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Narasimha Reddy, T.
- Groundwater Recharge Process Model in a Granitic Terrain - A Long Term Analysis
Authors
1 Groundwater Department, Andhra Pradesh, BRKR Govt. Offices Complex, Hyderabad-500 029, IN
2 National Geophysical Research Institute, Hyderabad-500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 44, No 6 (1994), Pagination: 645-662Abstract
Dulapally watershed in granitic terrain covers about 34 sq. km lying north of Hyderabad City in semi-arid tropics. Groundwater recharge has been estimated considering the soil-plant and agroclimatological conditions from daily rainfall and pan evoporation data during 1974 to 1990. The average annual recharge over 16 years worked out to be 124 mm. The temporal variation of the recharge estimates have been validated through simulation of well hydrographs in a nested squares finite difference aquifer model by feeding them as temporal input during transient condition.Keywords
Hydrogeology, Groundwater, Aquifer, Granitic Terrain, Andhra Pradesh.- Hydrogeological Conditions and Optimum well Discharges in Granitic Terrain in Parts of Nalgonda District, Andhra Pradesh, India
Authors
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: 61-74Abstract
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 inĀ· general between 60% to 80% of the yields recorded during drillng.