Comprehensive evaluation of rainwater utilization in China: potential, feasibility and strategy

Abstract

Rainwater harvesting is a promising alternative to alleviating urban water scarcity and reducing urban runoff. China is a big country with highly variable rainfall. However, the impacts of rainfall change on rainwater harvesting systems (RHSs) remain unclear in many regions of China. In this study, the effects of rainfall change on both rainwater utilization potential and feasibility across the seven geographical regions in different climatic zones of China were investigated, while location-specific and adaptive suggestions to increase efficiency of rainwater utilization were proposed. A water balance simulation model on a daily time scale was developed and the influence of rainfall characteristics, rainwater tank volume, daily water demand and rainwater harvesting area on roof rainwater utilization reliability was discussed. It is found that both time-based reliability and volume-based reliability are much larger in South China, East China and Central China than in the other 4 regions, which is consistent with the trend of a gradual decrease in rainfall characteristics from southeast to northwest. Moreover, according to the change of the water consumption structure from 2012–2020 in the seven geographical regions, a future water-saving strategy can be proposed where rainwater will be used to replenish the non-potable portion of domestic water consumption in cities. The findings of this study will provide reference and theoretical guidance for rainwater utilization projects in China.