Use of GA to Determine Areas of Accretionto Semiconfined Aquifer

The goal of any groundwater inverse problem is to identify the distribution of an input function or certain other variables describing the unique flow dynamics of an aquifer system. A genetic algorithm (GA) combined with a numerical modeling technique is useful in determining both the spatial distribution and the flux represented by the accretion component of the groundwater flow equation. The GA technique was compared to a modified Gauss-Newton iterative technique. Binary and hexadecimal representations provided mapping of parameters from genetic operators to the numerical model. The technique used the patterns that developed in the string representations to determine probability regions. Two synthetic test cases were used to test the effectiveness of the technique. The stability of the technique was evaluated by introducing random error into the observation data. The technique was capable of locating the accretion area and tended to converge to a flux most representative of the flux entering the aquifer. However, the technique was susceptible to typical problems affecting the inverse problem, such as nonuniqueness.