This paper uses an integrated approach of Remote Sensing, Geophysics and GIS to evaluate groundwater potentiality of Ojhala subwatershed in Mirzapur district of Uttar Pradesh. It is the study of area under hard rock formations in Mirzapur district of Uttar Pradesh which faces acute water scarcity problem both for irrigation as well as drinking purposes. Occurrences of groundwater in this type of area are confined in secondary permeable structures i.e. fractured and weathered horizons and in upper unconsolidated materials. The traditional methods of searching sites for drilling of bore hole, have not only had a poor success rate but even the places where such efforts have succeeded, the borewells are known to have dried up in a short period of time.
Groundwater constitutes an important source of water for various purposes like domestic needs, supply for industries and for agriculture etc. The conventional approaches for groundwater investigation are ground based surveys and exploratory drilling which are time consuming and uneconomical. Keeping this in view, the present study attempts to demarcate groundwater potential zones in hard rock areas using an integrated approach of remote sensing, geophysics and GIS.
Hydrogeomorphological and lineament maps have been prepared using IRS 1C LISS-III data by visual interpretation. Topographic information has been collected from SOI toposheet at 1:50,000 scale & TIN has been generated from elevation contour at 20m interval and spot elevation. Slope map has been prepared from TIN. Surface drainage map has also been prepared from SOI toposheet and satellite data on 1:50,000 scale. Hydrogeomorphologically, the entire area comes under valley fill (VF), moderately weathered buried pediplain (BPP-M), shallow weathered buried pediplain (BPP-S), ravine (RA), pediment on plateau P (PT) and dissected plateau (DPT) categories.
The drainage pattern is mainly dendritic but locally exhibits structural controlled. Surface electrical resistivity surveys were conducted at 68 sites to get subsurface lithological information, identification of horizontal and vertical disposition of aquifer system and for pin pointing of suitable drilling sites. The geoelectrical layer parameters of drilled sites were correlated with the lithological data to infer the subsurface lithology at other sounding locations. With geoelectrical and drilling data, overburden thickness and aquifer layer thickness maps have been prepared through GIS techniques.
To find out the more realistic ground water potentiality map of the area, the relevant layers which include hydrogeomorphology, lineament, slope, drainage, overburden thickness and aquifer thickness were integrated in Arc/Info grid environment. Criteria for GIS analysis have been defined on the basis of ground water conditions and appropriate weightage has been assigned to each information layer according to relative contribution towards the desired output.
The ground water potential zone map generated through this model was verified with the yield data to ascertain the validity of the model developed. The verification showed that the ground water potential zones demarcated through the model are in agreement with the bore well yield data. Since the present approach was built with logical conditions and reasoning, this approach can be successfully used elsewhere with appropriate modifications.