In this study on the GIS Development site, an attempt has been made to use remote sensing, geographical information system (GIS) and multi-criteria analysis of decision support for evaluation of groundwater in watersheds of Rawasen and Pili rivers, which are the tributaries of Ganga.
Groundwater is one of the prime sources of fresh water. Its exploration and evaluation depends on various methods and criteria, geology, geomorphology, slope etc. are the governing factors for the development of groundwater regime. The information on the above was acquired and integrated through these various techniques.
The main factors responsible for groundwater resource development are geology, geomorphology, landuse/landcover, slope, lineaments etc. Geologically the area is characterised by distinct rock types showing structural and stratigraphic controls. These rocks are quartzites, phyllites and schists of Garhwal and Tal group, red shales of Subathus, sandstone and shales of Siwaliks and Recent Alluviums. Alluviums, middle and Upper Siwalik sandstone and Garhwal quartzites are supporting good groundwater regime.
Geomorphology is one of the main controlling factor of groundwater. Genetically the landforms of the study area were divided in three parts i.e. Fluvial origin, Denudational origin and Structural origin (Fig. 2). The landforms such as flood plain, alluvial fan, fan terrace are supporting good groundwater condition. The landuse refers to the main activities and human intervention and are carried on land. Two level of classification was done in area by visual interpretation of satellite data of two seasons i.e. April and November. The maximum area was occupied by dense forest followed by agricultural land.
Slope map is generated from the contours and spot heights taken from the SOI toposheet consist of five classes from gentle to very steep slope. Gentle, moderately gentle and moderate slopes are supporting favourable conditions. The drainage system of an area gives important clues of the subsurface conditions, which helps in deciphering groundwater conditions of that area. The common drainage patterns observed in the study area are parallel to sub-parallel and dendritic. Parallel to sub-parallel pattern is dominant in siwalik group of rocks, whereas in garhwal group of rocks mainly dendritic to sub-dendritic pattern is found (Fig. 5). Water divide zones were delineated with the help of drainage map because they are the zones where no percolation of water takes place and are not suitable for groundwater storage (Fig. 6).
Lineament plays vital role in the development of groundwater regime. Lineaments were mapped from aerial photographs and satellite images. IRS LISS III-B AND 3 digital data is also used to delineate the lineaments by applying - 5 x 5 predefined directional filter. Which has enhanced the edge and helped in updating the lineament map. These lineaments were classified in four classes i.e. major, minor, fault and thrust depending upon their nature and extent. Fault and thrust were not considered in the study because of non-availability of any ground data to assess their behaviour. Major and minor lineaments were considered in study and buffer zones of 75m and 150m for major and 50 m and 100 m for minor lineaments are taken for study.