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National Water-Quality Assessment (NAWQA) Program
Lower Tennessee River Basin


Updated April 2, 1998


Chart showing schedule of activities for the LTEN study unit

The Lower Tennessee River Basin study is one of 14 NAWQA studies that began in Federal fiscal year 1997 (October 1996). Study planning and design, and analysis of existing data will be done during the first 2 years. After the 2-year planning period, surface- and ground-water and ecological data will be collected intensively for 3 years during a high-intensity phase. A lower intensity phase follows for the next 6 years during which water qual- ity is monitored at a selected number of sites and areas assessed during the high-intensity phase. Alternating high- and low-intensity monitoring phases allows the NAWQA Program to examine trends in water quality over time in a cost-effective manner, eventually assessing about two-thirds of the Nation's water resources.

During the planning period, existing data and results from previous studies will be reviewed to identify gaps in the current data and to help understand the primary physical, chemical, and ecological factors that affect water quality in the study unit. Information obtained from review of previous studies, along with reconnaissance of existing monitoring stations and candidate sampling sites, will be used to design a sampling program for the study unit.

During the high-intensity phase, new chemical, physical, and ecological data will be collected from selected areas at local and regional scales to describe the quality of water throughout the study unit. These data will be used to determine the water chemistry of streams and aquifers; the quantity and quality of suspended sediment and bottom sediments in streams; the variety and number of fish, benthic invertebrates, and algae in streams; and the presence of contaminants in fish tissues. Individual streams, aquifers, and biological species representative of the most important water resources and water-quality concerns in the study unit and the Nation are selected for sampling and analysis. A series of technical and nontechnical reports describing the results of high- and low-intensity-phase data collection and analysis are planned.


The NAWQA Program is designed to assess the status of and trends in the quality of the Nation's ground- and surface-water resources and to link the status and trends with an understanding of the natural and human factors that affect the quality of water. Consistent data collection and assessment methods in all NAWQA studies make this possible and are critical for providing uniform and comparable information on water quality for the Nation. Surface-water, ecological, and ground-water studies are done at local (a few square miles to hundreds of square miles) and regional (thousands of square miles) scales to help understand water-quality conditions and issues in a study unit. NAWQA study-unit data collected using this multiscale, interdisciplinary approach will be aggregated to provide national-scale water-quality assessments. Partnerships and cooperative studies between local, State, and Federal agencies can be developed to help meet specific needs. The basic design described in the following sections is similar among NAWQA study units nationwide.


Ecological studies in conjunction with surface-water sampling activities are conducted to provide insight into ecological variability over time, relations between water quality and community structure and stability, and ecological differences with respect to various environmental settings. Aquatic biological communities are surveyed at basic- and intensive-fixed sites during the 3-year high-intensity phase. These investigations are conducted along delineated stream reaches and include aquatic and riparian habitat assessments and annual surveys of fish, algal, and benthic invertebrate communities. Trace elements and synthetic organic compounds are analyzed in bed sediment and fish tissue at selected sites to determine their occur- rence and distribution and relation to land use and environmental setting. Ecological synoptic studies are conducted to evaluate spatial variability of biological communities or address issues of special concern within the study unit.