The shortfall in rains this season has begun to have an impact on groundwater in the city. The water level has witnessed only a marginal rise this July compared to last year, according to a study of Chennai Metrowater. For the past few years, the water level across the city had risen by a minimum of 0.50 metre annually. However, this year, there has been a rise of only up to 0.15 metre in areas, including those newly merged with the city.
The water level in sandy areas, including Ennore and Akkarai, has risen by 0.15 metre from 4.50 metre below ground recorded in July last year. In clay areas such as Manali and Semmencheri, the groundwater has gone up by .10 metre from 4.30 metre last July. Hard rock areas, where percolation is relatively slower, registered the least increase by 0.5 metre this year.
S. Prema, a resident of Villivakkam, said that water in her well has turned a bit hard over the past two months. She has had to use more water to wash clothes. Residents in other areas, including Sholinganallur, Kolathur and Valasaravakkam, also complained of a slight increase in salinity in the groundwater.
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The water quality has also slightly dipped compared to last year. The level of total dissolved solids, a parameter used to determine salinity in the water, in sandy areas was 200 parts per million (ppm) last year. This July, the TDS level across the city ranged between 400 ppm and 1,300 ppm.
Sources in the Metrowater said while water with TDS up to 500 ppm is considered fit for drinking, the permissible limit for TDS in water is up to 2,000 ppm.
Metrowater monitors the water table and the quality of water in 80 observation wells spread over the city, including the merged areas. The wells are located every 3 sq.km. or 5 sq.km.
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Rainwater harvesting
Harnessing every drop of rain gains significance as the water table has shown only a marginal rise. This year, Metrowater has turned its focus on added areas and insists on installation of rainwater harvesting structures. It has initiated random checks both in merged areas and the city. “We found that only a negligible percentage of the buildings checked have not maintained their structures properly,” said a source.
The water agency is in want of more manpower to conduct a detailed survey on the maintenance of the rainwater harvesting structures in the expanded Chennai Corporation. There is a proposal to rope in volunteers.
Metrowater is also in the process of writing to heads of 64 government departments to check and maintain their RWH structures. Besides campaigning and putting up boards on types of structures to be built according to the soil condition in all the Metrowater offices, pamphlets would also be issued. Residents may contact the Metrowater office at 28454080 for free consultation.