Reliability and efficiency of rainwater harvesting systems under different climatic and operational scenarios

Abstract

Global demand for clean water supply is on the rise due to population growth, climate and land-use change. Resource limitation, climate, leading to increasing water scarcity, demographic and socio-institutional shifts promote more integrated water management, such as: storm-water harvesting and re-use that may mitigate the risk of water restrictions for urban populations. There is a need to ascertain whether integrated strategies can achieve social and economic goals as well as good-quality ecosystem service and maintenance by long-term monitoring of existing reuse plant, design and feasibility analysis and probabilistic modelling of sustainable rainfall drainage, storage and re-use systems. Rainwater harvesting (RWH) systems may supply daily non-potable water for irrigation, toilette flushing, car washing and other uses. Optimal storage capacity size should correspond to that tank size for which further increases in size produced only a small increase in reliability. Design is usually performed with reference to tank efficiency, and previous studies evidenced how only in high-demanding scenarios there will be a marked dependence of the RWH system efficiency on the water demand. In this study, data taken from literature, and referred to many different place in the world, are re-examined in light of a new risk model. Efficiency, risk of overflow and risk of waterscarcity of RWH tank are examined under various climatic and operational scenarios (including system size and demand). Efficiency is compared with risk and their suitability as indicators of correct tank design is discussed.