Rains water hopes for water table, but deeper issues persist in Karnataka

Hubballi: With four of the five previous monsoons being above normal, groundwater levels have increased. Data shows that 96 per cent of the monitored wells in the state have shown an increase of 0-10 meters below ground level (mbgl) during the last five Novembers.

The decadal mean by 2024 had shown a water rise in around 74 per cent of the wells monitored.

While the government claims that this increase in groundwater is the result of filling up lakes, desilting works and other projects taken under MGNREGS, experts say excess rainfall in the last five years has only ensured that the surface-level water has improved and not the deeper aquifer that could improve long-term availability of groundwater.

Veena Srinivasan, executive director of WELLS Lab, says with four of five last years receving above normal rainfall, the unconfined aquifer (surface-level) groundwater was bound to increase.

“The government has taken several steps including filling of lakes and works under Atal Bhujal Yojana, Mission Amrit Sarovar groundwater recharge and rainwater harvesting works through MGNREGS,” she said.

However, given that a large part of Karnataka is on hard-rock aquifers, percolation of rainwater to deeper level is slow and scanty, Veena added.

“The overall stress on groundwater in Karnataka is immense and the fact that farmers and public are digging deeper for borewells and openwells shows that groundwater recovery may not be as high”.

The Karnataka Groundwater Authority monitors on average 1,100 to 1,300 wells once every four months.

According to data provided by the Authority, almost all of the 31 districts witnessed a rise in groundwater between zero and 10 mbgl during the post-monsoon study.

However, the bigger picture that the district-wise ground water level data highlights is the non-increasing of groundwater-level between 10 to 40 mbgl. The deeper the aquifer fills, the larger the quantity it stores.  

Take for example, in the post monsoon of 2024, of the 1,136 observation wells monitored in November 2024, nearly 32% of them showed a rise of groundwater by 2 mbgl, 36.4% between 2 and 5 mbgl and 27.3% between 5 and 10 mbgl.

Only 4% of monitored wells in the state (majority of them in the three coastal districts) showed groundwater level improving beyond 10 and 20 mbgl and none beyond 20 mbgl.

Rainwater harvesting expert Devaraj Reddy says unlike in the past when rainfall was continuous and for prolonged duration, currently we are receiving intense and short bursts of spells.

“A majority of the rainwater is running off the surface. The level of percolation is very low. Only the surface-level or visible water is restoring, while the deeper aquifer has remained empty. In many districts, extraction of groundwater is much higher than its recharge”.

‘Monitor defunct wells too’

Experts point out that the methodology adopted by the government is skewed as they have been monitoring open wells on survivor bias, with dry or defunct wells being systematically excluded from analysis.

Vivek Singh Grewal, hydrogeologist at Well Labs, says one of the biggest loopholes of the data collected by the Central Groundwater Board is that they often discard the dried wells and monitor wells that are in the valleys, which naturally get higher level of water.

“In hard rock areas, instead of measuring how much mbgl the groundwater has increased, the authorities should monitor when the wells are getting dried. Due to low aquifer storage, a majority of the wells in Karnataka dry up if a couple of consecutive years are dry,” he says.

A senior officer at Director of the Karnataka Groundwater Directorate says that groundwater-levels in coastal areas, which have been receiving excess rainfall, have improved substantially, while Bengaluru continues to extract groundwater beyond its recharging capacity.

Kolar, one of the highest groundwater-exploited districts, is also witnessing a rise in water-levels after implementation of Koramangala-Challaghatta (KC) Valley project. 

“The department has been encouraging people to opt for rainwater harvesting and use modern technology in cultivation. These efforts will surely improve groundwater levels,” he says.