Groundwater targeting in a hard-rock terrain using fracture-pattern modeling, Niva River basin, Andhra Pradesh, India

In hard-rock terrain, due to the lack of primary porosity in the bedrock, j oints, fault zones, and weathered zones are the sources for groundwater occ urrence and movement. To study the groundwater potential in the hard-rock t errain and drought-prone area in the Niva River basin, southern Andhra Prad esh state. India, Landsat 5 photographic data were used to prepare an integ rated hydrogeomorphology map. Larsson's integrated deformation model was ap plied to identify the various fracture systems, to pinpoint those younger t ensile fracture sets that are the main groundwater reservoirs, and to under stand the importance of fracture density in groundwater prospecting. N35 de grees -55 degreesE fractures were identified as tensile and N35 degrees -55 degreesW fractures as both tensile and shear in the study area. Apparently , these fractures are the youngest open fractures. Wherever N35 degrees -55 degreesE and N35 degrees -55 degreesW fracture densities are high, weather ed-zone thickness is greater, water-table fluctuations are small, and well yields are high. Groundwater-potential zones were delineated and classified as very good, good to very good, moderate to good, and poor.