An Innovative Approach to Predicting the Financial Prospects of a Rainwater Harvesting System.

Rainwater harvesting (RWH) systems are one of the most promising technologies for water supply, but the economic viability often barricades their implementation. To assess the economic viability of decentralized RWH systems at a regional level, this paper develops a generic method to investigate the effect of variations in building characteristics on the economic performance of rainwater harvesting systems in regions with fixed water tariffs and rainfall distribution characteristics. We simulated the financial efficiency (expressed as a benefit-cost ratio) of a large number of decentralized RWH systems in Guangzhou, China. We found that the financial efficiency of the RWH systems is closely related to the catchment fraction (i.e., the ratio of rainfall catchment surface to total floor area). Based on this dimensionless parameter, we derived explicit equations expressing the financial efficiency of RWH systems using a nonlinear regression method. In addition, we validated the analytical equations by the root mean square error test, normality test, and error distribution test. This analytical solution provides a simple and generic method for forecasting the investment potential of rainwater harvesting systems. This methodology can also be adapted to other regions where the variations in local water price and rainfall data need to be considered. [ABSTRACT FROM AUTHOR]