Water Quality in the Puget Sound Basin

Project Summaries


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4751-9BI-53 - Puget Sound National Water Quality Assessment (NAWQA)

Problem - The quality of the Nation's waters is highly variable and greatly influenced by the activities of man. The existing quality of the Nation's waters and the cause and effect influences from man's activities must be well understood to manage water resources to their maximum beneficial uses, while at the same time preserving the viability of aquatic ecosystems. The USGS National Water Quality Assessment (NAWQA) is undertaking a nationwide study to provide to Congress, the public, and water-resources managers consistent, scientifically defensible water-quality data and interpretation of significant water-quality processes that will allow them to identify existing and emerging water-quality issues and to make more informed water-resources decisions.

The Puget Sound NAWQA study investigates water-quality issues of national and local importance within the boundaries of the Puget Sound basin to provide input to the national assessment and to contribute to a better understanding of the local resource.

The Puget Sound basin is one of the fastest growing regions of the United States. During the 1980's, the population of the basin increased by 23 percent to 2.7 million people. By the year 2010, the basin's population is expected to increase by another 1.1 million. This increasing population and the resulting development will have significant influences on the land within the basin and will place significant demands on the region's water resources. Ground water will need to be further utilized as a drinking-water supply while land development in recharge areas increasingly threatens ground-water quality. Recreational use of surface water will increase while point-source discharges of sewage and industrial waste threaten surface-water quality. Riparian habitat will be influenced by greater stormwater discharges from developed uplands and the Puget Sound itself will receive increased loadings of contaminants from the cumulative activities of man within the basin. Local watershed planners and water-resources managers will attempt to anticipate and mitigate these negative pressures on the water resources of the Puget Sound basin, and to be successful, they will require defensible data on existing water-quality conditions and insight on the cause and effect influences and insight into the cause and effect influences of man's activities on the region's water quality.

Objectives - The long-term goals of the Puget Sound NAWQA are to describe the present status and emerging trends in the quality of the surface- and ground-water resources of the Puget Sound Basin and to provide a sound, scientific understanding of the primary natural and human factors affecting the quality of these resources. In meeting these goals, the study will produce water-quality information that will be useful to policy-makers and managers at the national, state, and local levels.

Relevance and Benefits - An important part of the USGS mission is to provide scientific information to manage the water resources of the Nation. To help assess the Nation's water resources, the USGS established the National Water-Quality Assessment (NAWQA) Program to (1) describe the status and trends in the quality of a large, representative part of the Nation's surface-water and ground-water resources using nationally consistent methods and approaches; (2) provide an improved understanding of the primary natural and human factors affecting these conditions; and (3) provide information that supports development and evaluation of management, regulatory, and monitoring decisions by other federal, state and local agencies. Three major program elements contribute to accomplishing the goals of the NAWQA Program: (1) investigations of major river basins and aquifer systems, referred to as study units; (2) regional and national syntheses of key findings from study-unit investigations and existing information related to important water-quality topics such as pesticides, nutrients, volatile organic compounds, trace elements, and ecology; and (3) coordination at local, State, regional, and national levels with environmental and natural resource managers and other users of water-quality information. The data and information provided by the NAWQA Project in this State are vital to the NAWQA Program nationwide.

Approach - The Puget Sound NAWQA study investigates the quality of fresh water in both the surface and ground-water flow systems in the Puget Sound drainage basin. The study does not address the quality of salt water in the Puget Sound itself. The study begins with a retrospective analysis of existing surface- and ground-water quality data that are used to assess what is currently known about the status of the quality of fresh water in the basin and to identify naturally occurring or man-induced water-quality constituents of concern within the study area. The retrospective analyses helps in the design of the field data-collection effort by identifying specific geographic areas, land-use categories, or stream reaches worthy of more intensive study.

The ground-water quality sampling design includes regional, targeted, and long-term sampling networks the purposes of which are to (1) describe ground-water quality for major hydrogeologic settings and to define the areal distribution of selected water-quality constituents, (2) to further define problem areas and identify the factors that affect current conditions, and (3) to define the long-term trends in ground-water quality. The targeted and long-term trend sampling networks are located within the glacial-valley filled aquifers of the Puget Sound basin. These are potentially productive aquifers, the land surface of which has been developed for industrial, residential, and intensive agricultural land uses.

The surface-water quality sampling design includes a limited number of long-term fixed-station sampling sites, a larger number of synoptic sampling stations, and studies of selected stream reaches, the purposes of which are to (1) provide information on the distribution, concentration, and seasonal variation of a broad array of water quality constituents which will allow estimates of loads of selected water-quality constituents to the Puget Sound; (2) define long-term trends in the concentrations and/or loads of selected constituents at key locations; and (3) identify the major factors that affect observed conditions and trends in surface-water quality. The fixed stations are located near the mouths of the larger rivers draining to the Puget Sound, the Green-Duwamish, Nooksack, and Skokomish, and selected tributaries to these rivers.