[Background] Runoff and sediment load play an important role in development and
utilization of water resources,shaping the river morphology,maintaining river ecological system. The
runoff and sediment load in the Yellow River have decreased greatly in the past several decades because
of climate change and anthropogenic influences. Better understanding the spatial-temporal variation in
runoff and sediment load and their relationship in the mainstream of the Yellow River can provide good
reference for watershed management and soil and water conservation. [Methods]This study attempted toinvestigate the changes of runoff and sediment load at 6 hydrological stations along the mainstream of the
Yellow River from 1950 to 2017. The linear-regression analysis,the non-parametric Mann-Kendall test,
the accumulative annual anomaly,the flow-sediment curve and wavelet transform were employed for
investigation. [Results]Annual runoff and sediment load at Tangnaihai station showed a non-significant
downward trend,whereas annual runoff and sediment load at Lanzhou, Toudaoguai, Longmen,
Huayuankou and Gaocun stations showed significant decreasing trends ( P <0. 05) . The annual streamflow
exhibited the most significant decrease at Gaocun station with average reduction rate of -5.12 ×10 8 m 3 /a,
while the streamflow at Tangnaihai station showed gently decrease ( - 0. 21 × 10 8 m 3 /a) . Positive
correlation between runoff and sediment load was examined at all the stations before 2000. A abrupt
changes of annual runoff and sediment load were examined in 1985. A periodical fluctuation of 0. 5 -1,
3 -5,and 7 -9 years was detected before the 1990s. Flow-sediment curve showed that sediment supply
from upstream of Toudaoguai station had increased 18. 2% since 1986 due to severe siltation in the
mainstream section of Ningxia and Inner Mongolia,but the sediment transport capacity had decreased
8. 3%. The construction of Xiaolangdi Reservoir altered the exponential relationship between flow and
sediment at its downstream stations( Huayuankou and Gaocun) after 2000. [Conculsions]Large-scale
hydraulic projects,soil and water conservation and water withdrawal by agriculture and industry are the
dominant causes for significant reduction in runoff and sediment load in the mainstream of the Yellow
River.
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