Yield characteristics of fractured aquifers and their relation to lineaments in Precambrian crystalline rocks of Bharathapuzha river basin, Kerala

Data collected from bore wells drilled by Central Ground Water Board in Bharathapuzha river basin in Kerala have been analyzed to understand the spatial distribution of yields in Precambrian crystalline rock aquifers and their possible relation to lineaments in the area. Bore wells show wide variation in yields in both charnockites and migmatites. Bore wells in the depth range of 50 to 100 m are most productive in the area and drilling of wells below 150 m may not be economical due to the dying out of fractures at depth. Bore well yields showed a decrease with increasing distances from lineaments in the area. Analysis of the yield data of bore wells with respect to the lineament orientations indicated that bore wells drilled along N-S and SE-NW lineaments are the most productive, whereas those located along NNE-SSW and ESE-WNW lineaments are the least productive. Yields of bore wells, in general, are found to be influenced by the ruptural deformations in the geologic past, with the high yielding wells lying mostly on the lineaments along the directions of compression.