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Recharging bore-wells

May 12, 2012

WATERWISE

Time to give back to the bore-well

www.rainwaterclub.org

Almost ubiquitous all over the city the bore-well used to symbolize independence and self sufficiency in water for many households and apartments. Never mind if the city water supply did not give water on a day, switch on the pump and you had as much water as you needed. Given that the city utility did not give water for new constructions every house and apartment that was getting newly built drilled a bore-well almost even before the ‘Bhoomi Pooja’ and the excavation for the foundation. No more is this independence and self sufficiency true.

The city has now a staggering 370,000 bore-wells to 500,000 bore-wells depending on who is doing the guesstimating. Many of them are unfortunately also going dry. Those in the old part of the city like Rajajinagar or Jayanagar were drilled at a time when groundwater was available at an unbelievable 100 feet or at best 150 feet. These old bore-wells from the 80’s and 90’s are being affected first as the groundwater table declines in the city centre too.

Those on the periphery of the city are being drilled to depths of 1200 feet sometimes. Staggering and unimaginable depths which need lots of energy too to lift water from such levels. These newer bore-wells too are going dry faster simply because of the uncontrolled numbers in the periphery where the city water lines do not reach and therefore the dependence on groundwater is almost cent per cent.

So what needs to be done about it? At the individual building level every bore-well must have a recharge structure. Rainwater from the rooftop must be filtered and led in to the bore-well to recharge it.  A slug test , filling in a certain volume of water and measuring how long it takes for the bore-well to absorb the given volume, establishes the acceptability and rate of recharge of bore-wells. This must be done first before the rooftop rainwater recharge system is put in place.

Recent slug tests have indicated a rate of recharge of 9000 litres per hour in some bore-wells tested. This will vary from bore-well to bore-well however and each should be tested before it is recharged. What a 9000 litre per hour recharge rate indicates is that a 100 sq mt roof area can be connected through a filter to the bore-well and it will be able to absorb the heaviest rain intensity in Bangalore which is 90 mm/hour. At any rate it can also handle the heaviest rain in a day reported which was 180 mm , this probably occurred over 6 hours.

While direct recharge of a bore-well may have a certain risk in terms of silting up or air locks it should not be such a problem for a dried up bore-well or one which has started to yield less water.

Indirect recharge through a recharge well adjacent to the bore-well is one another method that can be followed. The best however seems to be a combination of storage of rainwater into a sump tank and recharge of the excess water directly into the bore-well.

At larger scales, recharging storm-water through recharge wells and de-silting lakes are broader measures that need to be taken in a city fast crusting up and permitting no place for water to seep in to the ground.

At current costs the investments made by citizens and institutions in groundwater abstraction structures could be a staggering Rs 5000 crores in the city alone. All this would be dead capital if our groundwater runs out. It is in the interest of every groundwater user that recharge be taken up at a massive scale and that abstraction be limited. The entitlement of every groundwater user can be no more than what the user recharges and puts back into the groundwater bank. That is the law of nature and ecosystems. That is water wisdom.

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6 comments

  1. This is a great information. I became a fool, just believing a KSCST/BWSSB certified contractor by name Sri KB Manjunath of Sri Kalpavruksha enterprises,No 7, 1st cross, Lakshmipura main road, Nanjundapa building, Madanayakanahalli, Dasanapura post, Bangalore North (email:manjukalparuksha5@gmail.com) who charged me Rs. 30,000 for a 37X20 site water harvesting area, by saying that roof top water after popup filtering can be directly let into my borewell. After reading your material I realized that silt which enters the borewelll can clog the pores and may result in failure of well instead of recharging.I am thankful to your blog for providing this information. I feel periodic training of the 1000 and odd contractors is necessary. In addition, there is no monitoring of work of these contractors by the BWSSB. The BWSSB just believes the written statements of the contractor and the house owner. Most of them being uneducated about groundwater literacy, instead of rainwater harvesting recharging the borewell, can damage the well by directly letting the water into borewell.


  2. Hi Sir/Madam,

    you are giving very important information about borewells in hyderabad, In hyderabad so many

    areas are suffering from lack of sufficient water because your information is very useful to

    hyderabadies.

    Regards
    Venkat
    http://www.borewells-hyd.blogspot.com


  3. Your information about borewell is really useful. Thanks for sharing this informative article.
    Borewell drilling in Chennai


  4. I recently installed Jalsantosh Micro filter for roof rainwater harvesting: the filtered water directly connected to bore well ,any problem directly letting the water into borewell. is there any chance to collapse the borehole


  5. Dear sir,
    i have digged new borewel of 470ft for my house but it is failed and during the time of diging only white rock dust come out after 140 ft of use of cashing and please be advice what i will do as it is made with huge expenditure and no money is with me. If any advice for recoupment of water from my failure borewel avail may kindly be post. Otherwise recovery of cashing from the borewell may please be intimate


    • To the best of my knowledge and belief, I do not think we have borewell insurance.And in hard rock areas (where we are situated), with poor recharge of 5 to 10 percent and where virtually all urban land in Bangalore is cemented with no space for even rainwater to naturally recharge the aquifer, your experience is no exception. Community should realize that at least 10 percent of the site area irrespective of 30X40 or 40X60 or any size be left open with plants and also space for recharging borewell, so that some water goes in for recharging the precious groundwater source. The driller has drilled 470 feet deep and found no fractures / weathered zone for even drinking water. It is also hard to find other points in a small site to site water. I do not know whether geologist gave the point or who gave the point. In my site, in 1990, a geologist gave the point, and fortunately by god’s grace I am getting around 500 to 1000 litres every day if I pump. And in addition I have done roof top rain water harvest during rainy season which will recharge the well. I also use the water with great respect (means I do not use it for washing car etc). I do not know what answer I can give for this experiece, since all of us deserve equal responsibility towards groundwater recharge wherever we are located. But we are more worried about covering every milimeter of land with concrete, and do not want to have any plant / tree, instead want to have all pots…



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