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Evaluation of Different Rain Water Harvesting solutions
Written By psaram42 - 7 August, 2009
Bangalore Action drinking water Others Everything else RWH
1 The Background
Rain water harvesting has assumed increasing importance since a couple of years. This is because of the ever increasing scarcity of drinking and irrigation water needs. An important reason apart from increasing population, is the abuse of water in Industrial and domestic use.
In this thread I would like to discuss about currently known techniques being used / commercialized. These techniques can be classified as
1. In situ ground charging - GC-IS
2. Ground Charging at Lakes - GC-AL
3. Harvesting drinking water in situ storage tanks
The ground charging at Lakes seems to be the oldest method known to man, where as in situ ground charging is of recent origin. This method however is yet to pick up in our country. The GC-IS was started in Australia 40 years back and has been since implemented in countries like USA, Malaysia and some countries in Europe perhaps. As per BWSSB there are several different variations of RWH techniques. These techniques need to be evaluated on a scientific basis.
2 Analysis of a solution for Drinking water requirement by different RWH methods
Given Below is a spread sheet application which can be handy in the present context. It is helpful in getting any parameter given the other two, in the RWH context. You are requested to try out if you can lay your hands on a suitable spread sheet. Try and get one in metric units.
Table 1 A ready reckoner for calculating Catchment area
Annual Rain Fall
Water Requirement
Catchment Area
Inches
CFT per day
SFT
20
5
1095
20
5
1095
20
5
1095
This table can be used for getting a quick estimate for your RWH application. It is possible to utilize the whole of the site dimension for any residential building or an apartment block.
There are some Architects who are building houses and apartment complexes with RWH. There could be several techniques of RWH including the Australian one GC-IS known as Chari’s Technique in Bangalore. All these and any other known could be evaluated for their comparative merits and demerits, including cost effectiveness.
The success of the application to any situation depends upon the cost effectiveness analysis.
COMMENTS
RKCHARI - 7 August, 2009 - 12:08
Point 4 above should have read Cubic feet instead of cubic metre. Sorry for the mistake
Dear Friends,
I must hasten to apologise for making this forum into a 'promotion of my company's technology' platform. I wish to assure all praja members that that certainly was not my intention. I just got carried away in trying to explain our technology in comparison to traditional technology. But on reflection I realise this is really not the forum to do so.
As PSA says everyone is aware of this new RWH technology. Apparently people's acceptance depends on cost viability. And to support lower costs I understand people are willing to compromise on quality and efficiency.
So be it. Let the traditional methods be employed and I sincerely wish it all success.
Regards
RKC
Charis Technique - All the best.
Vasanthkumar Mysoremath - 8 August, 2009 - 09:53
/There could be several techniques of RWH including the Australian one GC-IS known as Charis Technique in Bangalore/
PSA Sir, your post has rightly pointed out that RWH in many forms are being followed depending upon the tropical conditions.
RKC, you did your best to float a product with Charis Technique and may be someday it will click but it may be a wee bit difficult to use Praja for such marketing technique/strategy. When your product becomes affordable, replicable, sustainable, I will be the first one to request for installation of one at my place.
During my interaction with NSS groups of various colleges, I have been successful in creating awareness for adopting micro RWH in many villages around Bengaluru and Mysoru.
- I used a few mugs of water for creating miniature models and by making small trenches in a slopy area, with inter connecting canals to feed the the other trenches dug in different lower levels in different directions so that when the upper level mini tanks get filled and overflow. This way I was able to convince some of the panchayat members and farmers that the lands in the upper portion need not remain barn due to non availability of some water for growing some kind of crop/vegetable etc., - otherwise, pumping/carrying water from the little tank at the bottom level could be a very taxing proposition.
- Digging trenchs as RWH is old hat but when it gets filled, the rest of the water overflows in a hapazard manner - still it may percolate and replenish the ground water but - if trenches at different levels are provided, connected with a systematic canal innovative idea may help store more water andavailable for that level of the land that may grow some crop or the other by using the water available at that level itself.
- Zenrainman and Mr.Charis Technique - any comments for improving my two paise idea?
RKCHARI - 8 August, 2009 - 13:37
Dear Mysoremath,
I suppose by trenches you mean storm water drains on either side of any road. If that be the case, then currently, in Bangalore at least most trenches are lined on three sides with rough granite lining, in the belief that storm water will move swiftly from point "A" to point "B".
Two processes do not actually happen in this methodology. The storm water does not get infiltrated as it is made to pass through impervious base and secondly open drains are invariably subject to people throwing any number of things into it ultimately leading the trench to clog which then makes rain water to overflow on to the road.
What is therefore workable in your solution is if the trenches are not lined with impermeable liner like concrete or rough granite slabs. But that too has its problems. Besides slush formation and muddy water flowing, the rate at which rain water falls and the rate at which it will get infiltrated is invariably seen to be a mismatch. So flooding and overflowing on to roads during heavy rains is inevitable. If unlined trenches are still meant to be channels taking the rainwater from point "A" to point "B", it still will carry only muddy water.
I am not too clear about trenches at different levels. How do you achieve that?
I hope my two paise worth is useful.
regards,
Chari
RKCHARI - 7 August, 2009 - 10:57
PSA,
As you are aware, installation of RWH systems in buildings (old and new) is mandatory after Karnataka Government passed the relevant bill last week.
Your calculation method in metric figures works something like this:
Rainfall Consumption / Day Total Catchment Area
in mm in Ltrs/Day in SQM
970 135 50.80
Information on any two of the above parameters will give you the third parameter.
Am not sure what you mean by GCM, but it certainly is not Chari's Technique!
It is a very simple technology where underground retention tanks are made in geometrically designed matrix tanks of a specific size to configure into modular tanks of any size. The geotextile wrapped around helps it ensure that only treated water gets infiltrated. The same tanks with geotextile wrapped around it can double up as retention tanks to store water if we wrap an impermeable liner before installing them underground. Modular nature of tanks allows it to be installed under roads, any building or car park areas etc. Capacity of rain that it can hold is unlimited - limited only by the size of the catchment area.
I personally think this tried and tested technology scores over other indigenous technology because:
1. It offers 100% harvesting of rains against normal 80 to 90%
2. It offers drinking quality water of 98.7% purity which no other RWH system offers; this is an open challenge by the Australian inventors of the system.
3. Being modular and being installed underground, it remains free from photosynthesis and algae formation which is a common feature in most concrete sumps. it also remains fresh because of a capilliary action that takes place automatically aerating the stored water.
4. Cost-wise the comparison should be made in terms of retention tank cost. Any Civil contractor will confirm that a concrete tank normally costs between Rs. 6.50 to Rs.7.50 per Cubic Metre. Our Tanks cost just Rs. 5.50 per cubic metre.
We believe we supply Water free of cost as it is God given. We only charge for our retention / infiltration tanks!!
Regards
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