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RWH-calculation

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thampan - 21 December, 2009 | Bangalore | Water | Analysis | Others | Everything else | RWH

 This blog entry is to capture some RWH calculations and upload an excel file to show the calculations.

  1. five membered family - living in 60x 40 plot, having daily usage per member of 150 liters of water
  2. 100% coverage for RWH - tank of 15000 liters will be sufficient for 78% of water needs
  3. 80% coverage for RWH - tank of 5000 liters will be sufficient for 67% of water needs.

Please find attached excel sheet, those interested can vary the green cells to check out efficiencies and coverage.

COMMENTS

Wow ! Good start

srkulhalli - 22 December, 2009 - 11:02

Thampan,

The XLS is very good to do a first cut estimate. One minor comment - your F5 , G5... etc should have $C$6, instead of $C$5 to take into account where you dont utilise all the water falling on the site

One thing I observer is the granularity is a month. This might be OK in most cases, but if the storage is small, it may still miss out in situations where the rain might be lumped only into a few days on the month.

I found one more XLS from rainwaterclub.

http://www.rainwaterclub.org/docs/Taluk_monthly_normal_rainfall.xls

Now if I put in the same data there as in your sheet, I find the numbers dont tally

216 sq m area, 750 litres per day - yours shows 75%

whereas the other one shows 151 days ~ 41%.

I think in this case they have looked at the daily spread and is probably more realistic, but the difference is huge. I havent really understood this XLS sheet though. 

Cost savings calculator?

silkboard - 27 December, 2009 - 13:17

Sweet - simple and easy to understand.

The sheet will be complete with some numbers on money front.

  • One time Investment required (aka Capital expenditure)
  • Maintenance costs
  • Money saved (taking current cost of water from BWSSB)

I know that cost is not the main incentive for citizens to 'upgrade' to RWH - after all, we pay peanuts for water - but when I ask the non-praja type people, there are cost perceptions around RWH.

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