Optimizing rainwater harvesting systems for the dual purposes of water supply and runoff capture with study case in Bandung Area, West Java.

Abstract

Rainwater harvesting (RWH) systems use runoff to meet water supply demand and may also benefit runoff reduction. We develop the Rainwater Analysis and Simulation Program (RASP) model to simulate an RWH system using storage volume, roof area, irrigated area, and water demand as inputs. A cost-benefit model of RWH was developed with subject to reliability target of water supply and runoff capture in each simulation. Near-optimal solutions were identified for each case using a constrained nonlinear programming algorithm. We apply the model to evaluate the RWH system in Bandung Area, West Java. Various types of buildings, ranging from residential houses, schools, dormitories, offices, apartments, condominiums, mosques, and hospitals, are studied to provide several optimal parameters for tank volume and number of users for various land-use scenarios. The resulting parameters are obtained through optimization to get minimal RWH’s capital costs and water purchase costs by applying several criteria related to the financial feasibility of the RWH system and by keeping the runoff coefficient not exceeding the pre-development value. The simulation results can be used as a guide for planners to consider the application of RWH in several types of buildings.