Spatio-temporal Analysis Of Water Conservation In The Northern Piedmont Of Qinling Mountains Based On In VEST Model And SWAT Model

The normal water content function of the ecosystem is related to the stability of the regional ecosystem,and the quantitative assessment of the water content function is important for the regional ecosystem management and ecological civilization construction.Different quantitative assessment models have more or less regional limitations,but applying two models together in the same watershed can effectively avoid errors and make the assessment results more accurate,in order to realize the detailed supervision of regional ecological environmental protection.In this paper,from the perspective of hydrological model selection,the middle and upper reaches of Fenghe River basin at the northern slope of Qinling Mountains is taken as the study area,and the annual,seasonal and monthly time scales of water production capacity and water holding capacity of the basin from 2008 to 2016 are assessed based on the traditional distributed hydrological model SWAT model,the latest ecosystem service assessment model In VEST model and the regional water balance method.The quantitative assessment of water production capacity and water holding capacity in the basin was conducted from 2008 to 2016 at annual,seasonal and monthly time scales.Geographic probes,correlation analysis,regression analysis and trend line analysis were also used to reveal the factors influencing the spatial and temporal variation of water production capacity and water holding capacity in the basin.The results of the study show that.(1)Both the SWAT model and the In VEST model can be useful in the study of water yield and water holding capacity of river basins.The results of the SWAT model are smaller than those of the In VEST model on an annual scale.The average multi-year water yield of the watersheds assessed by the In VEST model is 156-526 mm,while the average multi-year water yield of the watersheds assessed by the SWAT model is 12-265 mm;the average multi-year water holding capacity of the watersheds assessed by the In VEST model is44-491 mm,while the average multi-year water holding capacity of the watersheds assessed by the SWAT model is 5-264 mm.This may be caused by the principle of the respective models,the accuracy of the input data,the results of the model tests,the choice of the water content assessment method and the spatial heterogeneity with the comparison study area.(2)The assessment accuracy of the two models differs in different time scales.It is verified that the In VEST model is more suitable than the SWAT model in assessing the water content of Fenghe River basin at the annual scale;the SWAT model has obvious advantages at the seasonal and monthly scales.(3)There is a consistency in the spatial and temporal distribution characteristics of water production services and water holding capacity in the middle and upper Fenghe River basin on the northern slope of the Qinling Mountains.In terms of temporal distribution,from January to December,the water production capacity and water connotation capacity of the basin show a trend of strengthening first and then weakening,with January to April and November to December being weaker,May to October being stronger,and September being the strongest month for water production capacity and water connotation capacity of the basin.Among the seasons,summer and autumn are stronger in water production and water holding capacity,followed by spring and the weakest in winter.In terms of spatial distribution,the average annual,seasonal and monthly water production capacity and water connotation capacity of the river basin show that the closer to the main ridge of the Qinling Mountains,the stronger the water production capacity and water connotation capacity are.(4)Climate factor is the dominant factor in the spatial and temporal distribution of water production capacity and water connotation capacity in the middle and upper reaches of Fenghe River basin,but water production capacity also directly affects the distribution of water connotation capacity.Specifically,the water production capacity and water connotation capacity are stronger in the mountainous areas in the upper reaches of the river basin where precipitation is relatively high,and weaker in the middle reaches where evapotranspiration is strong and disturbed by human activities.At the same time,the intra-annual variation of water production capacity and water connotation capacity is consistent with the intra-annual variation of precipitation,and the water production capacity of the basin is strongest in the summer and autumn seasons(mainly July to September)when precipitation is high.(5)The analysis of the intra-annual water yield capacity of the middle and upper reaches of the Fenghe River basin found that the average requirements of the basin can be met from May to October under the premise of the SWAT model assessment results;the requirements can also be met in summer and autumn on a seasonal scale.The results of the above study can be helpful for the construction of ecological environment in the middle and upper reaches of Fenghe River watershed.