Number 61 September 1993 ISSN 1062-9149
The history of the earth sciences demonstrates that the "scale" at which scientists examine the Earth has a major effect on the kinds of insights gained from their studies. In geology, for example, roles exist for investigations at the quadrangle map scale (1:24,000) and for continental or global scale studies focused on plate tectonics. Further-more, geologic studies at one scale often enhance the understanding of the phenomena examined at the other scales. Similarly, in meteorology, there is a role for microscale climatic studies over distances of less than a mile, mesoscale studies of regional weather systems, and global circulation studies. Again, the overall science would be weakened by the lack of any one of these scales of study.
Investigations at different temporal scales also are needed. Some studies of earthquake phenomena, for example, measure processes that last for seconds or even milliseconds, and others chart the buildup of the stresses responsible for earthquakes over periods of decades to centu-ries.
[The National Water-Quality Assessment Program involves the examination of] the quality aspects of water resources at a unique combination of spatial and temporal scales. The spatial scale is primarily regional (several thousand square miles), and the temporal scale is primarily multiyear and decadal. The study design stems from the view that insights about water quality, which would be of great value to resource managers and policy makers, can be best achieved by examining water quality at these scales and by aggregating the findings of the studies with time and across the Nation. These assessments would rely on many of the data already being collected as part of smaller scale studies focused on local problems, although the questions under investigation would be quite different. The primary questions would concern the natural and human factors that give rise to different types of widespread water-quality condi-tions and the long-term fate of contaminants stored in aquifers, sediments, or biota.
Throughout its history, the Nation has made major investments in assessing natural resources..... The reason for these investments in information is that decisions our society makes about using or conserving these resources, investing in their improvement, or regulating their use will be better if they are based on sound information. The maintenance and the improvement of water quality is now one of the major areas of public investment and government regulation. Therefore, it is appropriate that serious attempts be made to document the need for, and the effects of, such governmental actions.
(excerpt from foreword by Philip Cohen, Chief Hydrologist, U.S. Geological Survey, to Concepts for a National Water-Quality Assessment Program (Hirsch et al., 1988))
In 1986, the U.S. Geological Survey (USGS) initiated the National Water-Quality Assessment Program (NAWQA). The goals of the program (Hirsch et al., 1988) are to:
The NAWQA Program consists of two major elements: 1) study-unit investigations and 2) regional and national syntheses of study-unit investigation results.
The water quality assessments to be undertaken in each study unit include four to five years of intensive and continuous data collection and analysis, immediately followed by five years of less intensive activities (mainly intermittent monitoring of water quality). Intensive assessment activities in each of the study units will be conducted on a rotational basis, with one-third of the units involved in intensive assessment activities at any one time. Study-unit staff include team members from a wide range of disciplines, including surface and ground water hydrology, geochemistry, water quality, ecology, geomorphology, statistics , and geographic information systems.
In the initial assessment period in each study unit, the present water quality conditions and the factors that influence these conditions will be described. Subsequent intensive assessment periods will focus on improving this understanding and assessing water quality trends over time.
Long-term assessment activities in the study units are a key attribute of the program, not only to define trends, but also to build an evolving understanding of water quality in each study-unit area. This understanding will be achieved through careful analysis and interpretation of long-term data sets on the chemical and biological characteristics of the water resource relative to carefully compiled data on physical hydrology and changes in land use and management practices within the study units. Intensive assessment of these individual hydrologic systems will form a firm base for resource decision making within the study units.
Some of the synthesis activities will address water quality issues affecting large contiguous hydrologic regions, while others will focus on large non-contiguous areas affected by similar specific water quality concerns (Leahy et al., 1990).
The national synthesis component of the NAWQA Program presently addresses two topics: 1) pesticides and 2) nutrients (nitrogen and phosphorus).
Specific questions to be addressed through the pesticide synthesis will include:
Objectives of the nutrient synthesis include:
A longer-term goal of the nutrient synthesis will be to compare and contrast, on a regional scale, the magnitudes of nutrients leaving urban, suburban, and rural areas in order to identify natural and human factors that influence nutrient concentrations in streams and shallow ground water. The ultimate goal of this work will be to better define the pathways through which nutrients enter streams and shallow ground water under different conditions (such as, corn belt versus wheat belt or urban versus agricultural land uses).
A national-level liaison committee to provide overall program guidance and an external scientific review committee to advise and comment on various technical aspects of the program have also been formed.
Hamilton, P.A. et al., 1992. Are Fertilizers and Pesticides in the Ground Water? USGS Circular 1080.
Rinella, J.F. et al., 1993. Persistence of DDT Pesticide in the Yakima River Basin, Washington. USGS Circular 1090.
Information about the NAWQA Program is also available on the World Wide Web at:
Hirsch, R.M., W.M. Alley, and W.G. Wilber. 1988. Concepts for a National Water-Quality Assessment Program. U.S. Geological Survey Circular 1021, U.S. Geological Survey, U.S. Department of the Interior, Reston, VA. 42p.
Jones, D.R. and M.A. Sylvester. 1992. National Water-Quality Assessment Program (NAWQA). U.S. Geological Survey Open-File Report 92-145. U.S. Geological Survey, U.S. Department of the Interior, Reston, VA. 1 sheet.
Leahy, P.P., J.S. Rosenshein, and D.S. Knopman. 1990. Implementation Plan for the National Water-Quality Assessment Program. U.S. Geological Survey Open-File Report 90-174. U.S. Geological Survey, U.S. Department of the Interior, Reston, VA. 10p.
Monitoring of both land treatment and water quality is necessary to document the effectiveness of nonpoint source pollution controls in restoring water quality. The Section 319 National Monitoring Program, administered by the U.S. Environmental Protection Agency, is designed to support watershed projects throughout the country that meet a minimum set of project planning, implementation, monitoring, and evaluation requirements. The requirements are designed to lead to successful documentation of project effectiveness with respect to water quality protection or improvement. The National Monitoring Program projects comprise a small subset of nonpoint source control projects funded under Section 319 of the Clean Water Act Amendments of 1987. The following article continues a series describing these projects.
The Idaho Snake River Plain 319 National Monitoring Program project (1,946,700 acres), is located in south central Idaho in an area dominated by irrigated agricultural land. The Snake River Plain aquifer system, which provides much of the drinking water for 40,000 people living in the area, underlies about 9,600 square miles of basaltic desert terrain. The system, composed of both shallow and deep water aquifers, is also used as an irrigation water source.
A wide range of agricultural crops are produced throughout the Snake River Plain region. Excessive irrigation, a common practice in the area, creates the potential for nitrate and pesticide leaching and/or runoff. Pre-project ground water monitoring indicated the presence of elevated nitrate levels in the shallow aquifer underlying the project area.
The goal of a five-year U.S. Department of Agriculture (USDA) Demonstration Project within the Snake River Plain (1,946,700 acres) is to reduce adverse agricultural impacts on ground water quality through coordinated implementa-tion of nutrient and irrigation water management. Modified paired-field comparisons of the water quality impacts of applied best management practices (BMPs) versus traditional practices are funded under Section 319 National Monitoring Program. The purpose of the comparisons is to evaluate effects of BMPs on nitrate levels.
The Demonstration Project is led by the USDA Soil Conservation Service and the University of Idaho Cooperative Extension System and involves extensive state and federal inter-agency cooperation. Participants include the Idaho Division of Environmental Quality, University of Idaho Water Resource Research Institute, USDA Agricultural Research Service, Idaho Department of Water Resources, U.S.Geological Survey, and Idaho Department of Agriculture. The Idaho Department of Environmental Quality and the Idaho Water Resources Research Institute will be responsible for the 319 portion of the project.
Project Time Frame
October, 1991 - October, 1996
Pre-Project Water Quality
Analysis of ground water data collected within the project area indicates the widespread occurrence of nitrate concentrations exceeding state and federal drinking water standards. In a study conducted from May 1991 through October 1991, 195 samples were obtained and analyzed for nitrate in 54 area wells. The average concentration was about 6.5 milligrams per liter (mg/l) and the maximum concentration was 28 mg/l. The Federal Maximum Contaminant Level (MCL) of 10 mg/l was exceeded in 16% of the wells at least once during the sampling period and was continuously exceeded in 5% of the wells.
Ninety-eight samples collected from the same 54 wells were analyzed for the presence of 107 pesticide compounds. Fourteen of the wells yielded samples with at least one detectable pesticide present, but all concentrations measured were below the Federal Safe Drinking Water MCL or Health Advisory for that compound. However, water resource managers believe that pesticide concentrations constitute a future concern for the Snake River Plain Aquifer.
Nonpoint Source Control Strategy
The nonpoint source control strategy focuses on nitrogen and pesticide management practices to reduce the amount of nutrients and pesticides reaching surface water and leaching into the ground water. Effectiveness of the following BMPs will be evaluated: irrigation management, nutrient management, crop rotation, and pesticide management.
An irrigation management program will be implemented for each participating farm. Recommended activities include changes in irrigation scheduling, tailwater management, repair of existing structural components, or conversion to another type of system.
Fertilizer evaluations will be conducted and recommendations based on soil tests, petiole analysis, crop growth stage, crop type, rotation, and water sampling will be adopted. Farmers will be asked to incorporate pesticide management strategies into their farming practices in the hope that these strategies will reduce overuse of pesticides.
Water Quality Monitoring Design
The 319 portion of the Demonstration Project water quality monitoring effort incorporates a modified paired-field network designed to evaluate the effectiveness of agricultural BMPs in preserving the quality of the ground water beneath two field plots (Forgeon and Moncur fields). The network consists of 12 constructed wells in each field: 8 centrally-located "permanent" wells and 4 peripheral "temporary" wells. The modified field design requires that all variables in each field be controlled except the variable being evaluated. For example, evaluating crop rotation requires strict control over other variables such as irrigation and nutrient management. Monthly grab samples will be taken from all wells.
In the Forgeon Field, a method involving aquifer testing in combination with water quality testing has been adopted in an attempt to eliminate seasonal variables, such as crop type, and irrigation method. nstead of look-ing solely at monthly water quality changes in individual wells, a comparison of time series data and annual "averages" under pumping conditions will be conducted in each half of the field. This should allow evalua-tion of ground water quality changes versus time as well as spatial changes as the zone of capture increases during the length of pumping. Budgetary constraints do not allow the use of this method in the Moncur Field, where monitoring data will be acquired from monthly grab samples from each individual well.
Variables to be measured include: total phosphorus (TP), total suspended sediments, nitrates, pH, temperature, specific conductivity, total Kjeldahl nitrogen (TKN), total organic carbon (TOC) 7 total ions, and 20 pesticides. Explanatory variables include precipitation, crop, and soil and irrigation water analysis. In addition, vadose zone suction lysimeters will be used to monitor nitrate transport.
Project Water Quality Objectives
The main goal of the 319 paired-field networks is to provide information to evaluate the effectiveness of applied BMPs in preserving the quality of the ground water resource beneath the two test fields. Representative ground water samples from the water table below the test fields will be analyzed primarily for nitrate as an indicator of BMP effectiveness. The specific objectives are listed for each of the paired fields.
Forgeon Field
There are presently no plans to implement a separate information and education campaign (I&E) for the 319 National Monitoring Program portion of the project.
Two brochures have been published through the Demonstration Project: one providing an explanation of the project for the general public and a second explaining the nitrate sampling results from the project area. A survey was conducted to assess attitudes of the general public and farmers toward the Demonstration Project. Presentations about the Demonstration Project have been conducted.
Water Quality Data Management
Water quality data will be stored in the U.S. Environmental Protection Agency (USEPA) STORET system, the USDA Water Quality Project's Central Data Base, and Idaho Environmental Data Management System.
For Further Information Contact:
Jeff Bohr and Stacy Camp
USDA-SCS
1369 East 16th St., Burley, ID 83318
Tel: 208-678-7946
John Cardwell
Division of Environmental Quality
1410 North Hilton, Boise, ID 83706
Tel: 208-334-5860
James L. Osiensky
Professor of Hydrogeology
University of Idaho
Moscow, ID 83843
Tel: 208-334-3517
WP7 may be applied to lands that meet two conditions: 1) lands adjacent to or surrounding permanent or intermittent streams, lakes or ponds; any intermittent or permanently flooded wetland; or sinkholes, Karst areas, and other ground water recharge areas and 2) where the adjacent contributing land is cropland, pasture, hayland, or rangeland.
Several other conditions apply to the practice. It must meet all federal, state, and local environmental laws. The participant must: agree to allow USDA agents access to the site to review and evaluate the practice; be implementing a conservation plan on the contributing area; and secure all necessary permits before starting construction of the practice. No open ditch or subsurface drains are permitted to cross land covered by WP7. The use of fertilizers and pesticides is only permitted if covered by an operations and maintenance plan developed for the practice by the designated technician. For further information, contact a local ASCS office to request a copy of Notice ACP-303.