| The hydrological connectivity of ditches is closely related to the ecological health of regional landscape.In the plain irrigation area,the network of rural ditches is dense,and is strongly affected by irrigation water conservancy projects and human management.The hydrological situation is complex,the water system is connected but blocked,and the ecological function of rural ditches is not ful y played.Fudong irrigation area in North Jiangsu Province is a typical ditch network system in plain irrigation area.There are a lot of irrigation facilities such as pumps,gates and culverts in the irrigation area.In recent years,the economy and agriculture in the irrigation area have developed rapidly,which also aggravates a series of water pollution problems in the ditch network.In this study,a typical plain irrigation area,Fudong irrigation area in North Jiangsu Province,is selected as the research area.A method of extracting irrigation and water conservancy projects in batches is proposed.Based on the ditch network connectivity index,the influence index of irrigation water conservancy project is created.The quantitative classification of the ditch network connectivity of Fudong irrigation area with or without the influence of irrigation water conservancy project is carried out by Using SOM self-organizing cluster analysis method,so as to judge the connection of irrigation water conservancy project to the regional ditch network structure The hydrological process connectivity of main canals and administrat i ve vil ages in Fudong irrigation area is analyzed by using water level difference and spatial interpolation.The results show that:(1)There are 39995 ditches in Fudong irrigation area,including 3754 first-class ditches,7371 second-class ditches and 28870 third-class ditches;there are 3929 irrigation and water conservancy projects in Fudong irrigation area,including 876 pump points,633 gate points and 2420 culverts.(2)The hydrological structure connectivity in different regions of Fudong irrigation area is quite different,The area with the best hydrological structure connectivity is the north of the irrigation area,and the south central of the irrigation area has the worst hydrological structure connectivity;Without the influence of irrigation works,there are 13 villages with poor connectivity and 48 vil ages with good connectivity and best connectivity.Under the influence of irrigation works,the number of vil ages with poor connectivity is reduced to 8,and the number of villages with good connectivity and best connectivity is increased to 53;As a whole,due to the influence of sluice and culvert,the hydrological connectivity of 26 villages in Fudong irrigation area has become poor,and that of 39 villages has been enhanced due to the influence of pump.(3)The monthly average water level of each hydrological station in Fudong irrigation area in 2019 shows a trend of first fal ing and then rising,and the lowest monthly average water level appears between June and August.The hydrologic a l process connectivity of the main ditch in the west of Fudong irrigation area is lower than that of Sheyang River.In 2019,there are 7 administrative vil ages with poor connectivity,31 with poor connectivity,55 with general connectivity,71 with good connectivity,and 32 with the best connectivity.From the point of view of hydrologic a l process connectivity value,the administrative vil age's hydrological process connectivity in irrigation period > annual hydrological process connectivity > non irrigation hydrological process connectivity.(4)There are 80 administrative villages with good comprehensive hydrological connectivity,mainly located in the north,middle and north of the study area and the south of Luoqiao town.There are 79 administrative villages with general comprehensive hydrological connectivity,mainly located in the south central of the study area.There are 37 administrative vil ages with poor comprehensive hydrologic a l connectivity,mainly located in Guhe town and Donggou town.Among them,Sanzao town is the best construction town with the best comprehensive hydrologic a l connectivity in Fudong irrigation area,with the largest number of administrat i ve vil ages with good comprehensive connectivity,totaling 17.There are also many administrative vil ages with good comprehensive hydrological connectivity in Xingou town and Guoshu Town,14 and 12 respectively.There are 15 administrative villa ges with the worst comprehensive hydrological connectivity in Guhe town. |
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