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Groundwater potential modelling in Chandraprabha subwatershed, U.P. using Remote Sensing, geoelectrical and GIS
Data used The followings data were used for the study :
Methodology 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 and resistivity data.  The thematic maps on hydrogeomorphology and lineaments were prepared using IRS 1B LISS-II data by visual interpretation on 1:50,000 scale.
Contour map and spot elevation map were prepared from SOI toposheets. Drainage map was prepared from SOI toposheet & satellite data. All the prepared primary input maps (hydrogeomorphology, lineament, contour & spot elevation, drainage and VES location) were digitized in Arc/Info, GIS software package and slope map was prepared from digital elevation data. Vertical electrical soundings (VES) data of 57 sites were interpreted and geoelectrical parameters of drilled sites were co-related with lithology and based on this 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.Using inferred lithology and thickness from geoelectrical parameters at respective locations, aquifer thickness and clay thickness maps were prepared through GIS. The different polygons in the thematic layers were labelled 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) very good (ii) good) (iii) moderate and (iv) poor in terms of their importance with respect to groundwater occurrence and suitable weights have been assigned. Finally thematic layers were converted in to grid of cell size 30 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. Table - 3:
 Analysis and DiscussionGeneration of thematic layers Hydrogeomorphology A 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) moderate weathered buried pediplain (BPP-M) (ii) Shallow weathered buried pediplain (BPP-S) and (iii) Dissected plateau (DPT) (fig. 2). Lineaments Lineament analysis for ground water exploration in Vindhyan formations has considerable importance as joints and fractures serve as conduits for movement of groundwater. It is not practical to map lineaments solely on the basis of satellite data without a thorough knowledge of the structural conditions in an area. For extraction of lineaments, the procedure of Moore and Waltz (1986) has been followed. In this study, lineaments derived from satellite data have been carefully matched with previously mapped structural features and a good degree of correlation between the two has been found. There are six azimuth directions (a) NE-SW (b) NW-SE (c) ENE-WSW (d) NNE-SSW (e) ESE-WNW (f) N-S (fig. 3). Drainage A surface drainage map has been prepared from SOI toposheet at 1:50,000 scale and satellite data. The study area is drained by chandraprabha river. The drainage pattern is mainly dendritic but locally exhibits structural control (fig. 4). Topography Topographic information has been collected from SOI toposheet at 1:50,000 scale and a TIN has been generated from elevation contour at 20m intervals and spot elevations. Most of the area shows more or less flat topography excepting a few parts. Elevation contour at 10m interval and slope in degree have been prepared from TIN and the same was verified by super imposing drainage. Nearly 40 percent of the of the total area shows 0-1 degree slope. Maximum slope of 9.2 degree is found in the area around Bharwagobar (fig. 5). |
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