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.