Flow issues regarding Norfork Dam.
I’ve attached a copy of an email generated by Jeff Williams, Trout Program Coordinator with Arkansas Game and Fish Commission regarding the issue of both turbines being down, water temperature and river flows.
Just wanted to give you a quick update on some flow issues we are currently dealing with on Norfork. Both turbines our down at Norfork as a result of leakage problems in the wicket gates. It is not known exactly how long they will be down, but the current estimate is about two months. The reservoir elevation is just in to the flood pool and in accordance with the control plan the Corps of Engineers needs to begin evacuating that flood storage. Since both turbines are down they have had to look at alternative means. Yesterday they opened the sluice gates at Norfork to begin releasing some of the flood water. Some of you may have realized this when the flow recording was reporting 0 units on line, but there was flow equivalent to 2 + units in the tailwater. As an aside, I suggested to the Corps of Engineers last night that sluice gate releases should be indicated on the recording. The sluice gates draw water from low in the reservoir so there was no concern regarding high water temperatures. However, the Corps had concerns about cavitation in the sluice gates and has opted for flood gate releases to lower the lake elevation. Twelve flood gates were opened about 1.5 feet at Norfork at 12:00pm today and the current discharge is about 2,300 cfs (less than one turbine’s full release capacity). As the lake receives inflow from last night’s rain the lake elevation will increase, but will also increase the flow over the flood gates to about 5,050 cfs (almost 2 full units). That is where the Corps will keep it at as long as downstream conditions allow. I went down to Norfork a little while ago to check the water temperature and at the boat ramp at Quarry Park the temperature was about 56 degrees Fahrenheit….no problems. Before leaving the office I had checked on the lake surface temperature and was told it was in upper 50’s to low 60’s so I did not anticipate a problem. If this situation progresses into June, however, then water temperature will become more of a concern. This may require tempering flood gate releases with small releases through the sluice gates, but it will be up to the Corps. Another issue that I initially had a concern with was the potential for gas bubble trauma. This can occur with high volume releases over the tops of dams and was the cause of the fish kill that occurred on the Arkansas River earlier this year. The releases can cause dissolved gases (oxygen and especially nitrogen) to become supersaturated. This means that the gases are present in a much greater amount than what would normally be found. The fish have difficulty in ridding themselves of the excess gases and it can result in a condition similar to the bends in humans. I also checked dissolved oxygen when I was at Norfork and found it to be within acceptable limits. I saw no signs of dead or dying fish and given the relatively low volume that is anticipated, I do not foresee a problem with gas bubble trauma at this time. We will continue to monitor this situation closely and coordinate with the Corps to limit impacts to the fishery. Please let me know if you have any questions. Thanks and have a great weekend.
Jeff
Jeff Williams
Trout Program Coordinator
E: j_williams@agfc.state.ar.us | P: (870) 424-5924 | M: (870) 404 – 0503
Arkansas Game and Fish Commission
201 East 5th Street
Mountain Home, AR 72653
P: (870) 425-7577 | F: (870) 425-6596
www.agfc.com