Characterization of Flow Circulation in a Tailwater Reservoir using an Acoustic Doppler Current Profiler (ADCP) and a 1:230 Scale Physical Model

Abstract

An Acoustic Doppler Current Profiler (ADCP) was used to measure flow circulation patterns in Lake Ogallala, a tailwater reservoir of Lake McConaughy in western Nebraska. Velocity transects were gathered at four locations in a shallow (less than 3 m deep) basin of the lake. The tests indicate that despite significant flow rates through the basin, large regions of the basin are stagnant, and do not have substantial oxygen exchange with the rest of the lake. ADCP measurements were verified with an Acoustic Doppler Velocimeter (ADV) and with a dye study of the basin. After a few seconds of time averaging, ADV and ADCP measurements were within 10 percent even for water velocities as low as 10 cm/s. The dye study confirmed that the north part of the Keystone Basin of Lake Ogallala experiences limited oxygen exchange with the bulk of the water flowing through the basin – a result that can also be inferred from ADCP measurements. Results of the ADCP tests will also be used to calibrate a computer model and a 1:230 scale physical model of Lake Ogallala that is nearing completion. Finally, all test results will be used in a multifaceted study of Lake Ogallala intended to help improve Dissolved Oxygen (DO) levels for an existing recreational trout fishery.