watershed hydrology and water quality - seswa · watershed hydrology and water quality ... 11.9...
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Watershed Hydrology Watershed Hydrology
and Water Qualityand Water Quality
Southeast Southeast StormwaterStormwater AssociationAssociation
Stormwater Solutions for Your JurisdictionStormwater Solutions for Your JurisdictionStormwater Solutions for Your JurisdictionStormwater Solutions for Your Jurisdiction
April 20, 2012April 20, 2012
Jeffrey L. Herr, P.E., D.WREJeffrey L. Herr, P.E., D.WRE
National National StormwaterStormwater LeaderLeader
Brown and CaldwellBrown and Caldwell
&&
Brett Cunningham, P.E.Brett Cunningham, P.E.
Water Resources DirectorWater Resources Director
Jones EdmundsJones Edmunds
Global Water PerspectiveGlobal Water Perspective
Freshwater accounts for less than 3% of the Freshwater accounts for less than 3% of the total water on the earthtotal water on the earth
Groundwater accounts for ~ 0.7% of the Groundwater accounts for ~ 0.7% of the earth’s freshwaterearth’s freshwater
< 0.1% of the freshwater on the earth is in < 0.1% of the freshwater on the earth is in surface waterssurface waterssurface waterssurface waters
Average Annual US RainfallAverage Annual US Rainfall
Region 4 Region 4
Rainfall and Water Use EstimatesRainfall and Water Use Estimates
SurfaceArea
AnnualRainfall
Estimated
Annual WaterState
(sq. mi.) (in./yr.)(MG) Population
Consumption
(MG)
Alabama 51,609 56.9 51,029,934 4,627,851 506,750
Florida 58,560 49.9 50,789,734 18,251,243 1,998,511Florida 58,560 49.9 50,789,734 18,251,243 1,998,511
Georgia 58,876 48.6 49,733,751 9,544,750 1,045,150
Kentucky 40,409 43.6 30,588,154 4,241,474 464,441
Mississippi 47,716 52.8 43,797,541 2,918,785 319,607
Missouri 69,686 33.9 41,063,941 5,878,415 643,686
North Carolina 52,586 42.5 38,800,509 9,061,032 992,183
South Carolina 31,055 51.6 27,840,970 4,407,709 482,644
Tennessee 42,244 48.5 35,596,272 6,156,719 674,161
Based on 300 gpdpcBased on 300 gpdpc
Understanding Hydrology, Understanding Hydrology,
Rainfall and RunoffRainfall and Runoff
Rainfall event distributionRainfall event distribution
Event runoff flow rates and volumesEvent runoff flow rates and volumesEvent runoff flow rates and volumesEvent runoff flow rates and volumes
Dry weather baseflow timing, rates and Dry weather baseflow timing, rates and
volumesvolumes
Watershed Hydrology Watershed Hydrology
Influenced by:Influenced by:
PrePre--development (natural)development (natural)
RainfallRainfall
Vegetative cover (ET)Vegetative cover (ET)Vegetative cover (ET)Vegetative cover (ET)
Soil characteristicsSoil characteristics
DepressionalDepressional storagestorage
Ground surface slopeGround surface slope
Groundwater systemGroundwater system
Minimal runoff typicalMinimal runoff typical
Watershed Hydrology Watershed Hydrology
Influenced by:Influenced by:
PostPost--development development
RainfallRainfall
ET reduced (less vegetation and ET reduced (less vegetation and depressionaldepressional storage)storage)
Fill soil characteristics (modifications due to filling and Fill soil characteristics (modifications due to filling and Fill soil characteristics (modifications due to filling and Fill soil characteristics (modifications due to filling and compaction)compaction)
DepressionalDepressional storage reducedstorage reduced
Addition of impervious areaAddition of impervious area
Addition of irrigation water and in some cases septic tank Addition of irrigation water and in some cases septic tank drainfielddrainfield dischargesdischarges
Vegetation modificationsVegetation modifications
Annual Runoff Depth vs. Land Use(50 inches annual rainfall)
15
20
25
30
Undeveloped
Agriculture Land
Single Use
17.0
19.9
28.8
0
5
10
15
Estimated Runoff Depth (in./yr)
Single Use
Multi Family
Highway
Commercial7.2
11.9
13.2
Development significantly increases surface water runoff volume.
Development Impacts on Development Impacts on
StreamflowStreamflow
Summary of Rainfall Event Characteristics at the Orlando Summary of Rainfall Event Characteristics at the Orlando
International Airport from 1/1/42 to 12/31/95International Airport from 1/1/42 to 12/31/95Rainfall Event
Range (inches)
Mean Rainfall
Depth (inches)
Mean Rainfall Duration
(hours)
Fraction of Annual
Rain Events
Number of Annual Events
in Range
0.00-0.10 0.041 1.203 0.427 56.683
0.11-0.20 0.152 2.393 0.142 18.866
0.21-0.30 0.252 3.073 0.080 10.590
0.31-0.40 0.353 3.371 0.055 7.312
0.41-0.50 0.456 3.702 0.048 6.325
0.51-1.00 0.713 4.379 0.129 17.102 (117)
1.01-1.50 1.221 5.758 0.051 6.733
1.51-2.0 1.726 7.852 0.024 3.145
2.01-2.50 2.271 8.090 0.011 1.4702.01-2.50 2.271 8.090 0.011 1.470
2.51-3.00 2.704 10.675 0.006 0.726
3.01-3.50 3.246 9.978 0.003 0.391
3.51-4.00 3.667 13.362 0.002 0.260
4.01-4.50 4.216 15.638 0.001 0.149
4.51-5.00 4.796 17.482 0.000 0.056
5.01-6.00 5.454 23.303 0.001 0.167
6.01-7.00 6.470 40.500 0.000 0.019
7.01-8.00 7.900 31.500 0.000 0.019
8.01-9.00 8.190 3.500 0.000 0.019
>9.00 10.675 46.250 0.001 0.075
Mean Annual Rainfall = 49.63 inches, Total number of events per year = 130
Conventional Low Imapct
Functional Lanscape DesignGood Drainage
CN alone
often
underestimates
Runoff Volume
for common
rain events
and annual
runoff volume.runoff volume.
SUMMARY OF LITERATURESUMMARY OF LITERATURE--BASED RUNOFF COEFFICIENTS FOR BASED RUNOFF COEFFICIENTS FOR
SELECTED LAND USE CATEGORIES IN CENTRAL AND SOUTH FLORIDASELECTED LAND USE CATEGORIES IN CENTRAL AND SOUTH FLORIDA
(Harper, 1994)(Harper, 1994)
LAND USE CATEGORYLAND USE CATEGORY PERCENT IMPERVIOUS (%)PERCENT IMPERVIOUS (%) RUNOFF COEFFICIENTRUNOFF COEFFICIENT
1. Low1. Low--Density ResidentialDensity Residential11 14.714.7 0.2680.268
2. Single2. Single--FamilyFamily 27.827.8 0.3730.373
3. Multi3. Multi--Family Family 67.067.0 0.6750.675
4. Low4. Low--Intensity CommercialIntensity Commercial 91.091.0 0.8370.837
5. High5. High--Intensity CommercialIntensity Commercial 97.597.5 0.8870.887
6. Industrial6. Industrial 86.886.8 0.7930.793
7. Highway7. Highway 85.085.0 0.7830.783
8. Agricultural8. Agricultural
a. Pasturea. Pasture
b. Citrusb. Citrus
c. Row Cropsc. Row Crops
d. General Agricultured. General Agriculture
0.000.00
0.000.00
0.000.00
0.000.00
0.3550.355
0.2820.282
0.2040.204
0.3040.304
9. Recreational/Open Space9. Recreational/Open Space 1.501.50 0.1630.163
10. Mining10. Mining 23.023.0 0.3610.361
11. Wetland11. Wetland 0.000.00 0.2250.225
12. Open Water/Lake12. Open Water/Lake 100100 0.5000.500
Runoff coefficients commonly overestimate
common storm and annual runoff volume.
Best Approach is to use DCIA Best Approach is to use DCIA
and Curve Number for and Curve Number for N-DCIA
ParameterDrainage Basin
1 2 3 6 7
Area (acres) 368.8 420.6 621.3 281.5 493.2
DCIA (%) 37.2 36.1 27.3 27.6 36.5DCIA (%) 37.2 36.1 27.3 27.6 36.5
Non-DCIA CN 76.5 82.4 76.4 79.2 84.6
tc (min) 81.3 66.7 77.0 61.1 57.4
DCIA is the primary source of runoff from
common events and thus annual runoff volume.
This is why LID is effective.
Summary of Rainfall Event and Annual Runoff Summary of Rainfall Event and Annual Runoff
Depths for SingleDepths for Single--Family Residential AreasFamily Residential Areas
RainfallRainfall
IntervalInterval
PointPoint
(inches)(inches)
EventEvent
RunoffRunoff
DepthDepth
(inches)(inches)
AnnualAnnual
RunoffRunoff
DepthDepth
(inches)(inches)
CumulativeCumulative
RunoffRunoff
DepthDepth
(inches)(inches)
RainfallRainfall
IntervalInterval
PointPoint
(inches)(inches)
EventEvent
RunoffRunoff
DepthDepth
(inches)(inches)
AnnualAnnual
RunoffRunoff
DepthDepth
(inches)(inches)
CumulativeCumulative
RunoffRunoff
DepthDepth
(inches)(inches)
0.050.05 0.000.00 0.000.00 0.000.00 2.752.75 1.211.21 1.731.73 12.7612.76
0.080.08 0.000.00 0.000.00 0.000.00 3.253.25 1.581.58 1.241.24 14.0014.00
0.150.15 0.000.00 0.170.17 0.170.17 3.753.75 1.971.97 1.171.17 15.1715.17
0.250.25 0.030.03 0.330.33 0.500.50 4.254.25 2.372.37 0.510.51 15.6815.68
0.350.35 0.050.05 0.440.44 0.940.94 4.754.75 2.792.79 0.450.45 16.1316.13
0.450.45 0.070.07 0.510.51 1.451.45 5.505.50 3.443.44 0.930.93 17.0617.06
0.750.75 0.130.13 2.392.39 3.843.84 6.606.60 4.334.33 0.940.94 18.0018.00
1.251.25 0.310.31 2.822.82 6.666.66 7.507.50 5.245.24 0.570.57 18.5718.57
1.751.75 0.560.56 2.542.54 9.209.20 8.508.50 6.176.17 0.170.17 18.7418.74
2.252.25 0.870.87 1.831.83 11.0311.03 9.509.50 7.117.11 0.580.58 19.3219.32
C ~ 0.32 (C = 0.37 in Table)
Summary of Rainfall Event and AnnualSummary of Rainfall Event and Annual
Runoff Depths for Commercial AreasRunoff Depths for Commercial Areas
RainfallRainfall
IntervalInterval
PointPoint
(inches)(inches)
EventEvent
RunoffRunoff
DepthDepth
(inches)(inches)
AnnualAnnual
RunoffRunoff
DepthDepth
(inches)(inches)
CumulativeCumulative
RunoffRunoff
DepthDepth
(inches)(inches)
RainfallRainfall
IntervalInterval
PointPoint
(inches)(inches)
EventEvent
RunoffRunoff
DepthDepth
(inches)(inches)
AnnualAnnual
RunoffRunoff
DepthDepth
(inches)(inches)
CumulativeCumulative
RunoffRunoff
DepthDepth
(inches)(inches)
0.050.05 0.000.00 0.000.00 0.000.00 2.752.75 1.851.85 2.652.65 24.2124.21
0.080.08 0.000.00 0.000.00 0.000.00 3.253.25 2.292.29 1.791.79 26.0026.00
0.150.15 0.020.02 0.340.34 0.340.34 3.753.75 2.752.75 1.641.64 27.6427.64
0.250.25 0.060.06 0.650.65 0.990.99 4.254.25 3.213.21 0.690.69 28.3328.33
0.350.35 0.100.10 0.880.88 1.871.87 4.754.75 3.693.69 0.600.60 28.9328.93
0.450.45 0.140.14 1.021.02 2.892.89 5.505.50 4.404.40 1.191.19 30.1230.12
0.750.75 0.300.30 5.515.51 8.408.40 6.606.60 5.365.36 1.161.16 31.2831.28
1.251.25 0.620.62 5.655.65 14.0514.05 7.507.50 6.326.32 0.680.68 31.9631.96
1.751.75 1.001.00 4.544.54 18.5918.59 8.508.50 7.317.31 0.200.20 32.1632.16
2.252.25 1.411.41 2.972.97 21.5621.56 9.509.50 8.298.29 0.670.67 32.8332.83
C ~ 0.55 (C = 0.85 in Table)
Paradigm for Water Quality TreatmentParadigm for Water Quality Treatment
0.6
0.7
0.8
0.9
1
Cu
mu
lati
ve P
rob
ab
ilit
y
Orlando International Airport
0
0.1
0.2
0.3
0.4
0.5
0 2 4 6 8 10
Cu
mu
lati
ve P
rob
ab
ilit
y
Rainfall (inches)
Estimating Annual FlowsEstimating Annual Flows
Runoff CoefficientsRunoff Coefficients–– Not from Rational MethodNot from Rational Method
–– Best from continuous simulationBest from continuous simulation
Modified CN methodModified CN method–– Separate DCIASeparate DCIA–– Separate DCIASeparate DCIA
–– Account for UCIAAccount for UCIA
–– Account for antecedent conditionsAccount for antecedent conditions
–– Harvey Harper methodHarvey Harper method
–– Account for high groundwaterAccount for high groundwater
Continuous Simulation ModelsContinuous Simulation Models–– SWMM, HSPF, SPAW, etc.SWMM, HSPF, SPAW, etc.
NRCS MethodNRCS Method
World’s Worst Hydrologic AssumptionWorld’s Worst Hydrologic Assumption
SIa
2.0=
National Engineering Handbook,
Section 4 – Hydrology, 1985
NRCS MethodNRCS Method
Considering
DCIA
separately
reduces
some of this
problem.
Figure source:
Pitt, 2012
Comparison of Pollutant Loading Models
Must Have Volumes Correct
LEMON BAY SITES
Alligator Creek Ainger Creek
Paper Field
Different methods and Different methods and assumptions assumptions
lead lead to to highly variable results.highly variable results.
Paper Field
Comparison of
Pollutant Loading Models
ANNUAL TOTAL NITROGEN LOADS (lb/yr) FROM BASEFLOW
SURFACE WATER RUNOFF & SEPTIC
988
4,063Baseflow
3,850
18,800
4,063
Total = 19,788
Surface
Water FlowSeptic
Total = 41,36027,130
10,380
Highly variable results with significantly different management Highly variable results with significantly different management
implications. Are septic tanks or surface water runoff the implications. Are septic tanks or surface water runoff the
primary source of tributary pollutants?primary source of tributary pollutants?
Importance of All Source TermsImportance of All Source Terms
Baseflow Direct Runoff Irrigation
Point Sources Septic Tanks Direct Rainfall
Roberts Bay, Sarasota County
Variations in Base Flow Variations in Base Flow
ConcentrationsConcentrations
Variations in Groundwater Variations in Groundwater
ConcentrationsConcentrationsConcentrations
will vary widely
based on land
use and redox
condition
This has
implications on
watershed
assessment
and BMP
design
Nitrogen TreatmentNitrogen Treatment
http://ecosystems.mbl.edu/research/clue/nitrogen.html
Average Water Use in the HomeAverage Water Use in the Home
The ResourceThe Resource
SE states receive 34 to 57 inches of SE states receive 34 to 57 inches of
rainfall each year rainfall each year
Rainfall volume is >>>> water demandRainfall volume is >>>> water demand
Much of our rainfall becomes runoff and is Much of our rainfall becomes runoff and is Much of our rainfall becomes runoff and is Much of our rainfall becomes runoff and is
lost to tidelost to tide
Stormwater runoff is naturally selfStormwater runoff is naturally self--
sustaining; pending major changes from sustaining; pending major changes from
climate change it will continue to rainclimate change it will continue to rain
Potential UsesPotential Uses
Irrigation for Ag, golf courses, commercial and Irrigation for Ag, golf courses, commercial and
residential propertyresidential property
Gray water for commercial and residential Gray water for commercial and residential
propertiesproperties
Cooling water for power generationCooling water for power generation
With minimal treatment (settling and/or filtration), With minimal treatment (settling and/or filtration),
could be used for cleaning, vehicle washing, etccould be used for cleaning, vehicle washing, etc
Any use if treated at a public water treatment Any use if treated at a public water treatment
facilityfacility
Questions?Questions?
Jeffrey Jeffrey L. Herr, P.E., D.WREL. Herr, P.E., D.WREJeffrey Jeffrey L. Herr, P.E., D.WREL. Herr, P.E., D.WRE
National National StormwaterStormwater LeaderLeader
Brown and CaldwellBrown and Caldwell
[email protected]@brwncald.com
&&
Brett Cunningham, P.E.Brett Cunningham, P.E.
Water Resources DirectorWater Resources Director
[email protected]@jonesedmunds.com