Rain Water Harvesting Pit

Published on by

I need to know how to calculate the volume of rain water seeped into the ground for 6x6x6 ft RW pit, if rain lasted for 15 minutes. We make RWH pits in to sensitize our community.

So, I want to write on the motivational Sign Board: 15 mins Rain: 1000 liters Water seeped into the ground, 30 mins Rain - something like that.

Please help with your experience. 

Taxonomy

4 Answers

  1. First thing ....You shoud know rainfall in 15 minutes or 1 hour in the area of your pit,  So you need  a rainguage for your calculation. (Please visit my FB page Jalmitra Vijay Kedia to make m your own Rainguage; made from 2 ltr empty Plastic bottle of Pepsi)

    Here are some calculations for your use:
    Volume of 6 X6X6 ft  empty pit is 6000 ltrand of a filled pit( with filter media like sand gravels and brickbats is approx. 40% i.e. 2,500 ltrs only .

    Time taken to percolate and empty this 2,500 ltr will depend on Porosity of soil ( below ground)  , where RWH Pit is dug.

    So Water percolated in the Ground will depend on How many times the pit got filled and emptied during Rains X 2,500 Ltrs. Pit will get filled from  rainwater coming to the pit.  .

    Rainwater will come to the pit from a " Rain catcment area"   a)  during rain and b) even after rain has stopped, if there is storm water in catchment. 

      1 cm rainfall in 100 sq mtr area Cathment area of the pit, is 1 cum water 1,000 ltr water. 

    Example :

    a) if 1 cm Rainfalls in 15 minutes and the cathment area of the pit is only 100 sqmtr : not more than 1,000 ltr water can percolate in the ground (bcoz available water is not more than 1,000 ltr ). 

    b) If 1 cm Rain falls in 15 Minutes and the cathment area of the pit is 500 Sq mtr , 5,000 ltr water is available for percolation and may percolate in the ground if that water ( more than 2,500 ltr) is available after rain has stopped, and flowing in the pit . Now the time taken to percolate 5,000 ltr waterwill depend on POrosity of the soil . it may be 1 hour or may be even 1 day 

     

  2. it depends upon with which velocity rain is falling down.

    Then calculate how much rain falled in inches in 1 hour with high velocity and also calculate how much rain falled in hour with low velocity.

    After that, calculate average and you will be able to calculate the volume of rate.

     

    1 Comment

  4. Please share your email address on pk@jugapro.com, we shall share a calculator for rain water harvesting potential.

    This tool shall allow you to calculate the rain water volume that might be going out of the drains. The actual infiltration capacity of rain water will depend on the soil strata, most of the deccan plateau has black cotton soil, which is almost impervious. The local communities can create slow sand filters over gravel trenches to collect water for reuse in non potable purposes, even though with some amount of discipline in maintaining the hygiene of the catchment area, rain water can be collected for potable use after tertiary treatment. Industry and bigger communities may use Geocellular blocks to create humongous capacity tanks underground without sacrificing the surface use of land.

    To beat the looming water crisis, every drop of water needs to be saved, indeed.

    1 Comment

    1. Thank You Pawan Ji. My Email:anilrajkot@gmail.com