Research On Water Conservation Function Of The Southern Slope Of Qilian Mountain Based On InVEST Model

Qilian Mountain is not only the most important water-supplying area for Heihe River,Shule River,Shiyang River and some other inland rivers along the Hexi Corridor but also an important water-source-recharge area in the upper reaches of the Yellow River and a key area for biodiversity conservation,which boasts the advantages and disadvantages of the ecological environment.It concerns the ecological security of about 6 million people in such three provinces as Qinghai,Gansu and Inner Mongolia,and its ecological status is very essential.In this paper,the “3S” technology was used to obtain and process the data required by the model,and the water conservation module in the InVEST model was used in combination with the physical and chemical properties of the soil to calculate the effective water content of the soil and to analyze the spatial variation law;the surface energy balance principle(SEBS)was used to estimate the amount of terrestrial evapotranspiration at different time scales on the southern slope of Qilianshan Mountain,and analyze its temporal and spatial variation.Finally.The InVEST model was used to estimate the water conservation of the southern slope of Qilian Mountain.The calculation results were correlated with soil physicochemical properties,land cover types,rainfall and evapotranspiration for the spatial overlapping analysis.The geography statistical principles were combined with ArcGIS.The spatial statistics and analysis techniques have been used to analyze the water conservation function of the south slope of Qilianshan Mountain as well as the relationship between supply and demand of water source conservation.Finally,a comprehensive grade evaluation of the importance of water conservation functions on the southern slope of Qilianshan Mountain has been obtained.Finally,here came to the following conclusions:(1)From 2000 to 2015,the overall water conservation of the entire study area showed an increasing trend and gained an increase of 94.23%.(2)With the increase of DEM,the total amount of water conservation showed a decreasing trend;with the increase of longitude,the average change rate from west to east was 0.097/1°E;with the increase of latitude,it decreased from south to north.The average rate of change to the north was 0.167/1°N.(3)The amount of water conservation gradually decreased with the increase of slope,and the maximum amount of water conservation was within the range of 0-5°,and the accumulation of water resources in the range of 6-15° basically stabilized.From 15 ° to 35 °,the accumulated amount of water source decreased slowly with the change of slope.When it was above 35 °,the rate of decline obviously accelerated,which indicated that the larger the slope was,the smaller the water conservation would be.(4)There was a positive correlation between water conservation and rainfall,and the correlation in the northwest of the study area is higher than that in the southeast.The water conservation of 99.78% in the study area is positively related to precipitation,which indicated that the rainfall had a great influence on both the increase and decrease of water conservation around the year.(5)The correlation analysis between water conservation and annual evapotranspiration showed that water conservation and evapotranspiration were negatively correlated in most regions while water conservation was negatively correlated with evapotranspiration in 99.01% of the study area.(6)Weights of seven factors which affected the water conservation on the southern slope of Qilian Mountain were analyzed,and the weights of each influencing factor were determined as: rainfall(0.5125),evapotranspiration(0.0391),temperature(0.0733),vegetation Coverage FC(0.2129),land use type(0.0918),slope(0.0318),DEM(0.0387).The index method and the composite index method were used to score the importance of water conservation functions on the southern slope of Qilian Mountain,and the highest comprehensive evaluation score was 0.948 while the lowest value was 0.102.The Quantile method was used to classify the evaluation results into 7 levels: Important(0.783-0.948),Highly Important(0.690-0.782),Moderately Important(0.610-0.689),More Important(0.541-0.609),Generally Important(0.481-0.540),Mildly Important(0.398-0.480),Influence Weak(0.102-0.397).The final grade evaluation results were basically consistent with the distribution of water conservation,which increased gradually from the northwest to the southeast and a trend of being low in thesoutheast and high in the northwest.