Surface water pumps to improve dissolved oxygen content of hydropower releases

This paper describes the development, installation, and performance testing of a surface water pump system at TVA`s Douglas Dam. Surface water pumps move a large volume of highly oxygenated surface water down to a level where it is withdrawn through the hydropower intakes to improve the water quality of hydropower releases. TVA has tested several different arrangements and types of surface water pumps at Douglas Dam since 1986. Operation of the current system during 1994 has demonstrated significant dissolved oxygen improvement capabilities. Varying conditions in the forebay stratification and hydropower operations control the system effectiveness. Under average conditions the system has demonstrated a capability to increase the dissolved oxygen content of the hydropower discharge by 1.5 to 2 mg/L. Installation and operating costs of the pumps are presented along with a discussion of experiences with equipment, flotation, and mooring design.