Economic Feasibility Analysis of Rainwater Harvesting System at Typical Public Buildings in Guangzhou

Objectives : Rainwater harvesting (RWH) is one of the most promising alternative water sources, since rainwater can easily be collected and used without significant treatment for non-potable purposes. However, the economical viability of these systems is not always assured. The objective of this study is to assess the potential water saving and financial performance of an RWH systems for a typical multifunctional building (with a rooftop area of 2,725 m²) in Guangzhou, China.Methods : The water saving and economic feasibility of the RWH system were examined using a yield after supply model for fourteen rainwater tank schemes (from 1 m³ to 30 m³).Results and Discussion : According to the simulation results, an annual potable water saving of 3,923.56 m³ can be achieved and a corresponding annual revenue of 11,496.04 CNY can be obtained from the RWH system. The economic viability expressed by benefit cost ratio is 1.50 and by payback periods are within 6.26 year, respectively. Sensitivity analysis indicates that the water price is the most important factor affecting the economic viability of an RWH systems. The widespread implementation of rainwater harvesting systems in the public buildings will not only lead to economic savings, but also go further to relive pressure on urban drainage systems and natural water body. Therefore, the actual benefits achieved by a RWH system will be greater than we predicted in current study.Conclusions : These results demonstrating that the application of RWH system is a very promising adaptation strategy for coping with the water crisis and climate change in urban areas of southern China.