Urbanization in the Etowah River Basin: Effects on Stream Temperature and Chemistry
Paul, Michael J.
Leigh, David S.
Lo, C. P.
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Urbanization represents one of the fastest land cover transformations in Georgia and around the world. Conversion of previously forested or agricultural watersheds to residential and industrial/commercial land use affects the hydrology and geomorphology of receiving streams. These changes may contribute to alteration in stream chemistry and temperature as well. We measured monthly baseflow water chemistry and took hourly temperature data for 1 yr in 30 tributaries to the Etowah River. The thirty watersheds had variable land cover from 5 to 61% urban (27 to 80% forested). We used a combination of multivariate and regression analysis to analyze relationships between chemistry, temperature, and land use. Watersheds with greater urban land use had higher mean soluble reactive phosphorus, nitrate, and ammonium concentrations, as well as greater specific conductance, and turbidity. Urban land use was the best predictor of phosphorus, whereas agricultural land use was the best predictor of ammonium. Nitrate concentration and conductance were best predicted using a combination of urban and agricultural land use. Increases in non-forested land use also affected stream temperature: annual mean daily temperature increased with deforestation, daily mean temperatures in summer increased with urban land use; and winter mean daily temperature increased with riparian agriculture. The changes in chemistry and temperature indicate that land use change affects the physical and chemical habitat of streams. Such changes have serious implications for native stream biota.