Reliability Analysis and Water Modeling Of Optimum Tank Size for Rainwater Harvesting in Two Salinity Affected Areas of Bangladesh

Abstract

This study focuses on the development of a simulation model to estimate the optimum and cost effective rainwater storage tank size for harvesting. The study objectives include estimation of the most satisfactory storage capacity of any specific roof area and the rational reliability of corresponding water supply. The runoff coefficient for various types of materials and the rooftop area for the concerned household are considered as variables. The daily rainfall intensity of the salinity affected districts such as Khulna and Patuakhali for the last 28 years (1971-1999) was collected from Bangladesh Meteorological Department (BMD).From data analysis, the maximum annual precipitation was found to be 4257mm for Patuakhali and 2762 mm for Khulna District. Two concepts named as Yield after spillage (YAS) and yield before spillage (YBS) were basically used to develop the program which originally provided an estimate of the actual rainwater availability and storage conditions. Volumetric reliability and time reliability –are two index that were employed to find the optimum size of the roof top rain water harvesting (RRWHS) tank size for drinking and cooking purpose and its probable functional time period over the year by observing the 28 years of rainfall data (1971-1999).