Evaluation of Aquifers in Deccan Basalts of Nanded District

Abstract

Deccan basalts of south-east Maharashtra, though homogenous, are newlinehydrogeologically inhomogeneous rocks. A proper understanding of the physical newlineframework of the basalts within which groundwater resides and moves is a key to the newlinehydrogeology of these rocks. Two types of basalt, the vesicular amygdaloidal basalt and newlinethe compact basalt, occur as alternate layers in the volcanic pile. Although the rocks are newlinegenerally inhomogeneous, structures in the basalt, such as joints and fractures, serve as newlinezones of groundwater flow. Deccan basalts behaves in an erratic manner as far as newlineoccurrence of groundwater is concerned. The aggregate porosities of weathered basalts, newlinevesicular basalts and fractured-jointed basalts must be determined. newlineIn order to study the potential of the Deccan basalts as aquifers, the properties of newlinetransmissivity and storativity must be considered. Nature of confined and unconfined newlineaquifers must also be considered. A relationship between porosity and specific yield must newlinealso be determined. It is important to find out whether in relation to aggregate porosity newlinethe specific yield is low or not. This might suggest that in Deccan basalts effective newlineporosity constitutes only a small fraction of aggregate porosity or not. It is also important newlineto find out whether the weathered basalts and vesicular basalts have higher newlinetransmissivities than fractured-jointed basalt and, therefore, form better aquifers or not. It newlineis also important to find out the variation in transmissivity values in various directions, newlineand from point to point, this might indicate whether the Deccan basalts are newlinehydrogeologically anisotropic and heterogeneous in nature or not. newlineIn the Nanded region, generally, three groundwater systems are operative. a) newlineGroundwater system consists of a vesicular amygdaloidal basalt underlain by a compact newlinebasalt and b) groundwater system consists of a vesicular amygdaloidal basalt overlain by newlinea compact basalt c) weathered granite / granite overlain by basalt newlineIn this regard it will be interesting to find out whether Grou