All of life depends on water, and all of us are citizens of a watershed. Our activities and the ways we use our water resources and the land adjacent to the water affect the quality of our drinking water, our recreational opportunities, and the health and diversity of aquatic plants and animals. Our activities also affect whether our rivers and streams will continue to be beautiful places to visit and vistas to contemplate. In this publication, you'll find information about watersheds and about monitoring the quality and quantity of surface-water resources. You'll learn how the U.S. Geological Survey (USGS) monitors streamflow and surface-water quality across the Nation and how USGS information can help you learn more about your water resources-whether as a citizen of your watershed or an active citizen monitor. This publication focuses on surface water, but keep in mind that surface water and ground water are interconnected. USGS also monitors the flow and quality of ground water, and investigates surface-and groundwater interactions. USGS and citizen monitoring The water quality of a nearby stream, a watershed, or a large river system can be enhanced only by collecting good information about conditions and by responding-most effectively at the local level-to that information. Informed citizens of a watershed often are in the best position to identify priority water issues and to understand the political, social, and economic context in which those issues are addressed. USGS works with citizen monitors in many watersheds across the Nation. Typically, watershed associations, such as the Alliance for Chesapeake Bay and Watershed Committee of the Ozarks, plan and conduct the activities of citizen monitors. Citizen monitoring enhances the monitoring conducted by USGS and other federal and state agencies by filling in geographic gaps or by increasing the frequency of sampling. Information collected by citizen monitors can also help USGS and other water-resource agencies know where to focus their broader data-collection activities and analysis. In turn, hydrologists from USGS and other agencies often train citizens during "side-by-side" data-collection activities. To learn about USGS monitoring activities in your state, call or e-mail the USGS representative. A list of contacts is at water.usgs.gov/district_chief.html.

What is groundwater vulnerability? It is an estimate of the relative risk of groundwater contamination by a particular constituent, such as nitrate. Where is the ground water most vulnerable? In the Puget Sound Basin, shallow wells in aquifers that have coarse-grained glacial deposits at the surface and a high percentage of urban (residential, commercial, and industrial) and(or) agricultural land use in the vicinity are most vulnerable to nitrate contamination. For example, shallow wells in agricultural areas overlying coarse-grained glacial deposits, like much of the Lower Nooksack Valley, or in urban areas overlying such deposits, like parts of Tacoma and Olympia, have a greater than 50% probability of nitrate concentrations at or above 3 milligrams per liter (areas in red on the vulnerability map to the right). Nitrate concentrations at or above 3 milligrams per liter (mg/L) are well above naturally occurring levels in the Puget Sound Basin (see Brown and Caldwell, 1985, for example), indicating an anthropogenic (human-related) source of nitrate.

Walleye had higher concentrations of mercury than other sport fish. Larger walleye had higher mercury concentrations than smaller walleye. Mercury concentrations in walleye fillets ranged from 0.11 to 0.44 parts per million (ppm). These concentrations do not exceed the current Federal standard (1.0 ppm of mercury) designed to protect the health of people who eat small amounts of fish. After reviewing these findings, the Washington State Department of Health concluded \hatpeople who regularly consume large amounts of Lake Roosevelt walleye may be at risk of adverse health effects from mercury and should limit their consumption of these fish (see back for specific recommendations). Why worry about mercury? Mercury, a metal like lead or tin, comes from many natural sources, such as oceans, volcanoes, and the weathering of rock in mountains. Human activities like burning fossil fuels and discharging industrial waste into the air and water also add mercury to the air we breathe, the water we drink, and the food we eat. We all have mercury in our bodies, but at levels that are typically not high enough to cause health concerns. It is possible, however, to accumulate too much mercury in the body.

In 2001, the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program began an intensive study to assess the vulnerability of public-supply wells to contamination from a variety of compounds. The study builds on previous NAWQA studies from 1991 to 2001 that found low levels of mixtures of contaminants in ground water near the water table in urban areas across the Nation (in about 90 percent of monitoring wells) and, less frequently, in deeper ground water typically developed for public supply (Hamilton and others, 2004). Data from more than 1,000 public-supply wells within major water-supply aquifers are being evaluated in this study, and data from more aquifers and wells are scheduled to be added in 2009 (see map, p. 4). This NAWQA study is focusing on the transport and chemical breakdown of selected anthropogenic contaminants from urban and agricultural sources, as well as contaminants from natural sources, within that part of the groundwater system contributing water to public-supply wells. Scientists are investigating how the linkage between contaminant sources and public-supply wells is affected by processes that occur below land surface-whereby contaminants are mobilized, dispersed, diluted, volatilized, adsorbed, and (or) degraded. Scientists are also investigating how the operation of public-supply wells can affect their vulnerability to contamination.

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