Hydrological Modeling and Evaluation of Rainwater Harvesting Facilities: Case Study on Several Rainwater Harvesting Facilities in Korea

In this study, a hydrological analysis of rainwater harvesting facilities was conducted using a model based on the IHACRES model. Using this model, the rainfall, rainfall loss, inflow to the storage tank, tank storage volume, overflow from the tank, and rainwater consumption data were simulated to evaluate the hydrological characteristics of the rainwater harvesting facilities. This study evaluated three rainwater harvesting facilities in Korea. The results of the study are summarized as follows. (1) The proposed model was found to well simulate the rainfall-runoff processes of rainwater harvesting facilities. (2) As the target amount of rainwater consumption increases, the amount of rainwater consumption also increases, but the number of days with available rainwater decreases. Especially in Korea, the difference in rainwater use when applying different target amounts of rainwater consumption is larger during the rainy compared to the dry season. (3) The effect of increasing the tank capacity was found to be limited to the months of October and November, just after the end of the rainy season. This result is also closely related with the climatic characteristics of Korea. (4) The flood reduction effect was estimated to be approximately 1% when using 10% of the entire city area as the rainwater collecting surface. This result is simply due to that the storage tank capacity is limited to a certain level. (5) The estimated benefit-to-cost ratio was less than 20% when a discount rate of 5.75% was applied, which was basically because the water supply is very inexpensive in Korea.