Streamflow changes and warming climate-induced flood risks for 1960–2016 in the Nenjiang River Basin, northeastern China

Understanding streamflow changes under climate warming is critical for water resource management and disaster prevention in mid- and high-latitude regions. However, the factors driving streamflow changes remain unclear. This study investigated long-term streamflow trends, influencing factors, responses to climate change, and future flood risks in the Nenjiang River Basin, a typical mid-latitude region in Northeast China that is highly sensitive to droughts and floods. Using data from 1960 to 2016, we applied the Mann–Kendall trend and mutation tests and random forest models, and modeled streamflow responses to climate change to explore streamflow–climate interactions. Results showed significant warming (0.24–0.41 °C/decade, p < 0.05) and increased winter precipitation (0.77 mm/decade, p < 0.05), accompanied by declining annual and autumn streamflow (−6.03 and −3.62 mm/decade, p < 0.05), with abrupt shifts in 1963, 1996, and 2013. Climate change dominated streamflow changes, although human activities contributed 65% during 2013–2016. Streamflow responded more to precipitation than temperature, except in spring. Extreme floods occurred in 1960, 1998, and 2013. Scenario analysis (2021–2100) showed the highest flood frequency under the high-emission pathway (SSP5–8.5). These findings have crucial implications for water resource management, flood risk control, farming systems, and food security.