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Although the simulated monthly runoff depth under the QQDC-A1B and SDC-A1B scenarios follows a similar temporal pattern, considerable differences remain between these two monthly runoff time series. The paired-sample Wilcoxon signed-rank test indicates that, in Boluo watershed, the June–August runoff in QQDC-A1B is significantly greater than that in SDC-A1B at a 5% significance level (Table 5). By contrast, the late spring (April–May) runoff in QQDC-A1B is significantly less than that in SDC-A1B at the same significance level. These runoff differences basically agree with the precipitation differences as shown in Table 3. The other two watersheds also have a similar situation (not shown in this paper).

Table 5

Statistical properties of the simulated monthly runoff depth under the QQDC-A1B and SDC-A1B scenarios in Boluo watershed

Runoff quartiles (mm)
Paired-sample Wilcoxon signed-rank test
MonthScenariosMinQ1MedianQ3Maxzcalzcrip-value
January QQDC-A1B 23.1 33.1 38.7 47.4 73.4 0.519= 1.96a 0.6089 
 SDC-A1B 22.9 33.0 38.0 46.5 69.1    
February QQDC-A1B 16.4 26.8 32.7 39.7 109.5 2.304> 1.64b 0.0098 
 SDC-A1B 16.4 27.0 31.9 37.5 91.5    
March QQDC-A1B 18.0 32.8 46.2 64.5 262.6 0.370= 1.96a 0.7113 
 SDC-A1B 18.9 34.8 47.1 64.7 238.7    
April QQDC-A1B 24.5 47.8 74.8 93.7 208.7 −2.345< 1.64b 0.0087 
 SDC-A1B 25.2 49.2 77.4 93.3 162.0    
May QQDC-A1B 22.8 87.9 125.1 193.4 317.1 −1.97< 1.64b 0.0236 
 SDC-A1B 23.0 89.6 128.4 193.5 329.0    
June QQDC-A1B 51.0 111.6 157.2 213.7 401.3 3.929> 1.64b 0.0000 
 SDC-A1B 50.8 106.8 149.5 205.0 363.2    
July QQDC-A1B 57.0 86.7 109.2 151.0 238.3 2.931> 1.64b 0.0012 
 SDC-A1B 57.2 86.4 110.7 138.7 231.0    
August QQDC-A1B 34.1 95.5 128.6 149.7 240.4 4.237> 1.64b 0.0000 
 SDC-A1B 35.8 92.8 121.1 139.4 180.1    
September QQDC-A1B 32.8 72.5 87.2 113.7 277.6 0.309= 1.96a 0.7611 
 SDC-A1B 34.5 72.5 86.6 116.2 263.4    
October QQDC-A1B 21.6 54.9 71.7 100.9 306.4 0.802= 1.96a 0.4250 
 SDC-A1B 24.1 56.8 68.9 98.0 168.8    
November QQDC-A1B 20.2 42.3 48.9 59.7 88.9 2.407> 1.64b 0.0071 
 SDC-A1B 18.6 41.4 46.8 58.8 81.4    
December QQDC-A1B 14.5 37.9 43.0 50.5 246.6 0.082= 1.96a 0.9354 
 SDC-A1B 14.9 38.6 43.7 51.0 74.2    
Runoff quartiles (mm)
Paired-sample Wilcoxon signed-rank test
MonthScenariosMinQ1MedianQ3Maxzcalzcrip-value
January QQDC-A1B 23.1 33.1 38.7 47.4 73.4 0.519= 1.96a 0.6089 
 SDC-A1B 22.9 33.0 38.0 46.5 69.1    
February QQDC-A1B 16.4 26.8 32.7 39.7 109.5 2.304> 1.64b 0.0098 
 SDC-A1B 16.4 27.0 31.9 37.5 91.5    
March QQDC-A1B 18.0 32.8 46.2 64.5 262.6 0.370= 1.96a 0.7113 
 SDC-A1B 18.9 34.8 47.1 64.7 238.7    
April QQDC-A1B 24.5 47.8 74.8 93.7 208.7 −2.345< 1.64b 0.0087 
 SDC-A1B 25.2 49.2 77.4 93.3 162.0    
May QQDC-A1B 22.8 87.9 125.1 193.4 317.1 −1.97< 1.64b 0.0236 
 SDC-A1B 23.0 89.6 128.4 193.5 329.0    
June QQDC-A1B 51.0 111.6 157.2 213.7 401.3 3.929> 1.64b 0.0000 
 SDC-A1B 50.8 106.8 149.5 205.0 363.2    
July QQDC-A1B 57.0 86.7 109.2 151.0 238.3 2.931> 1.64b 0.0012 
 SDC-A1B 57.2 86.4 110.7 138.7 231.0    
August QQDC-A1B 34.1 95.5 128.6 149.7 240.4 4.237> 1.64b 0.0000 
 SDC-A1B 35.8 92.8 121.1 139.4 180.1    
September QQDC-A1B 32.8 72.5 87.2 113.7 277.6 0.309= 1.96a 0.7611 
 SDC-A1B 34.5 72.5 86.6 116.2 263.4    
October QQDC-A1B 21.6 54.9 71.7 100.9 306.4 0.802= 1.96a 0.4250 
 SDC-A1B 24.1 56.8 68.9 98.0 168.8    
November QQDC-A1B 20.2 42.3 48.9 59.7 88.9 2.407> 1.64b 0.0071 
 SDC-A1B 18.6 41.4 46.8 58.8 81.4    
December QQDC-A1B 14.5 37.9 43.0 50.5 246.6 0.082= 1.96a 0.9354 
 SDC-A1B 14.9 38.6 43.7 51.0 74.2    

Zcal, Z-score of the calculated Wilcoxon statistics; Zcri, Z-score of the critical Wilcoxon statistics at a 5% significance level.

aTwo-tailed Z score of the critical Wilcoxon statistics at a 5% significance level.

bOne-tailed Z score of the critical Wilcoxon statistics at a 5% significance level; > QQDC-A1B monthly runoff is significantly greater than the SDC-A1B data; = QQDC-A1B and SDC-A1B monthly runoff is not significantly different; < QQDC-A1B monthly runoff is significantly less than the SDC-A1B data.

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