A MODEL FOR MANAGING GROUNDWATER WITHDRAWAL

An optimization model has been developed to simulate optimum values of withdrawal from a given aquifer system, based on the constraint that the groundwater table does not decline beyond a limit, in order to avoid overdrawing. The model generates a time-history based optimal strategy of groundwaler withdrawal for time-varying boundary conditions. The model was applied lo an unconfined aquifer to simulate optimal values of the groundwater withdrawal for historic recharge inputs. Groundwater storage available for withdrawal is dependent on the historic recharge inputs and the boundary conditions. The higher values of river water level than groundwater level will cause flow from river to aquifer. Similarly, the gradient of groundwater table causing lateral flow to the aquifer also increases the groundwater storage available for withdrawal. The model results show lhal lhe lateral inflow to lhe aquifer through lhe headcontrolled and gradient-specified boundary allows a high amount of groundwater withdrawal throughout lhe pumping period. The simulation results, due to the boundary conditions, historic recharge inputs, and restriction imposed on lhe groundwater level variation in the aquifer, can be used to design for lhe sustained availability of groundwater by tubewells (pumping wells) throughout the pumping period.