GROUNDWATER FLOWS IN HETEROGENEOUS SEMI-CONFINED AQUIFERS

It is widely recognized that geological formation heterogeneity plays an important role in groundwater flows. The objective of this study is to evaluate how the coupled effects of the leakage and the inherent spatial variability of the hydraulic conductivity influence groundwater flows in heterogeneous formations. To explore the effects of the leakage factor and the variability of the hydraulic conductivity field, the spectrally based stochastic continuum approach is chosen in which the random functions such as the hydraulic conductivity and the hydraulic head are expressed using the spectral representation technique. Perturbed forms of the flow equation can be solved for the spectrum of the head or flow in terms of the spectrum of the hydraulic conductivity field. The expression for the hydraulic head covariance is derived for the two-dimensional flow in a semiconfined aquifer which is bounded by a leaky layer above and an impervious stratum below. The head covariance functions are studied using two convenient forms of the logarithmic hydraulic conductivity process. The results demonstrate the significant reduction in the head variances and covariances due to the presence of a leaky layer. The hydraulic head correlation distance is also reduced greatly due to the presence of the leaky layer.