Nonlinear Response of Streamflow to Climate Change in High-Latitude Regions: A Case Study in Headwaters of Nenjiang River Basin in China's Far Northeast

Assessment of the response of streamflow to future climate change in headwater areas is of a particular importance for sustainable water resources management in a large river basin. In this study, we investigated multiscale variation in hydroclimatic variables including streamflow, temperature, precipitation, and evapotranspiration in the Headwater Areas of the Nenjiang River Basin (HANR) in China's far northeast, which are sensitive to climate change. We analyzed 50-year-long (1961-2010) records of the hydroclimatic variables using the ensemble empirical mode decomposition (EEMD) method to identify their inherent changing patterns and trends at the inter-annual and inter-decadal scales. We found that all these hydroclimatic variables showed a clear nonlinear process. At the inter-annual and inter-decadal scales, streamflow had a similar periodic changing pattern and transition years to that of precipitation; however, within a period, streamflow showed a close association with temperature and evapotranspiration. The findings indicate that the response of streamflow in headwater regions to climate change is a nonlinear dynamic process dictated by precipitation at the decadal scale and modified by temperature and evapotranspiration within a decade