Simulation based programming for optimization of large-scale rainwater harvesting system: Malaysia case study

• Determine optimal size of storage tank, system reliability, water saving for RWH.
• Deals with tropical rainfall which behaves differently from the temperate rainfall.
• Address the issue of water shortage and flood problems simultaneously.

Large scale rainwater harvesting (LSRWH) is a promising alternative to address security and flood issues in urban areas. The development and planning of a LSRWH for an eco-community involves comprehensive site-planning, systems planning and design, which includes the rainwater source collection (roof) to the storage tank, the distribution and allocation system. This paper describes a new technique for designing a LSRWH for a community of 200 houses with an average of 4 persons per house and an average total daily water demand of 160 m3. It was found that the optimal size storage tank for a 20,000 m2 roof area is 160 m3 with a 60% reliability. The application of this model to the case study revealed a significant water saving up to 58% .The total cost for this system is 443,861 USD over a life-span of 25 years.