Abstract:

Based on monthly streamflow data from 372 stations covering the period 1960-2000 and the monthly streamflow data from 41 stations covering the period 2001-2014 across China, human- and climate-induced impacts on hydrological processes were quantified for 10 river basins in China based on development of Budyko-based coupled water-energy balance model. Penman-Monteith potential evapotranspiration model was used to analyze evapotranspiration processes. Besides, elasticity coefficient was also quantified for the impacts of meteorological variables on streamflow changes. The results indicated that: (1) Compared to southern China, streamflow changes are more sensitive to climate changes and human activities in northern China. Generally, relative humidity changes have positive impacts on streamflow changes. However, the maximum temperature, minimum temperature, solar radiation, wind speed and LUCC changes tend to go against streamflow changes. The elasticity coefficients of streamflow changes for meteorological variables are: precipitation > LUCC > relative humidity > solar radiation > maximum temperature > wind speed > minimum temperature; (2) Climate changes during 1980-2000 generally help to increase annual streamflow, and the increase of streamflow by precipitation changes is most evident, and the increase of streamflow depth reaches 12.1 mm. However, impacts of meteorological variables on streamflow changes are shifting from one river basin to another, e.g. the maximum temperature and relative humidity help to increase streamflow in northern China but decrease streamflow magnitude in southern China; (3) In general, human activities tend to decrease streamflow. Changes of streamflow in the Yangtze, Songhua, Northwest, and Southeast river basins are 78.7%, 76.9%, 65.7%, and 84.2%, respectively, which can be attributed to climate changes. However, human activities play a dominant role in modifications of streamflow changes, such as Pearl River basin, Huaihe River basin, Haihe River basin, Yellow River basin, Liaohe River basin and southwest river basins, with fractional contribution being 59.4%, 77.3%, 66.2%, 69.7%, 75.3%, and 70.4%, respectively. Generally, the fraction of human activities and climate changes to streamflow changes in the river basins across China can reach 71.0% and 29.0% respectively in river basins, where climate changes play a dominant role in streamflow changes. The results of this study can be helpful to human mitigation to climate changes in terms of water resources management.

Key words: streamflow changes, elasticity coefficient, Budyko hypothesis, climate changes, human activities, China