Seeking urbanization security and sustainability: Multi-objective optimization of rainwater harvesting systems in China

Urban rainwater management need to achieve an optimal compromise among water resource augmentation, water loggings alleviation, economic investment and pollutants reduction. Rainwater harvesting (RWH) systems, such as green rooftops, porous pavements, and green lands, have been successfully implemented as viable approaches to alleviate water-logging disasters and water scarcity problems caused by rapid urbanization. However, there is limited guidance to determine the construction areas of RWH systems, especially for stormwater runoff control due to increasing extreme precipitation. This study firstly developed a multi-objective model to optimize the construction areas of green rooftops, porous pavements and green lands, considering the trade-offs among 24 h-interval RWH volume, stormwater runoff volume control ratio (R), economic cost, and rainfall runoff pollutant reduction. Pareto fronts of RWH system areas for 31 provinces of China were obtained through nondominated sorting genetic algorithm. On the national level, the control strategies for the construction rate (the ratio between the area of single RWH system and the total areas of RWH systems) of green rooftops (eta(GR)), porous pavements (eta(PP)) and green lands (eta(GL)) were 12%, 26% and 62%, and the corresponding RWH volume and total suspended solids reduction was 14.84 billion m(3) and 228.19 kilotons, respectively. Optimal eta(GR), eta(PP) and eta(GL) in different regions varied from 1 to 33%, 6 to 54%, and 30 to 89%, respectively. Particularly, green lands were the most important RWH system in 25 provinces with eta(GL) more than 50%, eta(GR) mainly less than 15%, and eta(PP) mainly between 10 and 30%. Results also indicated whether considering the objective MaxR made a nonsignificant difference for RWH system areas whereas exerted a great influence on the result of stormwater runoff control. Maximum daily rainfall under control increased, exceeding 200% after the construction of the optimal RWH system compared with that before construction. Optimal RWH system areas presented a general picture for urban development policy makers in China. (C) 2017 Elsevier B.V. All rights reserved.