Study On Spatio-Temporal Characteristics And Multi-Scenario Prediction Of Water Conservation In Qilian Mountain National Park

The water conservation function of the ecosystem can store precipitation and reduce flood peak in the season of heavy rainfall,and recharge the river in the form of groundwater in the season of low rainfall to maintain the regional water ecological balance.Qilian Mountain National Park is located in the northern margin of Qinghai-Tibet Plateau.It is the most important source of water flow in Heihe River,Shiyang River,Shule River and other river basins in Hexi Corridor area.It regulates regional water circulation and nourishes the arid northwest inland mainly through its water conservation function.Therefore,it is of great practical significance to quantitatively assess the water conservation level and predict the future evolution scenario for the construction of national parks and the coordinated protection of regional water resources.Based on InVEST model and water conservation repair,this paper quantitatively calculated the annual water conservation of Qilian Mountain National Park from 2001 to 2021,analyzed its temporal and spatial characteristics and influencing factors,and identified the main factors(precipitation and land use)affecting the water conservation of Qilian Mountain National Park.On this basis,by predicting the future changes of decreased water volume and land use under different scenarios,the spatio-temporal evolution characteristics of water conservation in Qilian Mountain National Park during 2022-2060 were studied under multiple scenarios.The main conclusions are as follows:(1)From 2001 to 2021,water conservation in Qilian Mountain National Park showed a slight upward trend,and the spatial distribution pattern was much lower in the west than in the east and slightly lower in the north than in the south.Among them,91.25% of the regional area showed an increasing trend and 6.56% showed a decreasing trend.The high value areas of water conservation were concentrated in the forest and grassland areas in the east,south and central regions of the study area,while the water conservation was relatively low in Subei County in the west,which was consistent with the spatial distribution characteristics of precipitation.(2)The influences of elevation,slope,precipitation,air temperature and land use on water conservation in the study area were compared and analyzed.The results show that the water conservation function of the Qilian Mountain National Park is most prominent in the area with an elevation of 3000-3500 m and a slope of 5-20 °.There was a significant positive correlation between water conservation and precipitation,and the correlation between water conservation and air temperature was significantly affected by altitude.The correlation between water conservation and air temperature was higher in lower altitude region,but lower in higher altitude region.The relationship of water conservation capacity of different land use types was forest land > grassland > cultivated land > water area > unused land > glacier snow cover.The results show that the interannual change of precipitation plays a leading role in the interannual change of water conservation,followed by the interannual change of land use,and the interannual change of air temperature has almost no effect.Accordingly,precipitation and land use were selected as the main influencing factors to carry out the prediction research of water conservation in different scenarios.(3)Under the two future scenarios,the annual precipitation in Qilian Mountain National Park showed a trend of fluctuation and increase in time,and the spatial distribution pattern was higher in the south than in the north and higher in the east than in the west.Under the natural evolution scenario,the main change of land use structure in the future is that the area of forest land,water area and unused land increases,the area of grassland decreases,and the area of cultivated land and glacier snow is almost unchanged.Under the ecological restoration scenario,the area of woodland and grassland increased,the area of unused land decreased,the cultivated land remained unchanged,and the water area,glacier and snow were consistent with the natural evolution scenario.(4)Water conservation in the study area showed an overall increasing trend under four future scenarios;When the precipitation scenario was constant,the water conservation in the land use ecological restoration scenario was higher than that in the natural evolution scenario.When the land use scenario is fixed,the annual average water conservation under SSP245(following historical development)scenario is higher than that under SSP119(sustainable development)scenario,but the relationship between water conservation and water conservation in specific years is not fixed.The spatial distribution pattern of water conservation was high in the east and low in the west,high in the south and low in the north,high in the forest-grassland area and low in the non-forest-grassland area.Under the SSP119/natural evolution scenario,61.58% of the water conservation area showed an increasing trend,while 32.14% showed a decreasing trend.Under the SSP119/ecological restoration scenario,64.40% of the areas showed an increase and 29.25%showed a decrease.Under the SSP245/ natural evolution scenario,89.07% of the regions showed an increase and 2.50% showed a decrease.Under the SSP245/ecological restoration scenario,90.146% of the areas showed an increase and 2.26%showed a decrease.