Thursday, 28 August 2014

Filing up a City's hopes

It was more two decades ago that this vast reservoir filled up. Built by the Wodeyars, it last filled up in 1992. It almost reached full capacity in 1999. But since then, this water body, once the lifeline of Bangalore, has only been able to hold varying levels of water but it has never been able to supply water regularly.
This is the Tippegondanahalli reservoir across river Arkavathy, which was built in 1933 after the Hesarghata reservoir dried up. For the last few years, the TG Halli, as it also called, has never had enough water.
TG Halli has been in the news in the last few days as  the water level in it has been steadily going up, thanks to copious rains in the catchment areas.
The TG Halli once supplied drinking water to areas in the west of the city, but encroachment of lakes, growing urbanisation and rapid expansion of the city have seen storage levels plummet.
The last time the reservoir was filled was in 1992 and after that the Bangalore Water Supply and Sewerage Board (BWSSB), which operates the TG Halli, gave up pumping water and shifted focus entirely on Cauvery water supply to Bangalore.
BWSSB officials are hoping that the water level in TG Halli rises further. Last Monday, saw TG Halli hold 26 feet of water and this is encouraging as last year at the same time, the water level stood at 17 feet.
Since Karnataka received good rains in September and October, the BWSSB hopes that the water level would go up further.
Constructed at the confluence of the Arkavathi and the Kumudvati rivers, TG Halli has a depth of 74 ft and its total storage capacity is 3 tmc ft. Officials say heavy rain in catchment areas like Doddaballapur (which recently recorded 11 cm of rainfall) has seen the water levels in the reservoir rise.
The BWSSB is not pumping any water from TG Halli though if need be it can pump about  350 mld. However, the water board wants to keep TG Halli supply as stand by.
If it was the then Dewan of Mysore, K Seshadri Iyer, who conceived of Hesarghatta reservoir, it was another Dewan-Sir M. Visvesvaraiah- who recommend TG Halli as a means to ease Bangalore’s growing thirst for water.
When Hesarghatta proved insufficient to meet the water needs and it went dry 1925, TG Halli was commissioned in 1933.
The first stage of TG Halli was designed to provide a daily supply of 27mld of water for a city's population of 3 lakh, but this too soon proved inadequate. The reservoir was once again deepened and the water works modified to cater to the population of one million in 1956..

However, with the city's population growing by leaps and bounds and the water proving inadequate, the State Government decided to supply water from the Cauvery. In 1964, the Government approved the first stage of the Cauvery Water Supply Scheme (CWSS). Five stages of CWSS have proved insufficient and the government is now looking at alternatives to boost daily water supply as the City currently faces a shortage of 225 million litres of water per day (mld).
This shortage is expected to go up by 1030 mld in 2036. BWSSB is thinking of supplying water from the Krishna and it has drawn up several other schemes but the best bet would be to revive the Hesarghatta and TG Halli reservoirs.
If the TG Halli lake has to be revived, the catchment areas of Devanahalli, Doddaballapur, Magadi and Nelamangala in Bangalore Rural and Ramanagra districts have to be cleared of encroachments and the lakes and tanks restored as they form a vital part of the regeneration programme. Fortunately, all thee areas have so far received good rainfall and the inflow to TG halli has been steadily rising. Usually, the reservoir starts filling up in September, October and November.
 In the last seven years, the water level had not gone up beyond 43 ft. If it fills up, Bangalore can get at least 135 million litres of drinking water every day.
Not many remember that till 1980, TG Halli  was one of the main sources of drinking water to the city and it supplied water to Bangalore West including the localities of Rajajinagar, Sunkadakatte and Vijayanagar. It was in 2012 that the BWSSB finally gave up on TG Halli and discontinued supply of water from it.
One of the many options that the BWSSB is now planning for TG Halli is to recharge the 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 proposes to divert the treated water to Nandi Hills which would flow into various lakes located downstream and ultimately to the TG Halli reservoir.
It involves construction of  four centrifugal pumps from K&C Valley till Nandi Hills and construction of 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 ground level reservoir.
The treated water would then be pumped using booster pumps to the identified hill surface facing the TG Halli catchment area. The water would be sent to tanks and lakes along TG Halli which would ultimately get filled.

The cost was estimated in 2005 at Rs 415 crore. Today, it needs at least a hundred crores more to take up this project, which also requires an annual  operation and maintenance cost of Rs 80 crore.
Apart from this step, the State and the BWSSB have to tackle the issue of   unplanned development, encroachment of catchment areas, altered drainage system, quarrying, denudation of forests and other related urban issues.

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