Deccan Herald 27.06.2013
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.
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.
