Connectivity Evaluation Of Typical Irrigation And Drainage System And Its Protection In Hani Rice Terraces

Water is the key resource for the existence of Hani Rice Terraces cultural landscape.In order to adapt to the steep mountainous environment,make rational use and maintain the stable supply of of water resources,the Hani people created and maintained an unique irrigation-drainage system.In this paper,we studied three types of irrigation-drainage systems in the core area of World Cultural Heritage of Honghe Hani Rice Terraces,namely,the Yakou River irrigation district(Simplified as YRID),the ARIDrigation district(Simplified as ARID)and the Quanfuzhuang River irrigation district(Simplified as QRID).Based on the principles and methods of geography,landscape ecology and hydrology,this paper analyzes and evaluates the pattern characteristics,structural and functional connectivity of irrigation-drainage system through Geographic Information System(GIS)technology.By using Statistical Product and Service Solutions(SPSS)and other statistical software,this paper analyzes the scientific and technological value of the woodcutwater-distribution-system and discusses the future protection measures of Hani irrigation-drainage system.The results of this study can provide a reference for the optimization of the irrigation-drainage system in Hani Rice Terraces,and ultimately contribute to the sustainable development of the world cultural heritage.The main conclusions are as follows:(1)The landscape pattern analysis of irrigation district shows that: the difference of landscape composition among the three study areas is not significant.Within the three irrigation district,the area of forest is the largest,followed by terraces.For the terraces itself,the patch is integrated and large,and the elevation and slope is significantly different.Slope of QRID terrace is mainly distributed between 5° to 20° and its altitude is 1600 m a.s.l.,while the slope of the YRID is between 10° to 35°,and the elevation is below 1400 m a.s.l..(2)The composition and management model of Irrigation-drainage system shows: The irrigation-drainage systems mainly consist of rivers,ditches,water-distribution-woodcut,ponds and other elements.Among them rivers and ditches are common elements in the three types of irrigation-drainage systems.The management models are: the ditch leader system of YRID,individual-community mixed management system of the QRID,and individual-ditch leader mixed management system of ARID.(3)The evaluation of irrigation-drainage system connectivity includes three aspects: water system pattern,structural connectivity and functional connectivity.The research results show that:1)Characteristics differences of water system pattern among the three systems are significant.The ditch frequency of the YRID,QRID and ARID are: 12.01/km2,45.83/km2 and 24.04/km2,respectively,and the ditch density are 5.09 km/km2,7.90 km/km2 and 6.26 km/km2,respectively.Water coverage rate of terraced fields in ARID is the lowest,and the highest is the QRID.2)Structural connectivity differences is also significant.In general,the Ratio of Line to Node(β)and the Connectivity Index(γ)are between 0.9 to 1.09 and 0.3 to 0.37,respectively,of which β and γ of QRID are 1.09 and 0.37,which indicates its connectivity level is excellent.However,β and γ of the YRID and the ARID are lower,which indicates their connectivity level are poor and medium respectively.Secondly,there is a circulation,and the Circulation Index(α)of QRID ditch network is 0.05,while the other two systems have no circulation,which shows that the optional path of the irrigation-drainage system is less.Thirdly,the Networks Connectivity Index(C)of the three systems are almost 1,which shows that the studied ditch networks should be improved.3)The functional connection of the three systems and the stability of the corresponding terraced water source were analyzed by using the Least-Cost Model.The results show that: the difference in functional connectivity among the three systems is significant which led to major difference in the stability of the water supply in the terraced fields.Among the three systems,the water stability of QRID is the highest,and its stable area has 67.83 percent of the total terraced area.The water stability of YRID is the worst,and its stable area accounts for only 31.94 percent of the terraced area.the water stability of the ARID is between the two,and the stable area is 48.17 percent of the total terraced area.In summary,the functional connectivity among the three systems,QRID is of the best,YRID and ARID are worse but is not much different.(4)According to the International Irrigation Engineering Heritage Value Evaluation Standard,this paper analyzes the heritage value of the irrigation-drainage system of Hani Rice Terraces,the results show that: Hani Rice Terraces irrigation-drainage system not only has the irrigation-drainage system but also include many other types of additional heritage aspects.Despite the high historical and cultural value,it has a very special woodcut-water-distribution-system which has a high scientific and technological value.According to the current problems faced by Hani Rice Terraces irrigation-drainage system,four kinds of protection are proposed.