Trends and variability in flood magnitude under climate change in the
Qilian Mountains, Northwest China
Abstract
Analyzing trends in flood magnitude changes and their underlying causes
under climate change is a key challenge for the effective management of
water resources in arid and semi-arid regions, particularly for inland
rivers originating in the Qilian Mountains (QMs). Sen’s slope estimator
and Mann-Kendall test were used to investigate spatial and temporal
trends in flood magnitude based on the annual maximum peak discharge
(AMPD) and Peaks-Over-Threshold (POT3M) flood series of twelve typical
rivers from 1970 to 2021. The results showed that in the AMPD series,
42% of the rivers had significantly decreasing trends, while 8% had
significantly increasing trends; in the POT3M series, 25% of the rivers
had significantly decreasing trends, while 8% had significantly
increasing trends. 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 the AMPD and POT3M
series; most rivers in the central region had non-significant trends,
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 the AMPD and POT3M flood series
in the QMs. Regional differences in precipitation, precipitation
intensity, and the ratio of glacial meltwater in the eastern, central
and western regions resulted in the differences in flood magnitude
trends between the east and west.