JBS Vol 22. Num 2. 2020 - Implications of Using Rainwater Harvesting as Supplementary Water Supply Source for Urban Bangladesh

The scarcity of safe water affects more than one-third of the current world population. Sustainable water supply management is vital for sustainable development in Bangladesh. Rainfall being abundant throughout the year, urban rainwater harvesting (RWH) has untapped potential in Bangladesh. The main purpose of this paper is to provide an in depth look into the practicality of using RWH as a dual water supply system alongside the existing municipal water supply to mitigate the non-potable water demand of urban Bangladesh, where Dhaka city was chosen to test out the hypothesis and calculate possible rainwater collection. Secondary data analysis was done for projections and calculations of available water savings, adjusted to monthly variations of rainfall. It was found 28% to 81% of the non potable water demand can be supplemented by RWH from April to October and a maximum of 103% can be fulfilled in the month of July for Dhaka city in 2030. For economic feasibility analysis, Net Present Value for two types of storage designs was calculated and the payback period was found to be between 2.5-3.6 years. This paper implies that RWH method is a viable option to meet non-potable water demand and demonstrates the water savings impact, design considerations, and economic analysis of the project.