Groundwater over-exploited in 4 taluks in Bengaluru Urban: study

In peripheral areas, the problems pertain to increase in number of borewells, deepening of borewells and drying up of rivers

Over-exploitation of groundwater, a problem raised several times before, has once again found mention in the Department of Water Resources (DOWR), Government of India, Aquifer Mapping and Ground Water Management Plan. According to the plan, in four taluks in Bengaluru Urban [Bengaluru East, Bengaluru South, Bengaluru North, and Anekal] groundwater is overexploited.

While in 36% of the district, coming under city limits, water quality issues abound due to pollution, apart from poor recharge, in the remaining 56%, the over-exploitation is due to the complete dependency on ground water and unmindful drilling of borewells.

J. Manjunath, Deputy Commissioner, Bengaluru (Urban) district told The Hindu that as per the DOWR study, the issues were different in urban and peripheral areas. In urban areas, apart from the demand and supply gap, urbanisation hindering recharge of ground water, the other issues were leakage of pipes, mining/theft/ pollution of groundwater.

In peripheral areas, the problems were pertaining to increase in number of borewells, deepening of the borewells and drying up of Arkavathi, Kumudvathi rivers and Hessarghatta reservoir.

Recommendations

“There were some recommendations for tackling each of these issues, which include dual piping for potable and non-potable water, reuse of greywater, adopting scientific augmentation of ground water recharge, reduction of unaccounted for water to less than 20%, and other measures in line with order of the National Green Tribunal to prevent pollution of water bodies,” he said.

Other recommendations included extending Cauvery water supply to peripheral areas, using grey water for irrigation and involving citizens’ groups and local communities in rejuvenation of rivers and water bodies.

The district administration had also taken up various activities, such as safeguarding the water bodies and restoring the original drain network by clearing encroachments, preventing sewage and effluents from entering the drains and water bodies, and filling up tanks and lakes with treated water.

Survey of lakes

“A survey of 837 lakes in the district has been taken up and an encroachment clearance drive to restore the original drain network is also underway. We are adopting a multi-pronged approach to improve percolation and recharge ground water levels,” he said.

Water experts, however, pointed out that though several reports and studies had pointed out to the issues mentioned by the DOWR, precious little had been done on ground.

‘Water management plan needed’

S. Vishwanath, water conservationist, said that as per rules, the Karnataka Ground Water Authority should devise a water management plan. However, the authority is woefully understaffed. “Apart from regulating permissions for drilling borewells, the authority should also ensure the borewells are metered. This will help understand how much water is being drawn, how many borewells have failed,” he said and added that as per estimates, there were over four lakh borewells in the city, of which a mere fraction were probably registered and far lesser metered.

Rules also stipulated that every borewell have a recharge structure. But, in reality, very few borewells that are drilled have such a feature. This, he said, was one of the main reasons for the over-exploitation of ground water.

With silt accumulated in many water bodies, there is no chance for ground water recharge. The water bodies had not even been measured for the recharge rate, he added .

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