Anil Lalwani’s research while affiliated with Savitribai Phule Pune University and other places

Deccan basalts of west-central India are hydrogeologically inhomogeneous rocks. A proper understanding of the physical framework of the basalts within which groundwater resides and moves is a key to the hydrogeology of these rocks, Two types of basalt, the vesicular amygdaloidal basalt and the compact basalt, occur as alternate layers in the volcanic pile. Although the rocks are generally inhomogeneous, structures in the basalt, such as sheet joints and vertical joints, serve as zones of groundwater flow. In the shallow subsurface, two groundwater systems are operative. Groundwater system A consists of a vesicular amygdaloidal basalt underlain by a compact basalt, whereas groundwater system B consists of a vesicular amygdaloidal basalt overlain by a compact basalt. Groundwater system A has a better developed network of openings and, as a consequence, this system has a higher transmissivity and storage coefficient than groundwater system B. Wells tapping groundwater system A have higher yields on average and irrigate more hectares of cropland than do wells tapping groundwater system B. This simple systems concept offers a practical methodology for understanding the geometry of the physical framework that contains groundwater in the Deccan basalts. The efficacy of the concept is in its widespread utility for the region. The concept may also be extrapolated to help understand the hydrogeology of deeper Deccan basalt groundwater systems.

In India, groundwater resources from the hard-rock regions in general and from the Deccan Volcanic Province in particular are being obtained from 115-mm, 152-mm and 165-mm diameter bore holes (commonly known as bore wells). With no definite criteria for pump selection, these bore wells are either overdeveloped or underutilized, and the groundwater resources are thereby being mismanaged. PUMPS is a computer program that helps select a proper pumping system on a bore well in the Deccan basalt, taking into account the productivity of the bore well and considering a stabilized drawdown above the main aquifer tapped by the bore well. This method of pump selection has yielded encouraging results and all the bore wells with pumping systems installed using PUMPS have proven to be effective in providing the required yields without overstressing the aquifers.

Water resources in most towns and cities of India will need to be largely augmented during the next few years so as to meet the growing demand stemming from burgeoning populations and urbanisation. Haphazard groundwater abstraction from many cities as a result of urbanisation is a common phenomenon. The effects, though not very clearly evident today, are not difficult to visualise. Groundwater use in most Indian cities under the present scenario is on an individualistic basis and can be looked upon only in the sense of an abuse of a valuable fragile resource. However, groundwater, if harnessed and managed systematically, can provide a viable option to compliment existing municipal supplies of water. Certain important inputs through a systematic management-oriented methodology are necessary to view groundwater as a useful compliment to existing urban water supplies in India.

DUGREC is a computer program to estimate hydraulic conductivities for the Deccan basalts of India. Large-diameter dugwells are still a very common source of water supply in the Deccan basaltic region of west-central India. It is easier to conduct accurate recovery tests rather than conventional pumping tests on large-diameter dugwells in the Deccan basalts of India. DUGREC is a program written in BASICA for IBM PC microcomputers and compatibles to calculate hydraulic conductivity values for the shallow unconfined Deccan basaltic aquifers using dugwell recovery data.