Date of Award

8-2001

Type

Thesis

Major

Earth and Space Science - Environmental Science Track

Department

Earth & Space Science

First Advisor

James A. Gore

Abstract

This project was part of a series of investigations designed by the Columbus (Georgia) Water Works to evaluate composition of the macroinvertebrate fauna of the mainstem of the middle Chattahoochee River, as well as its tributaries. An additional objective of the survey was to characterize impacts of storm events on urban streams and the mainstem of the Chattahoochee River. This portion of the study was designed to assess composition of benthic communites of an urbanized river in which flow regime is altered by a series of impoundments. Nine dams currently regulate flow of the mainstem of the middle reach of the Chattahoochee River. Invertebrates were collected quarterly from fall of 1998 through fall of 1999 in tailwaters of four dams, as well as at two non- impounded sites. A vast majority of invertebrates collected were members of the family Chironomidae. Data analysis was conducted to determine whether effects of a series of dams were cumulative, ameliorative, or neutral. Altered streamflow is an inevitable result of the impoundment of riverine systems. A modified flow regime involves a broad range of responses within the ecosystem. Macroinvertebrates are particularly sensitive to disruptions in flow, since most are able to survive only within a distinct range of hydraulic parameters, including discharge, velocity, and surface elevation. While disturbances in the macroinvertebrate fauna may be observed downstream of a reservoir, effects of a cumulative system of reservoirs may result in perturbations that are unique in complexity. Conclusions of this study suggest that homogeneity within the chironomid community may be cumulatively increased downstream as a result of a series of impoundments. The flow regime downstream of each impoundment is governed by the function of the reservoir. Hence, the suite of conditions that apparently resulted in the observed community composition in the middle Chattahoochee River may not be present in other lotic ecosystems that are regulated by a series of impoundments.

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