The natural valleys of Bangalore

Ask any water expert of geologist and he is more likely to say that Bangalore has four major natural valleys located within the water shed of two principal river basins, the Arkavathy to the west and South Pennar to the East.

The Bangalore plateau is made up of  the four valleys which take off from north and fall gradually towards the south. Of the four valleys, the three main are Vrishabhavathi, Koramangala and Chellaghatta and all of them run in a north to the south direction and divide Bangalore into three distinct and separate drainage zones.

The fourth valley is Hebbal and this runs from north of the ridge and continues in the north easterly direction. These are the four valleys but what is not all that well-known is that there are five other valleys and they too play a vital role in the natural drainage system of Bangalore.

The other lesser known five valleys, which  are minor in nature, are Marathalli to the East, Arkavathy and Kethamaranahalli to the North West and Kathriguppa and Tavarekere to the south.

All these five minor valleys lie outside the tributary area of the  major valleys-Hebbal, Chellaghatta, Koramangala and Vrishabhavati and and they drain independently.

The nine valleys together form a unique and natural drainage system and both excess rain water and sewage flow down the city.

However, almost all the natural channels-feeder, storm water, drains- have either been encroached upon or blocked in places and this had led to the reverse flow of water into the city and not outwards, leading to flooding of roads, footpaths and localities.

What has compounded the inability of the natural valleys to drain off the water is the almost century old underground drainage system of  the City. It was way back in 1922 that Bangalore got underground drainage and this commenced from the pete areas of Bangalore.

The underground drainage system received a massive support when the then Bangalore City Corporation (BCC) in 1950 began an extensive and comprehensive programme. Till 1964, it was the BCC that took care of water supply and sewerage. That year, the State Government decided to set up a separate agency to handle water supply, sanitation and sewerage and formed the Bangalore Water Supply and Sewerage Board (BWSSB).

Since then, the BWSSB has been in charge of water and sewerage for Bangalore City.

The BWSSB has set up three main sewage treatment plants- Vrishabavati, Koramangala-Chellaghatta and Hebbal- to deal with recycling of water. Two additional mini-plants have been built near Madiwala and Kempambudi

As far as water goes, the BWSSB supplies approximately 900 million litres (238 million gallons) of water to Bangalore every day. The is as against a demand of 1.3 billion litres.

Coming back to the drainage system, the lakes and tanks in the four main valleys of  Hebbal, Koramangala, Chellaghatta and Vrishabhavati were a vital clog of nature’s  drain. Apart from draining excess water, they also helped in supplying water and keeping the city cool.

These lakes formed the cascading chain system right from Nandi Hills and continued all the way down to Kanakapura, Ramanagar-Chennapatna, Hoskote, Anekal. The interconnectivity of the water bodies within the valleys is really unique in a city which has no major source of water nearby.

The slope of the valleys allowed rain water to drain from the municipal limits of Bangalore within five hours. The percolation into the ground was minimal. All this changed in the 1980s when prolonged drought led to the drying of tanks and lakes and the State Government itself  encouraged the formation of layouts on tanks and lake beds. In all, 43 tanks made way for residential areas and layouts such as HRBR Layout, HSR Layout, Sarakki, Katriguppe.

The valleys too were blocked at several places and the free flow of water ended abruptly, leading to water backing up in Bangalore, leading to urban flooding and massive rain damage to life and property. The sewerage lines here are interconnected by

several tanks.

Exhausting the Cauvery

Even as Karnataka and Tamil Nadu are getting set to engage in another prolonged battle over the sharing of the Cauvery water,  another little known fact has been completely glossed over and this directly affects the water supply to Bangalore.

Bangalore, as we all know, alone requires 1400 million liters of water per day or eighteen thousand million cubic feet (TMC) every day. Unfortunately, Karnataka can draw only 682.5 million litres a day as per the final award of the Cauvery Water Disputes Tribunal.

There is no way Karnataka can unilaterally increase its drawal from the Cauvery. The tribunal has allocated only 8.75 TMC for the entire urban and rural population in Cauvery basin in Karnataka.

One TMC equals 78 MLD and if you take this calculation, Bangalore city itself is already drawing more water than the entire allocation. So the question is how is the Bangalore Water Supply and Sewerage Board (BWSSB), which is the nodal agency for supply of water to Bangalore and surrounding areas, going to deal with the issue.

There is another peculiar problem. Bangalore city comes under two river basins-Cauvery and Pennaiyar. Only Cauvery basin areas of Bangalore can receive Cauvery water and this means that only half of the Bangalore is eligible for Cauvery as the rest fall under the Pennaiyar basin.

Bangalore has over 7 lakh water connections or consumers and a majority of them are supplied water from the Cauvery. Borewell accounts for 20 per cent to 25 per cent of water supplied and the Arkavathy, including TG Halli, a much smaller percentage.

The City has over 500 kilometers of water pipelines, apart from 250 kilometres of bulk supply lines that carry Cauvery water from all the four stages.  The Cauvery is transported over a distance of 95 kilometres from its source in Kanakapura taluk-Thorekadananhall- to Bangalore city.

Apart from the waters of the Cauvery, the borewells today supply 300 MLD of water and there are 312,000 borewells today and their numbers are increasing. The unchecked growth of borewells has led to a situation where the ground water level has depleted and it is common in almost all areas of Bangalore to drill more than 1200 feet to obtain good water.

Since all the water lines are interlinked, the question is how is the BWSSB going to delink the Cauvery basin areas of Bangalore from the non-basin areas and how will the other half get its share of water.

If and when the tribunal decided to enforce its order or if Tamil Nadu decided to take this issue up in a serious manner, what will Karnataka do. Should they not strive for a viable alternative.

With the Cauvery now no longer available for drawal of water, the State Government must act now itself to find other sources to quench Bangalore’s growing thirst for water. Or else Bangalore will face the same fate as Fathepur Sikri, near Agra, did after the Mughal Emperor Akber built it in 1569. The only other example of a City falling off the urban landscape due to severe water shortage apart from Fathepur Sikri is Bijapur in north Karnataka. After Bijapur fell to the Mughals in 1686, it soon turned into a ghost city after a series of famines, drought and severe water scarcity ravaged the province.

Coming back to Bangalore and its water supply, as it is, the gap between demand and supply of water has been increasing and the BWSSB has not been able to close the gap.

The per capita water supply that BWSSB provides is 100 to 125 liters per capital per day. However, the actual availability of water to slums and poor areas is as low as 40 to 45 liters per day. This when the per capita national standard is 150 to 200 liters per day

One of the best ways to solve the water woes is to plug the leakages which is as high as 40 per cent from the Cauvery water supply schemes only, meter the water outlets and introduce water auditing. Other measures such as rain water harvesting, recycling of water and better storage and conservation techniques can go a long extent in improving the water supply position.

But the first and foremost solution would be to revive the many tanks and lakes in and around Bangalore, desilt the storm water drains, clean encroachments from water bodies, tank beds and raja kaluves and also reintroduce the City’s lost greenery.   

However, the basic question here is how long can we turn a blind eye to the final report of the tribunal and continue to draw more water to Bangalore than it has been allocated. What happens if the tribunal decides to enforce the order.

Bangalore, therefore, has no go but to seek alternate avenues of augmenting its water supply even as it reduces or minimizes its dependence on the Cauvery.