Institute: South Carolina
Year Established: 2015 Start Date: 2015-03-01 End Date: 2016-02-28
Total Federal Funds: $26,097 Total Non-Federal Funds: $53,730
Principal Investigators: John Hains
Abstract: From the 1950s through the 1970s the United States Army Corps of Engineers (USACE) created many oxbow lakes along the Middle and Lower Savannah River Basins by creating navigation short-cuts. Over time, many of those lakes have become cut off from the main river channel and only receive water during high flow events. It is unclear how hydrologically dependent those systems are to the direct river connection or whether those systems have a sufficient groundwater connection to remain wet. Maintaining a sufficient amount of water is important for the oxbow ecosystem. Oxbows are not only critical habitat for foraging and spawning fish and numerous mussel species, some of which are considered threatened in the Savannah Basin, but have been shown to provide habitat that is essential to the overall productivity of the adjacent river system. If the direct surface water or groundwater connection to the river is not sufficient to sustain surface water levels then those oxbow habitats will be insufficient to sustain the necessary hydrology to support the biota that depend upon that habitat. Since the Savannah River already has limited productivity due to the serial reservoirs, decreasing links to oxbows could further limit productivity, which could impact ecosystem services and species diversity. These scenarios have been a concern of both states that share the resource (South Carolina Department of Natural Resources and Georgia Department of Natural Resources) and federal natural resources agencies (United State Fish and Wildlife Service, National Oceanographic and Atmospheric Administration-National Marine Fisheries Service) for some time but there has been little data available to know the actual threat. Since the Savannah River is a highly regulated system, the water level in the river, and thus the connectivity to oxbow lakes, is primarily controlled by discharges from Thurmond Dam. Over the next two years the USACE will be reassessing the flow release guide curves and operating instructions for reservoir management through the USACE Comprehensive Study with one of the emphasis areas of that process as ecosystem protection. Through five distinct project elements, elevation assessment of oxbow openings from historic documents, hydrologic assessments, chemical assessments, biological assessments, and development and submittal of a final report, this study will provide needed and timely data for that process as it relates to hydrodynamics, habitat preservation, ecosystem health, and the ecology of oxbow lakes within the Savannah River Basin.