RWH structures keep city’s water hopes afloat

Enthused by rise in groundwater, Metrowater asks residents to maintain them

rainwater harvesting, All elements are in separate layers colors can be changed easily.

Buoyed by the stable groundwater table and its improved quality for over a decade now, Chennai Metrowater has urged residents to maintain the rainwater harvesting (RWH) structures ahead of the monsoon.

The average water table in the city in November 2004 was at a depth of 8 m below the ground level. Though the drawal was more in the previous year, the average groundwater level remained at a depth of 5 m in November 2017.

In places like Villivakkam and Guindy, where the water table had dipped to a depth of 14 m, the level improved to 3 m in November 2017 after setting up of RWH structures, a study by Metrowater reveals.

145 observation wells

The study is based on data compiled after monitoring 145 RWH observation wells across the city that has nearly 8,73,700 RWH structures in 8,03,228 buildings. The Metrowater estimates that the groundwater recharge potential of these structures would be 2,750 million cubic feet.

Not only the groundwater level but also the quality has improved. This is reflected in the fact that the total dissolved solids (TDS) level remains below the 1,000 ppm mark in many parts of the city. For instance, the TDS level, which was 3,000 ppm in 2004 in some areas, has decreased to 900 ppm in 2017.

“We took 2004 as a benchmark as it was a drought year and a year after the RWH was made mandatory in city,” an official said. It was also a year in which piped water supply was replaced with tanker supply and people turned to groundwater resources, he added. According to officials, the groundwater table has remained relatively stable in the city though residents have been largely dependent on it for their daily needs for the past two years.

Given the dependency on groundwater, the Metrowater has asked the residents to maintain the structures to reap the benefits of the oncoming northeast monsoon and to ward off a crisis.

A team of officials is also engaged in inspecting buildings to assess the condition of the RWH structures. Residents may contact the Metrowater office at 044-28454080 for details on RWH maintenance.