WATER RESOURCES OF A LOW-GRADIENT WATERSHED IN THE ATLANTIC COASTAL PLAIN: TURKEY CREEK, FRANCIS MARION NATIONAL FOREST, SOUTH CAROLINA

Water is one of the earth’s most important resources, and is sensitive to climate variability as well as land use change and increasing demand. Public lands such as the national forests and rangelands in the U.S. have served as important testing grounds to understand processes affecting the water budget and water quality at the plot, hillslope, and catchment scales. Studies at the wildland-urban interface are also becoming critical as urbanization and related land use changes encroach on public lands. The Francis Marion National Forest near Charleston, South Carolina has been an active location for hydrological research in support of sustainable forestry, and more recently in response to climate-related and human-induced stresses on water resources in the Atlantic coastal plain region. Turkey Creek near Huger, SC is a USGS-gauged, third-order watershed of 7,260 ha in area. The current Turkey Creek Watershed Monitoring Initiative has built upon past research and is focused on hydrological processes in low-gradient, forested wetland-dominated landscapes common in the Atlantic coastal plain. We will present results on rainfall, stream flow, weather, groundwater, and water quality as affected by climatic variation including extremes over the past four years. Data reveal that runoff response was affected by the spatial and temporal distribution of the shallow water table. The runoff-rainfall ratio varied from 26% in the wet year of 2005 with 1527 mm rain to just 7% for the dry year of 2007. On average, the estimated base flow was approximately 23% of the total stream flow. Soils and geology of these sites provide the framework for understanding sensitive areas for groundwater recharge and baseflow, for example. Turkey Creek drains mostly back-barrier (lagoonal) settings of the Pleistocene Epoch high sea level stands with very poorly to well drained soils, whereas other parts of the lower coastal plain consist of former beach ridges or riverine and estuarine systems. These differences in soils and geology control runoff, recharge and baseflow to streams. This collective research effort will enable land managers and researchers to both protect critical areas of low-gradient watersheds and focus future watershed studies.