Developing design curves for rainwater harvesting in the coastal region of Bangladesh

![CDATA[The potable water crisis in the southwestern coastal zone of Bangladesh arises due to the saline intrusion into surface and groundwater. Rainwater harvesting can be a potential alternative water supply source in coastal regions as these regions receive a large quantity of annual rainfall > 2400 mm. Government agencies and non-government organizations (NGOs) have provided rainwater harvesting systems with a storage tank ranging from 0.5-5 m3 without assessing the optimal storage tank required for residents considering rainfall, family size, water demand, and catchment area and thus limiting rainwater harvesting (RWH) system’s functionality to the wet season only (6-7 months). The current study aims to develop design curves for a reliable RWH system for three climate conditions (wet year, dry year, and average year) using the mass curve and subsequent peak algorithm techniques for 13 coastal stations, considering the factors such as available catchment area (20-70 m2), rainfall loss, water demand 0.01 m3 /day, and household sizes (4-11). To assess the tank's reliability and determine the spilled volume, a spreadsheet-based daily water balance model was developed. Slight variations have been observed in dry and average-year climates, but reliability for the same tank during the wet year ranges between 82 and 85 percent. The economic analysis also reveals that the tank will have a return period of 6-10 years. The developed design curves can be used as a guideline for building a storage tank in coastal Bangladesh to provide optimal drinking and cooking water for the longest possible span of a year.]]