Quantifying the Impacts of Climate Change and Human Activities on Monthly Runoff in the Liuhe River Basin, Northeast China

Both climate change and human activities have had a significant impact on hydrological processes. Quantification of affecting factors on river regime changes is scientifically essential for understanding hydrological processes and sustainable water resources management in the basins. This study investigates the features of variations in meteorological and hydrological variables in the Liuhe River Basin (LRB) from 1956 to 2020 based on various observed records and statistical methods. It then quantitatively identifies the possible impacts of climate variability and human activities on runoff in the LRB using the empirical methods and the Budyko framework. The results show that (1) the runoff demonstrates a significantly decreasing trend over the past 65 years, but the rainfall has no obvious trend with significant interannual fluctuations, and potential evapotranspiration exhibits a weekly decreasing trend, particularly in summer. (2) The runoff series can be divided into two periods, i.e., the baseline (1956–1969) and change (1970–2020) periods, and the change period can also be divided into two stages, i.e., stage I (1970–1999) and stage II (2000–2020). (3) Human activities are the dominant factors in the runoff decline in the LRB, with the contribution rates being greater than 80% in the change period, particularly for stage II. The analysis of this study can provide a reference for the rational utilization of water resources in the LRB.