Evaluation and decomposition of factors responsible for alteration in streamflow in lower watersheds of the Han River Basin using different Budyko-based functions

Streamflow is documented as a key element of the hydrological cycle, and alterations in streamflow may result in hydrological disaster. The accurate quantification of streamflow under various climatological and anthropogenic factors, as well as decomposing their respective effects, remains challenging. In this study, we quantified and split the effects of climate variation and human action on streamflow changes in lower watersheds of the Han River. We utilized distinct methodologies and compared their outcomes. The methodologies include Budyko-based curve decomposition, the Budyko-based hydrological elasticity method, the conceptual eco-hydrological method, and the hydrological sensitivity analysis method. Subsequently, the hydrological change point was inspected in 1997. During the baseline period (1966–1997), variations in climate led to changes in the streamflow. In contrast, in the post-baseline period (1998–2013), the variation in the streamflow was attributed to the combined effects of climate variation and human action. Climate variation was observed to be a prominent accountable feature in streamflow alterations. The results obtained from different methodologies appeared to align with each other, showing that 70% to 91% (average 80%) of the alteration in the streamflow occurred in response to variations in climate-related parameters. The contribution from human action was less, accounting for 9% to 30% (average 20%) of the change. Moreover, the relative proportion of effects was perceived to be sensitive to the methods applied and the type of Budyko-based function. Further, the relative impacts of both factors can enhance the uncertainty in the management of water resources. Thus, this information is essential for the execution of water management on the spatial and temporal scales to reduce the risk of hydrological disasters in the watershed.