Managing bore-wells in urban areasJune 6, 2010
The trouble with borewells
|In the long run they will succeed only in depleting the water-table|
dire need: A borewell being drilled
A recent session of the Bangalore Mahanagara Palike resulted in the promise of four borewells per ward being dug to overcome the water shortage facing the city. That would add up to around 800 borewells , not really much considering that there are over 110,000 borewells listed by the BWSSB wherein it collects Rs. 50 per month as sanitary cess. Another ‘guesstimate’ would have it that Bangalore has at least 200,000 borewells pumping out anywhere between 100 million litres and 400 million litres of water per day from the aquifer. That is a phenomenally high number in an absent legal or institutional framework for managing groundwater.
Borewell rigs and drillers are having a field day. They work 24 hours a day, catching sleep on the site itself by turns. No log sheet of the drilling is left and the quality of work suffers too but they are only responding to a desperate city drilling away for water.
The new borewells as demanded by the corporators, if they strike water, will of course solve the problem of the citizens for the immediate future. In the long term they will however succeed only in further depleting the water table. The good news is that the water table is actually rising in the city centre.
The bad news is it is the leaking sewage and waste water which is making the water table rise. This ensures that over 60 per cent of the borewells tested have reported contamination by nitrate, especially in the three major valleys of the city — Koramangala-Challaghatta valley, Vrishbhavati valley and Hebbal valley. The new borewells drilled will, of course, have to be tested for water quality and many are likely to be found unfit for drinking. Will the problem of water shortage be solved then?
A borewell linked to a hand pump has a built-in demand management. You can pump out only so much water and that depends on the physical capability of the persons pumping. On the other hand, an energised borewell needs a switch to be turned on and water is sucked out at the rate of litres per hour. Unless a borewell is connected with a water meter, no information can be available as to how much water is being pumped out from it and in general from the overall aquifer. All borewells must have water meters in Bangalore and an institution, preferably the BWSSB, must take monthly reading to determine the withdrawal of groundwater.
In its own borewells the BWSSB must have water meters and keep a track of the water quality and quantity and the depth of the water table. This will give invaluable feedback for the correct management of groundwater. While the BWSSB is recruiting new staff, a hydro-geological/groundwater cell must be set up and staffed adequately.
Borewells with non-potable water must be marked and people warned from drinking the water. Alternative arrangements for potable supply must be made in these localities.
Linking water supply from borewells to the Cauvery waters must be considered. This will reduce the nitrates and high salinity level as well as enable treatment of all waters to reach potability limits.
Groundwater in urban areas is a complex matter. While natural rates of recharge can vary between six and 10 per cent, because of urban crusting, rates of recharge become much less in cities. Polluted waters also end up in tanks and further harm the groundwater. Septic tanks and pit latrines add their bits to the contamination.
A good sewage system and a well-functioning solid waste collection system is a must to maintain quality of both surface water and groundwater.
Focusing on a holistic approach to water in a city is the need of the day and in this lies water wisdom.