Deep bore well design and Rainwater Harvesting!!!
State owned "CPWD" Engineering and Consultancy wing has been the pioneer in environmental sustainability by adopting the design and criteria of the rain water harvesting (RWH) as back as 2002. This was the period when green was still a word associated with plants and trees, and sustainability was a vague term.
However there is not been much progress on the designing and execution of RWH pits, which is still relying design which would have been relevant in the mid last century, but not anymore. There are several reasons for that but in order to understand its shortcomings lets understand how this design works.
Any Rain water harvesting works on the following principals:
1. Catchment: Collect rainwater over a defined area.
2. Delivery: Transportation of rainwater to filtration chambers and then ultimately to RWH Pits.
3. Storage / Recharge: Storage of rainwater for further usage or for ground water recharge.
So what this design works beautifully well in all the three area, however it fails on the two parameters.
1. Maintenance and long term functionality of the RWH pits.
2. Quality of the recharged ground water.
First: This design is bound to choke with dirt and silt just after couple of months of existence. The simplest reason been is that it is not at all easy to clean. It requires a professional agency to perform it, which is both money and time consuming process.
Second: the deep bore well design charges untreated water to the ground water table. The rainwater contains many dissolved acids and compounds which also gets washed from atmosphere, rooftop, concrete and metallic surfaces thus polluting the ground water table itself.
That is where we should take the hint from what nature does. Nature spreads out the rain water and recharges it through the soil, thus washing it of any impurities as well. (However harsh chemicals and fertilizers are still untreated, but that is point of discussion for some other day).
So what if we simply have a bottomless trench running across the compound, equivalent to the capacity of the rainfall for the respective building. This would not only make the RWH more sustainable but easy to clean as well. How, that I would share next week. Till then have a great monsoon.