Remote Sensing and GIS Approach for Delineating and characterization of Groundwater Potential Zones in Hard Rock Terrain3. PHYSIOGRPHY  Figure 1 A greater part of the Giri catchment lies in the middle Himalaya and Siwaliks and is hilly with deep and narrow valleys separated by spurs and ridges. The Giri River originates at the altitude of 3,358m at Kupar Tibba on Kupar Dhar dividing Giri and Ton River watersheds in Shimla district and it meets the Yamuna river at the altitude of 438m at Rampur Ghat. Sixty four percent of the Giri catchment area falls under high altitude hills from 1500m to 3000m. The area under mid altitude hills ranges from 1000m - 1500m and low altitude hills less than 1000m are 30 and 5 percent respectively. Almost the whole catchment contains steep to very steep slopes. 4. CLIMATE Climate, varying with altitude, is sub-humid and subtropical in lower part of the track lying in the Siwaliks to wet temperate in the upper part in central Himalaya. The precipitation of the catchment varied from 824 mm at Kotkhai to 1,933 mm at Sarahan The mean precipitation of the catchment is 1,287mm (TABLE 1). A bulk of the precipitation occurs in monsoon season from June to September. Winter rains occur from December to March. The snow fall is a normal feature in areas above 1,800m. The droughts occur both in pre and post monsoon periods with March, April, May, October and November being generally dry months. The region has distinct seasons of summer (April-June), monsoon (July-September), autumn (October-November) and winter (December-March). Summers are hot in the Siwaliks with temperature rising to about 420C, while winters are cool. TABLE 1 - Precipitation data around the Giri Cathment (in mm)
5. DATA USED IRS LISS III and PAN images, LANDAST 7 ETM and PAN images, STRM DEM data, Survey of India Arial photographs and Topo sheets, Rupke Geology Map and Rain fall data provided by Regional Research Station of Himachal Pradash Agricultural University, Dheulakunan were used to generate various thematic maps for this study. 6. METHODOLOGY The study was carried out in several stages. Lithological boundaries, structure and geomorphic features were delineated from aerial photographs on the scale of 1:25,000 by stereoscopic analysis. Arial photographs and enhanced satellite data were interpreted by visual interpretation. Based on differences in dissection patterns and tonal variations, the lithological boundaries, as well as major geomorphic features were demarcated. Thereafter, thematic layers for geology, geomorphology, lineament and structure, drainage, slope, aspect etc. were generated. Occurrence of groundwater is related to subsurface conditions which requires very complex analysis; subsurface features are dependent on geology and landforms in the area Therefore, it is necessary to integrate different surface as well as subsurface features in order to acquire comprehensive knowledge on groundwater prospects of an area. In order to demarcate the groundwater potential zones the above thematic layers were integrated in the GIS environment. The different ranking and weightages were given for each thematic layer and their parameter respectively (TABLE 2). |