WATER CYCLE LANDSCAPE DESIGN AND ECOLOGICAL EFFECT ANALYSIS OF RAINWATER GARDEN IN SPONGE CITY

To address low efficiency of urban runoff control and insufficient reduction of runoff pollutants in China, this study designed a rainwater garden system based on Sponge City principles.The rainfall and hourly rainfall time series data for Sponge City were determined, using a Chicago rainfall pattern, based on local meteorological data including runoff coefficient, catchment area, and rainfall duration, and an evaluation system was established using the analytic hierarchy process.The water cycle landscape was visually planned, and a multi-layered garden structure was designed.Crucially, the soil composition (specifically, the proportional mixture of sand, loam, and clay) was systematically investigated as a key variable affecting the system's performance.Evapotranspiration was estimated via the crop coefficient method to analyze ecological benefits.Experimental results demonstrated that the optimized rainwater garden achieved a maximum runoff pollutant removal rate of 100% and a total runoff control rate of 87%.Specifically, Rainwater Garden No.3with a soil ratio of 80% sand, 15% loam, and 5% clay-exhibited superior performance in infiltration, retention, and storage due to its balanced structure and high hydraulic conductivity.Additionally, the annual evapotranspiration of lawns reached 839 mm/year.Other composite measures, such as rain gardens and sunken green spaces, which incorporate diverse vegetation, showed even greater evapotranspiration capacity.These results indicate that rainwater utilization measures significantly enhance the urban land water cycle and promote ecological sustainability.