The Deccan Basalts of Maharashtra, India —Their Potential as Aquifers

Abstract

ABSTRACT In order to study the potential of the Deccan basalts as aquifers, the properties of transmissivity and storativity must be considered. Analysis of large‐diameter dug wells tapping unconfined aquifers in the Deccan basalts shows that there exists a relationship between porosity and specific yield. The aggregate porosities of weathered basalts, vesicular basalts and fractured‐jointed basalts are respectively up to 34%, 50%, and 15%. On the contrary, specific yield has a maximum value of 7%, 4%, and 1% respectively. In relation to aggregate porosity the specific yield is low suggesting that in Deccan basalts effective porosity constitutes only a small fraction of aggregate porosity. It is found that this effective porosity is about 7%. The weathered basalts and vesicular basalts have higher transmissivities than fractured‐jointed basalt and, therefore, form better aquifers. The variation in transmissivity values in various directions, and from point to point, indicates that the Deccan basalts are hydrogeologically anisotropic and heterogeneous in nature.