Irrigation & DrainageUnited StatesDepartment ofAgriculture

AgriculturalResearchService

ProgramAid 1680

September 2001

A National Research Plan To MeetCompeting Demands and Protectthe Environment

Irrigation and drainage haveplayed central roles in the

remarkable success of Americanagriculture. Settlement of theAmerican West was tied closelyto irrigation, and drainage inhumid regions makes possiblethe high production of food andfiber we know today.

Irrigation is also vital to cropproduction throughout theMidwest, into the South, and inmany Eastern States, especiallyFlorida. Urban irrigation nowcomprises a large component ofthe irrigation market—forlandscaping, golf courses,athletic fields, and other recre-ational uses.

Irrigation continues to expandnationally, although acreageshave declined in some states dueto competing demands. As aheavy water user, irrigatedagriculture is but one of manyneeds for water, energy, andland resources. At the sametime, the growing globaleconomy and world populationare placing greater demands onirrigated agriculture to providefood and fiber.

Conditions such as theseinevitably mean changes inpublic policy and programs thatmanage and allocate water.Policymakers at all levels faceincreasing demands for water—for food and fiber, urban andenvironmental purposes, andNative American claims, as wellas for retaining U.S. globalcompetitiveness in agriculture.

Improvements in irrigation anddrainage technology are helping

the Nation cope with thesechallenges. We are using ournatural resources more effi-ciently and paying closerattention to safeguarding andimproving the environment.

Researchers are developingsophisticated systems thatproducers need to remaincompetitive in today’s globalmarkets. As farmers strive toadopt more efficient, effectiveirrigation and drainage prac-tices, more research will beessential for solving bothexisting and emerging prob-lems.

The Agricultural ResearchService (ARS) is the agencywithin the U.S. Department ofAgriculture responsible fordeveloping and improvingirrigation and drainage tech-nologies and managementpractices. With advice frommany users, ARS has identifiedthe following high-priorityproblem areas in irrigation anddrainage:

Crop Production Systemsirrigated crop productionprecision irrigation

Water Quantity Technologieswater conservationenergy conservationirrigation in humid areasdrainage systems

Water Quality & EnvironmentalImpact

salinity and trace elementswaste water reusethe environmenterosion

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Facts About Irrigation

• Irrigation made it possible for 16 percent of U.S. cropland toproduce 48 percent of harvested crop sales in 1997. Thatcorresponds to about 280,000 farms irrigating 55 million acresof crop and grazing land.

• The average value of crops produced per acre was $317 in1997. That same year, sales from irrigated cropland totaledmore than $950 per acre, compared with sales of less than$200 per acre from nonirrigated cropland.

• In the West, sales averaged about $850 per acre in 1997 on the38 million acres of irrigated cropland, accounting for one-thirdof all crop sales in the Nation.

• Irrigation in the East covers less than 12 million acres, but cropsales are valued at more than $1,250 an acre, the highest in theNation.

• The major irrigated crops included corn, hay, pasture, cotton,soybeans, and wheat in 1997.

• About 60 percent of irrigated crop sales were from orchards,vegetables, and horticultural crops. These crops make up about15 percent of the acres irrigated and represent 72 percent of theacres in orchard, vegetable, and horticultural crops.

ARS has drawn up a plan of action to guide research on irrigationand drainage. Forming the core of the plan are environmental andeconomic issues. The pages that follow offer a sketch of each of thenine problem areas, the national research goals, and the hoped-forlong-term effects.

Primary Locations

Contributing Locations

Phoenix

Irrigation & Drai

Fresno

Riverside

CA

AZ

CO

Ft. Collins

Akron

Bushland

TX

Prosser

WA

Kimberly

ID

Lincoln

NE

Sidney

MT

Lubbock

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inage Locations

BatonRouge

LA

Ft.Pierce

FL

Beltsville

Dawson

GA

Columbus

OH

Florence

SC

MD

Stoneville

MS

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Irrigated Crop Production

Crop ProductionSystems

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The purpose of irrigation is to produce crops that have eco-nomic and social value. The continued productivity of irri-gated agriculture will be critical as national and world popula-tions grow and demand more food and fiber.

Properly managed irrigation can increase crop yields, reducerisks commonly associated with agriculture, increase productquality, reduce pest pressures, and precisely deliver andmanage nutrients. Because irrigation management is specificto each crop, irrigation research must be crop-specific, mean-ing that cropping systems must be understood, including thoseinvolving high-value specialty crops with particular needs.

Research goal—To develop ecologically sound water, pest,and nutrient management practices and technologies forrotational cropping systems that maximize the economicbenefits of irrigated agriculture.

Long-term effect—Irrigated agriculture that is highlycompetitive in the global economy.

Precision Irrigation

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Precision irrigation applies water and agricultural chemicalsprecisely where they are needed. By using site-specific man-agement and variable-rate technology, precision irrigationenhances yields and reduces applications of nutrients andchemicals such as herbicides, pesticides, nematicides, andfungicides.

For precision irrigation to achieve its potential, we need tobetter understand a cropping system’s responses to existingpractices and recommended changes. This understandingmust encompass the proper management of all variableadditions or inputs, including one of the most important—water.

Research goal—To develop precision irrigation systems andtechnologies for site-specific management of high-valuecrops.

Long-term effect—Irrigation that makes effective use ofprecision technologies, thereby enhancing productivity.

Water Conservation

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Water QuantityTechnologies

Water conservation is one of the primary ways that irrigationhelps society meet competing demands for water.

We are not likely to satisfy increased water demands withnew water sources. The costs and environmental effects ofdevelopment would be prohibitive. As the largest water userin the United States, irrigation—of agriculture, turf, andlandscapes—must seek ways to conserve. This will require avariety of technologies.

Research goals—• To develop technology that quantifies and controls a

broad range of water supplies and uses.• To develop cultural and management practices for agricul-

ture, turf, and landscapes that maximize returns from thewater used.

• To develop improved practices and systems that mitigatethe adverse effects of irrigation on water quality and theenvironment.

Long-term effect—A national water supply that meets theneeds of irrigated agriculture and the public.

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Energy Conservation

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Energy conservation must work hand in glove with the use ofalternative energy sources and water conservation.

While water is ultimately a renewable resource, energy isnot—at least in the present state of technology. Like waterconservation, however, energy conservation has implicationsfor society and the environment. So the development and useof irrigation technology must incorporate the same concernfor conserving energy as it does for conserving water.

Research goals—• To develop irrigation technology and cultural and man-

agement practices for agriculture, turf, and landscapes thatmaximize returns from the energy used.

• To find ways to use renewable, efficient, and environmen-tally friendly energy sources—such as wind, solar, andbiofuels—in irrigation systems.

Long-term effect—Dependable and sustainable energy forthe Nation’s irrigation needs.

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Humid Areas

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With consistent planning and operation of water managementsystems, irrigation and drainage can be sustained in humidareas with minimal environmental impacts, while enhancingthe Nation’s agricultural productivity.

The profitability of irrigation and drainage in humid areasdepends on seasonal rainfall, adequate economic returns fromcrops, and irrigation and drainage expenses. To boost profit-ability and reduce risks, we need better methods for determin-ing when and how much to irrigate. And we need new waysto design and operate drainage systems.

Research goal—To develop the knowledge, techniques,systems, and models to design and operate sustainable agri-cultural irrigation and drainage systems in humid areas, withminimal environmental impacts and efficient use of waterresources, including waste water.

Long-term effect—Environmentally and economicallysustainable irrigation and drainage systems in humidareas.

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Drainage Systems

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Managing surface and subsurface drainage systems to controlcontamination of surface runoff and shallow groundwater, aswell as the depth of the water table, evolved first in humidareas and later in arid areas. In humid areas, controlled drain-age has reduced nitrate in subsurface drainage discharge.

Many questions remain about the best drainage practices forimproving crop production and the quality of runoff andsubsurface drainage discharge in humid, semiarid, and aridareas. We need different drainage systems to ensure efficient,environmentally sound crop production in all of these areas.

Research goals—• To develop drainage practices that enable crops to use

shallow groundwater efficiently, while reducing the use ofagricultural chemicals.

• To use controlled drainage systems in semiarid and aridareas that reduce the environmental effects of salts andtrace elements carried in drainage discharge.

• To use controlled drainage or water-table managementsystems in humid areas that reduce flood flows and theenvironmental effects of nutrients carried in drainagedischarge.

Long-term effect—Drainage systems that improve cropproduction while working in harmony with the environ-ment.

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Salinity and Trace Elements

Water Quality &Environmental Impact

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Use of crop irrigation on some lands is threatened by itseffects on soils, groundwater, and surface water. Crops extractnearly pure water, leaving soluble salts and toxic trace ele-ments behind to accumulate around the roots. Managing thisaccumulation is a continuous challenge. To preserve theland’s productivity, more water must be added to remove thesalts and trace elements from the root zone. Often, drainagesystems are needed to facilitate this process.

Research goals—• To develop methods for managing salts and trace elements

in irrigation and drainage waters that would eliminatetheir harmful effects on soils, groundwater, and cropproductivity.

• To dispose of the concentrated salts and toxic elements inwaste products and reduce the associated hazards.

• To develop instruments that measure salinity and modelsthat predict the effects of salinity on crops, soils, water-sheds, and aquifers.

Long-term effect—No loss of irrigated land or productiv-ity due to salinity and trace elements.

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Waste Water Reuse

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Irrigation is a primary—and desirable—way to use wastewater from agriculture, industry, and municipalities.

Water is limited in many parts of the United States. Onesolution to shortages is use of agricultural, industrial, andmunicipal waste waters for agriculture, municipal parks andrecreational areas, and other green spaces. These uses wouldoffset the demand for drinkable water. And they are permis-sible, provided they do not degrade surface and groundwater,cause soil salinization and deterioration, or result in real orperceived threats to public health.

Research goals—• To identify best management practices for irrigation using

waste water.• To overcome specific climatic and soil limitations that

prevent applying waste waters on agricultural lands andurban landscapes.

Long-term effect—Irrigation systems that reuse wastewaters without compromising the public’s health or theenvironment.

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The Environment

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Irrigation and drainage can improve or degrade ecosystemsand the environment. Problems associated with irrigatedagriculture include erosion, sedimentation of surface waters,chemical and nutrient contamination of water supplies, andsalinization. Too, water and chemical inputs for urban andrecreational irrigation are often far higher than necessary.

We need to understand how irrigation and drainage affect themovement of sediment and chemicals into water supplies.New, improved practices and strategies could enhance thehealth of ecosystems and the quality of the environment.

Research goals—• To determine the effects of irrigation and drainage prac-

tices on the movement of pesticides, nutrients, sediment,biological agents, salts, and trace elements into surfacewater and groundwater.

• To predict and validate the effect of irrigation and drain-age practices in fields, farms, watersheds, and river basins.

Long-term effect—Irrigated agriculture that is environ-mentally compatible.

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Erosion

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Irrigation enables farmers to use less than half the land areathey would otherwise need for the same yields. Unfortunately,irrigation often increases erosion. Because erosion theory andmodels and conservation practices are derived largely fromsituations involving rain, they do not perform well whenapplied to irrigated lands. Poor irrigation practices also causerunoff and erosion, which contribute to surface-water con-tamination.

Research goals—• To develop methods and a computer model for accurately

predicting infiltration, runoff, and erosion from irrigation.• To develop new conservation management and irrigation

practices that enhance infiltration, reduce runoff, andimprove water quality on a wide range of irrigated soils.

Long-term effect—Irrigated agriculture that maintainssoil resources for future generations.

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Frequent Questions AboutIrrigation• Is irrigation a good idea for small farms?

For small farms, getting access to water for irrigation is lessof a problem than stretching the supply of available water.Use of irrigation systems is increasing on small- and medium-sized farms and in greenhouse operations.

• Which countries lead in irrigated agriculture?

Four countries—India, China, the U.S., and Pakistan—account for more than half of the world’s irrigated land. Manynations, including China, Egypt, India, Indonesia, and Paki-stan, rely on irrigated land for more than half of their domes-tic food production.

• Can we win the salt and drainage battles, or is irrigationdoomed to decline?

In theory, most salt problems can be solved, but in reality,most remain unsolved. Engineers have devised many tech-niques to control waterlogging and the accompanying saltbuildup, but practically speaking, we have just started tomanage waterlogging, salinity, and drainage.

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• Will the increasing water requirements of our urban areasaffect the availability of water for agricultural irrigation?

Without a doubt, cities will continue to require more water,leaving less for agriculture. Unknown, however, is the amountof water that ultimately will be reallocated and the effect ofthat reallocation on food production, farmers, and smallcommunities.

• Can agriculture continue to irrigate?

In large part, the answer lies in agriculture’s ability to domore with less water and energy. As water becomes increas-ingly scarce, getting more benefit from every drop will bethe key.

For additional information

go to Water Quality and Management under the ARSNational Program web site http://www.nps.ars.usda.gov

For specific questions on related research projects or to obtainsingle copies of this publication (free, while supplies last),contact Dale A. Bucks, National Program Leader for WaterQuality and Management, at dab@ars.usda.gov, or write himat USDA–ARS, G.W. Carver Center, 5601 Sunnyside Ave.,Mail Stop 5140, Beltsville, MD 20705–5140.

ARS Mission

As the principal in-house research arm of the U.S.Department of Agriculture, ARS conducts research to developand transfer solutions to agricultural problems of highnational priority and provides information access anddissemination to—ensure high-quality, safe food and otheragricultural products, assess the nutritional needs ofAmericans, sustain a competitive agricultural economy,enhance the natural resource base and the environment, andprovide economic opportunities for rural citizens,communities, and society as a whole. For more informationabout ARS, visit the web site at http://www.ars.usda.gov/

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