SCALE DEPENDENT URBANIZATION EFFECT ON STREAM FLOW AND WATER QUALITY OF A HEADWATER WATERSHED IN SOUTHERN APPALACHIANS

Urbanization in mountainous regions has disturbed the natural water cycle and deteriorated the water quality of headwater streams. Specifically, the impervious surfaces (IS) from urban development have a detrimental impact on water quality and quantity. Studies on the impact of urbanization on headwater streams at multiple spatial scales are lacking. In the present study, water quality (pH, temperature, specific conductivity, and Cl^-, NO^3-, SO₄^2- levels) and discharge of seven headwater streams in the South Fork New River watersheds in Southern Appalachian, NC were monitored. These study areas provide an excellent representation of the effects of IS on water quality and stream flow since the watersheds have similar natural environments yet differing degrees of urbanization. LIDAR data was used to determine the percentage of IS at 25, 50, and 100 meter buffer zones around each stream. There were significant correlations (p<0.05) in percentage of IS and water quality parameters with the best correlations were found at 25 meter scale. The percentage of IS at a 25 meter buffer zone explained 99%, 93%, and 94% of variations of stream Cl^-, NO₃^- and SO₄^2- levels, respectively. Lower normalized discharge values, expressed as water depths per time, were associated with greater coverage of IS. The greatest correlation between normalized discharge values and coverage of IS occurs at a 100 meter buffer zone (R²= 0.82). Our results indicated that urbanization in this mountainous landscape has caused degradation of aquatic ecosystems. Urban planning has to be assessed carefully at varying spatial scales to protect the regions’ pristine yet vulnerable water resources.