Sponge City Reconstruction of Old Communities in Northwest China Semi-arid Areas: A Case Study of Huangshui Garden in Pilot Area of Xining City

The sponge transformation of old communities is a key and difficult task in the source management of sponge city construction. Taking Huangshui Garden in Xining City as an example, this research discusses the methods and techniques of sponge reconstruction of old communities under the semi-arid climate condition in northwest China, to realize the comprehensive goals of runoff control, peak-clipping delay and environment improvement. The use of surface organization runoff rainwater, and low impact development facilities to regulate and store rainwater, combined with drainage pipes and canals, have increased rainwater storage, transmission, and drainage capacity. Under the condition of two-hour rainfall once in three years, the discharge value of the rainwater pipe network in two parts of the community was reduced by 44.07% and 50.38% respectively, and the peak time was delayed by 5 minutes and 3 minutes, showing a certain peak clipped delay effect. Under the condition of rainfall once in 50 years, there is no waterlogging in the community. Through the construction of the SWMM model and the simulation of annual continuous rainfall in 2018, it is concluded that the total annual runoff control rate of the community reaches 82.5%, which achieves the design target. The research fully shows that the reconstruction method of Huangshui Garden is successful and effective, providing reference and experience for the sponge reconstruction of old communities in the semi-arid areas of northwest China in the future.