Town/City:

Madras

State/Province:

Madras

Country:

India

Latitude/Longitude:

12 49'10" N 80 12'10" E

Information supplied by

V.V.S. Gurunadha Rao, M. Thangarajan

Postmast@ngri.uunet.in

National Geophysical Research Institute, Uppal Road, Hyderabad, 500007, India

Dated Thu Jan 18 10:48:57 1996

Information Topics:

City Description:

The metropolis covers an area of 1170 sq km and the majority of the land has flat topography with a gentle slope towards the coast. Surface elevations range 10-12 m (AMSL) in the west. Madras has a population of about 50,000,000 with a growth rate of 10% per decade. There exist small scale industries in the industrial estates of Guindy and Ambathur. Other landuse includes Madras Refineries, a major Petrochemical Industry, and a Thermal Power Plant at Ennore. Landuse is mostly residential.

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Climate:

Average annual rainfall is about 1250 mm. Northeast monsoons from October to December provide 60% of the rainfall. Southwest monsoons provide the rest, but are unreliable. Potential evaporation is 2000 mm/year.

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Basic Hydrogeology:

Most of the groundwater structures are on top of alluvium to a depth of up to 10-15 m. Groundwater occurs in semi-confined to confined conditions. Gravels, coarse to fine sands, clays and silty clays constitute alluvial materials. Gravels and sands form the potential aquifers. The alluvium deposited by Adayar, Cooum and Koratalaiyar are limited in thickness (10-28 m). The dug wells' yields range from 5 to 100 m3/day. Groundwater quality results from depositional environment and overexploitation. The Buckingham canal is constructed at sea level in the centre of the metropolis and is causing extensive sea water seepage into the fresh water bearing segments. Sewerage released into this canal is causing even greater contamination to groundwater. Industrial units in Guindy and Ambathur are releasing toxic effluents and are likely to cause potential groundwater contamination in the future. Overexploitation of groundwater in Araniyar- Kortalaiyar alluvial aquifers north of Madras, has resulted in sea water intrusion. The excessive groundwater withdrawal in the Koratalaiyar alluvium has resulted in the reversal of the hydraulic gradient in the coastal aquifer. The fresh water, sea water interface has moved. The granular zone in the central metropolis does not favour saline water intrusion because of local groundwater pumpages far inland. Freshwater/ brackish water zones are floating lenses.

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Water Use:

Surface reservoirs like Red hills, Poondi, and Tamarapakkam supply drinking water. Groundwater is being augmented to the surface water sources from well fields at Minjur, Tamarapakkam, Panjetty, Poondi and Kannigaripet.

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Groundwater Issues:

No information.

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Groundwater Problems:

Saline water intrusion in the Araniyar and Koratalaiyar basins. Artificial recharge through a number of wells has been started to check the sea water movement by creating a fresh water ridge in the sub-surface in the Araniyar-Koratilaiyar basin. Studies of groundwater pollution due to industrial effluents around Guindy and Ambathur industrial estates. Saline water intrusion in the south and north alluvial aquifers due to overexploitation.

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Solutions:

Problems to be tackled through groundwater management studies, and conjunctive use of surface water and groundwater.

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References and Other Author(s):

To be supplied.
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Contacts:

Director, PWD (Groundwater Wing), Chepauk, Madras-600005

Centre for Water Resources, Anna University, Madras-600025

C.G.W.B. T. Nagar, Madras-17

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