The relationship between a stream’s macroinvertebrate community as quantified by Georgia Adopt-A-Stream’s Water Quality Index and the impervious surface of an adopted stream’s watershed was weak. Although the average WQI decreased with increasing watershed imperviousness, the R2 was only 8.3%--an admittedly poor fit. To further investigate, a more comprehensive analysis was performed using forward stepwise regression. This model, which included both imperviousness and the abundance of just 15 out of the 20 kinds of macroinvertebrates, achieved an R2 of 59.4%. Imperviousness alone may not be a good predictor of WQI, but a combination of selected macroinvertebrate data and imperviousness can yield a better fitting model. Furthermore, mayflies, aquatic sowbugs, clams/mussels, midges, and lunged snails, all of which were excluded from the model because they did not have a significant predictive value for WQI, generally seem to have specific habitat requirements which are dictated by stream-reach, rather than whole watershed characteristics.


I would like to thank Clayton State University’s College of Arts and Sciences for their support of this work through a CASE grant, as well as the volunteers and professional staff of Georgia Adopt-A-Stream for the data upon which this study was based.