Study On Surface Water Hydrological Connectivity In Qilian Mountain National Park

Hydrologic connectivity is related to the water-mediated transport of materials,energy,and organisms within or between elements of the hydrologic cycle.It reflects the hydrological consequences caused by topographic,land cover and climatic factors and is an important tool for describing and predicting hydrological responses to climate and landscape change.Hydrologic connectivity is also an important feature in maintaining the stability and function of wetland ecosystems,and is important for the water-dependent organisms that inhabit them,creating temporary habitats for them.The Qilian Mountains National Park is an important water source for the Yellow River and has two main functions: water conservation and biodiversity protection.Studying the hydrological connectivity of the national park based on surface water is important for maintaining the stability of wetland ecosystems and protecting biodiversity.In this paper,a water extraction model is established through the GEE platform to extract surface water in Qilianshan National Park from 2000 to 2020,and on this basis,the structural and functional connectivity of surface water hydrology is studied and its change influencing factors are analyzed,and the main conclusions are as follows.(1)Changes in surface water bodies in Qilianshan National Park,Between 2000 and 2020,the average value of the maximum water body area was 255.85 km2,and the overall area of water bodies showed a process of fluctuating down and then fluctuating up,with a decline of 2.05% in 2020 relative to 2000.The average area of seasonal water bodies over the past 21 years is 164.01 km2 and the average area of permanent water bodies is 91.83 km2.The change trend of maximum water body area and seasonal water body area is basically the same,and the area of water bodies fluctuates more,while the area of permanent water bodies does not change significantly,which proves that the change of maximum water body area in Qilianshan National Park is mainly influenced by seasonal water bodies.(2)In terms of surface water hydrological structure connectivity,the number of patches has been on a decreasing trend for 21 years,indicating that some small patches scattered among each other are gradually connected into large patches,and the fragmentation of patches is decreasing.between 2000 and 2020,the patch cohesion index decreased from 92.21 to 91.54,and the natural connectivity of surface water patches decreased.In terms of hydrological functional connectivity,the threshold value of functional connectivity index is 500,in which the average value of overall connectivity index over 21 years is 0.27 and the average value of possible connectivity index is 0.9,both of which show a decreasing trend.The overall high potential connectivity index proves that the potential connectivity between surface water patches is at a high level.The key areas of hydrological connectivity identified by the patch importance index are the tributaries of the Noma River,some main streams of the Shule River and some tributaries.Analysis of the relationship between structural and functional connectivity shows that structural connectivity in surface water hydrology does not necessarily correspond to functional connectivity.(3)The factors influencing hydrological connectivity are mainly divided into natural factors and human factors,among which temperature,vegetation cover and hydrological connectivity show a strong negative correlation,i.e.,with the increase of vegetation cover and temperature,hydrological connectivity decreases.The correlation between hydrological connectivity and precipitation varies in different time periods,and there is basically no correlation throughout the time period,and the runoff volume shows a low positive correlation with hydrological connectivity.Human activities that affect hydrological connectivity include mainly water and hydroelectric facilities,the improper planning and construction of which can lead to a reduction in connectivity.