Hydrologic Impacts of Land-Use Changes in Coastal Plain Watersheds

Conservation programs developed and implemented by the USDA have led to land-use changes of large areasthroughout the U.S. These changes in land-use may lead to changes in evapotranspiration and infiltration and subsequentlyto dramatic differences in hydrologic response. The impact of recent land-use changes was evaluated using observedprecipitation and streamflow data from the Little River watershed in south-central Georgia in the U.S. Land-use patternswithin the watershed were examined through classification of satellite images collected from 1975 to 2003. While somechanges in land-use were determined, analysis of the data indicated that the overall changes were less than the typicalclassification errors obtained. Based on the analysis of the satellite imagery, conservation practices implemented in the LittleRiver watershed have not significantly altered total forest acreage. In addition, 34 years of hydrologic data collected fromthis watershed do not indicate any significant changes in hydrologic patterns. The long-term average ratio of annual flowto annual precipitation for the Little River watershed has remained stable at approximately 0.27. Year-to-year variation ofthe ratio varied from a high of 0.41 observed during a year with above-normal winter rainfall to 0.06 observed during a yearwith very low annual rainfall. When subwatersheds of the Little River were compared, significant differences in theirresponsiveness to rainfall were found. Linear regression between precipitation and streamflow produced regressioncoefficients between 0.62 and 0.90. These differences were attributed to differences in physical characteristics and land-use.Long-term data from the watersheds indicate that streamflow response is dominated by annual and seasonal precipitationcharacteristics.