COMPARATIVE ANALYSIS OF THE ENVIRONMENTAL EVOLUTION OF TWO VIRGINIAN LAKES: LAKE PELHAM AND LAKE MOOMAW

High sediment influxes into reservoirs have well known detrimental impacts including the cumulative loss of storage capacity through siltation and declines of quality of life for inhabitant plants and animals. This study seeks to quantify the effects of anthropogenic and natural geomorphic processes in two Virginia reservoirs. Lake Pelham is located in Culpeper County, an area of relatively flat terrain and high human impact. Lake Moomaw is a nearly pristine reservoir located in the Blue Ridge Mountains and surrounded by forty-three miles of undeveloped forested shoreline. The ²¹⁰Pb isotope and the Revised Universal Soil Loss Equation (RUSLE) were used to comparatively analyze sediment accumulation rates in the reservoirs and watershed soil losses while taking into account anthropogenic and natural geomorphic watershed characteristics.

²¹⁰Pb isotope analysis results from three sediment cores show that the average accumulation rates in Lake Pelham range between 0.22 g/cm²/yr and 0.34 g/cm²/yr. All three locations show that modern accumulation rates have increased from historic rates at least 2-fold in Lake Pelham. Comparatively, average accumulation rates in Lake Moomaw were slightly lower, ranging from 0.19 g/cm²/yr to 0.26 g/cm²/yr. Sediment accumulation rates in Lake Moomaw have also shown less historical change. These preliminary results show that anthropogenic influences have a greater impact on sediment accumulation rates than natural geomorphic influences. However, the role of other important parameters like soil type, slope steepness and length, and watershed size will be explored in our ongoing RUSLE model analysis. Sediment trace metals analysis will also be used to verify the role of anthropogenic and natural influences.