Here are the main point concerning the geology and the hydro-geology tectonics of the area.
On the basement we have a fractured crystalline rock and in north-east/south-west, north-west/south-east, north-south directions striking joints in the granite basement. We have very high permeability in the recent alluvional sediment aquifer. We scrabbled sand and silt along the Nakkavagu river and some tributaries. Under its main aquifer we found highly to semi-weathered granite covering between 5 and 20 meters.
The alluvial is decreasing upstream to Nakkavagu and the ground water flow direction is generally directed from east to the west. Within the hard rock areas the ground water flow direction follows topography. Another important thing is that you can find influent ground water flow upstream and effluent ground water flow nature downstream of Nakkavagu river.