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City Ring water harvesting

A reader of my blog 'Rajendra Ranade' posted this city ring water harvesting procedure in response to 'Rain Water Harvesting System.

City Ring water harvesting.
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Current status
This is mainly applicable to the cities where there is acute water shortage, plus supply it is unreliable and irregular, contaminated. People are forced to buy water. In one case , i have read that per family water expense is of the order of 1500 rs per month. Water has to be piped from reservoirs/rivers from long distances water table has gone down dangerously. In any case, water can no longer be treated as free commodity and some reasonable charges will be borne by users.

The water harvesting in the city area is quite difficult . roads and pucca surfaces make the water run off. The water is dirty. It can contain a lot of dangerous organic and inorganic pollutants.

Also A concept:

Imagine a band of about 5 kms at a distance of 5 kms from the periphery of the city after considering expansion margins is to be defines. This ribbon will be having sparse population and only farm or fallow land. Some villages and grampanchayats etc will be there. It is to be devided into about 5km x 5km squares each squarish area, should be contoured to find run offs and taalaabs. Talaabs should be dug to collect this run off as needed , as close to city perphery as possible. all the run off water from the ribbon will be collected in these multiple ponds. Current depressions/tanks should be considered. From these ponds the water should be piped or transported to the city periphery. At suitable charges. The grampanchayats should make the "works" self financing by proper pricing in the long run.

So typically a city of about 10 km radius plus about 5 km expansion will have a ring band of about 18km radius. i.e. 3.14 x 35 = about 110 kms = about 22 tanks areas. Each with a water collection of over 25 sq km , at 40 cm rainfall collection = about 10 mn cu mtrs collection. 22 tanks = 220 mn cu mtr collection. At 50 ltrs/day/person, for 10 lak persons, we need about 18 mn cu mtrs per year.

These figures canl very a lot , but still they have great potential.

- Employment generation away from city
- Earning to grampanchayats

I have done these calculations many times over, with many mistakes. I hope
they are ok now.

This concept may be worth discussing.

regards
R M Ranade

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city ring water solution jan 2005

ltr/day/hd=50 dia city+10kms=30
days/yr=365 city area km sq=706.5
ltrs/head/ per yr=18250 ring outer dia=40
ltrs/cu mtr=1000 all area=1256
cu mtrs/per/yr=18.25 ring area sq km=549.5
population=1000000
need cu mtr per yr=18250000

usable rain mtrs=0.5
area needed sq mtr=36500000
sq mtrs / sq km=1000000
needed area km sq=36.5 549.5

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