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Variations in runoff and sediment discharge are important characteristic variables for revealing the coupled effects of climate change (including both the natural variability of climate and anthropogenic climate change) and human activities (including soil and water conservation measures, land use changes, and hydraulic engineering construction). Based on the meteorological data from 19 meteorological stations and the hydrological data from the watershed control station of Hongqi Station, the temporal and spatial evolution of runoff and sediment discharge and the water–sand relationship were analyzed, and the response mechanisms of runoff and sediment discharge changes were clarified using Mikhail Budyko's theory and other qualitative and quantitative methods. The results determined that: (1) The runoff and sediment discharge showed significant downward trends, with linear change rates of −0.28 × 108 m3/a and −46.10 × 104 t/a, respectively. The change points of the runoff and sediment discharge occurred in 1987 and 1996, respectively. (2) The spatial distribution of water and sediment was different, and the upper and middle reaches produced water, while the downstream produced sediment. (3) Comparing potential evapotranspiration and rainfall based on Budyko theory and the regression relationship, runoff is more closely related to rainfall, and runoff changes are more affected by it. The change in sediment discharge is most closely related to sediment concentration, followed by rainfall and potential evaporation. (4) The contribution rates of runoff and sediment discharge changes influenced by climate change were 24% and 3%, respectively, and the contribution rates by human activities were 76% and 97%, respectively. Human activities, including soil and water conservation measures, land use changes, and hydraulic engineering construction were the main influencing factors, and the impacts of human activities increased from 1960 to 2019. The research results are of great significance for erosion control and ecological restoration in the Tao River Basin under the conditions of the changing environment. [ABSTRACT FROM AUTHOR]

To explore the mechanisms driving variation in ET0 (reference evapotranspiration) in an arid inland region of Northwest China, daily meteorological data from 1960 to 2019 from 19 meteorological stations in the Taohe River basin and its surrounding areas were used to analyze the temporal and spatial distributions of ET0 and meteorological variables. Various qualitative and quantitative analysis methods were used to reveal the correlation between ET0 and meteorological variables. The degree of sensitivity of ET0 variations to meteorological variables and the contribution from each meteorological variable were clarified, and the mechanisms driving variation in ET0 were fully revealed. These are the results: (1) ET0 in the Taohe River basin presented a significant upward trend with a linear change rate of 0.93 mm/a, and a sudden change occurred in 1994. The spatial variation in ET0 ranged from 779.8 to 927.6 mm/a, with low values in the upper and middle reaches and high values in the lower reaches. The ET0 at 14 stations (73.68% of the total) was significantly increased (p < 0.05), and that at 5 stations (26.32% of the total) was not significantly increased (p > 0.05). (2) RH, Rn, and u2 did not change significantly, while Tmax and Tmin showed a significant upward trend. (3) Rn is a meteorological variable closely related to variations in ET0, and is the most sensitive variable for variations in ET0, followed by Tmax and u2. (4) Tmax is the meteorological variable that contributes most to the variation in ET0 (30.98%), followed by Tmin (29.11%), u2 (6.57%), Rn (2.22%), and RH (0.05%). The research results provide a scientific basis for the rational and efficient utilization of water resources and the maintenance of ecosystem health. [ABSTRACT FROM AUTHOR]

Farming-pastoral Ecotones in China (FPEC) is one of the most fragile ecological area in China. Landscape ecological risk assessment of FPEC based on terrain gradients has important strategic significance for ensuring national ecological security and the sustainable development of social economy. Based on the 30 × 30 m land use data and DEM data of FPEC in 1980, 1990, 2000, 2010 and 2020, this paper constructs a landscape ecological risk assessment model, and uses the methods of spatial autocorrelation analysis and terrain distribution index to appraise the dynamic change law and influential factors of FPEC landscape ecological risk on various terrain gradients. The results showed that: (1) In recent 40 years, land use/land cover changes (LUCC) has significantly changed, and the farmland area has increased continuously, mainly transferred from grassland, forest and bare land, particularly the bare land converted into grassland in recent 10 years, which leads to substantial increase in grassland area. (2) The overall ecological risk of the study area showed an upward trend, and the area of highest risk regions has increased more than twice during the study period, mainly distributed in the regions of "interference of human activities in low terrain" and "change of natural high terrain environment," these regions showed a high spatial concentration. (3) Ecological risk along with terrain gradient distribution is mainly limited by climate and terrain factors, the interference of human activities and natural environment change are the main influential factors of ecological risk increase in low and high terrain, respectively. Therefore, it is necessary to adapt to local conditions, and low terrain should rationally develop and utilize natural resources to reduce the interference of unreasonable production and human activities. In order to promote the sustainable and healthy development of FPEC, the policy of closing hillsides to facilitate afforestation should be adopted in the high terrain to reduce the impact of natural environment changes. [ABSTRACT FROM AUTHOR]

Abstract: Groundwater is widely recognized as the most significant water resource for irrigation and drinking purposes in the extremely-arid inland river region. However, land use is a major force altering the hydrological processes over a range of temporal and spatial scales. Therefore, understanding the interaction between land use and groundwater processes will definitely contribute to formulate a regional sustainable development strategy and recognize the impact of land use on the groundwater flow regime in the Tailan River basin. A numerical simulation of groundwater level for the inland river basin and scenario analysis under land use using FEFLOW is presented. Spatial data of the regional land use were processed using GIS, and the effects of land use on groundwater level were simulated. The amount of irrigation water and pumped groundwater have the most remarkable influences on groundwater level as main source/sink factors. Their variations were simulated according to the irrigation systems with different crops. Other factors including percolation and evapotranspiration of precipitation and condensed water jointly exerted influences on groundwater level. Changes to farmlands had the greatest impact on Tailan River basin for groundwater level, and unused land and Gobi had the least impact on groundwater level. Groundwater level maintained a decreasing trend in the irrigated zone, and increasing groundwater pumping would further intensify the water shortage in Tailan river basin. This coupled effects resulted from land use and extensive groundwater pumping were considered as the major human-induced factors influencing the groundwater system in the extremely-arid inland river basins. The results can provide useful support for land use. Understanding hydrological processes at the watershed level is essential in land use and water resource planning and management, and the proposed approach can be used as a management and planning tool for evaluating the local and overall impacts of land use management on the surface and groundwater flow regimes. [Copyright &y& Elsevier]