By Jamie Sykes, USACE Savannah District Fisheries Biologist
You may have read reports in the media about a recent fish mortality event at Hartwell Lake. As the fisheries biologist for the U.S. Army Corps of Engineers Savannah District, I’d like to provide some facts on this situation and tell you what we are doing about it.
On the weekend of Sept. 7, we received reports of striped bass floating on the surface in the lower portion of Hartwell Lake, from the dam upstream approximately 2.5 miles. We investigated the event immediately in coordination with the South Carolina and Georgia Departments of Natural Resources (DNRs). We will continue to monitor water quality and habitat conditions until we have cooler water temperatures in the late fall.
This mortality event had been a concern for several weeks. Striped bass habitat conditions in the lower portion of Hartwell Lake have been declining for the last two months with very little striped bass habitat available, which contains both cool water and adequate dissolved oxygen.
Due to exceptionally high rainfall at Hartwell this summer, we have released high outflows from the Hartwell Dam over the last few months. These high release rates were necessary to manage the flood conservation pool and reduce flood risk.
These sustained high outflows affected the temperature and dissolved oxygen levels in the lake, which in turn impacted striped bass habitat. Striped bass prefer cool and oxygenated water that is generally found from 40 to 80 feet deep in Hartwell Lake during the summer months. The high amount of rainfall and inflows that we experienced this spring and summer resulted in much of the water at this 40 to 80 foot level being released through high generation outflows. The cool water that was released through the dam was replaced by warmer water with lower oxygen levels, which impacted Striped bass habitat in the lower portion of Hartwell Lake.
Some anglers have suggested that spilling the water through the spillway gates would have been a better option for moving the large amount of water that has been generated through the Hartwell Dam. This perhaps would have prevented the release of some portion of the cool water from Hartwell Lake, but this option would have also seriously impacted the trout fishery in the Hartwell tailwaters and the trophy striped bass fishery in the upper portion of Richard B. Russell Lake. Both of these fisheries rely on the cool water being released through the Hartwell Dam. Releases through the spillway gates are from the surface of the Hartwell Lake and would be in excess of 80 degrees Fahrenheit in temperature. This water is much too warm for rainbow trout or striped bass.
Summer striped bass mortality events are common in other Southeastern reservoirs, particularly lakes such as Greenwood and Murray in South Carolina, and Lake Norman in North Carolina. However, this is the first summer mortality event that has occurred in Hartwell Lake in the 30+ years that Striped bass have been stocked. The weather conditions that led to this are very unusual. It is also important to remember that the water quality in Hartwell is generally very good and remains safe for fishing, boating, swimming, etc.