Methodolgy
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In order to demarcate the groundwater potential zones of study area different thematic maps on 1:50,000 scale were prepared from remote sensing data, topographic maps, depth to the water level data and resistivity data.
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The thematic maps on hydrogeomorphology and lineaments were prepared using IRS 1C LISS-III data by visual interpretation on 1:50,000 scale.
Drainage map was prepared from SOI toposheet & satellite data.
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Contour map and spot elevation map were prepared from SOI toposheets.
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All primary input maps (hydrogeomorphology, lineament, contour & spot elevation, drainage, well location and geo-electrical sounding location) were digitized in Arc/Info, GIS software package and slope map was prepared from digital elevation data.
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Depth to water level (pre & post monsoon) and annual water level fluctuation maps prepared through GIS.
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Interpretation of geo-electrical soundings data of 77 sites.
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Correlation of geoelectrical parameters of drilled sites with lithology.
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Based on above co-relation lithology was inferred at other sounding locations for identifying horizontal and vertical variation in subsurface lithology and estimating depth to the hard rock.
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Using inferred lithology and thickness from geoelectrical parameters at respective locations; aquifer layer thickness and overburden thickness maps were prepared through GIS.
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The different polygons in the thematic layers were labeled separately and then they were registered. In the final thematic layer initially each one of the polygons were qualitatively visualized into one of the categories like (i) excellent (ii) very good (iii) good (iv) moderate and (v) poor in terms of their importance with respect to groundwater occurrence and suitable weights have been assigned.
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Finally thematic layers were converted in to grid with related item weight and then integrated and analysed, using weighted aggregation method. The grids in the integrated layer were grouped into different ground water potential zones by a suitable logical reasoning and conditioning. The final ground water potential zone map thus generated was verified with the yield data to ascertain the validity of the model developed.
Analysis and Discussion
Generation of Thematic Layers
Hydrogeomorphology, Lineament & Drainage:
Hydrogeomorphological map was prepared from remotely sensed data. On the basis of specific relief and characteristic nature, the hydrogeomorphological features, present in study area were classified into (i) flood plain, (ii) alluvial plain, (iii) palaeochannels, (iv) Moderate weathered buried Pediplain (BPP-M), (v) Shallow weathered buried Pediplain (BPP-S), (vi) Ravines (RA) and (vii) Dissected plateau (DPT) (Fig. 2).
Structural lineaments delineated from satellite image were cross- verified in the field. They are NE-SW, NW-SE, ENE-WSW, NNE-SSW, E-W, N-S, NNW-SSE (Fig. 3).