Rain Water Harvesting- Deep Borewell Design and Its Alternative !!!
Continuing from the last week post (Deep bore well design and Rainwater Harvesting) which discussed why Deep Bore-well Design (DBD) may not be the right choice, this week we would discuss how Rain Water Harvesting (RWH) be uncomplicated without been easy to maintain as well.
The very first flaw that this design has is that it tends to concentrate the entire rainfall over a concentrated area. So the moment concentrate rains, you are also concentrating the pollution, the acids washed by rains, the silt accumulated and so on. However When nature does it, the rains is spread out and not stacked like a water gushing out of a hose pipe.
So in order to remove silt in DBD a either a de-silting chamber is constructed or the RWH itself is constructed with the help of coarse sand, pebbles and then stones as a de-silting mechanism. Once it is commissioned, maintenance becomes a huge challenge. Why, because now you need specialised people who can enter the pit which is having obnoxious gases. The silt and debris need to be extracted and taken out from deep inside the Pits to the ground level.
So people just start avoiding the maintenance. After a while when silt deposition has taken placed to certain level the water inside the pits turns into a sewage and then overflows to the deep bore-well pipe. Now the problem becomes even more acute as entire silt starts overflowing to the ground water table. This chokes the pipe further. So RWH just after a while turns into a huge unhealthy sink hole which doesn't do the service that it was supposed to do.
What could be the remedy?
Well every house or building has a storm water drain trench. What if we just create a harvesting pit out of this drain trench.
So let’s say a plot measuring 500m2 which has the potential to harvest 400,000 Liters of water in a year.
The peak rainfall may be 25mm.
So we only need a trench of the size 450mm X 450mm in the linear length of 60 meters, a space which could be easily carved in the drive ways. Now the advantage in this system is that de-silting drain could easily be cleaned even by the regular cleaner. No need to call the specialist for this job. So at no extra costs, (as you were in any ways building up a storm water trench for the storm-water drainage) you are able to have harvesting pits ready.