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<br />FOREWORD
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<br />The U.S. Geological Survey (USGS) is committed to serve the Nation with accurate and timely scientific
<br />information that helps enhance and protect the overall quality of life, and facilitates effective management of water,
<br />biological, energy, and mineral resources. Q!ttp://www.usgs.gov/). Information on the quality of the Nation's water
<br />resources is of critical interest to the USGS because it is so integrally linked to the long-term availability of water
<br />that is clean and safe for drinking and recreation and that is suitable for industry, irrigation, and habitat for fish and
<br />wildlife. Escalating population growth and increasing demands for the multiple water uses make water availability,
<br />now measured in terms of quantity and quality, even more critical to the long-term sustainability of our communi-
<br />ties and ecosystems.
<br />The USGS implemented the National Water-Quality Assessment (NAWQA) Program to support national,
<br />regional, and local information needs and decisions related to water-quality management and policy.
<br />(http://water.usgs.gov/nawqa). Shaped by and coordinated with ongoing efforts of other Federal, State, and local
<br />agencies, the NAWQA Program is designed to answer: What is the condition of our Nation's streams and ground
<br />water? How are the conditions changing over time? How do natural features and human activities affect the quality
<br />of streams and ground water, and where are those effects most pronounced? By combining information on water
<br />chemistry, physical characteristics, stream habitat, and aquatic life, the NAWQA Program aims to provide science-
<br />based insights for current and emerging water issues and priorities. NAWQA results can contribute to informed
<br />decisions that result in practical and effective water-resource management and strategies that protect and restore
<br />water quality.
<br />Since 1991, the NA WQA Program has implemented interdisciplinary assessments in more than 50 of the
<br />Nation's most important river basins and aquifers, referred to as Study Units.
<br />(http://water.usgs.gov/nawqa/nawqamap.html). Collectively, these Study Units account for more than 60 percent
<br />of the overall water use and population served by public water supply, and are representative of the Nation's major
<br />hydrologic landscapes, priority ecological resources, and agricultural, urban, and natural sources of contamination.
<br />Each assessment is guided by a nationally consistent study design and methods of sampling and analysis.
<br />The assessments thereby build local knowledge about water-quality issues and trends in a particular stream or aqui-
<br />fer while providing an understanding of how and why water quality varies regionally and nationally. The consis-
<br />tent, multi-scale approach helps to determine if certain types of water-quality issues are isolated or pervasive, and
<br />allows direct comparisons of how human activities and natural processes affect water quality and ecological health
<br />in the Nation's diverse geographic and environmental settings. Comprehensive assessments on pesticides, nutri-
<br />ents, volatile organic compounds, trace metals, and aquatic ecology are developed at the national scale through
<br />comparative analysis of the Study-Unit findings. (http://water.usgs.gov/nawqa/natsyn.html).
<br />The USGS places high value on the communication and dissemination of credible, timely, and relevant sci-
<br />ence so that the most recent and available knowledge about water resources can be applied in management and
<br />policy decisions. We hope this NA WQA publication will provide you the needed insights and information to meet
<br />your needs, and thereby foster increased awareness and involvement in the protection and restoration of our
<br />Nation's waters.
<br />The NA WQA Program recognizes that a national assessment by a single program cannot address all water-
<br />resource issues of interest. External coordination at all levels is critical for a fully integrated understanding of
<br />watersheds and for cost-effective management, regulation, and conservation of our Nation's water resources. The
<br />Program, therefore, depends extensively on the advice, cooperation, and information from other Federal, State,
<br />interstate, Tribal, and local agencies, non-government organizations, industry, academia, and other stakeholder
<br />groups. The assistance and suggestions of all are greatly appreciated.
<br />
<br />~ )R.~
<br />
<br />Robert M. Hirsch
<br />Associate Director for Water
<br />
<br />III
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