Tuesday 2 July 2013

The waters that go down the drain

One of the most frequent and devastating natural disasters that India has had to face for several decades now and almost regularly is floods.
The floods may be due to a variety of reasons-cloudburst, heavy rains, washing away of bunds or even the phenomenon of urban flooding. The flooding seems to be in almost all parts pf the country and in almost all the states, including Karnataka and its capital Bangalore.  
While Bangalore never had to face the flooding that other parts of India sees or what just Uttarakhand just saw, it is the prime example of how unplanned activities can lead Nature to take its revenge  and this is  shown by frequent flooding of  Bangalore.
Bangalore’s streets and many low-laying localities, particularly in the and around the Koramangala-Challaghatta valley record regular incidents of urban flooding, inundating localities, washing away wife and property, flooding roads and lanes and eventually leading to overflow of storm water drains.
Flooding in Bangalore may seem strange as it is not near any sea, river or ocean like Chennai, Delhi, Kolkata or Mumbai. However, the death of the City’s only river-Vrishabhavathi-and the flow of sewage into it which till date remains unchecked has contributed greatly to the imbalance in outflow of water from the city.
The Vrishabhavati is chocked with debris, garbage, filth and most of all silt in several places and this has blocked the effective flow of water. A minor tributary of Arkavathy, this river flows in Bangalore and even till the 1970s it supplied water for domestic, industrial and no-potable purposes to people living adjacent to it, including several villages.
The Vrishabhavathi is joined by Survanavathi at the junction of Gali Anjeneya Temple on Mysore road but today neither of the rivers exist. Both are filled with sludge and sewage and even fishes and /or any marine life cannot survive. The oxygen levels in these waters are almost non-existent and poison gas and chemicals make up a large percentage, posing a danger to those living nearby.
The chemicals in the water also pollute the ground water and make them unfit for drinking. The destruction of the Vrishabhavathi is directly due to the unprecedented growth of domestic, commercial and industrial activities and the increased generation of  foul, waste and sewage water.
Studies of water bodies, tanks and drainage of Bangalore by IISC, Bangalore University, ISRO, BWSSB, Central Ground Water Board, Central Water Commission and independent studies have said that the watershed has to be preserved , protected and nurtured if the ecology of water management of Bangalore, which has gone haywire, has to be set back into place.
The total catchment area of Vrishabhavathi is estimated to be a little over 350 square kilometers. The length of Vrishabhavathi river from Peenya, where it is said to originate-another myth is it originates near Bugle rock in Basavanagudi- to the
place where it joins Suvarnamukhi in Bangalore urban district is about 52.5  kilometre.
During summer or dry seasons, the water flow in the Vrishabhavathi is reduced and more than 300 MLD of domestic sewage flows into it. This is further compounded by the discharge of upto 10 MLD industrial and chemical waste.
The failure of the civic agencies and the Government in taking a tough and uncompromising stand against such pollution as also its failure to stand firm against encroachment, particularly of wetlands tanks and storm water drains, has only worsened matters.
The story of another of Bangalore’s river-Arkavathi-is also frighteningly similar. The Arkavathy takes birth at a small pond in the Channakesava Hills adjoining Nandi Hills or the Nandidoorga range of hills.
Arkavathy tumbles down the hill and drains into the Chikkarayyappanhalli Kere. This is the first of the many tanks or reserviors built to hold the waters of the Arkavathy which then empties into several smaller lakes and forms the Nagarkere in Doddaballapur.
The Nagarkere was once upon a time sufficient to meet the drinking water needs of the entire Doddaballapur town and surrounding villages. The command area of the tank was 60
hectares. It had a storage storage capacity of 2.27 million cubic
metre (Mcum) but it is today reduced to just 1.5 Mcum, thanks to silt, bad management and encroachment.
Then comes the 6.89 km Hesarghatta lake, built by the Wodeyar Kings to supply drinking water to Bangalore, Today, this tank is almost dry and ironically villages on the periphery of this once magnificent water body are facing a severe water shortage.
What many are not aware of is that a smaller tank did exist at the place where the Hesarghatta stands today. This small stone structure to hold water was built during the reign of the Vijayanagar Emperor Achutadeva Raya. It was in 1894 that this water body was enlarged.
We can say that Hesarghatta became the first external source of water supply to Bangalore which till then met its needs from local lakes and tanks such as Dharmambudhi tiull 1895, Ulsoor till the 1960s, Sankey and Millers tanks. It was way back in 1989 that the Hesarghatta reservoir overflowed its bund. Since then, it has been downhill for this waterbody.
The Arkavathy then comes down from Hesarghatta and joins the Kumudavathy at Tippegondanahalli or TG Halli. The Arkavathy moves further on and where the Kumudvathy merges with is the second large reservoir built for Bangalore city’s water in 1934. This reservoir, conceived by Sir M. Visveshvaraiah, once supplied 135 million litres of water daily to Bangalore but not any more. Its catchment area is 1,453 sq. kms., and covers parts of Doddaballapur, Nelamangala, Devanahalli, Magadi and Bangalore north taluks
While the Hesarghatta has remained dry for several years now, the TG halli has rarely filled up in recent years, leaving Bangalore at the mercy of the Cauvery for water supply.
Thus our ancestors had once planned Arkavathy as a cascading system of holding water and fulfilling the needs of not only Bangalore but villages and towns enroute to Bangalore. If the tank overflowed or filled to the brim, water would naturally floe into the next tank. However, the cascade system-there are 1,084 tanks along the riverway till T.G. Halli-has been ruptured and none of the lakes lakes in the Arkavathy basin are full.
This shows our failure to arrive at a sustainable river and catchment management plan. If quarrying is the main threat to the free flow of Arkavathy, encroachment, apathy and wanton urbanization are sounding the deathknell for  Bangalore’s fragile water bodies.
The average annual rainfall in and around Bangalore city or urban area is estimates at a little over  66,400 hectares metres (ham) and of this the Geological Survey of India has calculated that 17,000 ham is runoff water. The ground water recharge is just 3290 ham and this means that over 71 per cent of rain water is lost due to various reasons, including evapotranspiration or ET which is the  the sum of evaporation and plant transpiration from the land surface to atmosphere.
Interpolate this aspect with the Cauvery water supply to Bangalore. The BWSSB is able to pump in annually 24,923 ham as against the demand of 48,600 ham. Besides, the city today has close to 3.5 lakhs borewells supplying 12,500 ham, leaving a shortage of over 12,000 ham.
The best way to meet or make up for this shortage is to harness the water potential in storm water drains. The storm water discharge is pegged at 17,040 ham and this is apart from the sewage flow of  26,316 ham. If all this water is treated, there is no reason for Bangalore to suffer any water shortage and this hold true even when the Sun shines brightly and Bangaloreans sweat it out in scorching summer.  
(This is the fourth in the series of posts on Urban flooding and Bangalore.) 

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