GIS-aided planning tool for rainwater harvesting system - a case study in Taiwan

The water demand around the world has increased significantly while fresh water sources have become limited, and in some areas depleted. With limited resources, there is a growing awareness to utilize water in more sustainable manners. Rainwater harvesting system (RWHS) is an obvious green option. But the barrier of RWHS implementation often is its high initial cost and uncertain cost-effectiveness.

Traditionally, the RWHS was often evaluated only on its water saving, other associated benefits such as energy and treatment savings were often overlooked. The goal of this study is to employ a comprehensive approach to determine the optimum location and design for RWHS to achieve maximum cost effectiveness.

Eight hillside communities around Taipei, Taiwan were used as case study. GIS-aided simulations using historical rainfall data were performed to predict the performance at the studied community location. Average potable water demand and water-energy coefficient were assessed. Cost-benefit analyses were performed with water and corresponding energy savings considered.

Results indicate that with the current utility rate, implementing RWHS was cost effective for most of the studied communities when both water and energy saving were considered. The optimum locations and design of RWHS to achieve maximum saving were also identified. Environmental conservation planning should not just consider single factor as many were interconnected. This study demonstrates a more comprehensive approach to design and evaluate RWHS, and this model could be utilized to support decision-making in the future resource conservation planning.