For the first time in years, the Water Resources Department (WRD) will launch a project to install artificial recharge shafts on a large scale to boost percolation and help stabilise the water table in over-exploited and critical blocks in various districts across the State.

The State government has recently approved a proposal to install nearly 576 artificial recharge shafts in 23 districts at a cost of ₹6.74 crore. The WRD’s State Ground and Surface Water Resources Data Centre will implement the projects in districts, including Ranipet, Salem, Erode, Tirupattur, Vellore, Tiruvannamalai, Cuddalore, and Tenkasi. Officials said recharge shafts would be installed close to waterbodies or storage structures such as check dams to direct rainwater into the deeper aquifers.

Recharge shafts will be installed at a depth between 10 m and 100 m, depending on the site’s lithology. These structures will minimise evaporation loss and accelerate recharge rate depending on the type of aquifer, officials said. The project will be completed before the onset of the Northeast monsoon. According to the Tamil Nadu Groundwater Resource Assessment 2024, 392 of the State’s total 1,202 firkas have been identified as places were groundwater resources are over-exploited and extraction is over 100%. This is marginally lower than the 395 over-exploited firkas assessed in 2023.

Among the various groundwater recharge schemes, the WRD will drill several recharge shafts in various districts under the Groundwater Development Programme. “We expect the recharge rate to be 20%-30% faster than the natural recharge. Some of the over-exploited and critical blocks may move to safer category with replenished groundwater resources in a few years,” said an official.

Various factors such as specific site and depth of the shaft and ascertaining lithology will be determined based on the technical inputs of WRD’s geologists. The sites have been chosen based on the groundwater depletion level and deteriorating quality. For instance, the groundwater extraction rate in Vellore has exceeded 130% of its annual recharge capacity. Dharmapuri, Tirupattur, Salem, and Villupuram districts have also been identified with high extraction rates.

Though the Dynamic Groundwater Assessment for Tamil Nadu, March 2024, found districts such as Tirunelveli, Ramanathapuram, and Sivaganga did not have over-exploited blocks, the WRD has planned to install recharge shafts in these districts because of declining water quality.

Once the recharge shafts are in place, the impact will be felt for a radius of 500 m to 1 km. “We expect the changes in the water table and quality to reflect in our monthly and annual assessments. The project will be expanded to more places in a phased manner,” an official said.