Anthropogenic Impacts on Streamflow-Compensated Climate Change Effect in the Hanjiang River Basin, China

The relative importance of climate change and anthropogenic impacts on hydrology in the Hanjiang River Basin in China have become a hot topic because it has been manipulated by multiple activities, including reservoir regulation and interbasin water diversion that have abrupt impacts as well as land use change and irrigation that have gradual impacts. Using long-term data of streamflow, climatic variables, agricultural statistics, and land use maps during 1965-2017, the Mann-Kendall test was applied to detect hydroclimatic trends, and a Budyko-based covariate analysis was used to evaluate the individual and combined effects of climate variability and human activities on streamflow. Results indicated the following: (1) there was a significant increase of temperature, which may be human-induced to some extent; (2) the overall anthropogenic effect due to urbanization, reservoir regulation, increased irrigated areas, and loss of cultivated fields increased streamflow, which compensated the effects of climate change; (3) climate change was the dominant factor for streamflow decrease in the upper basin, while anthropogenic impacts in the middle basin overweighed climate change; and (4) an annual streamflow variation in the upper basin due to the regulation of the Danjiangkou Reservoir was nonignorable.