Rain Water Harvesting-Myths to Reality
https://storysangam.com/rain-water-harvesting-myths-to-reality/
Thanks a lot for your interest on RWH and Recharge!
This material and answers to most common queries on RWH are collated from experiences, discussion and from Biome Environmental Trust and it’s founder trustee, Vishwanath S or Zenrainman, Ram Prasad (FOL) sir or other sources.
NOTE: For Ground Water Recharging, everyone should use Recharge Well technique if they are not able to implement our Success Story(RWH+Borewell Recharge) mentioned in my blog: https://bengaluru.citizenmatters.in/bengaluru-rainwater-harvesting-3-lakh-annual-savings-borewell-recharge-37514
The annual rainfall in Bengaluru recorded in 2021, 2020, 2019 and 2018 are 1,500 mm, 1,200 mm, 950 mm, and 1,050 mm respectively. Bengaluru receives on an average rainfall of 931 mm annually.[Source, Indian express] There are ~100 days of rain.
Primary rainy season is from June to October when Bengaluru receives rain from South-West Monsoon. Secondary rainy season is from November — December when it receives rain from North-East Monsoon. Though Bengaluru receives higher rainfall in five months of a year, the highest rainfall occurs in the months of August, September and October. [Source: Citizen Matters]
Below is an expert’s interview on RWH which would help you clarify your doubts. https://www.youtube.com/watch?v=iQfZk_-1Iog
http://bengaluru.urbanwaters.in/recharge-well-primer-398 [Below infographic is created from the slides @ http://bengaluru.urbanwaters.in/wp-content/uploads/sites/3/2017/07/Recharge-well-primer.pdf]
Does it make sense to recharge my dried bore-well, how do my recharging helps?
You can easily understand “Bengaluru’s Geology & Ground Water” from the below image: how our aquifer(a body of rock and/or sediment that holds groundwater#) could be local, limited to a few square kilometers, or it could be spread across entire regions#; how each recharge systems like Lake, open well, recharge well etc. is recharging those aquifers(shallow/deep):
Some general queries and answers:
1. Is Rain water safe for Reuse (drinking, cooking, bathing etc.) & Recharge and is there side effect after many years of use? Can I live with Rainwater alone?
Yes! We are using RWH for all purposes for last 8 years and did not face any issues. Please refer to the expert, zenrainman [Biome Environmental Trust Founder Trustee, Vishwanath S].
https://twitter.com/zenrainman/status/1175243349860614144?s=20
https://twitter.com/zenrainman/status/1177464421242687488
Yes, there is no side effect of using rainwater, we are doing it for 8/9 years and Vishwanath sir is doing it for 20 years :)
Yes, we can live with rainwater
2. What is Recharge Wells and Rain Water Harvesting?
https://www.youtube.com/watch?v=iQfZk_-1Iog
http://bengaluru.urbanwaters.in/recharge-well-primer-398
Here is an image from BiomeTrust (https://biometrust.org/) explaining RWH and Recharge wells
Examples images of wells from WA:
3. What are the most important point we need to note while doing RWH for REUSE & Recharge?
We need to make sure the harvested rain water used for Reuse & Recharge is filtered and not contaminated
RWH system should not be anyway connected to any sewage pipeline system
Recharge wells should not be nearby any sewage lines
4. Do we need to involved a RWH expert to aid the process of execution or can it be done by simply calling the well diggers ourselves ? Would the well diggers be knowledgeable enough to suggest solutions on where to dig the well, what to keep in mind, how to channel water from storm water drains and other sources to the recharge well?
If an expert agency is required could you recommend one you used ?
Samir: As you are aware RWH wells are very simple and traditional structure found across India. Well digger mentioned by Biome along with a good plumber would be enough.
You can refer these contacts: http://bengaluru.urbanwaters.in/helpful-contacts
5. We are a community of about 120 independent villas with 6 borewell which are not yielding much. A hydro geologist surveyed and reported that we need 6 RCWs one for each borewell. How do we ascertain whether those would be enough or we would need more ?
Samir: Below details from Biome pdf(Recharge well primer)
For a layout, plan for one 5’x30’ well for each acre of layout.
The runoff from common areas which flows in Storm Water Drains/SWD is channeled into the wells
6. What are the things we should keep in mind before embarking on this project?
Samir: Now important point to note as referred in Biome document
Wells should be far away from Sewage line, soak pits, toilets, or building foundations and basement
As yours is a community area, make sure wells are placed near storm water drains and borewells so that storm water flow can easily enter wells, benefit of recharging reaches brorell fast and help reduce flooding. Please make sure in no away, storm water flow mix with any pollutant like sewage water.
Example RWH in community:
Rainwater runoff into a recharge well. This one is 2 feet in diameter and 12 feet deep. Recharge rate is 10,000 litres an hour. In 100 hours of rain it puts in 1 million litres into the unconfined aquifer #Bengaluru #groundwater #Amillionwells
Short video: https://twitter.com/zenrainman/status/1187039664101715969?s=20
Full video: https://www.youtube.com/watch?v=Dz_VGaPr610&app=desktop
7. What if we have terrace garden?
https://twitter.com/zenrainman/status/1247849272957005825?s=20
A greater recycling system. Trick is to use ecofriendly soap and detergents and to use it up immediately. All terrace garden requirements are met. #water #greywater.
Refer to the video is the tweet and comments.
Can you please share any Rainwater-harvesting-plumber-training?
http://biometrust.blogspot.com/2017/02/rainwater-harvesting-plumber-training.html
<<NOTE: RWH Basics, note: First Rain Separator: https://www.youtube.com/watch?v=5irFPHfCZR0&feature=youtu.be 5:34>>
8. When and why Alum get added into RWH?
Alum gets added to a well . Dirt and dust will settle down. About a kg.
https://twitter.com/zenrainman/status/1259147700227813378?s=21
9. How often do you need to add alum to the water for a well this size. What is the life of alum until it dissolves completely ? Can it also be used in 500 or 1000 litres tanks atop houses ?
The well has been desilted. Only if there is a lot of silt is alum necessary. Quantity depends on volume of water in well.
Treatment of Ablution Greywater for Recycling by Alum Coagulation and Activated Carbon Adsorption
In coagulation experiments, optimal overall removals of turbidity (95.8%), COD (31.6%) and BOD (50.0%) were achieved at 20 mg/L of alum dose.
10.Any example for a filter for rooftop rainwater harvesting?
https://twitter.com/zenrainman/status/1256082478353141763?s=21
A filter for rooftop rainwater. After filtering it can be led into a sump , well, recharge well or defunct borewell. Top cloth/sponge/netlon mesh needs cleaning every alternate rain. #Bengaluru has 60 rainy days and 970 mm rainfall.
Refer the video in the tweet
A good and simple filter for rooftop rainwater. Fill the drum 1/3 rd with crushed charcoal. Put one or two layers of mesh on it https://youtu.be/n8h0X4OI5as #water #rainwater
11. Can you give us some idea of Recharge Rate of wells?
Rainwater runoff into a recharge well. This one is 2 feet in diameter and 12 feet deep. Recharge rate is 10,000 litres an hour. In 100 hours of rain it puts in 1 million litres into the unconfined aquifer #Bengaluru #groundwater #Amillionwells
https://twitter.com/zenrainman/status/1187039664101715969?s=20
12. Any details you can share on the Manja test or the H2S vial test for bacteria in water?
https://twitter.com/zenrainman/status/1251872500763340801?s=21
The Manja test or the H2S vial test. For bacteria in water. Fill till 3/4 of the vial , observe for 36 hours. Brown , no faecal coliform. Black you have to treat water before consuming. Here testing rainwater.
13. Can anyone suggest any disinfectant tablet or similar kind that we can use in Overhead tanks or even in our sump to disinfect the water ( without adding hardness — we don’t want to do chlorine). Any information will be highly appreciated..!
Vishnu from Save Bellandur: Ef-Chlor 1.67gm Water Purification Tablets for Overhead & Underground Tank water 1-Tablet purifies 500 litres water-Jar of 50 tablets combo pack of 2 jar (100 tablets purify 50000 litres water) https://amzn.eu/d/3np0wv7
Go ahead and use it temp basis for few weeks, not much choice for now.
Most use underwater or overhead RO which keeps hardness below for drinking…
As for as other appliances using it for short term won’t impact hugely….
Also ask your STP operator for some input as they will also give some scientific solution.
14. Can a dried borewell be alive again?
YES, it happened to us and to many others!
https://twitter.com/navin_ankampali/status/1567392344739303424?s=20&t=vbAUaChWKNoGZwtlFTV4bQ
15. Why should I recharge ground water when we have a huge lake next to our property?
“…Little is known about how much of the infiltrated water actually recharges groundwater, as not all water lost through the base of a tank can be expected to reach the groundwater table, but some may be stored in the vadose zone or taken up by evapotranspiration (De Vries and Simmers, 2002). This is in particular discussed in a study by Boisson et al. (2014), which proposed a combined surface water and groundwater balance method in order to better consider flow within the unsaturated zone and found that only 53–88% of the potential recharge from the tank percolate reach the groundwater table.”
“…while recharge from tanks in the north Indian alluvial plains is relatively high and homogeneous (Bhanja et al., 2019), recharge to the lower-permeability crystalline aquifers dominant in southern Peninsular India is more complicated and likely much more spatially variable. Crystalline basement aquifers are formed by a combination of weathering and tectonic forces and can be best conceptualized as zones of varying degree of weathering, i.e. a weathered upper zone termed ‘saprolite’, which overlies a less weathered, but fractured rock layer, followed by fresher basement rock (Collins et al., 2020, Singhal and Gupta, 2010). In the southern Indian context, the thickness of the weathered zone is typically a few to several tens of meters, with fracture zones extending to depths of 200 to 300 m (CGWB, 2012). Below the relatively permeable weathered zone, recharge to the crystalline basement depends on the size (aperture) and distribution (connectivity) of fractures.”
“Depending on its permeability, aquifers can gain water at a rate of 50 feet per year to 50 inches per century. They have both recharge and discharge zones.”
Thanks for reading!
Samir Kumar Rakshit (@rakshitmca)
