National water-quality assessment program

(19,657 bytes)

Knowledge of the quality of the Nation's streams and aquifers is important because of the implications to human and aquatic health and because of the significant costs associated with decisions involving land and water management, conservation, and regulation. In 1991, the U.S. Congress appropriated funds for the U.S. Geological Survey (USGS) to begin the National Water-Quality Assessment (NAWQA) Program to help meet the continuing need for sound, scientific information on the areal extent of the water-quality problems, how these problems are changing with time, and an understanding of the effects of human actions and natural factors on water-quality conditions.

The NAWQA Program is assessing the water-quality conditions of more than 50 of the Nation's largest river basins and aquifers, known as Study Units. Collectively, these Study Units cover about one-half of the United States and include sources of drinking water used by about 70 percent of the U.S. population. Comprehensive assessments of about one-third of the Study Units are ongoing at a given time. Each Study Unit is scheduled to be revisited every decade to evaluate changes in water-quality conditions. NAWQA assessments rely heavily on existing information collected by the USGS and many other agencies as well as the use of nationally consistent study designs and methods of sampling and analysis. Such consistency simultaneously provides information about the status and trends in water-quality conditions in a particular stream or aquifer and, more importantly, provides the basis to make comparisons among watersheds and improve our understanding of the factors that affect water-quality conditions regionally and nationally.

This report is intended to summarize major findings that emerged between 1992 and 1995 from the water-quality assessment of the Apalachicola-Chattahoochee-Flint River Basin Study Unit and to relate these findings to water-quality issues of regional and national concern. The information is primarily intended for those who are involved in water-resource management. Indeed, this report addresses many of the concerns raised by regulators, water-utility managers, industry representatives, and other scientists, engineers, public officials, and members of stakeholder groups who provided advice and input to the USGS during this NAWQA Study-Unit investigation. Yet, the information contained here may also interest those who simply wish to know more about the quality of water in the rivers and aquifers in the area where they live.

Robert M. Hirsch, Chief Hydrologist

NAWQA Program helps U.S. Environmental Protection Agency (USEPA) implement new pesticide law

Since the enactment of the Food Quality Protection Act (FQPA), passed in August 1996, USEPA has been required to factor potential exposures to pesticides through drinking water into already complex procedures used to set pesticide "tolerance levels" in foods.

Incorporating potential drinking-water exposures into the pesticide tolerance-setting process has presented USEPA with many scientific challenges including:

• What reliable data are available on pesticide concentrations in surface and ground water in the U.S.? How do these concentrations vary with location and time?
• How can USEPA account for the considerable geographic variability in geology, hy-drology, land use, and agronomic practices in estimating profiles of pesticide drinking water exposures in various regions across the U.S.?
• What "real world" data are available to evaluate and improve computational models that USEPA uses to estimate pesticide drinking-water residues for new pesticides entering the market?
• What types of surface- and ground-water monitoring should USEPA require pesticide makers to conduct after new pesticides (or significant changes in use areas or practices) are approved to verify that actual pesticide levels do not exceed those estimated through USEPA's screening procedures?

Building on many years of productive collaboration between USEPA and USGS, the NAWQA Program marshaled a wide range of its data and expertise to help USEPA address these and other questions.

We do not have all of the answers yet by any means, but we in USEPA who are charged with implementing this part of the new FQPA are greatly impressed with the knowledge and expertise contributed by NAWQA Program scientists and managers to assist USEPA in addressing these questions. This collaboration has been facilitated by NAWQA's dedicating one of its senior hydrologists to work with USEPA to help both organizations better understand how NAWQA data and tools can help USEPA.

USEPA's Office of Pesticide Programs is a very satisfied "customer" of USGS and NAWQA water-resources programs.

Joseph J. Merenda, Director
Environmental Fate and Effects Division
Office of Pesticide Programs
U.S. Environmental Protection Agency