| Urban water ecosystem plays an important role in human drinking water,domestic water,agricultural irrigation,industrial water demand,and shipping water,This fact highlights the use of water outside the river.Unfortunately,people often neglect the water demand for aquatic life.Through literature investigation,the research progress of environmental flow in the past decades at home and abroad is summarized.Four types of environmental flow estimation methods are presented,and summarized according to different countries and different kinds of water bodies.Both shortcomings and future trends of development are analyzed.The theoretical basis of habitat simulation method is introduced in detail,and this method is applied in the Jinan section of Xiaoqing River.The method to determine target species by dominant species and relative importance index is proposed for the first time in this study,which can provide a suitable method for the selection of target species.With the combination of MIKE 21 FM hydrodynamic model and the target fish species habitat suitability curve,the recommended environmental flow in the Jinan section of Xiaoqing River is estimated.Finally,the degree of environmental flow to be satisfied is analyzed,and management suggestions are proposed on the basis of the actual situation of Xiaoqing River.The main conclusions of this study are as follows:(1)The habitat simulation method is based on the principle of Instream Flow Increasement Method(IFIM),based on the choice of the habitat of the organism,and quantifies the choice,and then estimates the environmental base flow.The habitat simulation method mainly includes three aspects:First,fish-based survey of fish in the study area,establishment of habitat suitability assessment criteria for target species,understanding of relationships between species and habitat;secondly,with MIKE 21 FM,River2D,PHABSIM and other software,a hydrodynamic numerical simulation model is developed to simulate the water depth,velocity,water temperature,sediment,water quality and other habitat factors in rivers under different water conditions;Thirdly,the habitat requirements of target species are quantified,and the habitat available area(HUA)under different simulation results is estimated by the habitat available area formula,and the environmental flow is determined on the basis of the flow-habitat available area relationship curve.(2)A total of 37 species of fish were collected from the waters in Jinan City,belonging to 5 orders and 12 families.Among them,23 species for Cyprinidae,accounting for 62%of the total species,followed by Perciformes,9 species,accounting for 24%of the total species,3 species for Catfish,accounting for 8%,and 1 species for Gillfish and Syncynidae,accounting for 5%of the total species;By calculating the relative importance index,the dominant species are Carassins auratus Linnaeus,the important species in spring are Hemiculter leucisculus and Misgurnus anguillicaudatus Cantor,the important species in summer are Abbottina rivularis and Misgurnus anguillicaudatus,and the important species in autumn are Hemiculter leucisculus and Pseudorasbora parva.In order to distinguish the seasons conveniently,and considering the limitations of literature and measured data,Misgurnus anguillicaudatus was selected as representative species in spring,Abbottina rivularis was selected as representative species in summer,and Pseudorasbora parva was selected as representative species in autumn.(3)When the Misgurnus anguillicaudatus is the target species,the environmental flow required for spring is 4 m~3/s;the environmental flow required for summer,when the Abbottina rivularis is the target species,is 12 m~3/s;the flow in autumn is 6 m~3/s when the target fish species is Pseudorasbora parva.Because there is no sampling work in winter,considering that the water demand of fish is not large in winter,the minimum environmental flow value is chosen as the recommended value of winter flow,that is,the environmental flow in winter is 4 m~3/s.In addition,in order to ensure the appropriate habitat conditions for the dominant species of Carassins auratus Linnaeus,the recommended value of environmental flow is 10 m~3/s.(4)In order to validate the rationality of the habitat simulation method,the hydrological method is further used to determine the environmental flow.On the basis of results obtained by using hydrological method,the minimum environmental flow in summer is proposed to decrease from 12 m~3/s to 8 m~3/s;When the streamflow is 8 m~3/s,the habitat useful area of Abbottina rivularis is 20.36 m~2/m,and when the current streamflow is 12 m~3/s,the useful area of habitat is 22.89 m~2/m.The difference is not large,considering the water uses outside the river,the recommended minimum environmental flow in summer can be reduced from 12 m~3/s to 8 m~3/s.(5)The environmental flow to be satisfied above Huangtai Bridge station of Xiaoqing River reached 100%.The reason may be that the human activities such as sewage discharge and water diversion increase the runoff in the river,which becomes the dominant factor affecting the increase of runoff.Following suggestions are put forward in view of the current situation of Xiaoqing River:firstly,the viewpoint of development should change to enhance the consciousness of environmental flow requirement,strengthen the system construction,and improve the water resources optimal allocation system;secondly,improve the water conservancy engineering facilities,improve the environmental dispatching and allocation capacity of sluice dams,increase the fishway facilities at the sluice dams;thirdly,install flow meters and water quality detection instruments at important sections,real-timely monitor the environmental status of river water;Finally,step by step,improve the technical standards,strengthen the basic theory of environmental flow,considering the actual situation of rivers in China,and the difference between rivers in north and south,suitable environmental flow technology should be developed for different rivers. |
