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Authors
Affiliations
1 Ground Water Department, Government of Andhra Pradesh, Hyderabad, IN
2 Department of Geology, Nanakram Bhagwandas Science College, Charkaman, Hyderabad-500002, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 49, No 1 (1997), Pagination: 61-74
Abstract
Ground water in study area underlain by peninsular Gneissic complex occurs in unconfined conditions in weathered zones and semi-confined to confined conditions in fractured zones. Productive fractured zones define narrow linear tracts closely corresponding to surface drainage. Fluoride content of ground water is low mostly in topographic highs and to lesser extent in tank beds or tank commands and in areas where fractures are not connected with fluoride bearing granites. For potability, most wells were drilled in topographic highs and some around tanks.
The aquifer is highly complex (anisotropic and heterogeneous) needing critical analysis to assess performance of wells, as recently yields of a large number of borewells drilled in granitic terrains of Andhra Pradesh are reported to have declined. This is attributed mostly to direct interference with other wells, improper construction of wells leading to silting and general decline in water levels due to various reasons. But rarely, it is realised that these aquifers are laterally limited. In this study pumping tests for 500 to 1000 minutes i.e., 2 1/2 to 3 log cycles of time were carried out and the data was analysed using graphical methods of Cooper and Jacob and Theis recovery method. [n four cases the test data was analysed by a micro processor based simulation technique. Optimum discharges were calculated keeping in view the effects of 'no-flow' boundaries, effective available drawdown and other field parameters. This has indicated that the optimum discharges of the wells are in· general between 60% to 80% of the yields recorded during drillng.
Keywords
Hydrogeology, Granite-Terrain, Nalgonda Dt., A.P.
