RAINWATER HARVESTING SYSTEM - MODEL I
Format for Artificial Recharge proposal inside and outside the project premises
A. Within the Premises
1. Details of Area may be taken from application and unit should be taken as square meter (m2) as per application.
2. Annual Rainfall of the district may be taken from revenue record/from IMD website.
3. Rainfall unit be taken as meter .
4. Annual Runoff generated may be calculated for determining the quantum of rainfall available for recharge.
5. Runoff Coefficient may be taken for different type of areas as per following details:
(a) Rooftop area - 0.80 to 0.90
(b) Paved/Road area - 0.60 to 0.70
(c) Open/ Greenbelt area - 0.10 to 0.20
6. Annual runoff generated within the premises of project may be calculated as Area (in sq.m) * Runoff Coefficient *Rainfall(in m)
7. Hourly Rainfall generated may be taken from intensity of rainfall as mentioned on IMD website; in general for Punjab and Haryana 25 to 30 mm/hr Rainfall may be taken.
8. Then Hourly Runoff generated within the premises may be calculated as Area* Coefficient*Intensity of rainfall (i.e. 0.025 to 0.03 m for Punjab/Haryana)
9. From the quantum of Hourly rainfall generated rainfall number of AR structures to be constructed within the premises may be designed.
10. Quantum of Rainwater through individual Recharge structure should also be calculated.
11. For example :
A recharge pit (Rectangular for this case) have 3 components (free board part, gravel filled part and recharge well part).
(i) Volume of water within free board will be = length *breath*depth
(ii) Gravel filled part will be (volume of water within the pore spaces of sand, gravel filled part)= length *breath*depth*0.35 (this is the porosity)
(iii) Recharge well through which ground water recharge may be done within Shallow aquifer; for this intake capacity of recharge well may be tested in field. In general
intake capacity of recharge well may be taken as 5 to 10 LPS (i.e.,18 to 36m3 /hr) depending upon the hydrogeology.
Therefore, total volume to be Recharge through a RWH structure will be – (i) + (ii) + (iii). Now no. of Recharge structure to be constructed within the premises will be Hourly
Rainfall generated within the premises, as mentioned in point no. (9) Divided by point no. (11) (Quantity of water recharge as shown in calculation for individual RWH structure).
12. For design of the structure cgwa.gov.in website may be referred.
Schematic diagram of Recharge pit:
B. Outside the Premises
1. Suitable pond may be adopted in the villages / if sufficient space is available within the premises new pond may be constructed or any building premises may be adopted within the same assessment unit. For this NOC/agreement should be obtained from the proprietor of the building.
2. NOC/agreement from Sarpanch/Panchayet regarding pond adoption may be taken by the industries. Preferably it should be geotagged. Dimension of the pond should be clearly mentioned in NOC by Sarpanch. Documents of revenue records, Khasra,Khatuni where the pond is situated needs to be given.
3. Depth of pond may be enhanced to accommodate more water for Harvesting.
4. Rainfall from catchment area will flow towards to pond and fill the pond.
5. A general calculation is given in following table for runoff computation.
6. Quantity of Recharge from ponds may be calculated in the following ways :
a) After considering 50% recharge after desilting and 60% recharge after constructing recharge structure.
b) As per GEC 2015 norms regarding GW resource assessment seepage from tanks and ponds may be taken as 1.4 mm/day over the average water spread area.
7. For pond recharge, if shallow aquifer exist within a depth of 5-10 meter, then recharge shaft may be inserted at the bottom of the pond or recharge well may be inserted when depth of sand zone occurs in more than 10 meter depth.
8. Design may be referred from cgwb.gov.in website.
9. Village waste water should not be allowed to be filled in the pond.