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The Soil and Water Assessment Tool (SWAT) model is diffusely applied to areas with uniform precipitation distribution and gentle slopes. However, the SWAT has apparent defects in the process of ecohydrological simulation in mid-high latitudes and arid regions. This model can merely be used in agricultural catchments with gentle slopes and uniform rainfall, and the simulation is not suitable for high-altitude alpine catchment. To this point, this paper makes appropriate improvements to the runoff module, and specifically corrects the key sensitive parameters. The global sensitivity and performance assessment of the model's parameters were carried out before and after the improvement using the monthly data of runoff and evaporation from 1990 to 2018 in the Kaidu River basin in northwestern China. It is indicated that the Modified SWAT simulates the performance of monthly runoff and evapotranspiration better than the original SWAT, which overestimates the runoff volume throughout hydrological changes in different periods. Compared with the monthly water production under different land use/cover conditions, the highest water production was found in forest and grassland. By modifying the SWAT algorithm, the structural non-determinacy of the Modified SWAT is significantly reduced, and the adaptability of the model is improved. Thus, the Modified SWAT shows a better simulation performance in arid areas with considerable terrain variation and scarce rainfall data. [Display omitted] [ABSTRACT FROM AUTHOR]

The determination of spatiotemporal variation in ecosystem service value and its drivers is fundamental to ecosystem service management and decision-making. This paper selects a typical oasis irrigation district in the arid regions of northwest China as the research object. Using the benefit transfer method to evaluate the ecosystem service value variation caused by land use and land cover change and characteristics of its spatial distribution based on multi-temporal land use and land cover data sets (1977, 1987, 1997, 2007, 2017). Meanwhile, the contributions of factors driving ecosystem service value and their interactions were explored using geographical detector. The results showed the following: 1) The land use and land cover structure was stable from 1977 to 2017, and the overall ecosystem service value increased slightly. The services provided by the oasis ecosystem dominated the fluctuations in ecosystem service value throughout the study region. 2) Ecosystem service value exhibited a strong positive spatial autocorrelation. The high values were concentrated in the oasis area in the north of the study area, while the low values mainly appeared in the desert ecosystem. 3) The land use degree and human activity intensity index of human factors are the main factors leading to the differentiation of ecosystem service value. Synergized interactions among human activities, changes in landscape patterns, and natural factors produced the spatial differentiation in ecosystem service value of the study region. The results suggest that in future decision-making for ecosystem management, the direction of human activities within the ecological environment should be controlled. Improve the diversity of patches, reduce the degree of landscape fragmentation, improve the ecosystem service function of LULC, optimize the allocation of ecological landscape resources. [ABSTRACT FROM AUTHOR]