Search

Conflicts between humans and land use in the process of using water and conflicts between humans and water resources in the process of using land have led to an imbalance between natural ecosystems and socio-economic systems. It is difficult to understand the impact of the processes of water production and consumption on land patches and their ecological effects. A grid-type, basin-distributed hydrological model was established in this study, which was based on land-use units and coupled with groundwater modules to simulate the water production and consumption processes in different units. By combining land use and net primary productivity, the runoff coefficient and the water use efficiency (NPP/ET) of different land units were used as indicators to characterize the interaction between water and land resources. The results showed that the average runoff coefficients of cultivated land, forest land and grassland were 0.7, 0.5 and 0.9, respectively. Moreover, the average runoff coefficients of hills, plains and basins were 0.7, 0.7 and 0.8, respectively. The NPP produced by the average unit, evapotranspiration, in cultivated land, forest land and grassland was 7 (gC/(m2•a))/mm, 0.7 (gC/(m2•a))/mm and 0.2 (gC/(m2•a))/mm, respectively. These results provide quantitative scientific and technological support in favor of the comprehensive ecological management of river basins. [ABSTRACT FROM AUTHOR]

Highlights • We analyze the impact contribution rates of human activities and climate change on evapotranspiration. • We predicted the actual evapotranspiration by Zhang model based on land use data. • We calculated the effects of human activities on evapotranspiration by the double cumulative curves. Abstract Climate change and human activities are the two most important factors affecting water resource in Yellow River Basin, and Yellow River Basin is the most serious and prominent water shortage area in China. It is of great significance to study the impact of climate change and human activities on hydrology process in mountain areas of for water resources management. In this research, one typical watershed in the third sub region of the Loess Plateau was studied through the adoption of Zhang model. Water balance equations were established through analyzing the actual evapotranspiration from 1986 to 2016. Also, responses of evapotranspiration to climate change and LUCC were quantitatively distinguished as while. The results showed that the actual evapotranspiration was acquired by the method of water balance. During the Mann-Kendall test, the data could not produce sudden break. The actual evapotranspiration decreased along with the increase of the potential evapotranspiration. Comparatively, it increased to certain degree as the rainfall, relative humidity, temperature and wind speed increased while decreased with longer sunshine hours. Human activities played a dominant role in evapotranspiration variations, contributing approximately 90% to its change. Only 10% was contributed by precipitation factor. Large-scaled activities of the conversion from the sloping farmland to terrace were implemented in the middle 1980s in the studying Luoyugou watershed, remarkably influencing the regime of runoff generation and accordant junction. This is consequently leading to spatial-temporal variability in evapotranspiration. [ABSTRACT FROM AUTHOR]

In the past 50 years, the decrease of river runoff in China has attracted wide attention from government decision-making departments and the public. The Baiyangdian catchment is one of the regions with the most serious water shortage and the most prominent human-water conflicts, and attribution analysis of the runoff change is of considerable interest at a range of spatial scales. The Budyko framework has been widely used to attribute changes in streamflow to the effects of climate and catchment changes. In this study, we used the elasticity method based on the Budyko framework to examine the sensitivity of streamflow to climate and catchment variables, which indicated that a 1-mm decrease in precipitation would induce a 0.3546-mm decrease in streamflow, a 1-mm decrease in potential evapotranspiration would induce a 0.1045-mm increase in streamflow, and an increase of 1 in the catchment characteristic coefficient would induce a 79.6711-mm decrease in streamflow. The absolute sensitivities of streamflow to climate variables decreased with increases in the aridity index, which indicates that the streamflow was more sensitive to climate change in wet regions. Among the total changes in streamflow (−43.41 mm), the effect of climate change was +3.86 mm (accounting for 7.55%), and the effect of the catchment characteristic changes is −45.99 mm (accounting for 89.95%) based on the sensitivity analyses. The results indicate that streamflow changes in the Baiyangdian catchment are mainly caused by catchment changes. [ABSTRACT FROM AUTHOR]

• We derived an analytical expression between vegetation and the Budyko parameter at a steady state. • We provided a solution for quantifying the effects of vegetation changes on evapotranspiration. • We discussed the spatial heterogeneity of vegetation effects on evapotranspiration. Due to its role in intercepting and evaporating water, vegetation has a great influence on the catchment hydrological process, and an increased quantitative understanding of how vegetation changes affect the terrestrial water cycle is of considerable interest for a range of spatial scales. In this study, we determine the effects of vegetation changes on evapotranspiration within the Budyko framework by adapting an analytical expression between vegetation and the Budyko parameter at a steady state. We then analyzed the attributions for evapotranspiration change in the Baiyangdian catchment and quantified the effects of vegetation change. The evapotranspiration changes during 1998–2017 in the Baiyangdian catchment were mainly caused by climate change, which accounted for 58.56%, and the contribution of the Budyko parameter (n) change to evapotranspiration was 40.04%. Among the impact factors, the effect of vegetation change on evapotranspiration was not the largest, with vegetation changes in the Baiyangdian catchment resulting in a decrease in evapotranspiration of 22.9715 mm, but only accounting for 10.23%. And we also discuss the spatial pattern of the sensitivities of evapotranspiration to vegetation based on the 66 catchments in the Hai River basin, and the results indicate that an increase in the normalized difference vegetation index (NDVI) would cause a decrease in evapotranspiration in dry regions (W < 1) and cause an increase in evapotranspiration in wet regions (W > 1). Evapotranspiration was more sensitive to NDVI changes in regions of W closer to 1. [ABSTRACT FROM AUTHOR]

Hydrological cycle changes that occur due to a changing environment is a hot topic in the field of hydrological science. It is of great practical significance to study the response mechanism of hydrological process change for future water resources planning and management. In this study, the effects of climate and watershed characteristic change on the streamflow in a typical tributary of the Yellow River (the Fen River watershed) are studied based on the Budyko hypothesis. The results show that: the sensitivity coefficients of streamflow to precipitation, potential evapotranspiration, and the watershed characteristic coefficient were 0.1809, −0.0551, and −27.0882, respectively. This meant that a 1 mm decrease in the precipitation would induce a 0.1809 mm decrease in the streamflow. Additionally, a 1 mm decrease in the potential evapotranspiration would induce a 0.0551 mm increase in the streamflow, and an increase of 1 in the watershed characteristic coefficient would induce a 27.0882 mm decrease in the streamflow. The streamflow of the Fen River watershed showed a significant decreasing trend during the reference period (1951–1977). In addition, the streamflow of the change period (1978–2010) decreased 26.87 mm; and this was primarily caused by watershed characteristic change which accounted for 92.27%, while climate change only accounted for 6.50%. [ABSTRACT FROM AUTHOR]