Feasibility Study of Rainwater Harvesting As a Saving Option of Ground water Case Study Area: Mirpur DOHS, Dhaka

Abstract

For the work purpose, Mirpur DOHS has been selected as case study area. We collected
rainfall data and community water demand data for the analysis. Our main focus is to save
groundwater and use rainwater from harvesting. After analysis we have got Annual average
rainfall is 6.47 m. Annual rainfall volume is 1310626 m3. Total Annual water demand in the
area from 25 liter/sec extraction in a day is 2365200 m3. Total annual water saving can be
made up to 55%. Monthly % savings have been also shown in the table in the result and
discussions section. Annual Water cost from demand at a rate of 11.02 Tk per 1000 L water
is 26064504 BDT. Net Cost savings from rainfall harvesting is 11621402 BDT which is 44%
of the total water demand cost. Net cost savings will not be achieved fully as there will be
some treatment cost for rainwater. Maximum rainfall over the past 11years in a single day is
448 mm. So, maximum rainfall volume in a single day from per roof is 70 m3. Underground
reservoir capacity in a building at Mirpur DOHS is 32' x 14' x 11' that means 139 m3 in
volume. So, harvesting rainwater can be easily accommodated in the underground reservoir
using a primary treatment option like filtration