Planning a reservoir for conflicting demands

Pagladiya, a north bank tributary of Brahmaputra is subjected to frequent floods during monsoon. Pagladiya dam project, is, therefore, planned for controlling and mitigating flood damages, providing irrigation and hydel generation; Detailed hydrological and simulation studies have, therefore, been carried out for fixing the optimum conservation, flood control and maximum water levels. ACRES Reservoir Simulation Program (ARSP) which is a versatile computer model capable of simulating multi-purpose demands has been utilised for fixing the rule curves for conservation storage during various monsoon months. Flood routing studies have also been carried out for fixing the top of flood storage level considering various scenarios as per Bureau of Indian Standard criteria. Both the normal operating conditions and emergency conditions have been considered for fixing the MWL. The paper describes in detail the problem, the objective of the studies and the methodology. BIS criteria for fixing the top of flood control storage and maximum water level have been briefly described. Detailed methodology using various scenarios and gate operation conditions have been considered, It has been possible to develop rule curves for obtaining;extra food cushion during earlier monsoon months, while ensuring filling of reservoir by the end of monsoon using ARSP. The use of computer models has helped in examination of a number of possible alternate scenarios of various combinations of flood, reservoir level and gate operating conditions. The detailed studies thus carried out helped in economical and safe design parameters for deriving optimum benefits from the available water resources.