Rain Water Harvesting FAQ

some frequently asked questions on rain water harvesting
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Rain Water HarvestingWe find that many people would like to do Rain Water Harvesting in their area. However, many have expressed doubts or lack of knowledge about Rain Water Harvesting and its efficacy. We have listed below some of the Frequently Asked Questions about Rain Water Harvesting. In case you too would like to know something about Rain Water Harvesting,  do contact us and we'll be glad to answer them.

Is rainwater harvesting really useful? Is there any evidence to prove it?

Yes.

Central Ground Water Board (CGWB) has done detailed studies on the effect of rainwater harvesting on aquifer systems. Using peizometers, it has taken pre and post monsoon readings of water table in areas that have done rainwater harvesting.

They have found a significant rise in water table.

Not only this, they have found a significant improvement in water quality in areas which have done RWH.

You could also see our study Impact Analysis of Rain Water Harvesting to read about the benefits achieved by doing the same.

Does it make sense to do rainwater harvesting in hard rock area like in South Delhi?

Yes.

Provided you use the right method. In hard rock area, it is essential that you take rainwater down to the ‘Fracture Zone’ or that area where there are well developed cracks in the rock. These cracks take water to the aquifer (or are part of the aquifer) in that area.

The safest way to ensure that you recharge the aquifer you are withdrawing water from, is to take the recharge well down to the water table.

Why can’t we just make a pit and allow water to naturally seep into the ground even in areas where water table is very low?

If the water table in your area is very deep and if you have exhausted water in one or more aquifers above the one you are currently withdrawing from, it is preferable not to just make a recharge pit because:

a) It will take a long time (many years) for the water to reach the aquifer from where you are withdrawing water.

b) Even after many years, the water that finally reaches the aquifer (and can be withdrawn by you) will be a small fraction of the water you had stored in the pit. The rest would have been added to soil moisture which evaporates very fast.

c) Unless you make a huge pit, you will lose a lot of recharge potential during heavy showers.

Can we use dried up tube wells for recharge?
Yes.

Dried tube wells are one of the best ways of recharge.

Can we use working tube wells for recharge?
Yes.

PROVIDED you take special care to avoid ALL contamination. Only absolutely clean rainwater should get into it.

How much will it cost to do rainwater harvesting in my locality?
It depends on many factors.

However, a 4m X 4m X 3 m recharge pit with a 40 m recharge well will cost anywhere between Rs. 75000/- to 1.25 lakhs.

How will rainwater harvesting benefit me?
a) By ensuring that your tube well or those in your neighbourhood do not dry up

b) By increasing the water table in your area. It will be insurance for the future.

c) By adding to the greenery in your area.

My neighbours let dirty water flow onto the road. Will it affect the RWH system?
Yes.
Will rainwater harvesting contaminate the underground water?
No.

PROVIDED you make sure that only rainwater gets into the RWH structures. The system can take care of mud and foliage, but biological impurities (garbage, excreta) and chemical contaminants (phenyl, petrol etc) have to be kept out.

You could also write to us at force [at] force [dot] org [dot] in for any of your queries related to Rain Water Harvesting.

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