4.1 Trend and mutation analysis of hydrometeorological elements
To reduce the uncertainty of the single mutation-point identification method, the hydrological and meteorological factor of the Qinhe River Basin in flood season were tested and analyzed using M-K, O-C, and C-A. Three abrupt change test results of hydrometeorological factors in the Qinhe River Basin were used as the basis for the division of hydrometeorological elements. The years 1982 and 1992 were selected as the two abrupt change years in the study area: 1971–1981 was the baseline period, 1982–1991 was the change period I, and 1992–2000 was the change period II. Table 2 gives the Stage division results of hydrometeorological factors.
Table 2. Stage division results of hydrometeorological factors.