Abstract
Aquifers in sedimentary basins provide a regional domain for the spatial variabilities in geologic, hydrologic, geomorphologic and hydrochemical phenomena. Their study should account for this spatial variability within the study area prior to any formal modelling. The classical semivariogram models are not capable of accounting for the spatial variability of the Wasia aquifer. A cumulative semivariogram scheme is adopted for spatial variability, which is then incorporated with the kriging technique to provide maps of regional variation concerning variables such as storativity, transmissivity, piezometric levels, total dissolved solids and groundwater flow velocity. Comparison between the cumulative and classical semivariograms are given on the basis of hydrogeologic variables observed in the field. The cumulative semivariogram models for the Wasia aquifer are of the Gaussian type except that of porosity, which has a linear model. The sample cumulative semivariograms are non-decreasing functions of distance and they have every objective advantage of the classical semivariograms. In general, the cumulative semivariogram modelling of the spatial variability is more effective and yields realistic regional variables. (Author 's abstract)