Experiments were carried out at various reservoir water levels with specified unit operation discharges for various unit operation conditions. From the observations and experimental results, it was concluded that air-entraining vortices were forming at the intakes when the reservoir water level was minimum, RWL=977.0 m. Flow separation zones were forming; along the inner lengths of the side walls surrounding the intake structure and behind the trashrack piers at any RWL tested. In order to reduce the strengths of the vortices forming and to prevent the intakes from air-entraining vortices, in the first phase of the experimental study, several anti-vortex devices; continuous plates constructed on top of the intakes, continuous projected head walls and continuous projected head walls with vertical unit-separation walls were tested under various flow and unit operation conditions to find the anti-vortex device that gave the best performance. It was also stated that the arrangements to be made on the geometries of the side walls and trashrack piers, if possible, will improve the flow conditions at the intakes.