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Vaigai, Palar bear brunt of groundwater exploitation

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ON THE BRINK: Indiscriminate exploitation of groundwater has wreaked havoc on the Palar riverbed. File photo.
ON THE BRINK: Indiscriminate exploitation of groundwater has wreaked havoc on the Palar riverbed. File photo.

Vani Doraisamy

Survey by the Institute of Water Studies paints a grim picture

Situation grim in most rivers in the StateHuman pressure expected to cause more problemsPharmaceutical, textile effluents causing pollutionPressure caused by human activity on the river basins is also expected to increaseDemand for water will go up to 30,944 million cubic metre

CHENNAI: One always knew this was happening but the statistics still alarm: data compiled by the State Environment Department has revealed that of all the river basins in the State, the Vaigai and Palar have suffered the worst in terms of relentless groundwater exploitation.

The survey, done by the Institute of Water Studies, says that of the 38 blocks on the Vaigai basin in which the study was conducted, three had gone beyond the brink (more than 100 per cent exploitation), four were extremely exploited (dark blocks: 85 to 100 per cent exploitation), ten were severely exploited (grey blocks: 65 to 85 per cent exploitation) and 20 were moderately exploited (less than 65 per cent).

Palar had 22 white blocks, 17 grey blocks and 8 dark blocks. Chennai rivers fared slightly better, with 15 white blocks, three grey and seven dark ones. Data for the Cauvery basin is still being processed. Among the major rivers, the Tamirabarani's score was perhaps the best with 13 white blocks, three grey and one dark one.

Statistics assembled for the IWS' Water Resources Plan also estimate that by the year 2014, the total demand for water in the State will go up to 30,944 million cubic metre (with a deficit of 2481 mcm over total potential) and by 2044, it will touch 31,389 mcm (a deficit of 2926 mcm).

The pressure caused by human activity on the river basins is also expected to increase. While the Chennai basins will support a population of 11.170 million by 2019 and 14.960 million by 2044, Palar's figures are 7.6 million and 9.95 million respectively.

Vaigai comes next with 4.150 million and 5.237 million respectively, followed by Tamirabarani at 2.890 million and 3.543 million respectively.

Industrial effluents

Taking their toll almost on a par with groundwater exploitation are untreated effluents being discharged into rivers. While pharmaceutical industries discharged 345 KLDs of effluents into the Adyar, textile effluents choked the Amaravathy (161 KLDs), Bhavani (1668 KLDs), Cauvery ( 9805.3 KLDs), Noyyal (21,463 KLDs) and the Tamirabarani (7623 KLDs), taking the total to 13,398 KLDs of toxic discharges that find their way into the State's waterways.

Even worse was the discharge from the man-made fibre industry into the Bhavani (32,500 KLDs) and the thermal sector into the Cauvery (75,000 KLDs).

Even many of the lesser-affected rivers such as the Varaha, Ponni, Vaippar and Kallar showed distress symptoms, necessitating a shift in the State's watershed management policy and river conservation programme.

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