Cooperative Fish and Wildlife Research Units Program: South Carolina
Education, Research and Technical Assistance for Managing Our Natural Resources

South Carolina Project

Edisto River Flow Effects on Summertime Water Temperatures: Are Thermal Tolerances of SWAP Fishes Exceeded at Low Flows?

January 2023 - December 2027


Participating Agencies

  • South Carolina Department of Natural Resources

The Edisto River has the highest number of water withdrawal registrations and the highest maximum monthly withdrawals of any river basin in the state of South Carolina (SCDHEC 2020). Reduced flows may negatively impact SWAP listed fish species through a variety of mechanisms, but elevated water temperatures during low flow events could be especially detrimental to SWAP species such as Striped Bass Morone saxatilis that require coolwater habitat. The genetically unique Striped Bass population endemic to the ACE basin seeks thermal refuge in the upper portions of the basin (e.g., North and South Fork Edisto River) during summer. For such species, decreased flow during summer may cause water temperatures to exceed thermal tolerances as has been observed for other coolwater riverine species. Key knowledge gaps limit our ability to understand how increases in summertime flow-dependent temperature may negatively impact species of greatest conservation need in the Edisto River Basin. First, there is no knowledge of the relationship between flow, summer air temperature, and water temperature. Developing a statistical relationship between these variables would be a first step towards assessing the thermal impacts of low flow during summer. Second, for many SWAP species, such as Bannerfin Shiner Cyprinella leedsi, there is no published data on thermal tolerance meaning that even if a relationship between flow and summertime water temperature were developed, we would be unable to understand the biological implications. These knowledge gaps are especially relevant given the large, predicted increases in water demand in the Edisto Basin and projected changes in temperature and precipitation due to climate change over the next several decades.This project will provide critical information necessary for protecting SWAP listed freshwater and diadromous fish species in the Edisto River Basin. Specifically, this project will determine maximum thermal tolerances for two SWAP freshwater fish species in the Edisto River Basin (Bannerfin Shiner [high priority], Edisto River Stiped Bass [moderate priority]) and create detailed maps of available thermal habitat under a range of current and projected, future flow scenarios for the two SWAP fish species listed above as well as the Shortnose Sturgeon [listed under ESA as endangered throughout its range]).