RESERVOIR SEDIMENTATION DRIVEN BY COMPLEX LANDSCAPE DYNAMICS THROUGH TIME

Large portions of the South Central United States rely on constructed reservoirs to meet a wide range of water resource needs. However, many of these have experienced significant sedimentation, and continuation of this trend threatens the landscape's ability to satisfy future demand. Many studies have employed the use of a variety of sonar technologies to quantify the reduction of reservoir capacity. However, an extensive investigation of watershed dynamics causing sedimentation is often lacking. Examining Flood Control Reservoirs constructed through a federal program over several decades, we examine the large-scale processes of entire watersheds contributing to a collection of small reservoirs. Using Lead-210 and Cesium-137 isotopes, we create a chronosequence and estimate rates of sedimentation during different periods. We pinpoint key erosion events with an analysis of historical weather conditions and streamflow data. Additionally, an intensive study of aerial photos and satellite imagery stretching back to the 1930s brings to light important landscape changes that affect soil erosion and transport. By quantifying long-term trends in vegetation shifts, management activities, and land use/land cover and correlating these with sediment isotope tracers and other environmental data, we reconstruct the processes leading to reservoir sedimentation. Observations indicate each reservoir is different and dependent upon a handful of local factors. This information can be used to make management recommendations for a specific local context. This new approach shows promise for application in many areas around the globe and can serve as a powerful tool to safeguard water resource sustainability in the future.