Research On The Management Plan Of Small And Medium Watersheds Based On The Concept Of Sponge Basin

With the continuous expansion of the field of human activities,the distance between the daily life of the residents and the surrounding small and medium-sized rivers is getting closer and closer,and the state of the river branches in towns is closely related to the quality of life of surrounding residents.In the flood control of the small and medium-sized rivers around the town,the flood in the upstream catchment area pouring into the river,especially the collected water during the peak of the flood,poses a great challenge to the flood discharge capacity of many small rivers,and the flood often cannot be discharged in time,resulting in flood overflow and flooding on both sides of the rivers.However,given the land use planning of the dense cities and towns,the treatment measures for the rivers may not be applied,so it is more appropriate to shift the focus of the treatment to the direction of flood stagnation in the upstream catchment area.Based on the idea of the management of sponge basin,developing the adjustable water storage in the upstream area and reducing the amount of flood water entering the downstream rivers are the effective ideas to solve the problem of flood and waterlogging in urban rivers.And for areas where the distribution of water during the flood season and non-flood season is uneven,the saving and utilization of unconventional water resources during the flood season,that is,flood recovery,is an important direction to solve the water problem in such areas with unbalanced water volume.This paper takes the Tong Gu River in Huadu District,Guangzhou as the research object.Based on the sponge basin concept,the management scheme of small and medium-sized rivers is studied,and the application of the sponge concept in flood control and water conservation in the river basin is deeply explored by taking the actual watershed as an example.The main research contents and achievements of this paper are as follows:(1)The concept of sponge basin was deeply analyzed,and the "sponge" in it was explored with the river basin as the basic unit.The potential storage capacity of the water body was fully developed,and the absorption of excess water during the flood season and the supplement of the gap in the non-flood period were realized.The results show that in the management of the Tong Gu River,the concept of sponge basin provides a good idea,and the two reservoirs in the upstream are developed and jointly called to form a "sponge" with strong potential,which greatly reduces the peak flow of the Tong Gu River when it encounters floods,and realizes flood recovery.(2)A simple and effective excavation and transformation method of reservoir was explored,which explored the potential storage of reservoir through the transformation of spillways.The main steps of this method are to deduct the corresponding ultra-high water level through the crest elevation,and then determine the flood control level according to the maximum flooded magnanimity required.Finally,the spillway was transformed combining the flood limit water level and regulation rules.The results show that in the application of the Xin Zhuang Reservoir as an example,the maximum storage capacity of the Xin Zhuang Reservoir was developed from 0.5079 million m3 to 2.2572 million m3 in the case of the design flood in the Tong Gu River with 20-year return period,making full use of the idle storage under the original low return period.(3)A one-dimensional and two-dimensional coupling model of the Tong Gu River was constructed.The MIKE hydrodynamic model was used to simulate and analyze the differences of the effect before and after the treatment based on the concept of sponge basin.The results show that through the multi-perspective analysis of the highest water level along the course,the depth of flood overflow,the maximum inundation range,and the evolution of flood inundation,the sponge treatment greatly improves the flood control capacity of the Tong Gu River,reducing the inundation area by nearly 40% and the area of high inundation area by nearly 90%.At the same time,a large number of flood resources have been saved for the water demand in non-flood season.