Rejuvenating lakes to lift depleting water table

Rejuvenation of City lakes has helped lift the groundwater level in the regions around these water bodies, a study by the Bangalore University’s Department of Environmental Sciences (DES) has found.

The State government’s rejuvenation project, taken up in 2009, had triggered criticism from many quarters.

The study by Dr Nandini, professor at DES, and researchers M Kumar, Shivashakti Velu and Sucharitha Tandon revealed that the groundwater level around the 12 lakes taken up for the project increased after draining and rejuvenation.

The lakes included Malathahalli, Ullal, Komaghatta, Ramsandra, Jakkur, Sampigehalli, Venkateshpura, Rachenahalli, Kothanur, Thalaghattapura, Sompura and Konnasandra.

Crores of rupees were spent during the regime of former chief minister B S Yeddyurappa.

“There is an increase of groundwater level from 3 cm to 9 cm (Mallathahalli, Ullal, Komaghatta, Ramsandra, Sampigehalli, Rachenahalli and Kothanur lakes) after rejuvenation of the water bodies. This might be attributed to adequate inflow into the lakes,” analyses Nandini.

She says the water quality in the targeted lakes had also improved. However, the change was not perceptible in five lakes (Jakkur, Venkateshpura, Thalaghattapura, Sompura and Konnasandra) after the rejuvenation. She attributes this to scarcity of inflow of surface water after the rejuvenation process.

Researchers say post-rejuvenation, the pollution load in the groundwater decreased and the water quality parameters such as pH,  e-coli (EC),  total dissolved solids (TDS), chlorine (Cl), sulphites (SO42-), phosporous (PO43-), nitrates (NO3-), sodium (Na), potassium were found to be within the maximum permissible limit.

“Except for a few parameters such as total alkalinity, total hardness, calcium and magnesium were found to be slightly above the acceptable limit and have marginally increased,” the report says.

Domestic waste water that was mixing with stormwater drain and entering into lakes like Mallathahalli, Jakkur and Sampigehalli, is now being processed through treatment plants.

“The Mallathahalli lake used to witness fish deaths often, before rejuvenation, due to eutrophication and algal bloom. It had high contents of phosphates and nitrates, which have now been taken care of by treating it,” says Nandini.

Besides, the Komaghatta lake along Nice Road, which was in a good shape and had earned a lot of criticism for being taken up for rejuvenation, has now shown further improvement.

Though the study states that the problems pertaining to e-coli still persist in some lakes, the researchers have said the microbial analysis of all the 12 lakes before and after rejuvenation has shown that the contamination has reduced in the groundwater after rejuvenation.

The researchers want to conduct the study annually for at least three years to observe more benefits of lake rejuvenation.