Since many of the people reading this blog might relocate and make Bangalore their home, want to spread this message in the R2I community - this is one area where I was able to contribute and tried to make some difference. Unfortunately, there is not much awareness in the general community about this ticking time bomb for Bangalore and as always government is least bothered, leaving people to handle this on their own. You can see lot of debate about turning the water from Western Ghat to Bangalore etc, which are mega-mega projects but not much about making Bangalore self-sufficient on water. Why? - since this is not where these politicians make money but with mega projects! BDA/BBMP mandates RWH for all constructions beyond 30x40 area sites but that is in the plan - nobody checks about implementation or proper maintenance once it is in the plan. For all the reasons you know, there may not be any rain water flowing into the RWH pits!
Key point with RWH is proper implementation and doing it in mass scale so that not even a single drop of water is wasted. With the current state of 'growth' (if you can call it that, I would say 'mess' or 'unplanned expansion' is a better word!), reality is that Bangalore will need to depend on Borewell water and complete Kaveri water supply is a 'pipe-dream'!. Fortunately, during normal years, Bangalore gets good amount of rains and is more than enough for the populace. With more and more concrete, most of this water flows into lakes, which are fully chocked and polluted. Most of the larger size apartments have STP(Sewage Treatment Plants), which recycle most of the water and that reduces the need for fresh water greatly. However, many of the mega apartments with 300-1000 families depend on tanker water, which is disaster waiting to happen.
Doing community RWH is simple - in the rain water drains, dig a pit, say 3' or 4' wide. Depth depends on the type of soil, you need to go up to a depth where you get soil that can absorb water quickly. Bottom is left open for water absorption and cement rings are used to cover the side walls. Between the cement rings and mud, granite stones(Jelly) are packed so that there is a 'breathing' gap for water to seep in. Top is covered with a removable slab, which can be opened up for cleaning of sludge every few years. 2 concrete mesh filters are placed - one right next to the pit with a pipe to feed the water to the pit and covered with small granite rocks to filter out debries. Another one is placed 5' away up on the drain, again covered with granite stones to filter out large debries like leaves etc.
Some people plaster the cement ring walls and bottom as well so that they can collect rain water and re-use for non-potable purpose. This is good for rain water collected from roof tops but not rain water drains. A good filter needs to be used in case of reuse of rain water. Also, it is necessary that the water doesn't get contaminated with construction dust or bird droppings etc in these cases. Also, water from first few rains are not used but left out. I have seen people going to elaborate level, where water from roof top is fed to a syntax tank (for gardening purpose, without the use of a pump), overflow fed to a collection sump, overflow from collection sump fed to a harvesting pit for ground absorption.
If you go with 3' rings, it would cost you around Rs. 1000-1500/feet. For community level pits, it is better to go to a depth of 15-20' and 4' rings. A 20' deep, 4' wide pit would cost around 25K, which is not at a lot for the value you are getting out of it.
Some of the useful websites with information on RWH:http://bwssb.org/rain-water-harvestingrwh-3/
http://www.rainwaterclub.org/
There is a theme park as well, maintained by BWSSB: http://bwssb.org/theme-park-maintained-with-rain-water-harvesting-9/
Please feel free to drop an e-mail if you are involved in this effort, need contact information for some RWH contractors or need more information.
Key point with RWH is proper implementation and doing it in mass scale so that not even a single drop of water is wasted. With the current state of 'growth' (if you can call it that, I would say 'mess' or 'unplanned expansion' is a better word!), reality is that Bangalore will need to depend on Borewell water and complete Kaveri water supply is a 'pipe-dream'!. Fortunately, during normal years, Bangalore gets good amount of rains and is more than enough for the populace. With more and more concrete, most of this water flows into lakes, which are fully chocked and polluted. Most of the larger size apartments have STP(Sewage Treatment Plants), which recycle most of the water and that reduces the need for fresh water greatly. However, many of the mega apartments with 300-1000 families depend on tanker water, which is disaster waiting to happen.
Doing community RWH is simple - in the rain water drains, dig a pit, say 3' or 4' wide. Depth depends on the type of soil, you need to go up to a depth where you get soil that can absorb water quickly. Bottom is left open for water absorption and cement rings are used to cover the side walls. Between the cement rings and mud, granite stones(Jelly) are packed so that there is a 'breathing' gap for water to seep in. Top is covered with a removable slab, which can be opened up for cleaning of sludge every few years. 2 concrete mesh filters are placed - one right next to the pit with a pipe to feed the water to the pit and covered with small granite rocks to filter out debries. Another one is placed 5' away up on the drain, again covered with granite stones to filter out large debries like leaves etc.
Some people plaster the cement ring walls and bottom as well so that they can collect rain water and re-use for non-potable purpose. This is good for rain water collected from roof tops but not rain water drains. A good filter needs to be used in case of reuse of rain water. Also, it is necessary that the water doesn't get contaminated with construction dust or bird droppings etc in these cases. Also, water from first few rains are not used but left out. I have seen people going to elaborate level, where water from roof top is fed to a syntax tank (for gardening purpose, without the use of a pump), overflow fed to a collection sump, overflow from collection sump fed to a harvesting pit for ground absorption.
If you go with 3' rings, it would cost you around Rs. 1000-1500/feet. For community level pits, it is better to go to a depth of 15-20' and 4' rings. A 20' deep, 4' wide pit would cost around 25K, which is not at a lot for the value you are getting out of it.
Some of the useful websites with information on RWH:http://bwssb.org/rain-water-harvestingrwh-3/
http://www.rainwaterclub.org/
There is a theme park as well, maintained by BWSSB: http://bwssb.org/theme-park-maintained-with-rain-water-harvesting-9/
Please feel free to drop an e-mail if you are involved in this effort, need contact information for some RWH contractors or need more information.
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