Changes in hydrological regime of rivers in the arid region of the upper Yellow River basin——a case study of the Zuli River
The Zuli River is an important first-order tributary in the semi-arid to arid region of the upper Yellow River.Its annual maximum flood flow(AMFF)reflects environmental changes in and serves as a key factor in flood control and storm water resource utilization.Based on 64 years(1957-2020)of observed hydrological data from three hydrological stations along the main stream of the Zuli River,this study employs hydrological statistics,t-tests,Mann-Kendall non-parametric tests,and Morlet wavelet analysis to examine the spatial and temporal variations,change magnitude,abrupt changes,and periodic characteristics of the AMFF.The results indicate that the AMFF in the Zuli River basin shows a decreasing trend overall,with significant(P>0.1)to highly significant(P>0.05)changes observed after the 21st century.The annual change rates in the upper,middle,and lower reaches are-5.0 m3/s,-6.4 m3/s,and-10.5 m3/s,respectively.The coefficient of variation(CV)and the modulus of the AMFF decrease with increasing cumulative frequency of flood occurrences and basin area,with variations ranging between 80%and 88%.The changes in AMFF can be divided into two periods:Ⅰ-Oscillation Period(1957-2000)andⅡ-Significant Change Period(2001-2020),with abrupt change points occurring in the first decade of the 21st century across the upper,middle,and lower reaches.In the 20th century,there was a main cycle of 10～12 years for the AMFF;thereafter,no obvious and stable main cycles were observed,but regular shorter cycles of 4～8 years existed.Changes in conditions such as rising temperatures,decreased precipitation during the flood season,and land use evolution have altered the frequency and magnitude of flood events.
Zuli River basinhydrological regimeannual maximum flood flowupper Yellow Riverarid region
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