Aquifer parameter identification and interpretation with different analytical methods

Abstract

Aquifer tests yield estimations of hydrogeological parameters through suitable analytical models from field data recorded as drawdown variations by time or distance. In practice, most often a single model is adopted with a set of assumptions, and unfortunately, field data deviations from the model type curves are not considered in interpretations. The is a rather mechanistic approach which implies assumptions that the aquifers is geologically homogeneous and isotropic. Such an approach cannot be true because within the aquifer test area there may appear heterogeneities and anisotropies which hinder the application of a single model. It is, therefore, necessary to try several available models for the same aquifer test data, in order to extract possible variabilities in hydrological parameters. Such an extensive study can only be done when there is a set of aquifer test data with main and observation wells at different distances and directions. This paper present an analysis of an aquifer test in a thick alluvial valley in Pakistan. The aquifer consists of extremely heterogeneous sediments. Different approaches including the Theis, Jacob, Hantush, and Singh analytical models, are used to analyse the drawdown data from several observation wells.