification, because, as the gate moves a
predetermined amount in each cycle, it seldomarrives at the exact position required. However,controls that make two small adjustments or lessin an hour are ususally considered satisfactory.
A controller that reacts too slowly cannotkeep pace with changes and lags behinddeviations of the controlled water surface. Bythe time a lagging controller has made sufficientadjustment of the controlling element to reversethe direction of water surface movement, theadjustment is often larger than needed tomaintain uniform flow. Unless the controlfunction is modified, the gate will continue tomove while the water surface is returning to th~dead band, increasing overshoot in correctiveaction. Similar lag then creates overshoot in theopposite direction so that long period cyclesdevelop. Flow conditions can amplify thesecycles.
In order to reduce these long period cycles,some operators have incorporated a frictionclutch and additional switches intofloat-operated equipment to provide an antihuntdevice. The antihunt device prevents additionalgate movement when the controlled watersurface is returning to the dead band, eventhough the water surface is outside the deadband. Use of the antihunt device increases therange of changes that can be accommodated bysingle speed floating control. The device is notcompletely effective because it can stabilizeuniform flow outside the dead band for someflow conditions. In addition, when installed fordownstream control it frequently preventsdesired gate movement.
The major portion of operating time on openchannel conveyance systems usually involvesuniform flow. When changed flow conditions arerequired, the changes are made as rapidly aspossible. In order for a controller to besatisfactory, it must not only provide a stablegate position for uniform flow, but also it mustbe able to change the gate opening rapidly tosuit flow changes. Single speed floating controlusually does not have the range of operationneeded to suit the extremes of both of theserequirements. As a result, most controllers areadjusted to provide gate movements slightly
15
larger than needed for uniform flow andantihunt devices are added to reduce the cyclingthat occurs with flow changes.
Pro po r tional speed floating controllers,available commercially, provide the flexibilitythat is lacking in single speed floating control.Proportional speed floating control provides atype of action in which the controlling elementmoves faster in its corrective action as thecontrolled variable deviates farther from itsdesired value, Figure 7. This changing speed ofmovement requires that the controlling elementbe operated by a variable speed motor in lieu ofthe constant speed motors usually installed tooperate gates on Reclamation canals.
Flexibility of some SOT/SRT floatingcontrollers has been increased by superimposingadditional control stages, with wider dead bandsand faster gate movement, upon a single speedfloating controller. This modification alsoprovides a type of action that is similar to butmore restricted than that provided byproportional speed floating control. Figure 8shows some of the control functions attainableby combining two stages of floating control. Theresults of mathematical model studies show thatone additional stage greatly increases thecapability of a controller. Two- or three-stagefloating controls can probably be designed toeliminate the need for an antihunt device oninstallations appropriate for floating control.
Flexibility has also been provided for somefloating controllers to accommodate rapidlychanging water surfaces by the addition of afunction that increases the width of the deadband each time the gate moves, Figure 9. Thismodification results in a gate movement thatstrongly resembles proportional control.Increasing the dead band width provides avariable rest time and cycle time so that thesecontrollers become set-ope rate-time/variable-rest-time (SOT/VRT) controllers. Thevariable rest time inherently provides antihuntaction with all its associated advantages anddisadvan tages.
Proportional control. With proportionalcontrol (more properly called
z TIME0 --
~ ~" ~~~~o;:7; ~~"~~=f~~~~'-"~~~~~-!~~;: I I
o. CONTROLLING WATER SURFACE( RESULTS OF CONTROL NOT SHOWN)
r--Opening i ~CIOSing l
b. CONTROL FUNCTION IN GATE OPERATION(ORIENTED FOR UPSTREAM CONTROL)
Figure 7.- Proportional speed floating control.
z'TIME
! ~:t~~~~\~o~~~~--~~~-~-- ~n~~!~:l~~t~~~~~-~~<Ii I I
----------------~ ---I -----o. CONTROLLING WATER SURFACE(RESULTS OF CONTROLNOT SHOWN)
I I2nd Stage contmuous
J [2nd. Stage continuous
opening
JJ Cclosing
I r~ C 'Ist Stage CYCles?Ir---+-~ ~-J ;
b. CONTROL FUNCTION IN GATE OPERATION WITH SOT /SRT 1st. STAGE(ORIENTED FOR UPSTREAM CONTROL)
"-Anti-HUnt 12nd. Stage continuous I
~2nd. St~ge
.
contmuousopenlng--V closing
~ ~ L ,StStage cycles J --J ---1 Antl-Hunt--j
c. CONTROL FUNCTION IN GATE OPERATION WITHANTI-HUNT AND SOT/SRT 1st. STAGE
f-Antl-Hunt-j II c2nd. Stage opening n I ~ II _t-r' cycleS) I IJr- ~ ~Ist Stage cycles JJ f-Antl-Hunt~
2nd. Stage closing cycles ~d. CONTROL FUNCTION IN GATE OPERATION WITH
ANTI-HUNT AND SOT/SRT BOTH STAGES
Figure 8.- Two-stage floating control.
~- - /
Increased dead bond for rising water surface
~~:~~:_-~ ;£~~- --- ---~~~~~~~~~ =~--
~<Ii
Normal dead bond:' ~ ---~
~ Increased dead bond for foiling,
water surface
o. CONTROLLING WATER SURFACE(RESULTS OF CONTROL NOT SHOWN)
':Jm ~openin~7.t{'I. Ill:
Equal closures
~ Vanable CYCles--J+..\ 1
b CONTROL FUNCTION IN GATE OPE RATION(ORIENTED FOR UPSTREAM CONTROL)
Figure 9.-S0TjVRT floating control.
16
proportional-positioned control), the position ofthe controlling element has a fixed relationshipto the controlled variable. A controlling gate hasa position for each water surface elevation thatis defined by multiplying deviation of the watersurface by a gain factor. The elevation of thecontrolled water surface varies from one edge ofthe proportional band for no flow to the otheredge of the band for full flow, Figure 10.
Because the controlled water surface must beexpected to vary throughout the proportionalband, proportional control is not appropriate forinstallations where it is necessary to maintain aconstant water surface elevation. Where designsprovide a range within which the water surfacecan fluctuate, or where fluctuation throughoutthe proportional band can be tolerated,proportional control becomes appropriate. Forexample, upstream proportionally controlledgates are most appropriate for flood controlstructures, because designs usually include anoperating range compatible with theproportional band. At such installations theproportional action of the gate combines withstorage that increases rapidly as the controllingwater surface rises to provide the usually desiredfunction of retarding flow from storm runoff.Flow through the gate is related to the amountof water impounded rather than inflow at anyspecific time.
Very little information is available on pastusage of proportional controls for automatingcanal control structures. Except for thelimitations imposed by the need for aproportional band, proportional control is
TIMEz +-
~ ~;;;O~O~:b~n~ ~ - - ~ ~ ~ ~--
~
- - - - - - -.- -
---- --~
'"I I~ I
o. CONTROLLING WATER SURFACEI RESULTS OF CONTROL NOT SHOWN)
!~i i
~Full closed i i~b. CONTROL FUNCTION IN GATE OPERATION
(ORIENTED FOR UPSTREAMCONTROL)
Figure lO.-Proportional control.
appropriate for either upstream- (supply-) ordownstream- (demand-) type operation.Adaptability to combination with dead time(lag), and the reset and rate modes of controlmake it most appropriate for downstreamcontrol. Resulting operation should inherentlybe very responsive to changes of any size at anypoint in a system, and have a high degree ofsa f e ty against overtopping the canal inemergency conditions.
The width of the proportional band and itsassociated range of controlled water surfacevariation is a function of gain factor. In canaloperation, an inverse relationship exists betweengain factor and stability of flow. Stabilityincreases as gain factor decreases. Theserelationships work against each other to createstability problems when a narrow proportionalband is desired. The width of proportional bandrequired to achieve stable flow in canals oftenbecomes unacceptable for gravity deliveries.However, the range of water surface variation isusually not large enough to have a serious effectupon pump discharges. Therefore, proportionalcontrol is generally appropriate for use on opensystems where deliveries are made by pumping.
Proportional Plus Reset Control. Proportionalcontrol can be made more acceptable for opensystems with gravity deliveries by the addition ofa reset function to eliminate the proportionaldeviation. Addition of the reset function does noteliminate variations of the controlled watersurface elevation that occur when flows change,but it does return this water surface to theelevation that existed before the change. Minordifferences in position of the controlled gateaccount for the characteristic differences shownin Figure 11 between water surfaces controlled byproportional control and those controlled byproportional plus reset control.
By recovering the controlled water surface tothe original target depth, proportional plus resetcontrol makes overall operation of the canalsimilar to traditional operation in that flowchanges also require appreciable changes in thestorage of each check reach. Gates at theupstream end of the canal will make largeradjustments to accommodate these storage
17
~
I
~ I ~110
/02:0,+110
~ IfU
o. DEMANDCHANGEAT CONTROLLEOWATERSURFACE
Z _h- 1-7 -_
;:To!:g::~eE.t~-~o_fl:>~~-
- - - - - -§ Initial offset l Adjusted offset
~ -- - -
Proportionol bond
OJuj~ - - - - - - - - Mo.lmum Offset-full flow:::.r - - - - - - --
b. CONTROLLED WATER SURFACE-PROPORTIONAL CONTROL
1..1
I £::::Torget depth
: ~c. CONTROLLEO WATER SURFACE-PROPORTIONAL PLUS RESET CONTROL
'"ZZOJ
"-0OJI-<!
'"
Adjusted position
Figure I I.-Characteristic results of control byproportional and proportional plus resetmodes oriented for downstream control.
changes. Water surface fluctuations will betemporary, disappearing as the reset functiontakes effect. As long as incremental flow changesdo not exceed 20 percent of design capacity,controlled water surface fluctuations areexpected to be no larger than those that occurfrom manual operation, and automaticoperation is expected to be highly responsive tochanges anywhere in the system. However,canals operated by proportional plus reset arenot as safe against overtopping as canalsoperated by proportional control becausedecreased demand causes upsurges similar to thedownsurges caused by increased demand. Thepossibility of power outages on systems withlarge pump deliveries may require additionalcanal freeboard.
Remote Control
Manual Operation. The capability forremotely operating control structures oftenresults in improved operation of waterconveyance systems. Any installation thatprovides the capability for remote controlshould also include telemetering of sufficientdata so that the operator can determine theresults of adjustments and also be alerted to the
development of undesirableconditions in the system.
or dangerous
Operation by remote manual control can bequite similar to operation by local manualcontrol. Schedules for operation of the variouscontrol structures should be developed based on~xperience. However, the additional flexibilityof controlling all structures from a masterstation permits a high degree of coordination inadjusting structures. Properly utilized, thiscoordination can greatly reduce the timerequired to accomplish flow changes in manyconveyance systems.
Automatic Operation. Automatic operationof remote control systems becomes desirable oninstallations where numerous adjustments mustbe made within a short period of time, or whereclose attendance by an operator is required overa long period of time. Additional equipment toaccomplish automatic operation is usuallylocated at the master station. This equipment isenergized to perform control functions either atpredetermined times or in response toconditions interpreted from telemetered data.
While special equipment can be assembled toperform some individual operationsautomatically, an interface with a computergreatly increases the flexibility of automaticcontrols for accommodating numerous andvaried control functions. In addition toprograming that accomplishes selected controlfunctions at predetermined times, a computercan also be programed to interpret telemetereddata and perform complicated control functions.Because of this extreme flexibility, theadaptability of a computer in providing aprogrammable master supervisory control(PMSC) appears to be limited only by theingenuity and imagination of the designer.
Equipment. Commercial equipment isgenerally available for manually performingremote control functions from a master station.Commercial equipment is also available fortelemetering data concerning most of theconditions encountered, and for automaticallyperforming many of the- control functionsrequired. Special arrangements of equipment can
18
usually be assembled from commerciallyavailable components to accommodate thosesituations where equipment is not readilyavailable. Some situations will requiredevelopment of new equipment and specializedcomputer programing.
The major portion of cost for a remotecontrol system is represented by thecommunication channels that are requiredbetween the master station and all remotestations. The type and number of circuitsrequired are determined by the manner in whichthe controls are to be operated and by theamount of data that is to be telemetered.Direct-current (dc) channels are suitable forsending impulse-type signals and usually requirea separate channel for each set of data. Voicegrade channels with tone transmittingequipment can accommodate large quantities ofdata.
Alternatives for providing communicationchannels include direct wire, radio, andmicrowave. For most reliable operation, directwire systems, whether buried or overhead,should be dedicated exclusively to the controlsystem. Radio or microwave systems mayrequire repeater stations where distances aregreat or where adverse topographic conditionsexist. Selection of the type of communicationsystem is usually based on economic factors. Acompletely separate backup communicationssy stem is always desirable and stronglyrecommended for extensive conveyance systems.
GENERAL APPLICATIONS
Open Channel Systems
Successful applications of feedback controlsfor the automatic operation of open channelconveyance systems are in use on Reclamationprojects in the following categories:
1. Two-position control of pumps,oriented for both upstream and downstreamcontrol.
2. Upstream control of the sluice gates indiversion dams and the inlet gates or valves of
headworks structures by both floating andproportional modes to maintain uniformdiversions.
3. Upstream control of wasteway gates incanals and spillway control gates in dams byboth floating and proportional modes to passexcess water.
4. Upstream floating control of gates inindividual canal control structures and in aseries of canal control structures to pass canalflows through the structures whilemaintaining desired upstream water surfacesat the other structures in the system.
5. Downstream floating control of gates inindividual canal control turnouts andhe adworks structures to maintain uniformflow through measuring structures.
Because of simplicity, two-position controlsare probably the most widely used mode offeedback control. The ON-0FF characteristicsof these controls make them most appropriatefor the operation of pumps. Oriented fordownstream control, they operate pumps tomaintain the water surfaces in reservoirs at theelevations desired for operating distribution andconveyance systems. Oriented for upstreamcontrol, they are commonly used to operatesump pumps to remove unwanted accumulationsof water from structures and drains. Theoperating ranges of pumps in a multiple pumpinstallation are often overlapped and staggeredto increase flexibility in total pump discharge.These controllers are usually activated by eitherelectrical probe or float-operated switches.
There are very few successful applications ofunmodified single speed floating controls onReclamation projects. Their use appears to belimited to installations where slower thannormal speed motors have been added to gatesoriginally installed for manual operation.Floating controls are usually activated by eitherprobe or float-operated switches. The antihuntfunction is much easier to perform whenfloat-operated switches are used.
Reclamation projects do not include anyopen-channel distribution or conveyance
19
systems that are completely automatic inoperation. The Friant-Kern Canal on the CentralValley Project in California and the West Canalon the Columbia Basin Project in Washingtonrepresent the most extensive applications ofautomatic canal operation among the variousReclamation projects. Both of these canalsutilize a large number of little man controllersthat have been developed by the operators. Theterm "little man" has been applied at differenttimes to such a wide variety of installations thatits definition is somewhat obscure. In general,t he term applies to single-stage f70atingcontrollers modified by SO T/SRT, and oftenincludes an antihunt device. Little mancontrollers have also been assembled thatinclude (1) two or three stages of floatingcontrols, (2) a l-revolution-per-day motor thatraises or lowers the target depth a fixed amounteach day (or filling or unwatering a canal, and(3) a 24-hour clock that can be set to open aturnout at some predetermined time.
Operators on the Friant-Kern Canal pioneeredthe development of little man controls. Thedevelopment of similar controls on theColumbia Basin Project was completelyindependent of the earlier effort. Bothdevelopments perform almost identicalfunctions but with considerably differentequipment. Schematic diagrams of thisequipment are shown in Figures 12 and 13. Bothof these developments, operated by floats,disclosed a need for an antihunt device.
Because f70ating controls are appropriate forsituations where there is no appreciable lag, theyare best suited for the control of water surfacesthat are adjacent to the controlling gates. Wherefloating controls do not achieve satisfactorycontrol, the failure is often due to excessive lag.Lag increases as the distance between thecontrolled water surface and the controlling gateincreases. Lag is created by a controlling gatethat moves too slowly, or by a sensed watersurface that is damped excessively in a stillingwell. The corrective actions of an antihuntdevice and the use of multiple stage controllerscan make some allowance for lag. But there aremany situations in which the use of floatingcontrols is not appropriate.
Incoming power source
Raise relay
Figure 12.-Schematic diagram for a ColumbiaBasin type little man controller.
Incoming power source
Lo~e~ .!~m~~ Lower relay
Raise relay
0\7'0
'"
Figure 13.-Schematic diagram for a Friant-Kerntype little man controller.
20
As a general rule, floating control can beconsidered appropriate for upstream control butnot for downstream control. An exception ismade to this rule for downstream control whenthe controlled water surface is locatedsufficiently close to the controlling gate so thatthe effects of lag are not objectionable.
Some attempts have been made to operate aseries of canal control structures by downstreamfloating controls of the little man type. Whilemost of these attempts have been unsuccessful,both the Friant-Kern and Corning Canals haveachieved a degree of control that operators havetolerated. Downstream control equipment isinstalled on the last three check structures of theFriant-Kern Canal to control water surfacesimmediately downstream from the structures.Adjustment of target depth is required for anysignificant flow change.
Controlled water surfaces on the CorningCanal fluctuate continuously through a range ofabout 1 foot in about 2-hour cycles. Additionallimit switches are required on the gates toprevent excessive gate movement to maintainfluctuations within this range. Operators toleratethese fluctuations because (1) canal demand isnot fully developed, (2) all deliveries from thecanal are pumped, and (3) the automaticdemand-type operation of the canal is betterthan they have been able to otherwise achieve.
Reclamation has for many years installedupstream proportional control equipment onspillway control gates of large dams and onsluice gates of diversion dams where automaticoperation is desired. Gate operation can beeither electrically or hydraulically powered.Hydraulically powered systems are presentlyconsidered to be the most reliable. Electricallypowered systems are activated by float-operatedswitching equipment that is very similar to theequipment required for floating control.Proportional action is provided by a travelingcrosshead interconnected with the gate to raisethe switches as the gate opens, see Figure 14.Hydraulic systems use large floats andcounterweights to unbalance forces that open orclose the gates in response to water surfacemovements in the floatwells. Control equipment
Gaielawermlcraswitch
0 ,...caunterwei 9 ht
Switch trip blacks attachedta flaat tape
Gate raisemicraswitch
""...
. j water surface,a .J~t~ ~I!,a.g';!'-,
r1~;lerc~~~:~ce,gate
a.'0
I'
~-'D--"'O0.,.:<0;:1
Figure 14.-Schematic diagram of equipment for propor-tional upstream control of electrically powered gate.
includes weirs and orifices that are designed tocontrol rates of flow into and out of thefloatwells at the rates required to provideproportional action in the gate, see Figure 15.Counterweights may be attached either to theoperating shaft of the gate or behind the pinbearing.
Pipe Systems
Several factors make complete automationmore readily attainable for pipe systems than foropen channels. The inherent downstreamcontrol of a pipe system in which sufficientpressure is maintained to deliver full capacity isa very influential factor. Another very importantfactor is the relative simplicity ofaccommodating surges by increasing the strengthof the pipe. Physical enlargement of the facilitiesby surge tanks or other devices is required onlyat isolated locations. To all of these factors mustbe added the fact that commercial equipment isreadily available for automatic control of pipesystems. Much of this commercial equipmenthas been developed to meet specific needs.
Recently constructed Reclamation pipesystems for both conveyance and distributionprovide a high degree of automatic control
21
0
Circular weir controls inflowto float well
(J.
Controlled watersu.r;al
e6.
...~: ---=-
:d~
Slip joint for.p.
adjustingweir height :D'
'0
.'.<J
. .
Inl~
Float :Q'.P.
Orifi ce controls outflowfrom float well
. '. ".". .: '. Q. :. '. :. .: 0.:"':" :' : ~ ;. :-:. q. .:?'. .
Figure IS.-Schematic diagram of equipment for upstream control of hydraulically powered gate.
utilizing feedback controls widely. Oldersystems are also being automated. Full pressuresystems utilize feedback controls widely toachieve virtually complete automatic operation.Low-pressure systems, and systems wherein flowis controlled to a great extent by gravity ratherthan pressure, combine feedback controls withremote operation to improve operation. Whileno Reclamation pipe systems are computercontrolled at this time, information is becomingavailable on computer controlled pipe systems
from several segments of the water controlindustry .
Design of these control systems requires athorough knowledge of both the conveyanceand the control functions performed byautomatic equipment. Investigations often revealthe need for special requirements or limitations.However, designers confidently approachautomation for pipe systems with the attitudethat any automatic operation desired by WDoperators can be provided. S rl
22
AESE~RLH ~~U UEUEl~~~E~TGENERAL
Research and development are necessaryto provide methods and equipment for
aut 0 mat ion of water system s. Theories,methods, and equipment have been developed toautomatically control a wide variety ofindustrial processes. The control theories andprinciples developed for industry are useful inthe research and development necessary forwater systems automation. Normally, theautomation satisfying the needs of industry isnot directly convertible to the needs of waterdistribution. For example, stabilizing thedischarge in a long canal requires a long periodof time compared to that necessary formaintaining a uniform voltage level in an electricpower network. Also, mechanisms used inindustry for process control are not directlyadaptable to control of water systems.
The research and development program underway in Reclamation is concentrating initially onthe problems of open channel automation.Valuable tools such as mathematical models andlaboratory models are used in this effort.Immediate application of improved controltechniques is needed for the operation ofexisting and new projects.
Papers and reports on completed phases ofthis program are written and published asprogress is made. The results of the research anddevelopment will be the basis for a watersystems automation manual to be published inthe future.
MATHEMATICAL MODELING
The mathematical model is becoming avaluable tool for the researcher, the designer,and the operator. The results of applying a
particular scheme of operation to a water systemcan be determined by constructing amathematical model of the system and imposingoperational and control concepts on the model.Designing the mathematical model withsufficient flexibility can result in a versatile tool.The ultimate mathematical model wouldsimulate any water system under any scheme ofoperation. This ultimate model does not appearto be practical at the present time. However,mathematical models of open-channel systemscan be versatile enough to accommodate a widerange of canal systems being studied under avariety of operating schemes. Likewise,mathematical models of pressure pipe systemsare usually designed not as unique modelslimited to one system but as models which canbe used to study a wide range of systems andassumptions of operation. Thus, the response ofa water system can be determined for anynumber of schemes.
The use of mathematical modeling readilypermits application of various principles ofcontrol theory to automation of water systems.Equations of flow are combined to describe theperformance of the conveyance and structures.Although a precise prediction of hydraulictransients in open channel systems is difficult toattain, mathematical simulation of the canal orpipeline provides an adequate model foranalyzing the results of applying various schemesof automatic control. The more complete andaccurate the equations and data used in themodel, the better will be the representation ofthe system and its operation.
A detailed theoretical and applied analysis ofthe hydraulics of a water system is necessary indeveloping the mathematical model andau toma tic control eq ua tions. Accurateknowledge of the surface and pressure wavetravel periods in various parts of the system is
23
needed to establish time constants for thecontrols. Resistance to flow through canals,pipes, and structures guiding the flowthroughout the system must be known inassembling a mathematical model that willaccurately describe the system.
The mathematical modeling techniquespresently in use or under study by Reclamationare analog, characteristics, and implicit methods.Each method may have a place in the researchand development of water systems automation.One may be beneficially used for study of theentire system, another for a detail of thatsystem. In Reclamation work, the characteristicsmethod has received the greatest attention indevelopment because of the promise of moreimmediate results. The implicit and analogmethods of developing the mathematical models
Iappear to be more general than thecharacteristics method. For example, theimplicit method is not limited to subcriticalflows and can give a detailed description ofsupercritical flow. However, flow processesencountered in the water systems automationprogram have yielded to analysis by the methodof characteristics. For this reason, an intensivestudy of the analog and implicit methods hasnot been required, but study of these methodswill be part of the future development ofmathematical models.
Currently, the most widely used mathematicalmodel is the computer program "Unsteady OpenChannel Flow, Method of Characteristics." Thisprogram simulates gradually varied unsteadyflow in open trapezoidal channels. It isparticularly adapted to irrigation canals whichare characterized by a series of open-channelreaches. The program is primarily intended forthe purpose of simulating the response of canalflow to anyone of several concepts of automaticcontrol.
Gradually varied unsteady flow in openchannels is characterized by two basic partialdifferential equations, a continuity equation anda momentum equation. Because of themathematical complexities involved in obtainingexact integration of these two equations,numerical finite-difference methods of
integration are normally employed to solvethem. In this program, a numericalfinite-difference method known as the methodof specified time intervals is used. This methodbelongs to the more general category ofsolutions known as the method ofcharacteristics.
By the method of specified time intervals,each channel reach is subdivided into a numberof subreaches of equal length and the depth andvelocity of flow are computed at each of thedelineating boundaries between the subreaches.The depth and velocity thus computed are notdetermined as continuous functions of times,but rather, computed values are obtained atdiscrete points in time only. The time intervalbetween discrete points in time is specified bythe user and is the same for all delineatingboundaries such that solutions are attained at allboundaries for the same coincident points intime. Details of this method are described inChapter 15 of the text by V. L. Streeter and E.B. Wylie entitled "Hydraulic Transients,"McGraw-Hill, Inc., 1967.
Each channel reach is bounded on either endby a control structure. These control structuresserve as connecting links between the series ofopen-channel reaches. Unsteady flow throughcontrol structures is simulated by a succession ofshort, steady-state conditions, using appropriatecombinations of steady-state equations tosimulate the physical facilities. Appropriatesteady-state equations representing anyparticular control structure are solvedsimultaneously with the unsteady-flowequations representing the adjacentopen-channel reaches to form an effective linkbetween the control structure and the adjoiningopen-channel reaches.
At each control structure, any combination ofthe following physical facilities may besimulated: in-line flow through orifice gates,in-line flow through stoplog bays, in-line flowover check gates, in-line flow through aninverted siphon, in-line flow through a minortransition in invert grade and/or channel section,diverted flow through a constant discharge
24
- . T T . . -- CONTROLLED GATE AT MILE 0.14 -- -. -- -. -- - - .. I- - -i"J' --,. . . I I I I I -
CONTROLLED WATER SURFACE AT MILE 1.9
~~~~.....-
turnout, and diverted flow through an overflowwasteway.
Positioning of the orifice gates may beaccomplished either by preselected schedules ofgate position versus time or by anyone ofseveral schemes of automatic feedback control.The several schemes of automatic control whichare provided include both the upstream conceptand the downstream concept of operation.
The major items of input consist of:
1. The physical and hydraulic properties ofeach open-channel reach (bottom width, sideslope, bottom grade, length of reach,Manning's friction factor, etc).
2. The physical and hydraulic properties ofeach control structure (number and size oforifice gates, number and size of stoplog bays,discharge coefficients, siphon head-losscoefficients, etc).
3. Initial depths and velocities of flow onboth sides of each control structure and at "alldelineating boundaries between subreaches.
4. Initial gate positions.
5. The specified time interval and the totalreal time to be simulated.
6. The parameters required to representthe scheme of automatic control to be used,or preselected schedules of gate positionversus time for gates which are not to becontrolled automatically.
7. Preselecteddischarge.
schedules of turnout
8. Identification and editing data requiredto identify and control the output.
The output consists of:
1. A tabulated listing of major items ofinput data.
2. Cathode-ray-tube plots (Fig. 16) ofselected physical and hydraulic data plottedagainst time (depth, velocity, discharge, gateopenings, etc).
The major limitations of the program are:
1. The program is valid for gradually variedunsteady flow only. No provision has beenmade for rapidly varied unsteady flow (borewaves).
SOUTH GILA CANAL --0 TO 10 CFS,OB=.05. TF=OO. -- 03/29/73HYF+RES-1 REACH, STA. 7+50- -97+95.6, K2= .00005/SEC. ,GAIN2= .0300/MIN., TO= 4.18, GF=2.0
04.4
4.00 120 240 "0
TIME IN "INUTES
480 '00 720 "0..0
Figure 16.- Typical cathode-ray-tube plot of output data from mathematical model studies.
25
2. The program is restricted to trapezoidalchannels only.
3. The program is valid for sub critical flowonly. No provision has been made forsupercritical flow.
4. Relatively short-time intervals must beused to achieve accurate results. For thisreason, considerable amounts of computertime are required for long channels whichmust be simulated over long periods of time(time periods of several days duration).Programs which use any of the methods ofsolution generally known as the implicitmethod are probably better suited forproblems of this category, since relativelylonger time intervals may apparently be usedsuccessfully with this method.
This program was originally developed byMichael J. Shand at the College of Engineeri,ng,University of California, Berkeley. Numerousmodifications have been made to the originalprogram since it was received at the Engineeringand Research Center.
Mathematical models have also beendeveloped for pressure pipe systems. While theanalysis of operation under various schemes ofautomatic control has been a part of thepressure pipe modeling, the main purpose of thepressure pipe models has been to facilitate waterhammer and hydraulic transient analysis.
LABORATORY MODELS
Physically modeling a control is a necessarystep in the research and development of acomplex system. A control has a sensor tomeasure the change in the controlled variable,such as water level, velocity of flow, gateposition, or soil moisture. A comparator withinthe control determines from the sensor whetherchanges are required from a previously madeadjustment. Local or remote interactionsbetween the control and the controlled structureare transmitted over a communications channel.
The mathematical model cannot definephysically the effect of a part of the control onother parts; therefore, components areassembled to study the control function.
A complete canal model or simple tank ofwater with inlet and outlet may be satisfactoryfor the development of a control. The facilityprovides, through the sensor, an electrical ormechanical input to the control that follows thechange of controlled variable indicated by themathematical model. Deviations in the control0 u t Put significantly different than thosepredicted by the mathematical model may because for further development of the facility,mathematical model, or control.
The use of laboratory models allows theresearcher to develop optimal controllers. Forexample, modular construction of the controlcomponents requires research and developmentto find compatible units. Size, reliability,stability of operation, and range are factors tobe judged in relation to initial cost andmaintenance in developing the control. Thedevelopment includes the selection ofcommercially available electrical and mechanicalparts that will lower the cost of the control. Thecontrol should be designed so that maintenancecan be performed with standard testinstruments. Specifications and procedures forinstallation, adjustment, operation, andmaintenance become a part of the research anddevelopment study.
CONTROL DEVELOPMENT
Laboratory Simulations
Studies are in progress on local proportionalcontrollers developed on operating canals andthrough contractual programs. Configurations ofthe controls differ depending on the location ofthe controlled structure relative to the sensedwater surface. Generalized controller designsincorporating the best features from individualdevices are planned objectives of the researchand development.
26
Studies of the methods, devices, and controlparameters* are in progress both in theEngineering and Research Center Laboratoryand at operating canals. Relatively simpleequipment is being used in the l-aboratory toinvestigate the characteristics of a control,Figure 17.
T he m athematical model providesinformation regarding water-Ievel fluctuationsand the response of the control structure.Parameters used in the mathematical model arebeing studied by installing a control in thelaboratory and then sensing water-Ievel changesthat follow the model prediction.Correspondence between the mathematical andphysical models of gate opening and time ofopening indicates the validity of the designassum ptions.
Figure 17. Laboratory evaluation of control components. (a)environmental chamber, (b) data acquisition equipment, (c)automatic control components. Photo P801-D-73320
Delay time and control circuits are assembledin a control configuration. Circuit responses tochanges in heat and humidity are evaluated in anenvironmental test box. Deviations frompredicted operating limits may be measured andcorrections made before using the control on acanal.
of the simulated environment are more quicklyhandled, leading to rapid progress indevelopment.
Upon completion of the laboratory assemblyand testing, control equipment can be furtherdeveloped at a field site. The field installationbecomes a research and development laboratory .Water control structures are operated by theautomatic controls to find weaknesses notdisclosed by the mathematical and laboratorysimulations. A period of intensive observationby operators or designers is necessary while theequipment undergoes the variety ofenvironmental changes occurring at a field site.Comprehensive evaluation may show the needfor further study in the laboratory or designoffice.
Equipment Operating Environment
The operating environment of an automaticcontrol in an irrigation water system is severeand does not have the uniformity provided forcomparable equipment in industrial processing.Extremes of heat, cold, moisture, dust, remotelocation, and vandalism will occur in waterdistribution systems. Thus, control systems mustbe designed to meet the operating characteristicsand the reliability needed for essentiallyunattended operation on a water controlstructure. Floating Control
Phases of the environmental research can beperformed in the laboratory .Equipment can bestudied in chambers having variable temperatureand humidity. Causes for deviations from acomputed level of operation can be promptlystudied and corrected in a minimum time.Modifications to equipment to overcome effects
Both analysis and development are in progresson floating controls. Water surface elevationsnear a control structure are used by operators inadjusting gate openings in open channels. Thedevelopment of floating controls to maintain anearly constant level at selected locations was anatural outcome of such operation. The controls
*See Appendix III
27
were developed independently and thus theassem bled apparatus performed similar functionsbut differed in the types of components. Intime, commercial devices also became available.
Because of a continuing need for the singlespeed or variable speed floating control, studiesare in progress to partially standardize thedesign. A basic unit will be designed for generalapplication. Options will be provided formodifying the control function to expand thecapability of the device.
Proportional speed floating controllers are notbeing developed because of their commercialavailability. If the commercial devices proveunsatisfactory, research and development. ofthese controllers will be included in theprogram.
Proportional Control
EL-FLO Controller. An analog proportionalcontroller called Hydraulic Filter Level Offset(HyFLO) was designed and placed in operationon the Corning Canal for testing. Studies ofprinciples and equipment were performed on theproject and at the E&R Center.!! ! 2** An"offset" (proportional band) was allowed in theoperation of Corning Canal, Red Bluff Unit,California, Figure 18.
Operation disclosed that the hydraulic filter(fluid time delay) became inoperative because ofairborne and waterborne debris. An electronictime delay was then developed and installed andthe controller was renamed the Electronic FilterLevel Offset (EL-FLO) Controller. Electroniccircuits and components were also improvedbefore the controllers were returned to the fieldfor trial. Subsequent operation has shown theelectronic time delay to be a reliable piece ofequipment.
Smith Controller. An open-channel responseof water delivery similar to that for a closedconduit system would greatly improveoperations. Response of this kind requireseliminating or minimizing the nonoperating time
**Numbers refer to reports in Reference List.
FEEDBACK PATH
MOTORANALOG
CONTROLLER FILTER
CONTROLLED uPSTREAM GATE
"TARGET"
"OFFSET"
~:~~~R L~~~TION------
Y, Y DOWNSTREAM
GATE
Figure IS.-Schematic of downstream controlby the HyFLO method.
(dead time) of the water control device. TheSmith Control Method incorporates a possiblemeans of eliminating the dead time.! !
The controller has two elements considered toact independently. These elements are a linearpredictor and a control to eliminate surges. Thetime lag is minimized by the use of an analogmodel of the canal in the controller. The modelin effect predicts the change in water surfacethat will occur at the sensing point. Byanticipation in the analog model the gate can bemoved to the necessary control opening toadjust the flow to the required steady state.
Principles of this controller are now beingstudied on the mathematical model. Promisingresults from the study could possibly lead to thedevelopment of an analog or digital controller.Such a controller would be capable of makingrapid and precise changes of flow for efficientwater delivery.
Proportional Plus Reset Control
An "offset" in the canal water surface wasallowable at Corning. For satisfactory delivery,an "offset" was not allowable in the South GilaCanal, Yuma-Mesa Project, Arizona. Therefore, areset control was added to the proportional
28
control circuitry. A long-tenn analog-typeintegrator for resetting was not available. As asubstitute, a circuit was designed to vary thespeed of a direct-current motor according to therate of change of the water level. The output ofa potentiometer connected to the motorprovides a voltage necessary to move a gate andreturn the water level to a target elevation.
Satisfactory completion of the proportionalplus reset controller will allow the use ofanother mode of control on Reclamation watersystems. :This mode of control has been usedwidely in industrial applications for some time.Completion is planned as a result of the fieldtrials in 1973 on the South Gila Canal.
Proportional Plus Reset PlusRate Control
Applications of proportional or proportionalplus reset control are sometimes less than idealbecause of the large initial overshoot of thecontrolling element. This large overshoot canoften be drastically reduced by the addition ofrate action to the controller. In applications toelectric power control, the addition of rateaction has reduced the initial overshoot by 50percent from the best conditions obtainablewith proportional or proportional plus resetcon t rol. The large overshoot in certainapplications is often due to a large dead-time orlarge transfer lag. Also, the proportional bandmust be set exceptionally wide and the reset rateunusually slow to avoid excessive cycling. Loadchanges then create a large error in thecontrolled variable and a long time is required toreach the set point. Rate action provides a largeinitial correction to bring the variable up to theset point rapidly, reducing the overshoot. Also,the time and magnitude of cycling are reduced.Development of rate action is planned in thenear future.
Computer-operated SupervisoryControls
Large water conveyance and distributionsystems may adapt to control from a centralizedcomputer system. Alternatives include the use ofa combination of local automatic and
centralized computer control systems. Each ofthese possibilities requires research a..'lQdevelopment because of the wide variety ofchoices.
Computers appear attractive for control ofwater because they can be programed to controlspecific parts of the system. These parts can becontrolled in entirely different ways to meetspecific conditions without the use ofspecialized components.. Also, as water systemcontrol theory develops, computers offer theflexibility of applying new methods of controlat a future time without major alterations to thecontrolled structures.
Initial studies indicate virtually any controlmethod using on-site control components can beprogramed into a computer. The computer thenprovides an equivalent control of the structurebut performs the control from a centrallocation. Progress in this area can occur onlythrough intensive research into the literature andcommercial applications and the development ofcomputer programs applicable to water systems.
Study of local control and supervisory controlis planned for the laboratory. A canal simulationmodel will be designed for investigating thecapabilities of the control modes analyzed in themathematical model. This model will include aset of response times and structures withcontrols to receive commands. As anintennediate step to field application, thelaboratory canal model will help resolvediscrepancies between the abstract mathematicalmodel and the field application of the control.
IRRIGA TION SCHEDULING -MANAGEMENT INTERFACE
An important development parallel to watersystems automation in the Bureau ofReclamation is the Irrigation ManagementServices (IMS). IMS provided infonnationrelative to the scheduling of irrigations on96,000 acres of irrigated land in six states duringthe 1972 irrigation season. Irrigation schedulingprovides benefits to the irrigator, the irrigation
29
district, to the Nation, and the Bureau ofReclamation. These benefits by their categoriesare as follows:
1. Benefits to the irrigator are:
Increased crop yields in quantity andquality
Better utilization and savings of laborBetter utilization and savings of waterReduced leaching of soil fertility and soil
additivesReduced restrictions during periods of
peak demandReduced drainage requirements
2. Benefits to the irrigation district are:
Better control of deliveriesReduced demand on the delivery system
during periods of peak demandSavings in cost and use of waterThe capability to forecast delivery
requirementsReduced drainage problemsReduced maintenance requirementsComputerized water recordsAn increased economical base associated
with the irrigation enterprise
3. Benefits to the Nation and the Bureauof Reclamation are:
Improved economics of irrigationReduced environmental impact of
irrigated agricultureImproved utilization of the natural
resourcesNew and detailed planning and
operational criteria for irrigation
Some of these benefits may be relevant to oneirrigated area and irrelevant to another. Thisprogram is most important in that it treats thecauses and not the symptoms of many of the illsassociated with irrigation.
Many of the benefits are identical or similarto those for automation. To a certain extentirrigation scheduling is a form of automationand a joint development is required. A recentfeasibility-grade design and cost estimate studyfor automating the Garrison Diversion Unit inNorth Dakota concluded that computerrequirements for programmable mastersupervisory control are compatible with W[]those required for irrigation scheduling. sn
30
tJL~~~E[) ~~ST~LL~T~[]~S
P ersonnel at the Bureau of Reclamation'sE&R Center are currently developing
local automation equipment for three existingcanal systems. These are the Coalinga Canal andCorning Canal, California, and the South GilaCanal, Arizona. Also under consideration arecomputer-assisted automation systems for useon major projects such as the Garrison DiversionUnit, North Dakota, and the Central ArizonaProject, Arizona. A brief description of theseinstallations is included below. Additionaldevelopment of automation is also beingperformed through various regional offices.Some of these developments relate to control ofthe Potholes and East Low Canals, Washington,and the Enders, Medicine Creek, Norton, RedWillow, and Trenton Darns, Nebraska andKansas.
COALINGA CANAL
The Coalinga Canal includes 12 miles ofconcrete-lined canal and is supplied from theSan Luis Division of the California Aqueduct,Figure 19. Water is introduced into the canal bythe 1,185-cfs Pleasant Valley Pumping Plant.Flow downstream from the pumping plant iscontrolled by three check structures.
The pumping plant is designed for essentiallyunattended operation. Six large pumping unitswill be operated manually to accommodatemajor changes in demand and three small unitswill cycle on and off automatically to suit minorfluctuations in demand. The plant is alsodesigned for possible future supervisory control(if this becomes a desirable feature).
The canal controls were originally designed tooperate using a three-stage upstream SOT/SRTfloating control and a regulating reservoir toprovide operation without waste. A delay in the
CALIFORNIA \AQUEDucr-\
,
\ tQ
\. ~o
(:)t
\~tV
(,0
~o'<r,"
~~ /
I'"/ ~oc.--;I)~-0«\
-s..°"P-;I)
G\«\
~-:z.
«\
v
Iu~q
~~
~«\c."P~~~-z.
-:z.-'G\~
"P~~~~ ..J~~Iu
-'
('I :NEV.v<
""",
°1>1-
~ V
0Qq
0:QQ
KEY MAP
STATE HIGHWAY 189
x
00"P
~-:z.
G\
"P0"P-z.
"P~
I 0I t--1
3I
2I
SCALE OF MILES
Figure 19.-Coalinga Canal.
31
completion of the project prevented utilizationof these controls. During the delay ongoingresearch into downstream control techniquesdemonstrated that proportional plus resetcontrol could better serve the water users byreducing scheduling and storage requirements ofthe system. Mathematical model studies havealso shown that use of downstream control willeliminate the need for the regulating reservoir.
I t is anticipated that communicationschannels will be provided by project-ownedburied cable 'between structures and an alarmcircuit will be extended to a master station by aleased circuit.
Design of the controls for this project is nowproceeding based on use of proportional plusreset downstream control. The project isexpected to be completed in 1973.
CORNING CANAL
The Corning Canal includes 21 miles ofearth-lined canal and is supplied from theSacramento River at the Red Bluff DiversionDam, Figure 20. Water is introduced into thecanal by the 50D-cfs Corning Pumping Plant andflow downstream from the pumping plant iscontrolled by 14 check structures.
The pumping plant is designed for unattendedoperation. Three 125-cfs pumping units and one53-cfS pumping unit are started or stoppedmanually to approximately satisfy the demand.The two remaining 53-cfs units cycle on and offautomatically to adjust for minor fluctuations indemand. The plant is also designed for futureautomatic control of the four remainingpumping units for on-off control by floatswitches operated from the canal water level.The use of automatic canal-side pumping plantscauses severe control problems on this canal dueto the fluctuating flow demands for the plants.Power failures at the canal-side plants also causesevere problems because the canal freeboardmust accommodate the rejected water.
The Corning Canal controls were initiallydesigned to operate with one of the first versions
of single-stage downstream SOT/SRT floatingcontrol (without antihunt). However, before thecontrols were installed it was recognized that asimilar downstream control system installationon the South Gila Canal in Arizona producedunstable control. To avoid a similar problem onthe Corning Canal the equipment was installedfor upstream control, but upstream control
RedBluff
( RED BLUFFDIVERSION DAM
KEY MAP
~~1010
~ x
Richfield
2 0I t--t
2I
6I
4I
SCALE OF MILES
Figure 20.-Corning Canal.
32
proved to be inadequate to maintain canal-sidedemands on the Corning Canal. Subsequently,the control equipment was modified todownstream control with antihunt and gatemovement limit switches, which allowed thecanal to operate with marginally satisfactorystability .
Recognizing the need to have a betterunderstanding of transient behavior of an openchannel and to have a stable and responsivedownstream control system, the RegionalOffice, Sacramento, sponsored an investigationof the downstream control concept through aresearch contract with the University ofCalifornia. The resulting research produced theHydraulic Filter Level Offset (HyFLO) methodof control for which equipment wassubsequently designed and installed to operatethe first check structure. The hydraulic filterportion of the equipment proved unsatisfactoryin actual operation and an electronic filter wasdeveloped and installed in place of the hydraulicfIlter. The Electronic Filter Level Offset(EL-FLO) equipment has been operatingsatisfactorily ( with minor equipment problems)on three check structures since April 1972. Thegate movements and water levels have beenrecorded and will be used to evaluate themethod of control and help verify themathematical model.
Closeup view of the EL-FLO Plus Reset Controller inside thestilling well just above the South Gila Canal Check No.2. Theelectronic recorder above the controller and the Type Frecorder below were used to collect data on equipment andcanal performance. Photo P801-D-73318
The canal controls were originally designed tooperate with the initial version of automaticsingle-stage downstream SOT/SRT floatingcontrol. Initial operation of the system wasplagued with unstable water levels and variousequipment problems. The downstream controlsthat were installed initially were fmallyabandoned and rewired as a combination ofupstream and manual controls.
The communications channels are providedby leased, buried cable between each structure.No alarm circuit is provided at the present time.
Additional EL-FLO equipment will bepurchased and installed so that all 14 checkstructures will have automatic downstreamcontrol. Completion of this portion of theproject is expected by 1974. Extensive mathematical model studies have
failed to reveal any modification that can bemade to the floating controls to achieve thedegree of control that is considered necessary .These studies have also shown that downstreamproportional control provides the desiredstability but the water-Ievel offsets that wouldbe required on this canal would be intolerable tothe gravity deliveries. However, the modelstudies show that proportional plus reset control
SOUTH GILA CANAL
The South Gila Canal includes 7.7 miles ofconcrete-lined canal and is supplieq from theGravity Main Canal, Figure 21. The canalincludes nine check structures and is designedfor a gravity flow of 110 cfs.
33
.N STATE HIGHWAY 9~
-.JG1['
-- ..c
"s" CANAL
4000.. .
Q«0II:
GILA GRAVITYMAIN CANAL,
.....
\J
«II:oq
PACIFIC ,SOUTHERN ~
~'-"A" CANA... L-~
0I
SCALE OF FEET
4000I
KEY MAP
Figure 21.-South Gila Canal.
should provide control that meets the desiredcriteria. Therefore, the South Gila Canal hasbeen selected as the prototype canal fordevelopment of this mode of control.
Also as a separate research feature on theSouth Gila Canal, the Bureau of Reclamationwill develop and install an upstream floatingcontroller with a set-operate-time!variable-rest-time (SOT!VRT) feature on the first section ofthe canal for operation of the canal headgate.The controller will operate essentially as adownstream controller by operating the gate inresponse to the water level a short distancedownstream from the headgate.
Communications channels are provided byproject-owned buried cable between structures.No alarm circuits are provided at the presenttime.
The controls for South Gila Canal areexpected to be operational by 1974.
GARRISON DIVERSION UNIT
Automation of the Garrison Diversion Unit isin the initial stages of development and portionsof the conveyances are already underconstruction. The initial structures are being
designed for manual operation with provisionsfor future automation. The conveyances willinclude several hundred miles of canal, 4reservoirs, 4 major pumping plants, and 53 canalcontrol structures, Figure 22. The project willinclude the McClusky, Velva, New Rockford,Warwick, James River Feeder, and Oakes Canalsand will utilize a portion of the James River forwater conveyance. The widespread and complexnature of the project makes automation a verydesirable feature as a means of minimizing thenumber of operating personnel required. Initialfeasibility studies have shown that automationof the project can be best accomplished with aProgrammable Master Supervisory Control(PMSC) system. Computers would be used toanalyze programed water schedules and performthe computations required for total automaticcontrol of all structures based on scheduled andactual water demand. The system may includeone central master station with possible satellitemaster stations at two or three other locations.Each master station would include displays ofsystem conditions using two or morecathode-ray tubes. Also under consideration isthe use of inexpensive versions of localautomatic feedback controllers to back up thePMSC system.
The types of communication channels to beused have not been determined but initial
34
CANADA
ZZ
~SOUTH
DAKOTAWYO.
KEY MAP
K
0(.,
1('
SNAKE CREEKPUMPING PLANT"
NEW ROCK-FORD CANAL
,,
\rWARWICK CANAL
O'VERS'ON CANAL)
,
,
.-JAMESTOWN RESERVOIR
_JAMES RIVER
,,
"'''R "''"VO'" \OAKES PUMPING PLANT- TAAYER PUMPING PLANT
ZOAKES CANAL. 1
20 0I t-t t--I
SCALE OF MILES
20 60I
40
> <
Figure 22.-Garrison Diversion Unit.
studies suggest a combination of leased orproj ect-owned buried cable, radio, andmIcrowave.
The distribution portion of the project isexpected to be included in the automatic systemfor the conveyances. This will make justificationof a PMSC-type automatic system moreattractive than any other type of system basedon existing technology.
The Garrison Diversion Unit is one of the fewprojects where major consideration has beengiven to automation during design of theconveyances. It is anticipated that this planningwill result in optimum efficiency of waterconveyance.
CENTRAL ARIZONA PROJECT
The Central Arizona Project will includeapproximately 275 miles of concrete-lined canal,10 pumping plants, and 3 storage reservoi.rs,Figure 23. The water conveyance features willinclude the Granite Reef, Salt-Gila, Tucson, andSan Pedro Aqueducts. Extensive studies ofautomation have not been made for this projectto date; but mathematical modeling is beingused to attempt to define the methods ofautomatic control that will be appropriate.Preliminary investigations indicate a PMSC-typesystem will be advantageous due to the size andcomplexity of the project.
35
oN
rPARKER DAM
A R z 0 N A
/GRANITE REEF
AQUEDUCT
PHOENIX
-.Jl-ll'
--TUCSONAQUEDUCT
.. Tucson.'-- SAN PEDRO --~ AQUEDUCT
"''''... ........
II
I NEW
...LX'COM E X I C 0
Figure 23.-Central Arizona Project.
The type of control to be provided for thepumping plants has not yet been defined, but itis anticipated that the plants will includelocal-automatic computer control withsupervisory control interfaces to the masterstation. When this project reaches the designstage, the technology may allow local-automaticcomputer control of each canal control structure
UTAH COLO.
KEY MAP
with supervisory control interfaces to the masterstation.
The communication channels for the CentralArizona Project have not been defined but it isanticipated that either leased or project- WDowned buried cable or radio will be used. S rl
36
LCiST LCi~~~[)EA~T~Ci~~GENERAL
I nformation on the costs of implementingwater system automation is incomplete
and the application of the limited data todiffering situations is difficult. The followinginformation is intended to serve as a generalguide in investigations leading to theimplementation of automation. For moststudies, this general knowledge will not besufficient and additional information will beneeded for a specific analysis. Economicanalyses of this type cover a definite periodduring which there are investment costs andannual costs. While this report does not includethe economic analysis of a project, it providesgeneral information on costs of automation.
On Reclamation projects, the investment costof automation has generally ranged from lessthan 1 percent to 3 percent of the total projectcost. This investment can usually be broken intothree components, namely, (1) communicationssystem, (2) automatic equipment, and (3) otheritems including installation, programing, anddebugging. On most widespread projects, Item 1,the communications system, is the mostexpensive component.
COMMUNICATIONS SYSTEMS
Data and control signals can be transmittedby either direct wire or radio/microwave. Directwire may l1e either buried or overhead cable.Communication facilities can be eitherproject-owned or leased from the telephonecompany. Each of these methods has advantagesand disadvantages. Project-owned buried cablehas proven to be quite reliable, except as it isaffected by cuts from excavating equipment,burrowing animals, or vandalism. For longdistances, however, buried cable can be very
expensive compared to radio or microwave.Also, rough terrain or rock trenching mayincrease the installation cost of buried cable. Anaverage installed cost for buried cable of $1 perfoot is often used in estimates. While the cableitself may be purchased for $0.25 to $0.50 perfoot, the installation often pushes the total tothe $1 per foot figure.
Voice grade telephone circuit leases typicallyrange from $0.50 to $4 per mile per month. Thedistance is usually figured point to point fromthe remote station through a telephoneswitching center to the master station. Thus, themileage is charged from the shortestpoint-to-point distance from the sensor throughthe telephone system to the control center.Also, telephone companies often add anadditional one-time construction charge oninstallations where special routing of dedicatedcircuits are involved. Less than desirable servicehas been experienced with some leasedcom m unication channels because ofadministrative and technical problems.
Investment costs for microwave or radiosystems are not directly proportional todistance. This cost is usually constant fordistances up to 50 or 60 miles. This distance issometimes restricted by topography. Repeaterstations are required for greater distances. Datatransmission by microwave or radio can beadversely affected by atmospheric activity. As aminimum, a simple radio transmitter andreceiver have a purchase price of about $1,500.Installation and auxiliary equipment willincrease this figure considerably.
Annual operation, maintenance, andreplacement (OM&R) costs are important incommunication system cost considerations.OM&R costs are included in the lease charge fortelephone circuits. However, some additional
37
O&M costs are usually required foradministration by the operating entity. Whenfacilities are owned rather than leased, OM&Rcosts should include replacement costs based onthe expected life of the installation. A buriedcable life of 35 years is used in Reclamationstudies. Microwave and radio can haveconsiderably higher OM&R costs than buriedcable. Replacement costs are based on a typicallife of 15 years for microwave and radioequipment in Reclamation usage. Also, thisequipment requires periodic preventivemaintenance to insure dependable operation. Animportant consideration in determining OM&Rcosts is the availability of qualified electronictechnicians at remote locations.
Communication costs are often small forlocal-automatic control installations because ofthe close proximity of the controlled watersurface and the controlling element. However,reliable system operation for manylocal-automatic controllers often requires alarmcircuits for notification of abnormal operatingconditions. The cost of providingcommunication channels for these alarm circuitsoften approximates the cost of communicationchannels for more elaborate control systems.
AUTOMATIC EQUIPMENT
Investment costs for automatic equipmentvary with the type of equipment considered.Local-automatic equipment can often beself-contained as is the usual equipment forautomatic operation of a motorized gate at acanal check, turnout, wasteway, or diversiondam. Such automation has been accomplished
for as little as $1,000 per gate. Most of theautomatic control installations on Reclamationprojects are of this type. The basic equipmentfor these simple installations usually consists ofa float or probe to sense water surface elevationsand additional components to energize the gatemotor. In contrast to these simple installations,the purchase price of computers for acomputer-controlled system can range from afew thousand dollars to several million dollars.Recent technological developments andcompetition have resulted in drastic reduction ofcomputer costs. This is particularly true forminicomputers which have many automaticcontrol applications.
OTHER ITEMS
Installation, programing, and debugging arelumped together for purposes of discussion ofcosts. For computer-controlled systems,programing and debugging can cost as much asthe equipment. However, once developed, theprograming is often usable at more than oneinstallation. This can result in a considerablesavings in cost for later installations after theinitial development has been accomplished.
A dependable source of electrical power is aprerequisite for satisfactory operation on mostReclamation water systems. With greater usageof automation, this will be even more essentialbecause a power failure can result in abnormaloperating conditions. Reliability of the powersource should be investigated in determining theneed for backup power. Backup power can beobtained by using batteries or engine generators.The more elaborate backup systems can wecost several thousand dollars. SJl
38
~~~E~()~X ~
DEFINITIONS
Many of the definitions used in the automation industry have been developed for a specificsegment of the industry and are too restricted for application to water-conveyance systems.Others have been expanded to become so broad that they offer no real definition. The followingdefinitions, although similar to those encountered in studying automation terms, are suggested asbeing better directed towards basic principles:
Algorithm. A rule of procedure for solvinga mathematical problem.
Analog. Anything that is analogous orsimilar to something else.
Automatic Control. Adjustment of thecontrolling element accomplished by anarrangement of equipment withoutattendance by an operator.
Automation. (1) The implementation ofprocesses by automatic means; (2) thetheory, art, or technique of making a processmore automatic; (3) the investigation, design,development, and application of renderingprocesses automatic, self-moving, orself-contrQlling. (From IEEE STD 100-72.)
Controlled Variable. A physical quantitycontrolled to a desired value.
Controlling Element. The principal item ofequipment adjusted to regulate the controlledvariable.
Downstream Control. Feedback controlutilizing a controlled variable downstreamfrom the controlling element as the controlledvariable.
Feedback Control. Automatic control thatsenses deviation of the controlled variablefrom a desired value and performs a controlfunction to take corr~ctive action. The
controlled variable becomes the controllingvariable.
Local Control. Adjustment of thecontrolling element accomplished at the site.
Manual Control. Adjustment of thecontrolling element accomplished by anattendant.
Master Station. A station from whichremotely located equipment is controlled andwhich receives telemetered data.
Programed Control. Automatic control byequipment that accomplishes predeterminedadjustments of the controlling element atpredetermined times.
Rate-of-flow Control. Feedback controlutilizing rate of flow (Q) through thecontrolling element as the controlled variable.
Remote Control. Adjustment of thecontrolling element accomplished from adistant point.
Remote Station. A station whereinequipment is controlled from the masterstation and from which data are telemeteredto the master station.
Supervisory Control. An attendant and/ orautomatic equipment maintaining surveillanceof physical conditions and/or telemetered
39
d at a; performing control functions tomaintain controlled variables at desiredvalues; and providing notification of abnormalconditions.
Telemetering. Sensing, encoding, andtransmitting data to a distant point for
interpretation.
Upstream Control. Feedback controlutilizing a controlled variable upstream fromthe controlling element as the controlledvariable.
40
~FJFJE~[)~X ~~
PARTIAL INVENTORY OF TYPES OF AUTOMATIONON RECLAMATION PROJECTS
This partial inventory is intended to present information on types of water-system automationin use on Reclamation projects. Automatic and remote control equipment is included. Theinventory is not all-inclusive but is based on information readily available at this time. One sourceof information was the "Survey of Automatic or Remote Control Equipment for WaterConveyance Systems" conducted with each region in 1970.
Automatic equipment has been installed on spillway gates at storage reservoirs. However,recent information is not readily available on these applications. Also, application of this type ofequipment is usually intended to function only in emergency flood control situations and as suchis different from most of the control equipment included in this report.
1. Carriage facilities-Canals.
2. Carriage facilities-Pipelines.
3. Diversion dams.
4. Major pumping plants.
5. Storage reservoirs-Outlet works.
41
1. Carriage Facilities - Canals
Section (initial reach)Initial Bottom Water Side
Length capacity width depth slopesCubic feet
Project - Name of canal Miles per second Feet Feet Automation(kilometers) (cubic meters (meters) (meters)
per second)
All-American Canal SystemCoachella Canal 124 2,500 60 10.3 2:1 Remote manual control of check gates
(200) (71) (18) (3)
Boise ProjectBlack Canyon Canal. 29 1,300 Upstream control of was'tewaygate -
(47) (37) Floating mode (SOT /SRT)
Central Valley ProjectCorning Canal 21 500 22 7.2 2:1 Downstream control of check gates -
~(34) (14) (7) (2) Proportional mode (EL-FLO)NI
Delta-Mendota Canal 115.7 4,600 48 16.6 1-1/2:1 Remote manual control of check gates(186) (130) (15) (5)
Friant-Kern Canal 151.2 4,000 36 15.5 1-1/4:1 Upstream control of check gates,(243) (113) (11) (5) Checks 1-9 - Floating mode
Downstream control of check gates,Checks 10-13 - Floating mode
Madera Canal. 35.9 1,000 20 9.2 1-1/2:1 Downstream control of turnout M.P.32.2 -(58) (28) (6) (3) Floating mode (SOT/SRT)
Pleasant Valley Canal 6.3 1,100 12 11.3 1-1/2:1 Present operation upstream control of canal(10) (31) (4) (3) checks - Floating mode
Planned operation downstream control of canalchecks - Proportional plus reset mode
1. Carriage Facilities - Canals - Continued
Section (initial reach)Initial Bottom Water Side
Length capacity width depth slopesCubic feet
Project - Name of canal Miles per second Feet Feet Automation(kilometers) (cubic meters (meters) (meters)
per second)
San Luis Canal. 101.3 13,100 110 32.8 2:1 Remote control (manual and computer assisted)(163) (371) (34) (10) operated by the California Department of
Water Resources
COlorado-Big Thompson Project~BoulderCreek Supply Canal. 15.7 200 12 4.6 1-1/2:1 Upstream control of check gates - Floating
~(25) (6) (4) (1) mode (SOT/SRT)
Charles Hansen Feeder CanalFlatiron Section. 3.8 930 13 8.8 1-1/4:1 Upstream control of check gate -
(6) (26) (4) (3) Proportional mode
Columbia Basin ProjectEast Low Canal. 82.6 4,500 68 15.5 1-1/2:1 Upstream control of check gates - Floating
(133) (127) (21) (5) mode (SOT/SRT)
Eltopia Branch Canal. 25.3 555 20 6.6 1-1/2:1 Upstream control of check gates - Floating(41) (16) (6) (2) mode (SOT/SRT)
Royal Branch Canal. 8.5 900 37 7.2 1-1/2:1 Upstream control of check gates - Floating(14) (25) (11) (2) mode (SOT/SRT)
Wahluke Branch Canal. 40.5 1,520 12 10.4 1-1/2:1 Upstream control of check gates - Floating(65) (43) (4) (3) mode (SOT/SRT)
West Canal. 82.2 5,100 38 16.4 1-1/2:1 Upstream control of 29 check gates - Floating(132) (144) (12) (5) mode (SOT/SRT)
1. Carriage Facilities - Canals -Continued
Section (initial reach)Initial Bottom Water Side
Length capacity width depth slopesCubic feet
Project - Name of canal Miles per second Feet Feet Automation(kilometers) (cubic meters (meters) (meters)
per second)
Deschutes ProjectNorth Unit Main Canal. 65 1,000 60 5.6 1-1/2:1 Upstream control of check gates and upatream
(105) (28) (18) (2) and downstream control of headworks gatea -Floating mode (SOT/SRT)
Gila ProjectSouth Gila Valley Canal 7.7 110 5 4.2 1-1/2:1 Present operation upstream control check
(12) (3) (2) (1) gates - Floating mode (SOT/SRT)Planned operation downstream control check
gates - Proportional plua reaet mode
~~KlamathProjecttlJ"Canal. 23.4 800 26 9.5 1-1/2:1 Remote manual control of headworks gates
(38) (23) (8) (3) Upstream control of check gates - Floatingmode (SOT/SRT)
Minidoka ProjectCross Cut Canal 6.6 591 26 5.7 1-1/2:1 Upstream control of check gates - Floating
(11) (17) (8) (2) mode (SOT/SRT)
Diversion Canal. 0.7 220 10 5 1-1/2:1 Upstream control of check gates -Floating
(1) (6) (3) (2) mode (SOT/SRT)
Milner-Gooding Canal. 70 2,700 50 12.6 1-1/4:1 Upstream control of check gates - Floating(113) (76) (15) (4) mode (SOT/SRT)
1. Carriage Facilities - Canals - Continued
Section (initial reach)Initial Bottom Water Side
Length capacity width depth slopesCubic feet
Project - Name of canal Miles per second Feet Feet Automation(kilometers) (cubic meters (meters) (meters)
per second)
North Side Canal. 8 1,700 Upstream control of check gates - Floating~(13) (48) mode (SOT/SRT)
~SouthSide Canal. 13 1,325 57 7.5 1-1/4:1 Upstream control of check gates - Floating(21) (38) (17) (2) mode (SOT /SRT)
Unit "A" Main Canal 4.4 240 14 4.5 2:1 Upstream control of check gstes -Floating
(7) (7) (4) (1) mode (SOT/SRT)
Pick-Sloan Missouri Basin ProgramThree Forks DivisionEast Bench UnitEast Bench Canal. 44.2 440 20 6.6 2:1 Upstream control of check gate - Floating
(71) (12) (6) (2) mode (SOT /SRT)
Solano ProjectPutah South Canal 32.3 956 12 10.3 1-1/2:1 "Q" controller at canal headworks -
(52) (27) (4) (3) Proportional mode
2. Carriage Facilities - Pipelines
Project and feature
Length
Miles(kilometers)
InitialcapacityCubic feetper second
(cubic metersper second)
Type
Diameter
Inches(centimeters)
Automation
Arbuckle ProjectWynnewood Aqueduct (Includes DavisBranch and~inery Branch). . .
Canadian River ProjectMain Aqueduct. . . . . . . . . .
~~
Norman Project
Norman Pipeline. . . . . . . . .
Ventura River ProjectMain Pipeline System. . . . . . .
Washita Basin ProjectFort Cobb Aqueduct. . . . . . . .
Foss Aqueduct. . . . . . . . . .
17.9(29)
322.7(519)
8.4(14)
33.9(55)
20.9(34)
50.8(82)
A. CONSTRUCTED
9.6(--)
183(5)
21.8(1)
16(--)
19.7(1)
Precast concrete
Pretensioned, non-cylinder prestressed,reinforced concrete
Precast concrete
Precast concrete
Precast concrete
24--12(61--30)
96--15(244--38)
33(84)
54--12(137--30)
33--15(84--38)
42--6(107--15)
Downstream control of pump units -ON-OFF mode
Downstream control - ON-OFF mode forPP #1 - Remote control (manual) PP #2
"0" controller - Proportional moderegulates flow into reservoirs
Central system remote control (manual)of upstream valves
Downstream control of pump units -ON-OFF mode
Downstream control of pump units -ON-OFF mode - Proportional controlfor chlorinator
Upstream control limits head inpipeline - Proportional mode
Downstream control of pump units -ON-OFF mode
2. Carriage Facilities - Pipelines - Continued
Project and feature
Length
Miles(kilometers)
InitialcapacityCubic feetper second
(cubic metersper second)
Diameter
Type Inches(centimeters)
Automation
~:t
Weber Basin Project
Davis Aqueduct. . . . . . . . . . 21.6(35)
355(10)
Precast concrete 84--21(213--53)
Upstream control - Floating mode forstream water intake to aqueduct
250 6 200 1 Remote manual control of(7) (2) (61) (1) diversion gate
90 12 1,370 25 Upstream control of sluiceway(3) (4) (418) (19) gate - Floating mode (SOT/SRT)
3,000 26 675 20 Remote manual control of diversion(85) (8) (206) (15) gates - See O&M Release 1132
3. Diversion Dams
Crest lengthProjectName of Division (Pick-Sloan Missouri Basin Program)Name of Unit (Pick-Sloan Missouri Basin Program)Name of Diversion Dam, State. Stream
Type of Structure
Diversion capacityCubic feetper second
(cubic metersper second)
Height VolumeThousandcubic yards(thousand
cubic meters)
AutomationFeet(meters)
Feet(meters)
Colorado-Big Thompson ProjectNorth Poudre Diversion Dam, Colorado. Cache la Poudre RiverConcrete ogee weir. . . . . . . . . . . . . .
HaDlDond Project
H8DlDondDiversion Dam, New Mexico, San Juan RiverRockfill' overflow. embankment wings. . . . . . . . .
~0=
Klamath Project
Lost River Diversion Dam. Oregon. Lost RiverConcrete multiple-arch weir. embankment wings. . . . . . .
Pick-Sloan Missouri Basin ProgramFrenchman-Cambridge DivisionRed Willow UnitRed Willow Creek Diversion Dam.Baffled apron weir. embankment
Nebraska. Red Willow Creekwings...........
Middle Loup DivisionFarwell UnitArcadia Diversion Dam. Nebraska. Middle Loup RiverConcrete gate structure. embankment wings. . . . .
90(3)
1.095(334)
35(27)
Upstream control of sluice gate -Floatingmode (SOT/SRT)
11(3)
850(24)
7,960(2.426)
14(11)
Upstream control of sluice gate -Floating mode (SOT/SRT)
8(2)
640 10 1,720 13 Remote manual control of canal(18) (3) (524) (10) headworks gates
48 5 74 3 Upstream control of sluice gate -(1) (2) (23) (2) Floating mode (SOT!SRT)
75 5 138 3 Downstream control of sluice gate -(2) (2) (41) (2) Floating mode (SOT!SRT)
3,650 18 1,128 35 Remote computer assisted control(103) (5) (344) (27) of gates
520 20 200 4 Downstream control of sluice gate(15) (6) (61) (3) Upstream control of diversion
gates with overriding control tolimit tunnel diversion - Floatingmode (SOT!VRT)
3. Diversion Dams - Continued
Crest lengthProjectName of Division (Pick-Sloan Missouri Basin Program)
Name of Unit (Pick-Sloan Missouri Basin Program)Name of Diversion Dam, State, Stream
Type of Structure
Diversion capacityCubic feetper second
(cubic metersper second)
VolumeThousand
cubic yards(thous and
cubic meters)
Automation
Height
Feet(meters)
Feet(meters)
Three Forks DivisionEast Bench Unit
Barretts Diversion Dam, Montana, Beaverhead RiverConcrete gate structure, embankment wings. . . . . .
~\C Rogue River Basin Project
Ashland Lateral Diversion Dam, Oregon, Emigrant CreekConcrete ogee weir, earth dike. . . . . . . .
Oak Street Diversion Dam, Oregon, Bear CreekConcrete weir, stoplogged crest. . . . . . . . . . . . . .
Salt River ProjectGranite Reef Diversion Dam, Arizona, Salt RiverConcrete ogee weir, embankment wings. . . . . . . .
San Juan-Chama ProjectBlanco Diversion Dam, Colorado, Blanco RiverConcrete ogee weir, embankment wings. . . . . . . . . . .
Diversion capacity Height Crest length VolumeCubic feet Thousandper second Feet Feet cubic yards
(cubic meters (meters) (meters) (thousandper second) cubic meters)
150 15 295 3(4) (5) (90) (2)
3. Diversion Dams - Continued
ProjectName of Division (Pick-Sloan Missouri Basin Program)Name of Unit (Pick-Sloan Missouri Basin Program)Name of Diversion Dam, State, StreamType of Structure
~=
Little Oso Diversion Dam, Colorado, Little Navajo RiverConcrete ogee wier. . . . . . . . . . . . . . . . . . . .
Oso Diversion Dam, Colorado, Navajo RiverConcrete ogee wier, embankment wing. . . . . . . . . . . . 650
(18)23(7)
790(241)
18(14)
Automation
Downstream control of sluice gateUpstream control of diversiongates with overriding control tolimit tunnel diversion - Floatingmode (SOT/VRT)
Downstream control of sluice gateUpstream control of diversiongates with overriding control tolimit tunnel diversion - Floatingmode (SOT/VRT)
100 295 4,000 Downstream control of pump units -(3) (90) (4,056) ON-OFF mode
94 31--49 1,090 Downstream control of pump units -(3) (9--15) (1,105) ON-OFF mode
84 111 1,500 Downstream control of pump units -(2) (34) (1,521) ON-OFF mode
83 111 1,450 Downstream control of pump units -(2) (34) (1,470) ON-OFF mode
83 101 1,300 Downstream control of pump units -(2) (31) (1,318) ON-OFF mode
85 103 1,025 Downstream control of pump units -(2) (31) (1,039) ON-OFF mode
4. Major Pumping Plants - 1,000 Total Horsepower or Greater
Project - Name of plant Numberunits
TotalcapacityCubic feetper second
(cubic metersper second)
Totalhorsepower
Dynamichead
AutomationFeet(meters) (metric horsepower)
Central Valley ProjectTrinity River DivisionCow Creek UnitWintu Pumping Plant. . . . . . . . . . . . . .
~~
Friant-Kern Canal Distribution System
Delano-Earlimart Irrigation District
Plant No. D-3 . . . . . . . . . . . . . . . . .
Sacramento River DivisionColusa County Water DistrictPumping Plant 2A. . . . . . . . . . . . . . . .
Pumping Plant 2Al . . . . . . . . . . . . . . .
Pumping Plant 2B. . . . . . . . . . . . . . . .
PumpingPlant2C. . . . . . . . . . . . . . . .
11
4
7
6
6
6
5 31 317 1,500 Downstream control of pump units -(1) (97) (1,521) ON-OFF mode
5 31 241 1,100 Downstream control of pump units -(1) (73) (1,115) ON-OFF mode
4 76 652 7,500 Downstream control of pump units -(2) (199) (7,605) ON-OFF mode
3 17 490 1,200 Downstream control of pump units -(--) (149) (1,217) ON-OFF mode
4. Major Pumping Plants - 1,000 Total Horsepower or Greater - Continued
Project - Name of plant Numberunits
TotalcapacityCubic feetper second
(cubic metersper second)
(metric horsepower)
Dynamichead
Totalhorsepower
Feet(meters)
Automation
Corning Canal Pumping Plant. . . . . . . . . . 477(14)
West San Joaquin DivisionSan Luis UnitDos Amigos Pumping Plant. . . . . . . . . . . .
~~
Chief Joseph Dam ProjectGreater Wenatchee DivisionBrays Landing Unit Lateral System
"A"Pumping Plant. . . . . . . . . . .
Pumping Plant No.1. . . . . . . . . . . . . .
East UnitBooster Pumping Plant. . . . . . . . . . . . .
Howard Flat UnitRiver Booster Pumping Plant. . . . . . . . . .
6 59--71(18--22)
Downstream control of pump units -ON-OFF mode
4,050(4,107)
6 13,200 107--125(374) (33-- 38)
Remote computer assisted control -Operated by the California Departmentof Water Resources
240,000(243,360)
The Dalles ProjectMill Creek Pumping Plant. 5 54 228 1,800 Downstream control of pump units -
(2) (69) (1,825) ON-OFF mode
~LateralDistribution System
~"A" Pumping Plant. 5 51 419 2,500 Downstream control of pump units -(1) (128) (2,535) ON-OFF mode
"F" Pumping Plant 5 43 307 2,150 Downstream control of pump units -(1) (94) (2,180) ON-OFF mode
Ventura River ProjectRincon Pumping Plant. 2 6 900 1,040 Downstream control of pump units -
(--) (274) (1,055) ON-OFF mode
Ventura Avenue Pumping Plant No. 1. 4 50 429 3,200 Downstream control of pump units -(1) (131) (3,245) ON-OFF mode
Ventura Avenue Pumping Plant No. 2. 3 48 220 1,800 Downstream control of pump units -(1) (67) (1,825) ON-OFF mode
4. Major Pumping Plants - 1,000 Total Horsepower or Greater - Continued
Project - Name of plant Numberunits
TotalcapacityCubic feetper second
(cubic metersper second)
Dynamichead
Totalhorsepower
Feet(meters)
Automation(metric horsepower)
I-FC-F&W 256 257 59 Remote manual control of outlet works(316) (317) (24) gates
I-P-FC 344 344 116 Remote manual control of outlet works(424) (424) (47) gates
5. Storage Reservoirs- Outlet Works
ProjectName of Division (Pick-Sloan Missouri Basin Program)Name of Unit (Pick-Sloan Missouri Basin Program)Name of Reservoir, State, Stream
Purpose
ActiveThousandacre-feet(million
cubic meters)
CapacityTotalThousandacre-feet(million
cubic meters)
Surface areaHundredacres(hundredhectares)
Automation
~~
Pick-Sloan Missouri Basin ProgramLower Bighorn DivisionYellowtail UnitYellowtail Afterbay Reservoir,Bighorn River. . . . . . . . . . . . .
Montana,
Three Forks DivisionEast Bench Unit
Clark Canyon Reservoir, Montana, BeaverheadRiver. . . . . . . . . . . . . . . . . . . .
Rio Grande ProjectCaballo Reservoir, New Mexico, Rio Grande. . .
P 3(4)
3(4)
2(1)
Downstream control of canal headworksgates - Floating mode (SOT/SRT)
~FJFJE~[)~~ ~~~
PARAMETERS OF DOWNSTREAM CONTROL
A basic parameter for a controlled water distribution system by the downstream method issteady flow, ~Qout = ~Qin' Figure 24. In simplified terms, the flow out of a controlled section isexpressed as:
~Qout = ~G * B * Cd v'2g*~H, where
~G = change in gate opening
B = gate width
Cd = gate discharge coefficient
~H = differential head across gate
The flow into a controlled section may be expressed in terms of an elementary wave travelingdownstream in a trapezoidal channel.
~Qin = ~ Y*T(V+C) where
~ Y = change in upstream depth
T = top width of water surface
v = channelvelocity
C = wave celerity (v' gAIT) where A equals the cross-sectional area of the total flow
The ratio of ~Qout/~Qin must be unity for steady flow expressed as:
~Qout ~G LB * Cd~
) =~Qin ~ Y .~ T(V+C) I
The ratio of ~G/~ Y, by definition, is the GAIN for the controller and is the first main controlparameter:
GAIN =~G =T(V+C)
l:1Y B * Cd v' 2g.6.H
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FEEDBACK PATH
MOTORANALOG
CONTROLLER FILTER
CONTROL A F
CONTROLLED UPSTREAM GATE
Q~O~Q(rnO)() STATIC WATER
').LEVEL
Q=O P -
WATER LEVELSENSOR LOCATION~
II II
TARGET
~OFFSET"
~y y
0DOWNSTREAM
GATE
Figure 24.-Schematic of Downstream Control by the HyFLO Method.
The GAIN equation shows that the controller is dependent upon the characteristics of theupstream channel and the flow (submerged or free-flow) through the controlling check gate.After the GAIN is computed, the value of f:y,Y can be found by arbitrarily selecting a value for f:y,G(usually 0.10 foot).
f:y,Gcan be expressed in terms of the operate time, f:y,to, of the gate motor hoist. The change ingate opening has a displacement of f:y,G= x * f:y,to, where x is the rate of gate movement in feetper second. Solving for f:y,to gives:
f:y,to = f:y,G/x
The "offset" of the water level required for the increase or decrease of flow is the secondcontrol parameter, Figure 24. The maximum "offset" is defined as:
Offset(max) = G(max)/GAIN
where G(max) is the maximum gate opening required to discharge the maximum desired flow.
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The "offset(max)" would have to be a value less than the difference in elevation between themaximum safe operating level or spill crest and the normal water surface operating level. Anattempt to use an offset less than determined above would require the GAIN of the controller tobe larger. In turn the ratio of boQout/boQin would be larger than unity and could cause excessiveopening or closing of the gate (overshoot) and instability of control would result in unsteadyflow.
The above analysis can be used to determine approximate values of the control parameters,GAIN and "offse1(max)-" The approximate method provides a first approximation of the controlparameters for a particular installation. Greater accuracy can be achieved through mathematicalmodeling before selecting final values.
The "time lag" of the system is the third control parameter. The need to minimize thepossibility of unsteady flow requires that the gate changes be made out of synchronization withthe waves caused by the gate movement. Mechanical, fluid, or electrical delay units between alevel sensor and the control may be necessary to prevent an amplification of the wave.
Wave travel time between the sensor and controlled structure is computed from therelationship C = ygA/T. Selection of the response time of the system may be made frommethods proposed by the University of California, Berkeley!!. For steady flow and stableoperation of the canal, gate movements must not coincide with the wave travel period.
57
AEfEAE~LES
1. Amorocho, J. and Strelkoff, T. S.,HydraulicTransients in the California Aqueduct, ReportNo.2, California Department of WaterResources, Davis, California, June 1965
2. Bureau of Reclamation Federal ReclamationProjects-Water and Land ResourceAtcomplishments, 1971
3. Buyalski, Clark P. and Fults, Dan, CorningCanal Automatic Downstream Control FieldS ca Ie Application of' the FeedbackMethod-Prototype Test Program Procedure,Bureau of Reclamation, Regional Office,Sacramento, California, February 1969
4. Buyalski, Clark P., Basic Equipment inAutomatic Delivery System, Paper Symposium,Nat. Irrig., Irrigation Today and Tomorrow,Lincoln, Nebraska, November 1970
5. Golze, A. R., Aqueduct Control SystemSaves $100 Million, Power Engineering, Volume73, No. 10, pp 30-35, October 1969
6. Gray, H. R. and Humes, J. D., ExperieTlce inOperation of Automatic Water Level ControlStructures in Large Irrigation Canals, Report No.8, pp 28.2.97-28.2.109, ICID Symposium,October 1970
7. Harder, J. A., Shand, M. J., and Buyalski, C.P., Automatic Downstream Control of CanalCheck Gates by the Hydraulic Filter LevelOffset (HyFLO) Method, Paper for Symposium,International Committee, Irrigation andDrainage, October 1970
8. Langley, Maurice N., Automation ofIrrigation, Paper, American Society of CivilEngineers' National Irrigation and DrainageSpecialty Conference, Phoenix, Arizona, pp1-21, November 1968
9. Mann, T. E., Automation for Small IrrigationProjects, Prepr. 1289, ASCE Na.tional WaterResources Engineering Meeting, Phoenix,Arizona, January 1971
10. Schuster, J. C., and Serfozo, E. A., Study ofHydraulic Filter Level Offset (HyFLO)Equipment for Automatic Downstream Controlof Canals, Bureau of Reclamation TechnicalReport REC-ERC-72-3, January 1972
11. Shand, Michael J., Final Report AutomaticDownstream Control Systems for IrrigationCanals, Report HEL-8-4, University of CaliforniaHydraulic Engineering Laboratory, Berkeley,California, August 1971
12. Shand, Michael J., Final Report-TheHydraulic Filter Level Offset Method for theFeedback Control of Canal Checks, Universityof California Hydraulic Engineering Laboratory,Berkeley, California, June 1968
13. Streeter, V. L., and Wylie, E. B., HydraulicTransients, McGraw-Hill, Inc., 1967
14. Sullivan, Edwin F. and Buyalski, Clark P.,Operation of Central Valley Project Canals,Paper, ASCE National Irrigation and DrainageSpecialty Conference, Phoenix, Arizona, pp97-126, November 1968
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