Trends and variability in flood magnitude under climate change in the Qilian Mountains, Northwest China

Abstract

Analyzing trends in flood magnitude changes and its driving factors under climate change is a key challenge for effective water resources management in arid and semi-arid regions, especially for inland rivers originating in the Qilian Mountains (QMs). Based on the annual maximum peak discharge (AMPD) and Peaks-Over-Threshold (POT3M) flood series of twelve typical rivers from 1970 to 2021, spatial and temporal trends in flood magnitude were investigated using Sen’s slope estimator and Mann-Kendall test. The results showed that in AMPD series, 42% of the rivers were significantly decreasing trends while 8% was significantly increasing; the POT3M series differed in that 25% of the rivers were significantly decreasing trends while 8% was significantly increasing. The regional differences in the QMs from east to west were that rivers in the eastern region (e.g., Gulang, Zamu, and Xiying rivers) showed significantly decreasing trends in AMPD and POT3M; most rivers in the central region had no significant trend, while the Shule river in the western region showed a significantly increasing trend. Temperatures and precipitation showed a fluctuating increasing trend after 1987, which were the main factor contributing to the change in flood magnitude trends of AMPD and POT3M flood series in the QMs. Regional differences in precipitation, precipitation intensity, and the ratio of glacial meltwater in the rivers of the eastern, central and western regions resulted in differences in flood magnitude trends between the east and west.