Abstract
A finite element model of transient groundwater flow is coupled with genetic algorithm to solve the problem of determining an optimal aquifer yield. The model is applied to a shallow depleted leaky phreatic aquifer of Comilla region, Bangladesh. The amount of leakage is also predicted by this model. The whole study area is sub-divided into six small regions to get distributed optimal discharge and leakage for a droughty period. The model suggests that the present pattern of discharge ranges from 31.6 to 131.0 mm in different sub-areas, and that the optimal pattern of discharge ranges between 44.8 mm and 113.1 mm. Only 9.2 percent of overall cut-off of water withdrawal from the present level of utilization with some modified water use pattern from each sub-area could effectively solve the problem of water levels going below the suction limits which make suction lift pumps inoperative. According to the model, the amount of leakage of six months in different sub-areas ranges from (+) 30.6 to (-) 37.6 mm which has very significant role in controlling the discharge pattern. The estimated irrigation water requirement from the upper leaky phreatic aquifer is 207.2 mm, while the present level of discharge, obtained by the model, is 406.6 mm. This indicates that 96.2 percent higher water is being withdrawn from the upper aquifer with serious water management problems. The results show that the methodology employed is very effective and efficient to obtain global optimal solution to the problem.
