Summary

Water-quality data from selected surface-water monitoring sites across the Southeastern United States were assessed for trends in concentrations of nutrients, suspended sediment, and major constituents and for in-stream loads of nutrients and suspended sediment for the period 1973–2005. The assessment area includes river basins draining into the southern Atlantic Ocean, Gulf Coast, and the Tennessee River—Hydrologic Regions 03 (South Atlantic–Gulf) and 06 (Tennessee), respectively. This study is one of several major river basin studies conducted as part of the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Program to assess national water-quality trends during a common time period from 1993 to 2004.

This report presents datasets used in trend analysis and load estimation, including concentration and streamflow. Water-quality monitoring station information, map locations, and ancillary data on basin characteristics, including regional landscape variables and agricultural nutrient sources are presented. Methods of data compilation and modification used prior to performing trend tests and load estimation are described, and tables of trend-test results and load estimates are presented.

Temporal trends for varying time periods in nutrient, suspended-sediment, and major ion concentrations were analyzed for 44 sites using data retrieved from the USGS National Water Information System (NWIS) database. Temporal trends for varying time periods in nutrient concentration were analyzed for 290 sites using data retrieved from the U.S. Environmental Protection Agency Storage and Retrieval (STORET) database. In addition, annual in-stream loads and yields of nutrient constituents and suspended sediment were estimated for 48 sites using data retrieved from the NWIS database.