FY 2010 Annual Report 

National Program 211 - Water Availability and Watershed Management 

Introduction 

Water is fundamental to life and a basic requirement for virtually all of our agricultural, industrial, 

urban, and recreational activities, as well as for the sustained health of our natural ecosystems. 

Since 2009, global concerns about climate change have come to the forefront and National 

priorities have increased to meet the need for renewable biofuel feedstocks. In 2010, Secretary 

Vilsack formally announced the establishment of five regional USDA Biomass Research Centers 

to help ensure the availability of dependable supplies of the feedstocks needed for the production 

of advanced biofuels to meet legislated goals and market demand, and enable as many rural 

areas across the country as possible to participate and benefit economically. Both issues have 

significant consequences for water availability and quality. At the global scale, food security is 

strongly associated with the availability of fresh water. During the last century, Earth’s human 

population tripled, but the global demand for Earth’s finite supply of available fresh water 

increased six-fold. Currently, the United Nations estimates that more than a billion people live 

without access to clean water, while more than 2.4 billion people lack the basic sanitation needed 

for human health. In December 2010, Secretary Vilsack approved the USDA Global Food 

Security Action Plan, subsequently endorsed by US-AID and the State Department (Visit the 

Feed the Future website at http://www.feedthefuture.gov). In advanced economies, clean water 

availability has become increasingly threatened due to contamination from agriculture (crop 

fertilization and animal manure), urban sources (storm runoff, pharmaceuticals, disinfection 

byproducts) and industry. Against these serious and growing problems, the importance of 

conserving water resources has never been greater. 

The goal of the USDA/ARS Water Availability and Watershed Management National Program is

to manage water resources effectively and safely, while protecting the environment and human 

and animal health. To achieve this goal requires characterizing potential hazards, developing 

management practices, strategies, and systems to alleviate problems, and providing practices, 

technologies, and decision support tools for the benefit of customers, stakeholders, partners, and 

product users. Research in this National Program addresses six component problem areas: (1) 

the effectiveness of conservation practices; (2) irrigation water management; (3) drainage water 

management systems; (4) integrated soil erosion and sedimentation technologies; (5) watershed 

management, water availability, and ecosystem restoration; and (6) water quality protection 

systems. 

The mission of this National Program is twofold: (1) to conduct research on the processes that 

control water availability and quality for the health and economic growth of U.S. citizens; and 

apply this new knowledge (2) to develop new and improved technologies for managing the 

Nation’s agricultural and water resources. Advances in knowledge and technologies provide 

producers, action agencies, local communities, and resource advisors with the practices, tools, 

models, and decision support systems they need to improve water conservation and water use 

efficiency in agriculture, enhance water quality, protect rural and urban communities from the 

ravages of drought and floods, improve agricultural and urban watersheds, and prevent the 

degradation of riparian areas, wetlands, and stream corridors. 

Both within USDA and across the Federal government, ARS leverages agency resources by 

coordinating its activities with other government agencies through active participation in a variety 

of intergovernmental committees including: (1) the Committee on Environment and Natural 

Resources (CENR) (the relevant National Science and Technology Council committee for water 

research) Subcommittee on Water Availability and Quality (SWAQ); (2) the National Agricultural 

Research, Extension, Education and Economics (NAREEE) Advisory Board, which evaluates 

USDA Research and Development Programs and provides recommendations to the Secretary 

and REE Undersecretaries; (3) the Mississippi River/Gulf of Mexico Watershed Nutrient Task 
Force, charged by Congress with conducting a reassessment of (i) nutrient load reductions and 

the response of the hypoxic zone, (ii) water quality throughout the Mississippi River Basin, and 

(iii) economic and social effects; (4) the Advisory Committee on Water Information (ACWI) 

Subcommittee on Sedimentation; (5) the USDA Drought Team and the USDA Working Group on 

Water Resources; (6) the Conservation Effects Assessment Project Steering Committee; (7) 

various working groups of the US Climate Change Science Program; and (8) the USDA Water 

Team.

Problem Area 1—Effectiveness of Conservation Practices. 

Improved conservation practices reduce sediment and nutrient losses from agriculture. Ideal 

practices will reduce the cost of inputs for the producer, improve the sustainability of land 

resources, and minimize the impacts of agriculture on water quality. Assessments of the impact

of conservation practices across large, complex watersheds depends on the development of

reliable assessment criteria, an understanding of the physical processes that occur within the field 

and watershed, and the integration of this knowledge into improved, validated models and tools to 

evaluate and predict the impact and result of management options. 

Selected Accomplishments

Sediment and nutrient benefits of Conservation Reserve Program land use conversion 

quantified. Through the Conservation Reserve Program (CRP), approximately 1.7 billion dollars 

are spent each year to remove cultivated lands from production for conservation purposes, but 

specific environmental benefits of the CRP have rarely been directly quantified. ARS scientists in 

Oxford, MS showed that in the Mississippi Delta, converting 280 ha of cropland to trees reduced 

sediment concentrations and nutrient loads in runoff by an order of magnitude relative to adjacent 

sites with similar topography and soils that were under reduced tillage crop production, with

associated positive impacts (e.g., reduced nutrient concentrations and sediment loads; improved 

water clarity and fisheries) on the water quality of the receiving water body, Beasley Lake. These 

findings support continued federal investment in the CRP.

Geospatial tools improve conservation effects assessment in the Chesapeake Bay region. 

Conservation practices such as winter cover crops have significant potential to reduce nitrogen 

and phosphorus pollution from agricultural fields to the Chesapeake Bay, but verifying and 

quantifying these potential benefits over large areas can be difficult. In collaboration with the U.S.

Geologic Survey (USGS) and the MD Department of Agriculture (MDA), the Choptank River 

Conservation Effects Assessment Project (CEAP) Watershed completed five years of research to 

support the development and implementation of geospatial tools to aid in cover crop 

management. Field-specific data on conservation program enrollment were combined with 

satellite imagery analysis to rapidly verify, quantify, and certify cover crop performance. 

Following successful development of these methodologies, MD has begun ‘beta-testing’ 

technology transfer of the geospatial cover crop management toolkits at the Talbot County, MD

Soil Conservation District. Part of the strategy is to automate the aggregation of site-specific data 

on conservation program performance to match watershed and county boundaries, providing

useful, rapid appraisal of cover crop success in protecting water quality, while maintaining farm 

data privacy as required in Section 1619 of the Farm Bill. Continuing this collaboration among 

the MDA, USDA, USGS, the US Fish and Wildlife Service, and other partners, should

substantially improve the contribution of winter cover crops in preventing nutrient release from 

agricultural fields to the Chesapeake Bay. 

Object Modeling System Version 3.0 (OMS3) released. In 2010, ARS scientists and their 

collaborators at Fort Collins, CO, released OMS3—a new framework for computer model 

development and broad application. OMS3 provides an open-source approach for object- and 

component-based modeling, and contains multi-threading capability for high performance 

computing on multi-CPU desktops (particularly for complex, spatially distributed models). OMS3 
also supports Natural Resources Conservation Service (NRCS) infrastructure for information 

technology and the use of existing model code. Researchers have implemented on-demand 

documentation of simulation projects, including model variables and parameter sets, to produce 

indexed PDF technical documents. ARS, NRCS, the U.S. Geological Survey, and their university 

partners are currently implementing simulation projects in OMS3 that will significantly reduce the 

costs of model development, deployment, maintenance, and ongoing application.

Model that simulates water quality in large river basins improved. The U.S. Environmental 

Protection Agency (EPA) and state environmental agencies have identified approximately 15,000 

impaired water bodies in the U.S., with agricultural production frequently identified as a major 

contributor of nonpoint sources of water contamination. At the same time, USDA’s mission

mandates that it: 1) thoroughly analyze the risks and benefits of USDA conservation programs to 

human health, safety, and the environment; 2) determine alternative ways of reducing risk; and 3) 

conduct cost-benefit assessments. In response to this mandate, ARS scientists at Temple, TX, 

developed new algorithms for the river basin scale model, SWAT (Soil and Water Assessment 

Tool), to simulate landscape routing, septic tanks, and urban runoff and management practices, 

and are currently testing these routines at watersheds across the U.S. To assess the 

environmental impact of USDA conservation programs, SWAT was applied in and validated for 

the Upper Mississippi River Basin (490,000 km2

), with scenario runs used to identify locations

where conservation practices such as conservation tillage, terraces, and the CRP, would be most 

efficient and provide the greatest benefit, thus helping to guide USDA conservation policy. In 

addition, EPA is using the model in more than 30 states to aid in the selection of land 

management alternatives to resolve water quality concerns. 

Assessment of conservation practices in the Little River Experimental Watershed (LREW), 

GA, identifies riparian forest buffers as the most comprehensive approach to reducing 

sediment, nitrogen, and phosphorus pollution. OMB has tasked USDA with quantifying the 

effectiveness of federally funded conservation programs. ARS scientists at Tifton, GA, used the 

Soil Water Assessment Tool (SWAT) to simulate the water quality effects of upland conservation 

practices (CPs) commonly adopted in the LREW for erosion or nutrient control, comparing these 

results to the simulated impact of existing riparian forest buffers. Erosion CPs produced the 

greatest reductions in sediment and phosphorus while nutrient reduction practices were most 

effective in reducing total stream nitrogen. ARS scientists also evaluated three different 

prioritization scenarios for implementation. Prioritizing based on nonpoint source pollutant load 

yielded more efficient water quality improvements than the other implementation schemes. 

Riparian forest buffers offered the most comprehensive reduction of all three pollutants. 

Simulation results indicate that current levels of riparian forest cover may be the single largest 

contributor to reducing nonpoint source pollution in the LREW. 

Planning tool allows watershed managers to simultaneously evaluate cost and 

effectiveness of sediment/contaminant Best Management Practices (BMPs). Tools to 

design and evaluate BMPs are essential for the effective management of agricultural watersheds. 

ARS scientists at Oxford, MS developed a BMP planning tool by coupling the ARS watershed 

model, AnnAGNPS, with a channel routing model developed by the National Center for 

Computational Hydroscience and Engineering at the University of Mississippi. The tool allows 

users to work at different scales to minimize sediment and nutrient loadings to the streams and 

rivers of an agricultural watershed, while keeping costs at a minimum. The BMP Planning Tool 

gives watershed managers the ability to evaluate the effectiveness and cost of a wide range of 

BMP scenarios for controlling the delivery of sediment and the associated contaminants to the 

streams and rivers of a watershed simultaneously. 

Knowledge of soil moisture availability improves fertilizer nitrogen use by corn in midAtlantic landscapes. The sloping landscapes of the mid-Atlantic region have a distinct hydrology 

that can result in substantial differences in soil moisture availability during the growing season. 

ARS scientists at University Park, PA, demonstrated that improving nitrogen use efficiency by 

corn requires a better agronomic understanding of the interaction between soil moisture and 
nitrogen availability at a particular landscape position in the field. When soil moisture availability 

during the growing season is adequate, corn grain yield is directly related to nitrogen availability, 

but when soil moisture availability is low, nitrogen fertilizer has little effect on grain yield. Results 

support the ongoing improvement of precision nitrogen recommendations in sloping, mid-Atlantic 

landscapes, to minimize nitrogen loss to aquatic ecosystems that eventually drain into 

Chesapeake Bay. 

Problem Area 2—Irrigation Water Management. 

Agricultural producers depend on the availability of surface and groundwater to supply irrigation 

needs and mitigate drought, and while just 17 percent of all harvested cropland in the U.S. is 

irrigated, these areas contribute over 40 percent of our food supply including the predominance of 

fruits, nuts and vegetables with high market value. Improving the efficiency of irrigation practices 

can increase the availability of water for other uses (urban, industrial, ecosystem, recreation and 

the environment). Irrigated areas of the United States have grown from 7.8 million acres in 1900 

to 56.6 million acres in 2007. About 42 million acres of irrigated land are in the 17 western 

States. The remaining 14 million acres of irrigated land are in the humid East. The East is 

experiencing faster growth than any other region, gaining almost 190,000 acres annually from 

1997 to 2007. As demand for biofuel feedstock increase there is increasing pressure to produce 

more food on less land using irrigation technologies. The increased demand for water from all 

sectors leads to an emphasis to produce more crop per drop and to increase the efficiency of 

irrigation practices. Climate change induced variations in precipitation and snowmelt also place a 

greater need for efficient methods to trap, store, and deliver water needed for irrigation.

Selected Accomplishments

Water network updates regional water use projections in northern Texas for next 50 years. 

In the northern Texas High Plains, where irrigation accounts for 90% of all water use, accurate 

and representative water use estimates are necessary to sustain agricultural production. ARS 

and Texas AgriLife Research updated and improved data on plant and evaporative water loss 

(i.e., evapotranspiration (ET)) from the Texas High Plains ET Network (TXHPET), using them to 

estimate water use and irrigation water demand for all crops grown in the Texas Panhandle. The 

ET data are used with Farm Service Agency crop acreage data and precipitation on a county 

basis to run the Texas A&M–Amarillo (TAMA) irrigation demand model, modified to include new 

crop categories and yearly and forecasted ET data inputs. These new estimates reflect both 

regional production potential as well as actual reductions in water use by producers using new 

and improved irrigation management techniques, and are being used by regional water planners 

for water demand planning purposes, by water conservation districts for establishing groundwater 

pumping regulations, and for regional socio-economic and sustainability analyses. 

Guidelines and protocols developed for regional-scale salinity assessment in the Red 

River Valley. Land managers and policy makers across the globe need a regional-scale tool for 

measuring and inventorying soil salinity in agricultural fields where salt buildup can lower crop 

yields. A scientific team led by an ARS scientist at Riverside, CA, used Moderate Resolution 

Imaging Spectroradiometer (MODIS) satellite imagery to assess and map soil salinity in 300,000 

hectares of North Dakota’s and Minnesota’s Red River Valley (RRV). Rising salinity levels in

RRV soils have been linked to increasing in precipitation and rising water tables resulting from 

climate change. The team found that 53 percent of the variability in soil salinity measured in situ

was correlated with a vegetation (crop) index derived from MODIS satellite imagery averaged 

over 7 years of data collection, and whether the land was eligible for inclusion in the Conservation 

Reserve Program (a federal program that sets aside marginally productive land for conservation 

purposes). The observed relationship between soil salinity measured in the field and the satellitederived vegetation (crop) index provides NRCS with protocols and guidelines for mapping soil 

salinity over hundreds of thousands of hectares in the RRV, with applicability in many other 

regions of the world as well. 
New FAO guidelines developed for water quality criteria for irrigation. Increased use of 

marginal waters and treated wastewaters for irrigation increases the need for accurate water 

quality criteria degrading pH, sodium absorption ratio (SAR), and salinity. ARS scientists in 

Riverside, CA used new field and laboratory experiments to refine earlier water quality criteria 

relating infiltration hazard to pH, SAR, and salinity. These guidelines replace earlier FAO criteria 

that did not consider pH and underestimated the adverse impact of even slight increases in SAR 

on water infiltration. Results from this work provide water quality specialists, water planners, 

regulatory agencies, and producers with an improved ability to evaluate the infiltration hazards 

associated with application of a specific irrigation water composition. The improved guidelines 

ensure safer use of saline waters for irrigation and thus extend the supply of fresh water 

resources. 

Improvements made in remote sensing for water use efficiency. The estimation of 

evaporation of water from plants (ET) with satellite and airborne remote sensing has great 

promise for increasing crop water use efficiency in irrigated lands because spatial water use 

patterns are readily distinguishable. Thermal infrared remote sensing in particular can be 

especially helpful for detecting crop water stress. However, implementing remote sensing image 

data into farm-scale routines has been very difficult because of cloudy skies, infrequent images, 

or coarse resolution. ARS scientists in Maricopa, AZ demonstrated that these problems can be

reduced by combining spatially-oriented remote sensing data with time-oriented land surface 

temperature data from fixed ground-based sites. This combined data approach can reasonably 

forecast crop ET up to 10 days without additional remote sensing data. This information will be 

valuable for scientists and engineers involved in developing decision support tools for irrigation. 

Conservation tillage increases cotton yield under drought conditions. Current climate 

models predict that as greenhouse gasses continue to accumulate in the atmosphere, periods of 

drought in the southeastern US will increase. For southeastern agriculture to adapt to these 

predicted changes requires production practices that maintain productivity during extended rainfree periods. In collaboration with Clemson University, ARS scientists at Florence, SC, found that 

compared to conventional tillage, conservation tillage resulted in a 25% increase in cotton yield in

drought years. Researchers and extension personnel can use these results to develop improved 

cotton production practices to ensure sustainable cotton production in a changing climate. 

Problem Area 3—Drainage Water Management Systems. 

Specific guidelines and tools are needed for nutrient and pesticide management in both surface 

and subsurface drainage water management systems. Automation of these systems, including 

the integration of weather forecasts, could enhance water conservation benefits during short-term 

drought periods in humid areas. Long-term soil quality improvement, increased water availability 

(quantity and quality), and wildlife benefits are all possible with improvements in wetland 

management practices. Improved drainage water management can also improve water use 

efficiency in irrigated agriculture while reducing the long-term effects of salinity and trace 

elements under different cropping systems. The combined effects of improved subsurface 

drainage water management practices and alternative cropping systems for irrigated agriculture

need to be incorporated into an environmental and economic decision support system that fully 

evaluates the cost-effectiveness of these systems. 

Selected Accomplishments

Potential of drainage water management to improve water quality in the Midwestern US 

quantified. Drainage water management (DWM) is a promising technology for reducing nitrate 

losses from artificially drained (or “tiled”) fields, but while there is an extensive history for the 

practice in North Carolina, little is known about the efficacy or cost effectiveness of the practice 

under Midwest conditions where artificial drainage is widely used. ARS scientists at Ames, IA

used soil and land cover databases combined with modeling to estimate that 4.8 million ha of 
land currently used to grow corn in the Midwest would be suitable for DWM, with the potential to 

reduce nitrate loss by approximately 83,000 metric tons (91,300 tons) per year. Considering the 

cost of control structures, redesign of new drainage systems, and payments to farmers to adjust 

the control structures to reduce nitrate losses, the cost per kg of nitrate removed from drainage 

water by DWM was estimated at $2.71 ($1.23/lb). While this is more than the current cost of 

nitrogen fertilizer, it represents a competitively priced alternative method for removing nitrate from 

agricultural drainage waters that does not involve taking arable land out of production. Both 

farmers and state and federal action agencies can use this information to set priorities for the 

expenditure of conservation funds to improve surface water quality. 

Closing the curtain on phosphorus losses from agricultural fields to drainage ditches. The 

loss of phosphorus in shallow groundwater leaving fields of the Delmarva Peninsula can account 

for more than 90% of the phosphorus exported by drainage ditches to tributaries of the 

Chesapeake Bay. ARS scientists at University Park, PA installed a curtain of gypsum (calcium 

sulfate) along the border of a field from which high loads of phosphorus had previously been 

recorded in groundwater. During the first rainstorms after installation, the new curtain (or 

permeable reactive barrier) removed 38-59% of the dissolved phosphorus in groundwater. 

Efforts are underway to expand the testing of this practice for enhancing water quality to other 

areas in the region.

Problem Area 4—Integrated Soil Erosion and Sedimentation Technologies. 

Soil erosion, sediment movement, and deposition processes involve the interactions of land

management practices with climate, soil, and landscape properties. Because erosion affects soil 

properties progressively over time and generally results in decreased soil quality and reduced 

resistance of agricultural systems to stresses, soil erosion control is essential for sustainable 

agricultural production systems. Sediment generated by soil erosion has costly, negative off-site 

impacts on downstream channel evolution, flooding, and water and air quality. Better erosion 

control technologies and improved decision support systems for planning and assessment are 

needed. In both cases, local effects on a field, farm, or channel, and off-site impacts at the larger 

watershed scale are necessary. 

Selected Accomplishments

Updated Water Erosion Prediction Product (WEPP) (version 2010.1) released. The updated 

Water Erosion Prediction Product (WEPP) model (version 2010.1), released in January 2010,

contains significant improvements in the prediction of soil freezing and thawing, snow 

accumulation, and runoff resulting from snowmelt. Cooperative work between ARS-NSERL, ARSPullman, and Washington State University resulted in this updated version. In validation studies 

using data from Pullman, Washington, and Morris, Minnesota, the new model performed

significantly better than the previous version. The updated WEPP model will impact thousands of 

users throughout the U.S. and the world, providing better predictions of runoff, soil loss, and 

sediment yield from hillslopes and small field-scale watersheds. Users in areas experiencing 

substantial erosion from snowmelt on thawing soils should notice particularly better performance. 

Improved technology to measure sediment improves ability to assess conservation 

practices for erosion. Measurements of the concentration of sediment in the streams of 

agricultural watersheds are difficult and expensive to collect. Yet streams are responsible for 

moving the majority of sediment eroded from the land. In collaboration with National Center for 

Physical Acoustics, ARS scientists at Oxford, MS developed a new technology using acoustic 

attenuation that contributes to the measurement of fine suspended sediments in streams. 

Results showed that this new acoustic technology could be used to measure a useful 

concentration range of fine sediment (<0.062 mm) in water. The technology is amenable to 

remote, autonomous deployment, is relatively inexpensive, and gives much more detailed 

information than traditional manual sampling techniques. 
Sedimentation rates in Mississippi Delta lakes impacted by watershed management 

practices. Measuring the performance of costly watershed management practices is a problem 

with far-reaching impacts. Civilization and intensive agriculture have caused erosion rates many 

times higher than that of undisturbed land, but since the effects of erosion control measures are

not often measured, the return on the investment of funds used to control erosion is largely 

unknown. Sediments stored in lakes are a valuable archive for recovering information on the 

erosion history of the surrounding watersheds. ARS scientists at Oxford, MS, examined 

sediments from five natural oxbow cutoffs in the Mississippi River alluvial floodplain, using 210Pb 

decay rates and bomb-pulse derived 137Cs to date episodes of sediment deposition and develop 

trends in sedimentation rates associated with management practices. Radioisotope dating 

methods worked best when used in concert with known dates for implementation of management 

practices. Using these methods, changes in sedimentation rates over intervals as short as 15 

years were detectable. 

A beta version of a predictive overtopping breach erosion model completed. Present and 

future USDA Small Watershed Dams will require assessments to determine hazard classification, 

population at risk, and emergency action plans, and for prioritizing rehabilitation of aging 

infrastructure. A physically based dam embankment failure predictive model is essential for

conducting these in-depth assessments. A cooperative effort between the ARS Hydraulic 

Engineering Research Laboratory, NRCS, and Kansas State University, has resulted in the

development of a computer engineering application tool WinDAM B (Beta version). The 

application software allows engineers to evaluate embankment overtopping erosion, breach 

timing, breach location, breach failure, and flood discharge, for flood overtopping of 

homogeneous earthen embankments. This computer tool will be important in evaluating existing 

structures, with potential for determining hazard classification, developing emergency action 

plans, and reducing costs associated with rehabilitation. 

Problem Area 5—Watershed Management, Water Availability, and Ecosystem Restoration. 

Agricultural lands, including crop, pasture, and range lands, constitute over 70% of the 

continental U.S. and play a dominant role in the management of the Nation's watersheds and the 

water resources needed for human consumption, recreation, agriculture, industry, wildlife habitat, 

aquatic ecosystems and a healthy environment. The confluence of unprecedented demands for 

freshwater, rapidly changing land use to accommodate rural and urban growth and biofuel 

production, recurring droughts, and regional climatic variations means that the Nation’s 

freshwater resources, agricultural production, and ecosystems are under more pressure and at 

greater risk than ever before. Thus, there is a need to accurately quantify and manage our water 

resources to support these many uses across heterogeneous agricultural and urban landscapes. 

Watershed management based on multiple objectives that include water supply, water pollution, 

urban development, climate variability, recreation, ecosystem protection and habitat restoration is 

a complex task necessary not only to support the goals of the Clean Water Act and the 

Endangered Species Act, but also to address concerns of watershed coalitions, policy makers 

and the public. 

Selected Accomplishments

Information derived from satellites—a more efficient way of predicting drought? Compared 

to traditional networks monitoring precipitation and other weather-related information, satellites 

have the potential to more readily and accurately assess and predict drought. ARS scientists at 

Beltsville, MD used thermal infrared (TIR) imagery from the Geostationary Operational 

Environmental Satellite (GOES) satellite to model hourly plant and evaporative water loss (ET) for

a 10-km grid covering the entire contiguous United States, and then used this information to 

develop an Evaporative Stress (i.e., Drought) Index. Compared to standard drought indices, this 

satellite-derived index captured spatial and temporal variations in rainfall patterns without the 

need for expensive precipitation monitoring. Such an index would be particularly useful in parts 
of the globe where current monitoring networks are inadequate, but where accurate drought 

prediction could help to improve food and water security. The model developed by ARS has 

been revised to use standard National Oceanic and Atmospheric Administration (NOAA) satellite 

and meteorological data, and is being incorporated into the NOAA Climate Prediction Center’s 

North American Drought Briefing, as well as evaluated by the National Drought Mitigation Center. 

Climate change affects intermountain hydrology. A variety of studies have found links 

between increasing temperatures, declining snowpacks, and earlier streamflow in snow fed 

streams in the Western U.S., but in all of these studies, the linkages are based on observations 

collected from multiple locations, and are thus somewhat indirect. ARS scientists at the Northwest 

Watershed Research Center in Boise, ID analyzed 45 years of air temperature, snow, 

precipitation, and streamflow data measured at the same location, the Reynolds Creek 

Experimental Watershed. Over the period of record, average air temperature has increased about 

2 degrees C, snow disappears more than a month earlier at lower elevations, and while total 

annual precipitation has remained constant, the onset of streamflow now occurs earlier in the 

season. In the intermountain west where the vast majority of agriculture is irrigated, water 

allocations are based in part on water discharge in early spring following snowmelt, with the 

snowpack functioning as a reservoir to retain water in the upper portions of the watershed. 

Without building additional reservoirs, the earlier snowmelt and onset of streamflow will mean that 

less water will be available during the growing season to support irrigated agriculture.

Aerial photography used for mapping giant reed infestations along the Texas-Mexico 

portion of the Rio Grande. Giant reed is an invasive weed throughout the southern half of the 

United States, with the densest stands growing along the coastal rivers of southern California and 

the Rio Grande in Texas. ARS scientists at Weslaco, TX, used aerial photography to map giant 

reed infestations and estimate infested areas along the Texas-Mexico portion of the Rio Grande. 

Based on the aerial photographs and ground surveys, the 898 km portion of the river from San 

Ygnacio to Lajitas was found to be infested with giant reed, with the densest populations located 

between Laredo and Del Rio. Between Lajitas and San Ygnacio, the total area infested was 

estimated at 5985 ha, with 3670 ha or 61% on the U.S. side and 2315 or 39% on the Mexican 

side. In addition to the methods for quantifying giant reed, this study provides the first accurate 

estimates of giant reed infestations along the Texas-Mexico portion of the Rio Grande. The study 

will help to estimate water use by giant reed, and will also help both land owners and government 

agencies manage and control of giant reed infestations. 

Soil moisture active passive In Situ Sensor Testbed (ISST) successfully installed. As part 

of the Soil Moisture Active Passive (SMAP) satellite validation program, an in situ test bed for soil 

moisture sensors was developed and installed in Marena, OK. The test bed includes all of the 

major soil moisture technologies currently used by national and international soil moisture 

networks, as well as new and emerging technologies like the Cosmic Ray Soil Moisture 

Observing System and the Global Positioning System Reflectometry project, which will be 

deploying large-scale networks in the near future. In addition to in situ instrumentation, the study 

will include regular gravimetric sampling and vegetation sampling, which are critical to satellite 

validation. This test bed will be ongoing through the launch of the SMAP satellite and will be a 

part of the validation program. This test bed has international cooperation with scientists from 

Japan and The Netherlands participating in sensor deployment and analysis. 

Drought affects water and carbon cycling in a desert grassland invaded by mesquite. One 

of the most widespread changes currently occurring in the southwestern US is the encroachment 

of woody plants (shrubs and trees) into grasslands, which affects water and nutrient cycling in

these ecosystems. ARS scientists at Tucson, AZ measured water and carbon dioxide exchange 

between a grassland experiencing woody plant encroachment by mesquite and the atmosphere 

over a four-year period, determining how precipitation influenced these exchanges. Seasonal 

drought strongly influenced both water and carbon dioxide exchange. In contrast to current 

thinking, that woody plant encroachment might increase carbon sequestration, this particular 

grassland functioned as a net source of carbon to the atmosphere, the magnitude of which 
increased with increasing drought severity. Results highlight a complex relationship between 

vegetation change and climatic variation in precipitation that influences carbon sequestration in

these water-limited ecosystems. 

Problem Area 6—Water Quality Protection Systems. 

Nutrients and pesticides (insecticides, herbicides, fungicides) applied to agricultural fields, and 

pharmaceuticals (antibiotics and hormones) used in livestock production, can move from their 

point of use into surface and ground waters, where their presence raises concerns about their 

impact on aquatic and terrestrial ecosystems and human health. To evaluate fully the risks of 

using these chemicals and compounds in agriculture, there is a need to know their sources, 

transport behavior, fate, and biological impact at different concentrations and in different 

combinations in the environment. ARS conducts research to better understand and predict the

source, fate, transport and environmental effects of nutrients, emerging contaminants and 

inorganic ions. This work provides the basis for the development of best management practices 

across a range of climates, soils, and agricultural and urban settings. To better design and refine 

existing practices, new scientific information needs to be developed that clearly delineates how 

agricultural contaminants move and are transformed within the environment. 

Selected Accomplishments

Design and management criteria to support fish, amphibian, and reptile populations in 

wetlands created to treat agricultural runoff. The ability of created wetlands to reduce 

nutrient, pesticide, and sediment loadings in agricultural runoff can be optimized by design and 

management, but addressing these priorities may result in wetlands that are less beneficial as 

habitats for aquatic vertebrates (e.g., fishes, amphibians, reptiles) exhibiting worldwide population 

declines. ARS scientists in Columbus, OH documented differences in fishes, amphibians, and 

reptiles in two wetland types created by the wetland-reservoir-subirrigation system (WRSIS), and 

used this information to develop design and management criteria to increase the ecological 

benefits of these agricultural water-recycling systems. Differences in amphibian abundance and 

species composition between WRSIS wetlands and reservoirs suggest their potential to provide 

habitats for different communities, with wetlands favoring amphibian populations and reservoirs 

favoring fishes. However, this was not the case for ‘pond-type’ wetlands that, similar to 

reservoirs, favored fishes. To alleviate this problem, design and management criteria were

developed to enable WRSIS wetlands to be managed as amphibian habitat, and reservoirs to be 

managed as fish habitat. These criteria can be used by federal, state, and private agencies 

creating agricultural wetlands, to assist them meeting their conservation and restoration goals. 

Denitrifying bioreactors reduce nitrate loads in stream waters. Farmers need low-cost and 

simple technologies to help reduce the export of excess nitrogen in subsurface drainage waters

to sensitive aquatic ecosystems. Denitrifying bioreactors introduce solid carbon substrates into 

the flow path of contaminated water. ARS scientists at Ames, IA summarized bioreactor design 

alternatives, effectiveness, and the factors limiting their performance. Two common designs 

successfully removed nitrate in the field at rates of up to 22.0 g N per cubic meter per day. 

Removal rates varied with the design, the rate of water flow, and incoming nitrate concentrations. 

These bioreactors may also reduce the transport of veterinary antibiotics (sulfamethazine, 

enrofloxacin) present in manure, and the herbicide atrazine, commonly applied to corn, without 

affecting denitrification rates. Denitrifying bioreactors are cost effective and complementary to 

other practices that can decrease nitrate loads to surface waters. This information will be of use 

to farmers and state and federal action agencies in setting priorities for the expenditure of 

conservation funds to improve surface waters affected by excess nitrate.