Optimal sizing of rainwater harvesting tanks for domestic use

Abstract

Rainwater harvesting is an alternative that can contribute to solving water scarcity problems. However, since the design of a Rainwater Harvesting (RWH) system is influenced by several variables, the correct selection of the appropriate storage tank capacity could be a difficult task for people who do not have basic hydrological knowledge, like the proprietors of a house, or members of civil organizations. The objective of this study is to develop regional models to estimate the optimal volume of rainwater collection tanks in communities of the Upper Mixteco River Basin (UMRB) in Oaxaca, Mexico. Based on the analysis of daily rainfall data from 12 weather stations, and the application of the water balance method, simulations of the tank operations of different capacities were carried out for a number of users, as well as catchment areas and demand fractions. As a result, the spatial variation of the optimal tank capacities was obtained, which, together with the annual mean rainfall data, were used to obtain exponential regression equations. It was determined that the capacities of the tanks will be greater in localities in the north of the basin, where it rains less, while, towards the southwest, smaller capacity tanks are required. On the other hand, the regional equations will allow to quantify in a practical way, the capacity of the tank for the functional design of the RWH system in the UMRB.