Chennai Metrowater will soon start monitoring groundwater level and quality in the expanded areas of Chennai Corporation. It will also intensify rainwater harvesting campaign and assess the impact of RWH structures in the newly-merged localities.
The monitoring would help in understanding the groundwater level in those areas where rainwater is not being harnessed properly. For this purpose, the water agency is in the process of identifying observational wells.
Creating public awareness of the benefits of rainwater harvesting coupled with good rains over the past few years had improved the groundwater level in the city. Metrowater is expected to adopt a similar strategy to popularise RWH in the suburban areas that were merged with the civic body. The pressure on the water agency would be less if the newly added localities also harness rainwater effectively. The demand for drinking water in the Chennai Corporation limits has increased from 800 million litres a day to around 1,100 mld following the inclusion of the suburban areas.
“In the city, we study the groundwater table during the end of the monsoon as the fluctuations in the level would have settled. Good rainfall for eight years consecutively and proper maintenance of the RWH structures in most buildings has helped sustain groundwater resources,” an official of Metrowater said.
At present 50 observation wells are being monitored in the city. The average groundwater level in the city has registered an increase of 0.30 metre last month compared to December 2010. The water table during December 2011 was at 1.90 metre below ground level.
The water table now has improved by a minimum of four metres as compared to 2003, which experienced drought. The level then had receded to 7 metre below ground as the city recorded only half of its annual quota of rainfall of 1,200 mm.
According to a recent study, the water level in sandy areas such as New Washermenpet, George Town and Besant Nagar is between 1.5 m and 2 m. The level in clay areas, including Kolathur, Pulianthope and Virugambakkam, was at 0.5 m to 1 m last month compared to 2.2 metre during the same period the previous year. In hard rock areas such as Guindy, Taramani and Velachery, the level stood at 2 metre. However, the water table was below 4 m in some localities such as T.Nagar, Saidapet and Vallalar Nagar.
The water quality has also improved in the city. The level of total dissolved solids ranged between 200 parts per million (ppm) and 1,500 ppm across the city in December last year. The permissible limit of TDS is 500 ppm.
While the TDS level in areas such as Chetpet, Purasawalkam, K.K. Nagar and MKB Nagar is below 500 ppm, the water quality is comparatively poor in coastal areas such as Besant Nagar and Thiruvanmiyur.