Relationship of Roof Areas and Rainwater Harvesting Tank Sizes for Squatter at Sion Village, Sarawak, Borneo Island
- 1 Faculty of Engineering, Computing and Science, Swinburne University of Technology, Sarawak Campus, Sarawak, Malaysia
- 2 Faculty of Computer Science and Information Technology, Universiti Malaysia Sarawak, Sarawak, Malaysia
- 3 Faculty of Engineering, Computing and Science, Swinburne University of Technology, Sarawak Campus, Sarawak, Malaysia
- 4 Faculty of Engineering, Universiti Malaysia Sarawak, Sarawak, Malaysia
- 5 Faculty of Engineering, Universiti Malaysia Sarawak, Sarawak, Malaysia
Abstract
The rainwater harvesting system (RWHS) is widely recognized as a viable water source for drinking and non-drinking purposes, helping mitigate stormwater runoff. In 2019, an RWHS was installed in Sion village, a squatter that lacks connection to the potable water supply grid, with each household receiving a standardized tank size of 1.816 m 3 . However, the optimal tank size for rainwater harvesting can vary depending on roof sizes and water demands. Since the roofs in Sion village vary in size, this study aims to investigate the relationship between roof size and tank size, considering reliability percentage and installation cost. This investigation utilized the Tangki NAHRIM software and analyzed six different tank sizes: 0.682 m 3 , 1.136 m 3 , 1.589 m 3 , 1.816 m 3 , 2.270 m 3 , and 2.724 m 3 , across roof sizes of 60 m 2 , 85 m 2 , 100 m 2 , 160 m 2 , and 200 m 2 . The study set a benchmark for reliability between 80% and 89%. The reliability percentage gradually improves with increasing roof and tank sizes, but the installation cost increases as well. A minimum tank size of 0.682 m 3 was found sufficient to achieve a reliability of 85.02% for roof size of 85 m 2 , 85.57% for 100 m 2 , 88.84% for 160 m 2 , and 90.07% for 200 m 2 . Similar reliability percentage increment trends were observed for the tank sizes of 1.136 m 3 , 1.589 m 3 , 1.816 m 3 , 2.270 m 3 , and 2.724 m 3 . A tank size of 1.136 m 3 provides a reliability percentage of 95.50% for a roof size of 60 m 2 , making 1.136 m 3 the minimum optimal tank size for this roof area. Results revealed that all the investigated roof sizes achieved higher reliability percentages than 85%, starting from the tank size of 1.136 m 3 . Moreover, the tank size of 2.724 m 3 achieves a 100% reliability percentage for all roof sizes investigated except 60 m 2 . The payback period for various tank sizes with different roof areas ranges from 8.4 to 10.1 years against the water tariff charged by the Kuching Water Board (KWB). Thus, RWHS emerges as the most cost-effective alternative besides water mains for providing potable water supply to Sion village.
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