The variation characteristics of river runoff play an important guiding role in flood and drought disaster prevention of river basin

ecological management and water resources utilization. Based on the measured daily flow of Yuluoping Station in Malian River Basin from 1956 to 2020

from the three aspects of magnitude

intensity and frequency

this article constructs fourteen extreme runoff indexes

including annual maximum 1-day runoff(Max1d)

annual maximum 3-days runoff(Max3d)

annual maximum 7-days runoff(Max7d)

annual minimum 1-day runoff(Min1d)

annual minimum 3-days runoff(Min3d)

annual minimum 7-days runoff(Min7d)

strong runoff(R95)

extremely strong runoff(R99)

weak runoff(R10)

extremely weak runoff(R5)

strong runoff frequency(Rd95)

extremely strong runoff frequency(Rd99)

weak runoff frequency(Rd10) and extremely weakrunoff frequency(Rd5). The trend

mutation and periodicity of extreme runoff in Malian River Basinare analyzed by Mann-Kendall trend test

cumulative anomaly

sequential clustering and wavelet analysis. The results indicate that Max1d

Max3d

Max7d

R99 and Rd99 show a downward trend

R95

R10

R5

Rd95

Rd10 and Rd5 show a significantly downward trend

Min1d shows an upward trend

Min3d and Min7d show a significantly upward trend. The mutation years of Max1d

Max7d

R95

R99

Rd95 and Rd99 were 2004

the mutation year of Max3d was 2005

the mutation years of Min1d

Min3d and Min7d were 1970

and the mutation years of R10

R5

Rd10 and Rd5 were 1995 and 2008. The periodicity of 14 extreme runoff indexes can be mainly divided into 3～10a interannual scale medium oscillation period and 11～40a interdecadal scale long oscillation period.