INTEGRATED REMOTE SENSING AND GIS TECHNIQUES FOR GROUNDWATER STUDIES IN PART OF BETWA BASIN

Abstract

Groundwater is a precious resource of limited extent in hard rock areas. In order to ensure a judicious use of groundwater, proper evaluation has to be performed. A groundwater development program needs a large volume of multidisciplinary data from various sources. Integrated remote sensing and GIS can provide the appropriate platform for convergent analysis of diverse data sets and for decision making for groundwater management planning. In the present study, an integrated remote sensing and GIS based methodology has been developed and tested for the evaluation of groundwater resources of a hard rock area in a part of the Betwa basin, in the state of Madhya Pradesh, India. Two sub-basins, namely, the Kethan and the Narayan, have been studied. There are three components of this study - demarcation of groundwater potential zones, identification of artificial recharge provided by the existing reservoirs and suitability analysis for future artificial recharge sites. The area mainly comprises Deccan Trap basalt and a small part is underlain by Vindhyan rocks. Groundwater occurrence in basalt is restricted to the weathered and fractured parts. In this area, monsoon groundwater recharge can not meet the demands for groundwater throughout the year. As a result there is water scarcity in the dry season. Although artificial recharge structures at suitable locations in the area can appreciably improve the groundwater conditions, much thought has not been given to utilize this. In this work, the present status of artificial recharge has been evaluated and suitable sites for future artificial recharge structures have been suggested through integrated remote sensing and GIS technique. Three types of data have been used for the present study, namely, remote sensing data e.g. IRS-LISS-II and LISS-III data, field data e.g. depth to water level, rainfall data and the existing maps e.g. topographic, geological, soil and landuse maps. In order to bring these into a single spatial georeferencing scheme, all the data have been registered to the base map, prepared from the Survey of India topographic maps. Thematic information layers on geology, geomorphology, lineament and soil have been prepared from processed remote sensing data, supported by ancillary information. Digital elevation model (DEM) has been generated from elevation contours which provide a wealth of hydrogeologic information. Information layers on water level and rainfall have been produced through interpolation. Drainage network has been extracted from DEM, assuming the surface to be insulated. From the comparative study of the two, it is inferred that areas showing misfit between the two indicate recharge areas. These areas are the areas covered by weathered basalt, having channel fills, having high lineament density and having deeper soil. Based on information derived from integrated analysis and field checks, information layers on geology, geomorphology, lineament density, slope and soil depth have been assigned appropriate weightage. Weighted index overlay has been performed to delineate groundwater prospective zones. The result shows that channel fills hold the highest potential for groundwater. Recharge estimation also supports this. Remote sensing images of the area show that irrigation tanks are also augmenting groundwater recharge, as indicated by good growth of dry season vegetation downstream from the tanks. Tanks situated on a gentle slope provide better recharge due to the hydraulic gradient provided by the gentle slope. The weathered and fractured basalts permit a high intake of water, as well as help to maintain the required rate of recharge. Presence of yellow clay, however, hinders the flow of water. On the basis of this observation and field checks, suitable sites for artificial recharge have been suggested through a combination of Boolean logic and weighted index overlay methods. Slope has been assigned the highest weightage followed by geomorphology, lineament, geology, soil depth and depth to water level. Then, the most suitable zone from the output of weighted index method has been integrated with stream order, lineament buffer zone and landuse through Boolean logic model, and suitable sites for artificial recharge have been selected.