BWSSB plans to recharge TG Halli reservoir with treated water

BWSSB plans to recharge TG Halli reservoir with treated water

Processed sewage from K&C valley plant to be used for the purpose

BWSSB plans to recharge TG Halli reservoir with treated water

Though the Bangalore Water Supply and Sewerage Board (BWSSB) has commissioned its last and final drawal of 500 million litres of water (mld) from the Cauvery basin, through Cauvery IV stage II phase project, the Board is still far from reaching 12 lakh consumers in 110 villages in the Bruhat Bangalore Mahanagara Palike jurisdiction.

The BWSSB is looking for new sources of water to fulfil the growing demand in the City. It is estimated that the City would face a shortage of 610 million litres of water (mld) by 2025.

Therefore, the BWSSB is now planning to re-pursue its 2005 project that proposed to meet the growing demand by recharging the Thippagondanahalli (TG Halli) reservoir and the Arkavathy surface water source, by using treated sewage from the  Koramangala and Challaghatta valley (K&C) waste water treatment plant.

Treated water

The project proposed to divert the treated water to Nandi Hills which would flow into various lakes located downstream and ultimately to the TG Halli reservoir.

The project plans to instal four centrifugal pumps from K&C Valley till Nandi Hills and construct a ground-level reservoir (GLR) at the foot of the hills. The proposed plan is to pump 200 mld of treated sewage using the centrifugal pumps, each having 50 mld capacity to an elevation of 980 metres into the proposed GLR.
Booster pumps

The treated water would be lifted using booster pumps to the identified hill surface facing the TG Halli catchment. This will be distributed/sprinkled using the distribution system and holding tanks, as a thin film over the surface, and get it naturally aerated which would ultimately drain into TG Halli reservoir.

Though the project aims to recharge the reservoir for drinking water supply, it will indirectly encourage farmers to use it for irrigation also. Of the 200 mld treated water, it is assumed that about 135 mld will reach the reservoir which could be further supplied to the City.

In case of excess water during monsoon, it may overflow into the downstream command area for irrigation. The cost estimated in 2005 was Rs 415 crore. However, a BWSSB official said the project can be executed at a cost of Rs 500 crore with an annual operation and maintenance cost of Rs 80 crore.

In 2000, a study conducted by the Indian Space Research Organisation and Indian Resource Information and Management Technologies Ltd revealed that unplanned development in the catchment areas was one of the main reasons for the deteriorating water quality and reduced inflow into the TG Halli reservoir.

Altered drainage pattern

Increasing urbanisation and industrialisation in catchment areas have altered the drainage pattern and this, in turn, has affected the inflow into the reservoirs.
In 2003, the government declared TG Halli reservoir as sensitive zone under the Environment (Protection) Act, 1986.

Despite several studies and recommendations made to conserve the reservoir and its catchment area, no concrete plans were executed.

The reservoir was the maiden source of water supply to the City and was supplying 30 mld till November 2012, when the BWSSB decided to discontinue supply after water levels dropped below the threshold levels. However, with the recent rains, the levels have increased to 2,513 feet as against its total capacity of 2,574 feet.