The impact of paleo-channel on groundwater contamination, Andhra Pradesh, India
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Nakka vagu, a tributary of the River Manjira in the Medak district of Andhra Pradesh, has a catchment area of ∼500 km2. Patancheru is an industrial development area (IDA) near the vagu. There are about 350 industries of varied nature (pulp, plastic, bulk drugs, pharmaceuticals, paints and steel rolling mills) that are engaged in the manufacture/processing of their respective products and that use water extensively. The hydrogeological setup has a bearing on the widespread contamination in the area because of discharge of industrial effluents into open land and streams. Several dug wells and boreholes situated in the study area have been monitored for water level fluctuations and quality variations. Pumping tests have been conducted to evaluate aquifer parameters. The geology, drainage, chemistry and other related anthropogenic factors play a major role in the spread of pollution in the area. Hence, it is very important to determine the degree of vulnerability to pollution based on hydrogeological factors. Amidst the granite terrain, the Nakka vagu has been identified as a paleo-channel (composed of clay–silt–sand facies); its presence in the area has immensely increased the spread of groundwater contamination. The transmissivity of the alluvial aquifer varies from 750 to 1315 m2/day. The adjoining granite has a transmissivity that varies from 30–430 m2/day. The thickness of the valley fill in the discharge region is about 10–12 m, with a lateral spread of 500–700 m, east of Nakka vagu.
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