Study On The Technical Model Of Constructing Ecological Water System In Medium And Small Watersheds In The Water-Deficient Areas Of Northern China

Due to the extensive economic growth and resource development model in the early stage of Reform and Opening,the water ecosystem was seriously degraded in the northern regions where water resources conditions were insufficient.In the past ten years,China has paid more and more attention to the construction of water ecological civilization.However,for small and medium watersheds in the water-deficient areas of the north,a governance model suitable for such watersheds has not yet been formed.This can be attributed to the lag of the study of river basin governance theory in China.The lack of systematic water environment governance in the early stage neglects the tributary and the complexity of the water ecological environment of the basin itself.The ecological water system construction aims to improve the physical,chemical and biological structural integrity of river ecosystems,and comprehensively improve the hydrology,hydrodynamics,water quality and water ecological status of the river system through systematic planning and management.The combination of theoretical support and problem-oriented,and the research on the technical model of ecological water system construction are of great significance for guiding the management of small and medium watershed systems in the north.Based on the analysis of relevant basic theories,this paper explores the technical model of ecological water system construction in the middle and small watersheds in the north of China from the perspectives of theoretical methods and examples.The main research results are as follows.(1)Starting from the essential connotation of water system,the fundamental goal of ecological water system construction and functional attributes,the ecological water system is defined as the whole unit of the basin water system.It is a general term for all forms of water.It is a general term for all forms of water,including the complete physical and chemical structure,the stable ecological process,natural and social attribute functions continuing to meet the balanced needs of eco-factors for benign symbiosis within the system,and reasonable and compliant social service needs.(2)This study is oriented to the needs of water shortage in small and medium watersheds in the north and the ecological water system construction.It is based on the different demands of different water ecological environment protection stages,the interference limits corresponding to the restoration of river ecosystem stability and the correlation between the level of anti-interference and the structural elements of aquatic ecosystems.Then it constructs a river basin type division index database,and determines the river segment type index system including 17 indicators based on the index classification under the principles of comprehensiveness,representativeness,and non-interference.(3)Under the research on the classification and integration of river management technology and the stage orientation,and based on the different stages of governance,we have explored and extracted the ecological water system construction technology model applicable to different stages.That is,the systemic ecological water system construction technology model of “point-line-face-management” in the water quality improvement stage,coupling ecological water system construction technology mode of “structure-function” in the functional recovery stage,and the regulatory ecological water system construction technology model of "water and land integration" in the ecological regression stage.(4)Taking the Qingjian River Basin(Xuchang Section)as an example,16 rivers including the main stream,all the first and second tributaries and the three-level tributaries involved in the central water system are taken as the object,and 36 pieces are extracted according to the objective control node distribution.In the river section,77 samples were laid in the river section according to certain principles.By analyzing the reliability of the three water period surveys and data collection data,19 classification indicators of river segment types were determined.According to the distribution of river basin stages and the types of river sections,combined with watershed planning,the basin ecological water system is divided into three functional spaces.And the ecological water system construction target is set recently.Focusing on the goal of comprehensive improvement of water ecological environment quality in the recent construction of ecological water system,10 key river sections were selected,and the technical models of ecological water system construction in key river sections were classified and designed.