Water quality changes across an urban-rural land use gradient in streams of the West Georgia Piedmont

Abstract

Conversion of forested land to suburban and urbanized landscapes is occurring at extreme rates, especially in the Southeastern United States. Specifically, Georgia is ranked second in the total amount of land developed from 1992 to 1997. To examine the effects of land use on water quality, eighteen small watersheds within the Middle Chattahoochee Watershed of western Georgia were chosen for investigation. Watersheds were selected to reflect an increasing impervious surface gradient and also to represent a wide array of land uses, including urban, developing, pastoral (primarily grazed pastures), mixed species forests (composed of deciduous and evergreen species), and pine forests (predominately composed of mixed pine species including some actively managed pine plantations). Grab samples were collected from May 2002 to January 2006 and analyzed for concentrations and yields of NO3-, Cl-, SO4-, Na+, NH4+, K+, P, total dissolved and suspended solids, dissolved organic carbon, and fecal coliform counts. Hydrology was examined by installing in situ pressure transducers in each watershed and recording stage intervals every 15 minutes. In general, urban watersheds revealed higher concentrations and yields of total dissolved solids, Cl-, SO4-, NH4+, K+, dissolved organic carbon, and fecal coliforms than other land uses. All water quality parameters were positively correlated with % impervious surfaces and negatively so with % forest cover. Variation in yields of water quality parameters across years decreased with increasing forest cover. These results suggest that the amount of forest cover within a watershed is vital to protecting stream ecosystems. This study will help to clarify the effects of land development on the physicochemical and biological properties of stream water in the Georgia Piedmont.