Study On The Adaptability Of Ecological Water Quantity Calculation Method Based On Regionalization And Classification In Southern Plain River Network

Environmental flow plays a crucial role in maintaining balance and fundamental functions of the water ecosystem.Moreover,it is of great important practical significance for ecological civilization construction.The southern plain river network region.which has abundant water resources,is still facing a series of complicated problems,including degradation,water area shrinkage,and biodiversity decline due to climate change and excessive utilization.Because of the insufficient research on these problems,the contradiction between city,industry,and ecological water is still serious.Therefore,it is an essential and urgent task to study the ecological flow of the southern plain river network.In this study,the relevant studies on the development course,the concept,calculation methods,and accounting cases of ecological flow worldwide were summarized.The southern plain rivers network was chosen as the research target.Then,the connotation and nature of ecological water quantity in the southern plain river network are defined by clarifying the category and characteristics of the river network.With the method of Principal Component Analysis(PCA),this paper also constructs the classification system of the southern plain rivers network based on the previous works’ basics.With the results of spatial partitions and water categories classification,the adaptability of the ecological water level accounting method was evaluated.The ecological water level accounting method under spatial partitions and water categories classification,which is suitable for plain river networks in southern China,was explored.Finally,the river network of the Lixiahe Plain in the Yangtze River downstream area was considered the specific area of the southern plain rivers network to realize the practical application of the study on the adaptability of ecological flow calculation method in southern plain rivers network based on regionalization and classification.Research indicates:(1)The ecological flow is more appropriate to characterize the ecological water level.(2)The southern plain rivers network can be divided into four groups:rivers in the humid region,rivers in the subhumid and semi-arid region,lakes in the humid region,lakes in the subhumid region.(3)The frequency curve method,Qp method,and the minimum water level method in recent ten years are suitable for calculating the basic ecological water level of rivers in humid and semi-humid,and semi-arid regions.The wet perimeter method,the general standard method,and the water depth method according to the national regulations on the level of inland waterways are suitable for the calculation of the ecological water level of biological habitat,the water level of water demand for dilution,and self-purification,and the water level for shipping function of rivers in humid areas respectively.The water loss method,minimum water level method,annual guarantee rate method,and rate of change method are suitable for calculating the basic ecological water level of lakes in humid and subhumid areas.The minimum bio space method is suitable for calculating the ecological water level of lake fish habitat in the humid area.The water changing cycle method and the material balance method are suitable for calculating the water level of lakes in wet areas to meet the requirements of dilution and self-purification.The water level that meets the shipping function is not considered for the time being.(4)According to the research on the adaptability of the ecological water level accounting method of Lixiahe Plain River Network,the recommended basic ecological water level is 0.32m,and the recommended appropriate ecological water level is 0.68m.This study will help make up for deficiencies of ecological flow research in the southern plain rivers network.Meanwhile,it provides technical support for the determination of water quantity and rational utilization of water resources.The classification system for the southern plain rivers network can reference other plain rivers network areas,which helps construct the water level targets of rivers and lakes in the next stage.