The Environmental Effect Of Low-Head Impoundment Structures With Bottom Water Overflows On Trout Streams In The Southern Appalachians

A study was made by the USDA, Soil Conservation Service in cooperation with the Georgia Game and Fish Commission and the USDA, Forest Service in the summer months of the years 1964-67. The purpose was to determine the extent of thermal pollution in the tailwater and the effect of this pollution on rainbow trout. The study was made at a single-purpose, Public Law 566 floodwater-retarding structure on Hall Creek, which is a tributary of Hightower Creek in Towns County, Georgia. The conservation pool has 4.3 surface acres and is 17.5 feet deep. Normal streamflow is discharged through a bottom water overflow that extends down from the pool surface 10 feet. The structure contains 27 acre feet of stored water in the conservation pool; inflow is approximately 2.5 efs at low flow during summer droughts and normal inflow is 5.7 cfs. The structure is located at 2,228 feet above mean sea level. The instruments used in the study were two single-pen 7-day, clock-wound instruments and one double-pen 7-day, clock-wound instrument for taking both water and air temperature. The single-pen instrument locations were 1,200 feet above the structure on the main stream and 2,700 feet below the structure for recording water temperature. The double-pen instrument was located immediately below the structure to record both air and water temperatures. Tailwater temperatures varied from above structure water temperatures by as much as 9°F. The normal rise was 2° to 4°, with a random sample average of 3.00 F. This paper presents the findings of a 4-year 1964-67 cooperative study of the effects a single-purpose floodwater retarding structure with a deep water overflow has upon a marginal trout stream when it has the limitations presented. The study was made by the USDA Soil Conservation Service in cooperation with the Georgia Game and Fish Commission and the USDA Forest Service. The study was made on Hall Creek, a tributary of Hightower Creek, a feeder stream of TVA Lake Chatuge in Towns County, Georgia. Hall Creek watershed contains 1,314 acres with 1,280 acres in mixed hardwood - pine woodland. The remaining 34 acres is idle land formerly used for pastureland or cropland, which is reverting to woodland. Approximately 1,000 acres of the watershed is in the Chattahoochee National Forest administered by the United States Forest Service. The study structure site is 2,228 feet above mean sea level. The streamflow ranges from 2.5 cubic feet per second during dry periods to a normal flow of 5.7 cubic feet per second during most of the year. Much higher flows occur during and immediately after rains.

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