National Water-Quality Assessment (NAWQA) Project
Assess the status and trends of aquatic ecological conditions (invertebrates, fish, algae and habitat) in rivers and wadeable streams.
Relate ecological conditions to chemical stressors (such as nutrients and pesticides), physical disturbances (such as habitat and hydrologic alterations) in the context of different environmental settings and land uses.
Enhance understanding of factors that influence the biological integrity of streams and how these stream ecosystems may respond to diverse natural and human factors.
Develop key ecological indicators of aquatic health.
Gerard McMahon 1, Jerad D. Bales 1, James F. Coles 2, Elise M.P. Giddings 1, and Humbert Zappia 3
1U.S. Geological Survey, 3916 Sunset Ridge Road, Raleigh, North Carolina 27608, USA
2U.S. Environmental Protection Agency, 1 Congress Street, Suite 1100 (HBS), Boston, Massachusetts 02114, USA
3U.S. Geological Survey, 2350 Fairlane Drive, Suite 120, Montgomery, Alabama 36116, USA
ABSTRACT. This paper presents the results of a study on the use of continuous stage data to describe the relation between urban development and three aspects of hydrologic condition that are thought to influence stream ecosystems--overall stage variability, stream flashiness, and the duration of extreme-stage conditions. This relation is examined using data from more than 70 watersheds in 3 contrasting environmental settings--the humid Northeast (the metropolitan Boston, Massachusetts, area); the very humid Southeast (the metropolitan Birmingham, Alabama, area); and the semiarid West (the metropolitan Salt Lake City, Utah, area). Results from the Birmingham and Boston studies provide evidence linking increased urbanization with stream flashiness. Fragmentation of developed land-cover patches appears to ameliorate the effects of urbanization on overall variability and flashiness. There was less success in relating urbanization and streamflow conditions in the Salt Lake City study. A related investigation of 6 North Carolina sites with long-term discharge and stage data indicated that hydrologic-condition metrics developed using continuous stage data are comparable to flow-based metrics, particularly for stream flashiness measures.