Hydromorphogeological investigations in a typical khondalitic terrain using remote sensing data

In order to examine the influence of tectonic and morphological characteristics on the occurrence and movement of ground water in Khondalitic (garnetiferrous sillimanite gneiss) suite of rocks, hydromorphogeological studies were carried out in a typical Khondalitic terrain situated in Viziangaram district of Andhra Pradesh, India. Different land forms have been identified with the aid of visual interpretation of Landsat imagery together with ground truth data in order to prepare hydromorphogeological and lineament maps. Drainage map and topographic slope map have been prepared using toposheets. These maps and other collateral data like well yields and geophysical data have been analysed to evaluate the ground water prospective geomorphic units. Ground water prospect areas are located in shallow buried pediplains and wash plains in such a way that they are identified on gently sloping uplands situated between the lineaments. Non potential areas are those, which are, low-lying areas near the streams and high slope areas near the residual hills. It is found near low lying areas i.e., beneath the streams that the khondalite must have transformed itself into kaoline and acting as barrier evidently preventing lateral movement of ground water forcing it to accumulate in flat upland areas between two streams or lineaments. From the lithologic cross sections it is found that there are four distinct subsurface layers namely (1) top soil, (2) highly weathered khondalite (kaolinised layer), (3) moderately weathered and fractured khondalite (aquifer layer) and (4) basement of granitic gneiss.