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The Loess Plateau of China is subject to severe water shortages, and the runoff reduction observed in most watersheds exacerbates the problem. Quantifying the contributions of environmental changes to runoff reduction is thus very important for water resources management. Taking the Jing River catchment as the study area, the changes in runoff for the period of 1961–2010 at three gauge stations—the catchment outlet (Zhang Jia Shan, ZJS) and the two others from the upper reach (Yang Jia Ping, YJP, and Yu Luo Ping, YLP) were analyzed in this study. Using the Budyko framework, the spatiotemporal variations of the contributions of precipitation ( P ), potential evapotranspiration ( ET 0 ), and land surface conditions (represented by the parameter n in the Choudhury–Yang equation) to runoff changes were evaluated. A significant downward trend in runoff was detected for the ZJS and YJP stations. The sensitivity of the runoff changes to the different environmental factors considered was different. The sensitivity coefficient was the greatest for P , intermediate for ET 0 , and smallest for the land surface condition ( n ). However, the sensitivity coefficients are becoming greater over time. The decrease in P was the dominant factor in the runoff reduction at the three stations, but its effect was largely offset by the increase in n at YLP. The contribution of land surface alteration to runoff reduction has been increasing in recent years, which indicates that the improvement of vegetation coverage and the construction of terraces and check dams have strengthened their impacts on runoff. Therefore, careful attention should be paid to the hydrological effects of soil conservation measures on runoff. [ABSTRACT FROM AUTHOR]

ABSTRACT Potential evapotranspiration represents the maximum evaporative capacity for a region, which underscores the importance of analysing its changes and attribution to provide information for water resource management. This study focused on the northern Loess Plateau of China, investigated the changes in potential evapotranspiration ( ET0) using data from 34 stations during 1960-2013 and conducted its temporal and spatial attribution through the differentiation equation method. The results show that the annual mean ET0 is 1004.9 mm with a decreasing trend at the rate of 0.33 mm year−1. The lowest values were found in the northeast and southwest regions, while the greatest ET0 was in the northwest region. An 'evaporation paradox' existed as a whole, but not obviously. The ET0 was most sensitive to actual vapour pressure ( ea), followed by solar radiation ( Rs), mean temperature ( Tmean) and wind speed ( U2). The inter-annual variation in the sensitivity of ET0 in relation to climatic factors showed that ET0 became more sensitive to U2 and Tmean but less sensitive to Rs and ea from 1960 to 2013. Temporally, the increasing Tmean resulted in the increase of ET0; while its effect was weakened by the other three factors, especially by decreasing U2. The contributions of climatic factors to the ET0 spatial variation trends were also analysed along two transects, but the dominant factors were different for each transect. Furthermore, the possible impacts of human activities on ET0 changes were also discussed. [ABSTRACT FROM AUTHOR]