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The trend and abrupt changes of the water level–discharge rating parameters at Zhicheng during 1980–2014 were calculated by the MK and Pettitt tests (Table 1). and show increasing trends with the 99% confidence level, whereas b displays a decreasing trend at the same confidence level. The parameters , b and all display an abrupt change point in 1993 with the 95% confidence level. The parameter changes indicate that the river width–depth ratio dramatically decreased and the river channel depth increased during 1980–2014. The river channel morphology exhibits drastic changes.

Table 1

Results of the MK and Pettitt tests for the rating parameters

  MK test
Pettitt test
ParameterData periodsZTrendChange pointp
 1980–2014 5.04** Increasing 1993 0.004** 
 1980–2014 −5.01** Increasing 1993 0.004** 
 1980–2014 4.596** Decreasing 1993 0.013* 
  MK test
Pettitt test
ParameterData periodsZTrendChange pointp
 1980–2014 5.04** Increasing 1993 0.004** 
 1980–2014 −5.01** Increasing 1993 0.004** 
 1980–2014 4.596** Decreasing 1993 0.013* 

*Significant at p < 0.05.

**Significant at p < 0.01.

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