water through plant absorption andevaporation. If the soil moisture contentremained high, plants would utilizewater in the top eight inches of soil, but,in a water-stressed environment, plantswere capable of extracting water from asdeep as 24 inches below the topsoil.

“Plants are opportunistic,” he said.“They will use as little energy as possibleto maintain themselves. If homeownersirrigate lightly and frequently, and donot build water reservoirs deep in thesoil, drought conditions that dry thetopsoil could possibly injure or even kill

Texas A&M University System Agriculture Program • New Mexico State University College of Agriculture and Home Economics

See Landscape on page 7

Using sensors placed

in 64 different areas

and depths, specialists

with the Texas A&M

Department of Soil &

Crop Sciences

measured both

potential and actual

evapotranspiration of

an entire landscaping

system consisting of

trees, turfgrass and

shrubs.

Identifying water needs for yardsDeep and infrequent irrigation key for efficient water use

A mature walnut tree sits on a lawn ofSt. Augustine grass, dotted with crapemyrtles, rose bushes, ficus trees anddwarf yaupon hedges. The landscape,along with the sandy loam soil at theTexas A&M Research and ExtensionCenter in Weslaco, makes it the ideal sitefor studying water requirements of acommon residential landscape system,not just of individual plants.

Using sensors placed in 64 differentareas and depths, Roger Havlak,extension program specialist for turfgrassand water management with the TexasA&M University Department of Soil &Crop Sciences, measured both potential

evapotranspiration from weather stationsand actual evapotranspiration. Potentialevapotranspiration is the maximumamount of water lost in a croppingsystem in a given time period from bothplants and evaporation. Actualevapotranspiration is the soil moistureloss of a landscaping system consisting oftrees, turfgrass and shrubs.

Havlak found that the top eight inchesof soil lost the greatest fraction of soil

by Jenna Smith

“Plants are opportunistic. They will use

as little energy as possible to maintain

themselves. If homeowners irrigate lightly

and frequently, and do not build water

reservoirs deep in the soil, drought

conditions that dry the topsoil could

possibly injure or even kill the plants.”

2

Alfredo Montoya, a grower whosefamily dates back eight generations inAlcalde, said he feels vindicated by a NewMexico State University (NMSU) studythat shows traditional acequia (ditch)irrigation systems provide broadecological and social benefits to localcommunities.

“The knowledge of how beneficialacequias are has been passed down fromgeneration to generation, but there’s beenlittle public recognition of it outside ourcommunities,” said Montoya, who is anAlcalde acequia commissioner. “Theacequias help keep the countryside lushwith vegetation and wildlife, and theyhelp recharge underground water

Sam Fernald, a New

Mexico State Univer-

sity watershed man-

agement specialist,

measures subsurface

water levels and

quality near the

Alcalde acequia at

New Mexico State

University’s Sustain-

able Agriculture

Science Center.

Acequias aid in aquifer rechargeStudy shows multiple benefits from acequia irrigation

supplies and the Rio Grande. We’vealways known that, but now there’s ascientific study that proves it.”

The study, conducted by researcherswith the Agricultural ExperimentStation, shows that seepage from acequiairrigation canals replenishes shallowaquifers, contributes to riparianvegetation growth and helps maintainsurface water levels downriver, said SamFernald, a watershed managementspecialist directing the research.

“The study is continuing, but we’vealready confirmed these things,” Fernaldsaid. “We now know for sure thatacequia seepage creates shallowgroundwater flow that benefits aquifersand protects deep groundwater qualitywhile flowing directly back to the river.”

“There may be benefits to lining someditches, but if irrigators are gettingenough water through their canals, thisstudy suggests it may be better to leavethem just the way they are,” Fernaldsaid.

The research began in 2001 withfunding from the Rio Grande BasinInitiative. The study is documentinginteraction between surface andgroundwater flows along rivers andirrigation canals in northern, central andsouthern New Mexico, Fernald said.

The study is most advanced in Alcalde,where Fernald and researchers at theNMSU Sustainable Agriculture ScienceCenter drilled nine wells to measure

by Kevin Robinson-Avila

“The acequias help keep the countryside

lush with vegetation and wildlife, and they

help recharge underground water

supplies and the Rio Grande.”

3

“We now know for sure that acequia

seepage creates shallow groundwater

flow that benefits aquifers and protects

deep groundwater quality while flowing

directly back to the river.”

water flow and quality in three areas:along the acequia, out in the field wherecrops are and along the river bank. Theyused 2-inch-wide slotted pipes thrust 20-to 40-feet down. As water ran throughthe pipes, electronic indicators measuredgroundwater levels and quality.

“We did find a lot of seepage from theditches, up to 10 to 12 centimeters perday,” Fernald said. “But we also foundthat the water rapidly seeps into shallowgroundwater, and a lot of it flows directlyback to the river.”

Final measurements are still beinganalyzed, but over the length of theacequia, about 5 percent of waterrunning through the canals is seepingout and flowing back towards the river,Fernald said. “That doesn’t seem like ahuge amount at first glance, but add itup over a whole season and that’s a lot ofwater returning to the river,” he said.

In addition to recharging aquifers, theshallow subsurface flow from seepagealso protects deep groundwater qualityby washing away residue from

agricultural chemicals, nutrients andsalts, Fernald said. And seepage along theacequias provides water for trees, shrubsand pastures to grow in areas far fromthe river, providing food for wildlifewhile improving rural aesthetics andland values.

Fernald is now organizing a secondresearch site in Albuquerque, where soiland irrigation systems differ from thosein northern New Mexico.

In southern New Mexico, Fernald isstudying surface and groundwater flowsbetween the Rio Grande and bosques

along the riverbank. Researchersinstalled 67 wells at a bosque on theNMSU Chihuahuan Desert RangelandResearch Center to measure water leveland quality.

“The bosque acts like a ripariansponge that filters and cools the waterbefore flowing back to the river,” Fernaldsaid. “That helps downriver users whoplan to treat water for drinking, and itbenefits fish that need cool water tosurvive.”

In Alcalde, Cooperative ExtensionService is already disseminating researchresults.

“This is important, because accuratemeasurements of return flow to the riverand other acequia benefits must beconsidered when policy-makers evaluateagricultural water use,” said SteveGuldan, Alcalde science centersuperintendent.

Montoya said the research could helpgrowers maintain the traditional acequiasystem. “It comes at an opportune timewhen there’s fierce competition for waterin the state,” he said. “It demonstratesthat acequias benefit local communities,not just agriculture.”

Fernald is studying

interaction between

surface and ground-

water flows along

rivers and irrigation

canals in northern,

central and southern

New Mexico.

4

A popular irrigation practice made itsway into the United States from Israel inthe early 1970s. For the first time,however, subsurface drip irrigation,characterized by a closed, low-pressuresystem, is being pumped using a recycledwater source.

A team of researchers at the Texas A&MAgricultural Research and ExtensionCenter in El Paso, Naomi Assadian andGeorge Di Giovanni, along with TexasCooperative Extension Specialists JuanEnciso and Jaime Iglesias, is evaluating ablend of reclaimed and untreatedwastewaters as alternatives to Rio Grandewater for a subsurface drip irrigationsystem on spinach.

Research Technician

Nick Ronquillo prepares

columns, where the

irrigated vegetables

are monitored. For

the first time, subsurface

drip irrigation is being

pumped using a

recycled water source.

Identifying new water sourcesArid regions look to water efficiency of subsurface drip

Assadian said there are plenty ofopportunities and consistent supplies ofwastewater from urban and ruralcommunities for crop irrigation.However, wastewater may containmicrobial and chemical constituents thatmay be harmful to soil and plants, and

by Jenna Smith

“In the future, there should be minimal

costs for using lower quality wastewaters

for agricultural purposes. Farmers could

provide an important recycling service

for themselves and for local

communities.”

5

may potentially affect food safety.The water used in this study was

collected from a wastewater treatmentplant in El Paso. The untreated wastewaterwas high in nitrogen, and the reclaimedwastewater was high in sodium.

Both types of water underwentconventional wastewater and recycledtreatments. About 33 percent of theoperating costs of the treatment plant arespent removing nitrogen from theserecirculated wastewaters.

“Instead, nitrogen-rich water could bediverted for irrigation,” Assadian said.“Nitrogen is an important macronutrientfor plants.”

Subsurface drip irrigation involves anunderground network of hoses withholes, or emitters. Water is released throughthese emitters at a specific rate, allowingplant roots the first opportunity at water.

“Compared to surface irrigation,subsurface irrigation methods decreasewater losses from wind, evaporation orleaching,” Assadian said. “We can alsocontrol how much and how often wateris administered, and keep water applicationcontained in targeted areas. Moreimportantly, for reclaimed wastewaters, ithas the potential to minimize pathogenmovement to the soil surface.”

Initial installation costs of subsurfacedrip irrigation systems are high, so mostcurrent users in the desert Southwest aresmall landscapers and homeowners.

Assadian said that subsurface dripirrigation will become a more valuableand common irrigation delivery systemas water availability decreases and waterprices rise in the El Paso region.

“Crop selection will also be an

Spinach is being

grown in columns,

where the moisture

content is weighed

and measured.

Spinach is the perfect

test plant for re-

claimed water use,

because it is eaten

both raw and cooked.

important factor in successful use ofalternative irrigation water sources.Crops such as spinach and asparagus aresodium-loving plants,” Assadian said.“By planting these types of crops, wemay help draw salts from the soil toreduce salt accumulation.”

She said the project demonstrates thepotential for a win-win situationbetween urban communities and

agriculture in the Rio Grande Basin.Communities could supply essential

water and nutrients for crop production,and, in turn, agriculture eliminates acostly waste stream for communities.Because agriculture uses less fresh waterfor irrigation, more is available for otheruses.

“In the future, there should be minimalcosts for using lower quality wastewatersfor agricultural purposes,” Assadian said.“Farmers could provide an importantrecycling service for themselves and forlocal communities.”

“Crop selection will also be an important

factor in successful use of alternative

irrigation water sources.”

6

Publication describes

Elephant Butte policies

A publication describingthe Lower Rio GrandeValley’s water resourcesand New Mexico’s ElephantButte Irrigation Districtpractices is now availablethrough New MexicoCooperative Extension.

Interpreting the ElephantButte Irrigation District forWater Users assists watermanagers, producers andall other water users inunderstanding the policiesthat govern water use anddistribution throughoutthe irrigation district aswell as water rights issues.

As the main waterprovider for southernNew Mexico and West

Texas, Elephant ButteReservoir must receive aspecified amount of watereach year to meet theneeds of its water users.This publication addressesthe ways in which thereservoir is supplied andhow the irrigation districtmanages the reservoirwater supply.

Project conference set

for April in New Mexico

The Texas Water ResourcesInstitute and the NewMexico State UniversityCollege of Agricultureand Home Economics willhold the third annual RioGrande Basin InitiativeConference April 4-7, 2004in Las Cruces, New Mexico.

B.L. Harris, projectdirector for the Rio GrandeBasin Initiative andassociate director of theTexas Water ResourcesInstitute, said the purposeof the meeting is to promotecommunication amongproject participants inTexas and New Mexico,and to promote collaborativelinking with otheragencies.

“Accomplishments willbe highlighted, andinteractive discussions forfuture plans will be afocus,” he said. “Betterintegration, project activityprioritization andexpanded collaborationare goals of the meeting.”

Homeowner survey to

reduce urban water use

Homeowners movingtoward a water-conservinglandscape and workingwith a reduced waterbudget would be satisfiedwith flowers, healthyleaves and plant

robustness, according toa survey of Las Cruceshomeowners availablefrom the New MexicoAgricultural ExperimentStation.

The survey investigateslandscape preferences andattitudes of residentialhomeowners in hopes ofreducing urban water use.

According to the survey,more than 50 percent ofhomeowners reported

having a Southwest,desert-type landscape, butwhen asked how theycould help reduce wateruse in the Las Crucesarea, more than 80 per-cent of residents said theywould use desert plantsin their yards.

Respondents to thesurvey also admitted thatwater shortages in thearea would cause them todecrease personal wateruse, followed by environ-mental concerns, highwater bills, water rateincreases and city regula-tions.

Every drop counts

http: //spectre.nmsu.edu:16080

/rio_grande

The Texas Water

Resources Institute

and the New Mexico

State University

College of Agriculture

and Home Economics

will hold the third

annual Rio Grande

Basin Initiative Conference

April 4-7, 2004 in Las

Cruces, New Mexico.

Fifty percent of

homeowners reported

having a Southwest,

desert-type landscape,

but when asked how

they could help

reduce water use in

the Las Cruces area,

more than 80 percent

of residents said they

would use desert

plants in their yards.

7

ings that may be realized if potentialevapotranspiration was used,” he said.“This could certainly be a useful tool formunicipalities to use in their day-to-dayassessments for conserving water.”

The potential evapotranspiration valuefrom the weather station was an excellentpredictor of water loss rates within theWeslaco landscape system. However,because of the differences among plantvarieties and soil types throughoutTexas, Havlak and the turfgrass staff atTexas A&M plan to introduce an addi-tional five to ten sites within the next fiveyears.

“We plan on setting up a site at theTexas A&M University Riverside Campusby April 2004 so that we can begincollecting data on that site prior tosummer,” he said. “We also hope to locatesites in West Texas and New Mexico,both located within the Rio GrandeBasin, in the near future.”

Havlak has given talks nationwide towater users and to agencies within theturfgrass industry. Local weather sta-tions and county extension offices canalso provide homeowners with informa-tion on proper irrigation techniques.

the plants. Thus, deep and infrequentirrigation is recommended.”

Havlak said system zoning is anotheruseful tool for water conservation. Itinvolves applying water in differentzones, separated by water requirementsof the plants and application methods.Because water loss rates are normallydifferent among plants in landscapes, hesaid, this approach is also recommended.

Havlak used the ratio of actual evapo-transpiration to potential evapotranspi-ration to calculate the landscapingcoefficient for the Weslaco landscape.Landscaping coefficients remained lessthan 1 during the study with monthlycoefficients ranging from 0.51 to 0.67.

“We are already working with severalmunicipalities to analyze and comparehomeowner water consumption rates toweather station potential evapotranspira-tion rates to determine the number ofhomeowners possibly overwatering theirlandscapes as well as the potential sav-

Continued from page 1

Landscape

The Texas Evapo-

transpiration Network

can be accessed at

http://texaset.tamu.edu.

The turfgrass site at

Texas A&M is

http://aggie-turf.tamu.edu.

Rio Grande Basin Initiative Outcomes

February 2004, Vol 3. No. 1

B.L. Harris, Project Director,

Associate Director, Texas Water Resources Institute

Craig Runyan, Project Director,

Water Quality Coordinator,

New Mexico State University Plant Sciences

Rachel Alexander, Editor

Send comments or subscription requests to

Outcomes Editor, Texas Water Resources Institute,

2118 TAMU, College Station, Texas, 77843-2118.

Call (979) 845-1851 or e-mail

riogrande@tamu.edu.

http://riogrande.tamu.edu

Increasing Irrigation Efficiency

in the Rio Grande Basin

through Research and EducationThrough Extension and research efforts, theTexas A&M University System AgricultureProgram and the New Mexico StateUniversity College of Agriculture and HomeEconomics are implementing strategies formeeting present and future water demandin the Rio Grande Basin. These strategiesexpand the efficient use of available waterand create new water supplies. Thisfederally funded initiative is administeredby the Texas Water Resources Institute andthe New Mexico State University WaterTask Force with funds from the CooperativeState Research, Education, and ExtensionService.