MODELING GROUND WATER RECHARGE IN PARTS OF ARAVALLI
-AN INTEGRATED APPROACH

Chandrashekhar Bhuiyan
Ph.D. Student (since 1998)

Groundwater is not only an important component of the hydrological cycle but also the most important  source of water for drinking, domestic, industrial and agricultural uses. In a densely populated country like India, ground water resource is of  extreme importance. In many places of the world including India, this indispensable resource is under stress due to continuous failure of monsoon and excessive extraction and use. To overcome the problem, proper assessment and management of ground water is essential. To understand the ground water condition of an area, various models have been proposed and evolved by various  hydrologists, yet the problem still persists, more correctly the problem has become more acute in many areas resulting severe draught. The situation is worse and more complex in the hard rock terrain where exploration of ground water is more difficult.  The present work aims to understand the ground water scenario from the geological point of view as geology of the area concerned is the main control of ground water recharge, and potentiality.  In a hard rock terrain, where primary porosity is negligible, the accumulation and     flow of ground water is a function of the density, orientation length, width and intersection of fractures and joints. The other important parameters controlling and influencing the occurrence and movement of ground water are – landforms, land use/cover, slope, altitude, vegetation and lithology beside the meteorological parameters. Assessment of ground water resources of an area requires proper identification and mapping of geological structures, geomorphic features     along with sound information regarding slope, drainage, lithology, soil as well as thickness of the weathered zones.

Amongst the latest available technologies, the remote sensing technique has acquired the supreme position over the conventional methods in studying the hydrogeology due to its synoptic view, repetitive coverage, high ratio of benefit to cost and availability of data in different wavelength ranges of the electromagnetic spectrum. Through digital image processing of the remotely sensed satellite images, the controlling features of ground water can be identified accurately and thus the terrain can be classified properly in terms of ground water potentiality and prosperity. Geographic Information System (GIS) has been found to be one of the most powerful techniques in assessing the suitability of land based on the spatial variability of hydrogeological parameters. GIS offers many tools to extract the information about the ground water prospect of an area by integrating information regarding  geologic structures, geomorphology, soil, lithology, drainage, land use, vegetation etc.

Rajasthan, the second largest state of India, situating in the N-W part of the country is largely an arid state for most of its part. Due to scarcity of surface water Rajasthan is dependent on ground water resources to a great extent. In the mountainous hard rock terrain of Aravalli, ground water is the only source of water.Inadequate rainfall and over exploitation causes depletion of ground water table resulting draught in most  part of it during summer. The objective of this work is to understand the  hdrogeology of the terrain and its influence in ground water recharge and then to develop an appropriate ground water recharge -forecast model. With the help of remote sensing and GIS it is possible to determine the relative importance of the different hydrogeological parameters in controlling the ground water recharge. Then with the help of GIS based statistical operations it is possible to generate an accurate geo-statistical model of ground water recharge, for the terrain. Using the available water table fluctuation data, through correlation and regression analysis, it is possible to test the validity and accuracy of the model generated. An accurate ground water recharge model is of extreme importance for assessment of ground water resources and thus to develop a suitable ground water management scheme.