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Colorado Water Science Center


National Water-Quality Assessment (NAWQA) Program
South Platte River Basin Study

by Kevin F. Dennehy 1


In 1991, the U.S. Geological Survey (USGS) began to implement a full-scale National Water-Quality Assessment (NAWQA) Program. The long-term goals of the NAWQA program are to describe the status and trends in the quality of a large, representative part of the Nation's surface- and groundwater resources and to provide a sound, scientific understanding of the primary natural and human factors affecting the quality of these resources.

The NAWQA Program consists of two major elements: study-unit investigations and regional and national syntheses of study-unit results. Study-unit investigations, the building blocks of the NAWQA Program, are designed to address study unit and local water-quality issues and to provide the framework upon which regional and national water-quality assessments are made. The South Platte River Basin was among the first 20 NAWQA study units selected for full-scale implementation.

The South Platte River basin includes parts of three States, Colorado (79 percent), Nebraska (15 percent), and Wyoming (6 percent) and has a drainage area of approximately 24,300 square miles. The principle river within the basin, the South Platte River, originates in the mountains of central Colorado and flows about 450 miles northwest across the Great Plains where it joins the North Platte River at North Platte, Nebraska.

The three-State study area is inhabited by about 2 million people; 96 percent reside in Colorado. The study area is characterized by diverse population density that ranges from sparsely populated mountainous areas in the headwaters and rural agricultural areas downstream from Denver to the densely populated Denver metropolitan area in the south-central part of the basin.

Major activities to be performed as part of the South Platte River basin investigation include the compilation of available water-quality information, sampling and analysis of water-quality for a wide array of physical, chemical, and biological properties, and the interpretation and reporting of results. During federal fiscal year 1992, a retrospective analysis of available hydrologic and biologic data will be completed. Additionally, some reconnaissance sampling will occur to fill in data gaps. Subsequently, there will be a 3 year period of continuous and intensive data collection and analysis, immediately followed by approximately 5 years of low intensity assessment activities.

1 U.S. Geological Survey, Box 25046, MS 415, Denver Federal Center, Lakewood, CO 80225

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