Influences of rainfall characteristics on water saving and stormwater control performances of rainwater harvesting...

Rainwater harvesting systems (RHS) are extensively executed to manage stormwater control and water shortage issues in cities. However, the influences of rainfall characteristics on the performances of RHS are still not deeply explored. In this research, a methodology framework is developed to explore the influences of rainfall characteristics on stormwater control and water saving performances of RHS, by using daily precipitation data during 1968-2017 at 30 stations across the Beijing region as a testbed. The proposed methodology framework applies a water balance model, which requires daily rainfall and water demands, catchment area, tank size, runoff losses and first flush as input data, to assess water saving efficiency (WSE), reliability (R), and stormwater capture efficiency (SCE) of RHS, and a clustering approach to determine if same rainfall patterns produce similar/equivalent outputs of RHS. Rainfall characteristics are quantified using 10 rainfall indices, and their influences on the performances of RHS are investigated. Results demonstrate that WSE, R, and SCE of RHS emerge less scattered when clustering becomes more accurate. Equivalent outputs of RHS for combined water demand can be obtained by dividing 30 stations into eight clusters. Furthermore, 6 rainfall indices (mean annual rainfall, standard precipitation index, rainfall concentration degree, ratio of dry and rainy days, consecutive number of dry days per year, average duration of dry days) are found significantly influencing the stormwater control and water saving performances of RHS. Therefore, they are recommended to be carefully considered to quantify rainfall characteristics and support the performance evaluation and design of RHS.