Groundwater potential modelling in Chandraprabha subwatershed, Uttar Pradesh- a case study in GIS development

This study on the GIS Development site attempts to select suitable locations for groundwater exploration in hard rock areas using an integrated approach of remote sensing, geoelectrical & GIS. This is because water plays a vital role in the development of any activity in the area and the availability of surface and ground water governs the process of planning & development. The surface water resources are inadequate to fulfill the water demand. Productivity through groundwater is quite high as compared to surface water, but groundwater resources have not yet been properly developed through exploration.

The study area is situated in a part of Sonebhadra, Mirzapur and Chandauli districts of UP, India, bounded by longitudes 83000’39’’ E & 830 09’28’’ E and latitudes 24043’15’’N & 24051’56’’ N falling in SOI toposheet no. 63 P/1 & P/2. Geologically the area comprises of upper Vindhyan formations consisting of sandstone, quartzite and shale (CGWB 1985). Hydrogeomorphological and lineament maps have been prepared using IRS 1B LISS-II data by visual interpretation.

Topographic information has been collected from SOI toposheet at 1:50000 scale & TIN has been generated from elevation contour at 20m interval and spot elevation. A 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 BPP-S, BPP-M and DPT category. The drainage pattern is mainly dendritic, but locally exhibits structural control.

Vertical electrical soundings (VES) were conducted at 57 sites in the study area for identifying horizontal & vertical variation in subsurface lithology and depth to the hard rock. The geoelectrical data of layer parameters was correlated with the lithological data obtained from 16 drilled sites in the study area.

The study revealed that the aquifer thickness varied between 2 m to 39 m, clay thickness 1 m to 46 m and depth to the hard rock 4 m to 66 m below ground surface. Discharge of drilled sites varied between 135 lpm to 640 lpm. The resistivity of clay, clay kankar varied between 4 ohm-m to 23 ohm-m. Aquifer resistivity ranged from 30 ohm-m to 110 ohm-m. Using the geoelectrical data, clay thickness & aquifer thickness maps were prepared through GIS technique.

The groundwater potentiality of the area was assessed through integration of the relevant layers, which included hydrogeomorphology, lineament, slope, aquifer thickness and clay thickness, in Arc/Info grid environment. Criteria for GIS analysis was defined on the basis of groundwater conditions and appropriate weightage was assigned to each information layer according to relative
contribution towards the desired output.

The groundwater potential zones map generated through this model were 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 were in agreement with the bore well yield data. Thus, the above study clearly demonstrated the capabilities of remote sensing, geoelectrical and GIS technique in demarcation of the different groundwater potential zones.

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