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You are here: Home / About WQIC / Working Group on Water Resources / Water Quality: A Report of Progress / Agricultural Nonpoint Source Contamination  Printer Friendly Page
About the Water Quality Information Center
Working Group on Water Resources

Water Quality: A Report of Progress

Published Sep 1997

Agricultural Nonpoint Source Contamination: How USDA is Addressing the Problem

Our Nation has made tremendous progress in addressing the various aspects of water pollution. As a result of the Clean Water Act, industrial discharges have been controlled by permits; raw sewage discharges have been reduced by the construction Of sewage treatment plants; and phosphorus discharges have been greatly reduced by a combination of technology, education and laws (e.g., the widespread banning of phosphorus-based detergents). Because of such efforts, Lake Erie (once proclaimed "dead") has been resurrected, the Cuyahoga River (which once caught fire) has been rendered non-flammable, and many major rivers have improved water quality.

We have not dealt with all of the problems, of course; combined sewer overflows still occur in over 1,000 communities. The high costs of remediation preclude programs to deal with the problem. Fiscal reality overshadows the problem, and its expensive solutions.

"Biosolids" disposal also presents some challenges. Many disposal schemes disregard the nitrogen content, while agriculture is being "encouraged" to control the application of fertilizers and animal manures to reduce the environmental impacts of excess nitrogen.

This nation has implemented one of the world's best, most aggressive, most progressive water pollution control programs; it is not unreasonable to ask ourselves what more we want, how much more we can afford, and how it should be spent. We have made significant progress; the remaining problems are the tough (i.e., expensive) ones.

The restoration of the chemical and biological integrity of the Nation's waters is an elusive goal, complicated by the lack of documentation of the sources and extent of the impairment, on the one hand; and the lack of specification of achievable and realistic levels of remediation in chemical, biological or ecological terms, on the other.

Such a lack of information data has been identified as a key barrier to State and local efforts to control nonpoint source pollution. There are few credible data on the scope and impacts of nonpoint source pollution, or on the effectiveness of potential solutions.

Human activity contributes to the degradation of water resources, but the actual extent is unknown. Such a lack of information facilitates generic pronouncements, which cannot be addressed. The Federal and State governments, and their component Departments and agencies, must be concerned with practical solutions to identified site-specific problem Cities, industries, farmers, ranchers and other landowners may be convinced to alleviate identified nonpoint source (NPS) problems, but they are hesitant to invest in unspecified, or untried, solutions to generic problems.

Given this situation, some important questions should be addressed:

  • What are the remaining water quality problems?
  • Which are the most important in terms of environmental impact?
  • How should we address them in a realistic manner?

These questions are relevant to everyone who makes or implements water quality policy. A pragmatic approach must recognize both that there are problems, and that they are being addressed. Many States are conducting successful interagency programs to address agricultural N.S. pollution. More could always be done, given the necessary resources and policy direction. The difficulty lies in the reality that resources are in short supply, and that unfunded mandates have become a rallying point among those who must spend real dollars to solve real problems.

Some sectors of the public and their governmental representatives perceive the existence of an acute, widespread, water-quality-associated health crisis that stems from widespread water pollution, and that is threatening public health and welfare. This perception persists without the benefit of any supporting data.

EPA estimates that about one-third of our assessed surface waters do not meet designated uses, and that agriculture is the source of 60 percent of this impairment, largely from diffuse or NPS problems. These estimates are applicable only to the assessed one-third of our surface waters; these data do not constitute a representative sample of the Nation's waters; and, according to the EPA, "States are generally constrained by diminishing resources and competing needs to monitor most often on those waters with known or suspected problems."

EPA's national "Pesticides in Groundwater Survey" provided data, reliable on a national scale, that indicate the absence of any massive national problem. Pesticides are likely to be detected in only 4 percent of our water wells; the likelihood is somewhat higher in rural wells than in urban ones; and nitrate contamination is more widespread.

The "detection" of chemicals in water does not imply anything about health effects or legal limits; detection levels are usually well below such effect levels, and the disparity among these levels is sure to increase as our detection capabilities develop. The survey also reported a number of "statistical associations" between water contaminants and human health problems but pointed out that such associations do not establish any cause-and-effect relationships.

A high level of potential vulnerability requires, among other factors, substantial rainfall in excess of evaporative demand, readily permeable soils, and substantial use of agricultural chemicals. The real differences in these parameters among (and even within) States makes any national synthesis a highly dubious basis for defining policy or program needs.

The USDA Water Quality Program identified the Cornbelt area as a major research focus in it's "Management System Evaluation Area" projects, based on the widespread use of agricultural chemicals in the area; on the precedence of cropland; (implicitly) on an excess of precipitation to move agricultural chemicals into water resources; and on Congressional concerns about the contamination of groundwater by agricultural chemicals in the Cornbelt.

The USDA has long been at the forefront of programs to control soil erosion and associated sediment problems. The Soil Conservation Service was established in 1934 (now the Natural Resources Conservation Service), and has delivered technical assistance to reduce on-farm soil erosion and its off-farm effects.

The USDA and its State cooperators have developed and implemented a number of programs to address matters of agricultural contamination from both point and nonpoint sources. In the 1970's, considerable research emphasis was placed on the point-source aspects of the treatment and handling of animal wastes, and the influence of agriculture on water contamination. This resulted in many new handling and treatment processes.

Federal programs to address agricultural NPS pollution began with the joint USDA-EPA Model Implementation Program, in 1977. It funded NPS projects in seven States to demonstrate interagency cooperation, accelerated farmer adoption of Best Management Practices (BMP's), and the effects of those BMP's on water quality. Interagency cooperation was achieved, and farmer adoption of BMPs was significantly accelerated over the life of the projects; water quality impacts were, and are, the most difficult to document.

In the early 1980's, USDAs experimental Rural Clean Water Program established projects in 21 States, with funding of $70 million for the 10-year program. Significant adoption of BMP's occurred in all of the areas; some were reflected in improved water quality. These projects were successful in stimulating the farmers' adoption of specified BMP'S, and in demonstrating the effectiveness of deliberate programs to stimulate such adoption.

But farmers' adoption of pragmatic BMP's is not always reflected in short-term changes in water quality. For example, 10 years of BMP adoption covering 74 percent of critical acres resulted in no significant reduction in nutrient loads in either tributary streams or in St. Albans Bay, Lake Champlain, VT. Reducing nutrient exports may take many years, depending on the amount of input reduction, and on initial field concentrations,

In the late 1980's, there was considerable concern in the Congress about the contamination of groundwater by agricultural chemicals, and the need for efforts to protect against such contamination. The resulting USDA Water Quality Program is based on the following guiding principles:

  • The Nation's water resources must be protected from pollution by fertilizer and pesticides without jeopardizing the economic viability of U.S. agriculture.
  • Pollution must be halted; and more environmentally benign farm production practices must be instituted.
  • Farmers must be responsible for changing production practices to avoid polluting water resources.

Since the program was launched in 1990, the USDA through its participating agencies has instituted:

  • Management Systems Evaluation Area (MSEA) projects in five Midwestern States, representing the Cornbelt, designed to evaluate current production systems, to develop new ones, and to transfer the information to farmers;
  • Sixteen (16) Demonstration projects, to accelerate the transfer of research results to farmer adoption:
  • Seventy-four (74) Hydrologic Unit Area projects, to accelerate the application of BMP's in identified critical hydrologic units;
  • Seventy-one (71) Water Quality Special projects, designed to accelerate adoption of improved management practices, especially through cost-share programs;
  • Fifty-nine (59) in-house research projects to assist the MSEA efforts, and to increase understanding of the movement and fate of agricultural chemicals in the environment;
  • Ninety (90) cooperative research projects, in which University researchers are investigating various aspects of agricultural chemical management, movement and fate.
  • One hundred and seventeen (117) Water Quality Incentives Program projects.

These have been conducted in collaboration with the U.S. Geological Survey, EPA, State water quality agencies, and units of State and county government. Protocols have been established to involve a wide array of local, State, and Federal inputs to the selection of such projects, and to assure that they reflect State and local priorities for enhancing or protecting water quality.

The USDA and its State cooperators are achieving results; but there are no credible water quality data against which these results can be evaluated. Most USDA program results must be reported in terms of "surrogate parameters," rather than in terms of water quality improvements. The USDA role is one of encouraging and assisting farmers to adopt management practices and systems that should enhance or protect water quality. Since the connections between NPS pollution and the quality of the receiving waters remain diffuse, the impacts of agricultural programs must be estimated by recording the extent of farmer adoption of such practices.

These cooperative projects are producing significant results. Through FY 1991, they resulted in the adoption of water quality practices by 10,000 producers on 552,000 acres of farmland; and reduced applications of nitrogen by 2.7 million pounds, phosphorus by 1.7 million pounds, and pesticide applications by 239,000 pounds. In addition, over 9,000 people received water quality training in FY 1990-92, including more than 4,000 people from non-USDA agencies. These projects have since gathered momentum, and the accomplishment numbers are expected to increase substantially.

The USDA has responded to the results of EPNs National Pesticide Survey, which indicated some potential problems of nitrate in groundwater. hi 1992, USDA allocated some $700,000 for research on analyses for and management of nitrogen from soils, manures, and fertilizers. We have also encouraged our State staffs and counterparts to address the complex, field and crop-specific management practices for nitrogen management.

The "Pre-Sidedress Nitrogen Test" (PSNT) for rapid, on-site assessments of the status of plant nitrogen in corn, and its use by farmers from Vermont to Iowa, is reducing the application of excess nitrogen fertilizers in corn production. While the procedure is being used on only a small proportion of the total corn acreage, and while PSNT is not universally applicable to corn growing areas, it is an indicator of the kinds of technology that will likely reduce nitrogen loadings to water resources.

Position papers on nitrate fertilizers and on the extent of the nitrate contamination of groundwater have been developed. These have been widely distributed, to help agency personnel and farmers understand that there are identified areas where nitrate contamination of water is a problem. (Conversely, these papers help policy makers understand that it is not an ubiquitous national problem.)

The Management Systems Evaluation Area (MSEA) program has found that modifications in tillage herbicide and nitrogen management practices in a corn-soybean rotation system will lead to improved surface and groundwater quality and more profitable systems. For example, use of ridge tillage with accompanying banding of herbicide in the row with Sidedress nitrogen appears to reduce negative effects on groundwater quality. As a guide to supplemental nitrogen applications, the chlorophyll meter shows promise for reducing leaching in irrigated corn production.

The MSEA program has shown that increasing surface residue cover and the soil organic content appears to increase degradation rates of herbicides. Management of weed populations through scouting and proper selection of postemergence herbicides can reduce movement to groundwater and surface water. Mapping of yields along with the nutrient availability and other soil productivity factors within fields can provide the information for precision inputs of fertilizers and herbicides.

The USDA also has conducted a separate Conservation Reserve Program (CRP), which has retired some 35 million acres of highly erodible lands from crop production. Grasses have been planted on 28 million of these acres, trees on 2 million acres, and the remaining 5 million acres have been converted to windbreaks, filter strips, and wildlife and wetland areas. These conversions will reduce sediment loadings to surface waters by 210 million tons per year, phosphorus loadings by 66 percent, and nitrogen loadings by 75 percent. The CRP may generate $3.5 billion to $4 billion in water quality benefits.

Other USDA programs address the safe and efficient use of agricultural chemicals, and their environmental fate. USDA programs have eradicated the boll weevil from Virginia, North Carolina and South Carolina. Programs to foster the use of integrated pest management, integrated crop management, and sustainable agriculture also contribute to reducing the environmental loadings of agricultural chemicals.

The USDA continues to forge new approaches to the abatement of agricultural NPS contamination. The Colorado River Salinity Control Program (CRSCP), begun in 1987, is the prototypical "Watershed Approach" to pollution prevention. This program to reduce salt loadings to the Colorado River helps fulfill U.S. obligations to Mexico for water quality.

Since 1987, the CRSCP has resulted in a salt load reduction of 190,000 tons; and the conservation of some 200,000 acre-feet of water. This has been done at a total USDA cost of $24 million, making the unit costs of salinity reduction about $120 per ton, and of water conservation about $120 per acre-foot.

Compared to removing salinity by reverse osmosis processes, and to the cost of water conservation by other programs, this unheralded program has been a tremendous success.

The USDA and U.S. agriculture continue to address the matters of pesticide or nutrient contamination of the Nation's water resources. But the policy and regulatory communities must address these matters with some sense of reality; to be sure that we are reaction to real (rather than perceived) problems; that we are addressing problems to which agriculture contributes, and for which there are practical solutions, and that prescribed programs will enhance or protect water quality in some demonstrable ways.

The USDA represents the interests of U.S. agriculture, its productivity, and its $18 billion annual positive balance in international trade, and provides leadership for an appropriate balance between efficient agricultural production and the legitimate demands for enhancing and protecting environmental quality.

American farmers are becoming more environmentally sensitive; and they are adopting improved management practices as they become convinced of the desirability to do so. But they can hardly be faulted for a limited response to generic allegations and insupportable estimates of the problems. If a cause-and-effect relationship between their agricultural operations and adverse impacts on water quality can be presented, operators usually can be convinced to make significant changes in their practices. The crucial element is a convincing connection between agricultural practices and water quality. In the case of agricultural NPS contamination, such convincing connections are--by definition--hard to establish.

At the extreme, abandoned farmlands may result in reduced loadings of agricultural NPS pollutants to our Nation's waters. Where they are not simply abandoned, their likely replacements--housing developments, shopping malls, roads and parking lots--may not enhance environmental quality. Where they are abandoned, they will likely be accompanied by increased erosion, eroded tax bases, and infrastructure deterioration.

Pollution prevention is now a topic of conversation everywhere. It is generally acknowledged to be more efficient than treating pollution. There are two associated difficulties: there are no definite end points against which to gauge progress; and it is impossible to prove that prevention is less costly than remediation of something that never happened. The latter point is especially critical in times of tight budgets.

"A government of the people," etc., must set realistic expectations for environmental programs. There are no "no-cost" solutions: the Nation's financial resources are limited; and someone must always pay the bill. NPS pollution is diffuse and hard to identify as to source; and site-specific solutions cannot be applied to generic problems.

Current Situation
Composite samples of finished drinking water were collected from locations around Lake Erie, which has the most agricultural watershed of the five Great Lakes, has highly variable tributary flows, and serves as a drinking water supply for a large population. Over the course of the study (3 years), no herbicide in any composite sample exceeded any of its short-term or lifetime Health Advisory Levels. It was concluded that "no significant adverse health effects are to be expected from exposure to herbicides through Lake Erie drinking water."

Data from years of assorted records for several tributaries leading to Lake Erie were analyzed. There were statistically significant reductions in total phosphorus and soluble reactive phosphorus concentrations; nonsignificant downward trends in sediment concentrations, and significant increases in nitrate concentrations in rivers from agricultural watersheds.

Exposures to atrazine through drinking water in Ohio, Illinois, and Iowa were analyzed. Three different approaches to the problem, based on the differing availabilities of data, indicate that there is no documentable human health risk from atrazine ingested through drinking water. The analyses showed that 94 percent of the assessed Ohio population, 97 percent of the assessed Illinois population, and 99 percent of the assessed Iowa population had exposures less than one-third of the lifetime Health Advisory Level.

A widespread well testing program analyzed more than 40,000 samples for nitrate, and more than 10,000 for pesticides. The extent of nitrate and pesticide contamination in rural wells varies considerably from region to region, in response to geologic and hydrogeologic factors and variations in land use. Except in localized problem areas, extreme, high nitrate concentrations are not found in more than 2 percent of the wells, and extreme, high pesticide concentrations are found in fewer than 1 percent of the wells. Over one-half of the samples were free of nitrate, and more than 95 percent were free of herbicides.

The scope of pesticide contamination of Florida's surface waters has been characterized as well. The data from 35 separate agencies, collected over a 12-year period, indicate that a total of 40 pesticides have been detected in surface waters; but that the impact of such sporadic and low levels of detections is below adverse levels.

Remaining Challenges
While there is no national water quality crisis, some local problems do exist, and need to be addressed. Some of these problems are associated with agricultural production practices. In some cases, appropriate solutions require only the application of known technologies. Most farm-based manure management problems fall into this category.

The storage, handling, and utilization of manures in ecologically sound management systems is no mystery; but the continued intensification of animal production systems without regard to the adequacy of the available land base for manure recycling presents a serious policy problem.

The safeguarding of drinking water supplies from agricultural sources of non-chemical contamination (bacteria, viruses, and parasitic protozoa) requires not only knowledge of the biology of such species and the chemistry of purification, it also requires specific knowledge of the sources of such contamination.

The development of production systems that reduce the introduction of chemicals into the environment presents a continuing challenge. Systems to reduce such introductions are discussed extensively in the proceedings of the conference on "Clean Water-Clean Environment-21st Century," sponsored by the Working Group on Water Quality.

There is a continuing need to develop and deliver programs of education and technical assistance to farmers. Such programs are crucial to the voluntary adoption of improved practices.

It must be remembered that farm audiences are no less dynamic than other populations; and that as conditions change, as production systems change, as world markets change, as technologies change, farmers also change. They must be kept abreast of these changes if they are to compete in world markets, and if they are to contribute to a quality environment.


  • The USDA and American agriculture have made significant progress in reducing the loadings of sediment, pesticides, and nutrients to the Nation's water resources.
  • Farmers still respond to incentives, the potential for input cost savings, and environmental concerns.
  • USDA programs continue to reduce agricultural NPS contaminant loadings. USDA agencies are providing effective research, education, and technical and financial assistance.
  • We are now operating on the relatively flat part of the "response curve," additional increments of water quality will be increasingly difficult and expensive to attain.
  • As our Nation develops priorities and goals, the USDA and American agriculture will continue to respond with programs and strategies to achieve safe levels of water quality.

Last Modified: Feb 25, 2011

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