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Water-Quality Trends for Streams and Reservoirs in the Research Triangle Area of North Carolina, 1983-95
Prepared in cooperation with the Triangle Area Water Supply Monitoring Project Steering Committee
By Carolyn J. Oblinger Childress and Neeti Bathala
This report presents the results of analyses of trends in concentrations of nitrogen, phosphorus, suspended sediment, suspended solids, sodium, chloride, iron, zinc, manganese, and chlorophyll a at 34 stream and reservoir sites that are part of the Triangle Area Water Supply Monitoring Project. Trend results are discussed in relation to broad-scale changes in land cover that have occurred in the area since the mid-1970's.
Data used for trend analysis of stream sites are from samples collected by the U.S. Geological Survey (USGS) from 1982 through 1987 for a study for the U.S. Army Corps of Engineers (Garrett, 1990a and b), by the North Carolina Division of Water Quality (DWQ) from 1982 through 1995 for the statewide ambient water-quality monitoring network, and by the USGS from 1988 through 1995 for the Triangle Area Water Supply Monitoring Project (Childress and Treece, 1996; Ragland and others, 1996). These three sources provide stream water-quality data, collected monthly, which are ideally suited for trend analysis. Using continuous streamflow data from USGS gages, stream water-quality data were statistically adjusted to eliminate the effects of changing streamflow.
Lake samples were collected from 1988 to 1995 by the DWQ for the North Carolina Lake Assessment Program and by the USGS for the Triangle Area Water Supply Monitoring Project. Generally, these data were collected only between April and October and were collected at variable time intervals.
Abstract
Introduction
Methods of Land-Cover Estimation
Trends in Land Cover and Water Quality
Sample Collection and Analysis Methods
Trend Analysis Methods
Significant Findings
References
Triangle Area Water Supply Monitoring Steering Committee
- Chatham County
- Orange County
- Town of Apex
- Town of Carrboro
- Town of Cary
- Town of Chapel Hill
- City of Durham
- Town of Hillsborough
- City of Sanford
- Orange Water and Sewer Authority
Acknowledgments
The Division of Water Quality of the North Carolina Department of Environment, Health, and Natural Resources maintains a Surface Water Ambient Monitoring System with approximately 380 sampling locations throughout the State. The USGS wishes to acknowledge the assistance of the Division in collecting water-quality samples and providing data from ambient monitoring sites located within the study area.
Copies of this report can be purchased from:
- U.S. Geological Survey
- Branch of Information Services
- Federal Center, Box 25286
- Denver, CO 80225-0286
- Water-Resources Investigations Report 97-4061
For Further Information Contact:
- District Chief
- U.S. Geological Survey
- 3916 Sunset Ridge Road
- Raleigh, NC 27607
- Phone: (919) 571-4000
- Home Page: http://wwwnc.usgs.gov/
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Last modified: Thu Jun 18 15:50:48 1998