Hydrogeologic framework of the Deccan terrain of the Koyna River basin, India |
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Authors: | Pradeep K Naik Arun K Awasthi A Anand Prakash C Mohan |
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Institution: | (1) Central Ground Water Board, Central Region, N.S. Building, Civil Lines, Nagpur-400001, India,;(2) Department of Earth Sciences, University of Roorkee, Roorkee-247667, India,;(3) Present address: Department of Environmental Science and Engineering, Oregon Graduate Institute of Science and Technology, 20000 NW Walker Road, Beaverton, Oregon 97006, USA, e-mail: pnaik@ese.ogi.edu, Fax: +1-503690-1273, |
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Abstract: | The Koyna River basin in India drew the attention of geoscientists after an earthquake (magnitude 7) in 1967. Since then,
detailed geological, tectonic, and seismic investigations of this river basin have been carried out by several workers. However,
very little study has been done on its hydrogeological framework. The present work aims at filling this gap. Basalts, laterites,
alluvium, soils, and talus deposits form shallow unconfined aquifers, with transmissivity of 27–135 m2/d and a regional specific yield of 0.012. In shallow basaltic aquifers, the lower part of the highly weathered and highly
jointed horizon above, and the poorly weathered and highly jointed horizon below, form the most potential zone for groundwater
occurrence. Well yields in the deeper basaltic aquifers are directly related to the occurrence of lineaments, whereas at a
shallower level they are related to geomorphic features. Spring discharges are highly dependent on their source aquifers and
areas of recharge. They have a mean winter discharge of 46 m3/d and a summer discharge of 28 m3/d.
Chemically, groundwaters are dominated by alkaline earths (Ca2+, Mg2+) and weak acids (HCO3
–, CO3
–); they are calcium-bicarbonate type (53%) and calcium-magnesium-bicarbonate type (27%) at shallower levels; and calcium-magnesium-bicarbonate
type (29%), sodium-bicarbonate type (24%), calcium-bicarbonate type (19%), and calcium-magnesium-sodium-bicarbonate type (19%)
in deeper aquifers. The Koyna River basin is characterized by both scarcity and abundance of groundwater. In the water-scarce
areas in the dissected plateaus, artificial recharge of aquifers through construction of several recharge structures at suitable
locations is highly recommended. In the water-abundant areas in the central valley, on the other hand, expanded consumptive
use of water resources is encouraged.
Electronic Publication |
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Keywords: | Deccan terrain general hydrogeology lineaments hydraulic properties hydrochemistry |
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