Reliability of Rainwater Harvesting System Using Yield-After-Spillage Algorithm

Malaysia receives a lot of rain yearly, making rainwater harvesting system a high potential for usage in commercial buildings, industry and residential areas. The rainwater collected can be used for irrigation systems and as a source of indoor non-potable use. This study is conducted to test the reliability of rainwater harvesting system at Sultan Abdul Aziz Shah Airport in Subang, Selangor. The yield-after-spillage algorithm is used to perform the rain data analysis and calculation of reliability of rainwater harvesting system. The parameters analyzed in this study are annual rainfall pattern, roof surface area, storage tank size and rainwater demand. Generally, the result of the analysis shows that the reliability of rainwater harvesting system increases as the parameters of roof catchment area and tank capacity increase, but decreases when water demand increases. The maximum reliability is 51.1% for moderate water demand and 30.6% for high water demand during the year with average yearly rainfall. High reliability can be achieved with a minimum roof surface area value of 5000 m2 and tank size of 140 m3 for an average rainfall year. For moderate water demand, the increase in the reliability is less than 5% after exceeding 100 m3 tank size with roof surface area of 20,000 m2. For these specifications and by using the rainfall data from 1994 to 2014, at least 29.3% of the water can be supplied from the rainwater storage tank.