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Under the dual impacts of global climate change and human activities, how to accurately and quantitatively assess and identify changes in watershed runoff is crucial to the rational development and utilization of water resources. Different methods of identifying runoff change attribution are applicable to different environments. In this study, we used five different methods, including the double mass curve (DMC), the soil and water assessment tool (SWAT), and the three Budyko hypotheses based on Fu, Choudhury‒Yang, and Milly‒Zhang formulas to explore the impact of human activities and climate change on runoff change in the Jinghe River basin (JRB). The results show that annual runoff of the JRB decreased considerably, and human activities accounted for more than 90%. Specifically, the results of the SWAT model and the three Budyko hypotheses are highly consistent except for the DMC method, which is not recommended in basins with significant changes in factors other than precipitation. More importantly, the Budyko hypothesis based on the Milly‒Zhang formula uses the vegetation water utilization coefficient to consider the impact of vegetation change on runoff, which is most consistent with the simulation results of the SWAT model and is recommended for the attribution analysis of changes in the Loess Plateau represented by the JRB. [ABSTRACT FROM AUTHOR]

The correlation between runoff and sediment challenges ecological preservation and sustainable development in the Yellow River Basin. An understanding of the key factors influencing variations in runoff and sediment transport in crucial river basins is essential for effective soil erosion management within the context of ecological and economic development. The Mann–Kendall test, Pettitt test, and Morlet wavelet analysis were employed in the Wuding River Basin to analyze the trends in runoff and sediment changes from 1960 to 2020. We explored the double cumulative curve method to assess the contribution rates of precipitation and human activities to the variability of runoff and sediment transport. We explored the primary factors driving the changes in runoff and sediment transport through random forest regression analysis. (1) From 1960 to 2020, annual precipitation in the Wuding River Basin increased minimally, while annual runoff and sediment transport decreased strongly with abrupt changes. Abrupt changes in annual runoff and sediment transport occurred in 1971 and 1979, respectively. (2) The relationship between runoff and sediment transport changed in approximately 1972 and 2000. The distribution of monthly runoff became more uniform during Periods II (1973–2001) and III (2002–2020) compared to that during the baseline period (1960–1972, Period I), while sediment transport became increasingly concentrated in the flood season. (3) During Period II, the contribution rates of climate and human activities to runoff and sediment transport were 11.94% and −14.5%, respectively, compared to the baseline period. During Period III, the contribution rates of climate and human activities to runoff and sediment transport were −11.9% and −17.7%, respectively. Human activities substantially reduced runoff and sediment, with greater impacts on sediment reduction. Climate weakly influenced basin sediment transport variations. (4) The normalized difference vegetation index (NDVI) and grassland area extent had the greatest impact on runoff, while the NDVI and forest area extent affected sediment transport. [ABSTRACT FROM AUTHOR]

Revealing the impact of future climate change on the characteristics and evolutionary patterns of meteorological and hydrological droughts and exploring the joint distribution characteristics of their drought characteristics are essential for drought early warning in the basin. In this study, we considered the Jinghe River Basin in the Loess Plateau as the research object. The standardized precipitation index (SPI) and standardized runoff index (SRI) series were used to represent meteorological drought and hydrological drought with monthly runoff generated by the SWAT model. In addition, the evolution laws of the JRB in the future based on Copula functions are discussed. The results showed that: (1) the meteorological drought and hydrological drought of the JRB displayed complex periodic change trends of drought and flood succession, and the evolution laws of meteorological drought and hydrological drought under different spatiotemporal scales and different scenario differ significantly. (2) In terms of the spatial range, the JRB meteorological and hydrological drought duration and severity gradually increased along with the increase in the time scale. (3) Based on the joint distribution model of the Copula function, the future meteorological drought situation in the JRB will be alleviated when compared with the historical period on the seasonal scale, but the hydrological drought situation is more serious. The findings can help policy-makers explore the correlation between meteorological drought and hydrological drought in the background of future climate change, as well as the early warning of hydrological drought. [ABSTRACT FROM AUTHOR]

The naturalized streamflow, i.e., streamflow without water management effects, in the Yellow River basin (YRB) has been significantly decreased at a rate of -3.71×108 m 3 yr -1 during 1982–2018, although annual precipitation experienced an insignificantly positive trend. Explicit detection and attribution of naturalized streamflow are critical to manage limited water resources for the sustainable development of ecosystems and socio-economic systems. The effects from temporally explicit changes of climate variables and underlying surfaces on the streamflow trend were assessed using the variable infiltration capacity (VIC) model prescribed with continuously dynamic leaf area index (LAI) and land cover. The results show a sharp increase of the LAI trend and land use change as a conversion of cropland into forest grass in the basin. The decrease in naturalized streamflow can primarily be attributed to the vegetation changes including an interannual LAI increase and intra-annual LAI temporal pattern change, which account for the streamflow reduction of 1.99×108 and 0.45×108 m 3 yr -1 , respectively. The impacts of the LAI change are largest at the subregion of Longmen–Huayuankou where the LAI increasing trend is high and land use change is substantial. Attribution based on simulations with multiyear average LAI changes obviously underestimates the impacts of the interannual LAI change and intra-annual LAI temporal change on the natural streamflow trend. Overall, the effect of climate variation on streamflow is slight because the positive effect from precipitation and wind speed changes was offset by the negative effect from increasing temperature. Although climate variation is decisive for streamflow change, this study suggests that change in underlying surfaces has imposed a substantial trend on naturalized streamflow. This study improves the understanding of the spatiotemporal patterns and the underlying mechanisms of natural streamflow reduction across the YRB between 1982 and 2018. [ABSTRACT FROM AUTHOR]

At present, much attention has been paid to the ecology, economics, and social benefits of erosion control projects: however, the evaluation of an erosion control technology itself has been neglected. This study selected six soil conservation measures applied to the Loess Plateau, and a comprehensive evaluation model was developed considering the maturity of the technology, application difficulty of the technology, technology efficiency, and the potential of technology promotion. The relation between a condition attribute and a decision attribute is evaluated using rough set theory, and the decision attribute is completely dependent on the condition attribute, which indicates that the index system can better evaluate the soil conservation measures applied to the Loess Plateau. Rough set theory was used to determine the weights of evaluation indexes, which overcomes the limitation of relying only on expert opinions or index data to determine the weights. According to the comprehensive scores, the six soil conservation measures can be grouped into three levels: the first level includes economic forests, check dams, and terraces; the second level includes afforestation and conversion to grassland, and the third level includes enclosures. The results can provide a scientific basis for the promotion and application of the high-ranking soil conservation measures in the Loess Plateau. However, the comprehensive evaluation of the soil conservation measures applied to the Loess Plateau is a very complex problem. To maximize the eco-environmental benefits, land use patterns should be rationally adjusted, and corresponding soil conservation measures could be suitable for meeting the regional development goals. [ABSTRACT FROM AUTHOR]

Climate variation and underlying surface dynamics have caused a significant change in the trend of evapotranspiration (ET) in the Yellow River Basin (YRB) over the last two decades. Combined with the measured rainfall, runoff and gravity recovery and climate experiment (GRACE) product, five global ET products were firstly merged using a linear weighting method. Linear slope, "two-step" multiple regression, partial differential, and residual methods were then employed to explore the quantitative impacts of precipitation (PCPN), temperature (Temp), sunshine duration (SD), vapor pressure deficit (VPD), wind speed (WS), leaf area index (LAI), and the residual factors (e.g., microtopography changes, irrigation, etc.) on the ET trend in the YRB. The results show that: (1) The ET estimates were improved by merging five global ET products using the linear weighting method. The sensitivities of climatic factors and LAI on the ET trend can be separately calculated using proposed "two-step" statistical regression method; (2) the overall ET trend in the entire study area during 2000–2018 was 3.82 mm/yr, and the highest ET trend was observed in the Toudaoguai-Longmen subregion. ET trend was dominantly driven by vegetation greening, with an impact of 2.47 mm/yr and a relative impact rate of 51.16%. The results indicated that the relative impact rate of the residual factors (e.g., microtopography, irrigation, etc.) on the ET trend is up to 28.17%. The PCPN and VPD had increasing roles on the ET trend, with impacts of 0.45 mm/yr and 0.05 mm/yr, respectively, whereas the Temp, SD, and WS had decreasing impacts of –0.19 mm/yr, –0.15 mm/yr, and –0.17 mm/yr, respectively. (3) The spatial pattern of impact of specific influencing factor on the ET trend was determined by the spatial pattern of change trend slope of this factor and sensitivity of ET to this factor. ET trends of the source area and the Qingtongxia–Toudaoguai were dominated by the climatic factors, while the residual factors dominated the ET trend in the Tangnaihai–Qingtongxia area. The vegetation restoration was the dominant factor causing the increase in the ET in the middle reaches of the YRB, and the impact rates of the LAI were ranked as follows: Yanhe Rive > Wudinghe River > Fenhe River > Jinghe River > Beiluohe River > Qinhe River > Kuyehe River > Yiluohe River. [ABSTRACT FROM AUTHOR]

• The Budyko model with time-varying parameters improved the model accuracy. • The elasticity coefficient method was adopted to attribution analysis. • n had a strong linear relationship with climatic and vegetation factors. • Precipitation and vegetation coverage were dominant factors affecting runoff change. The evolution of basin runoff is related to water resource development and the safety of the ecological environment. This study took the Wuding River Basin (WRB) as the study area, using trend analysis, significance tests, and the elasticity coefficient method to identify the impact factors of basin runoff change. Based on four Budyko equations and stepwise multiple linear regression analysis, a fitting equation of time-varying underlying surface parameters that considers various factors was constructed, and the contribution rates of climatic and vegetation changes to runoff change were quantified. The WRB Runoff decreased significantly (p ≤ 0.05) at a rate of −0.175 mm∙a−1 during 1982–2019, and precipitation and potential evapotranspiration showed significant increasing trends. Sensitivity of runoff changes to time-varying underlying surface parameters, precipitation, and potential evapotranspiration decreased sequentially. Simulation accuracies of the Budyko equations for runoff changes were significantly improved with time-varying underlying surface parameters. The change of vegetation factors was the dominant factor leading to runoff reduction, and the impact of climatic factors on the runoff change was characterized by "promotion first, inhibition later." The results provide a reference for water resource development and utilization and the hydrological–ecological response in the Loess Plateau region under a changing environment. [ABSTRACT FROM AUTHOR]

The changes in runoff and sediment load in the Loess Plateau of China have received considerable attention owing to their dramatic decline during recent decades. In this paper, the impacts of land-use and climate changes on water and sediment yields in the Huangfuchuan River basin (HFCRB) of the Loess Plateau are investigated by combined usage of statistical tests, hydrological modeling, and land-use maps. The temporal trends and abrupt changes in runoff and sediment loads during 1954–2012 are detected by using non-parametric Mann–Kendall and Pettitt tests. The land-use changes between 1980 and 2005 are determined by using transition matrix analysis, and the effects of land-use and climate changes on water and sediment yields are assessed by using the Soil and Water Assessment Tool (SWAT) hydrological model and four scenarios, respectively. The results show significant decreasing trends in both annual runoff and sediment loads, whereas slightly decreasing and significantly increasing trends are detected for annual precipitation and air temperature, respectively. 1984 is identified as the dividing year of the study period. The land-use changes between 1980 and 2005 show significant effects of the Grain for Green Project in China. Both land-use change and climate change have greater impact on the reduction of sediment yield than that of water. Water and sediment yields in the upstream region show more significant decreases than those in the downstream region under different effects. The results obtained in this study can provide useful information for water resource planning and management as well as soil and water conservation in the Loess Plateau region. [ABSTRACT FROM AUTHOR]