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Based on the mean annual streamflows from 1960 to 2011, the five quartiles were determined to be Qmin = 0.20 m3 s–1, Q25 = 0.65 m3 s–1, Q50 = 0.96 m3 s–1, Q75 = 1.38 m3 s–1, and Qmax = 4.02 m3 s–1. The chance for a year with a mean annual streamflow of smaller than Q50 = 0.96 m3 s–1 was greater after 1994 than before this year (Figure 5). This is also true for daily streamflows (Table 3). On average, 51% of the post-1994 days, but only 35% of the pre-1994 days, had a streamflow less than Qmin = 0.20 m3 s–1. In contrast, the percentage of the days with a streamflow of larger than Q50 was determined to be much greater before 1994 than after this year regardless of time scale. However, the occurrences of the daily spring streamflows in any magnitudes were roughly the same before and after the abrupt change year.

Table 3

Occurrence of daily streamflowa

Percent of days with a streamflow (m3 s–1)
Period and time scale< =Qmin< =Q25> =Q50> =Q75> =Qmax
1960–1993 35 49 37 26 
Spring 88 91 
Summer 16 65 46 11 
Fall 14 42 43 30 
1994–2011 51 75 17 11 
Spring 91 95 
Summer 10 53 31 19 
Fall 51 77 17 12 
Percent of days with a streamflow (m3 s–1)
Period and time scale< =Qmin< =Q25> =Q50> =Q75> =Qmax
1960–1993 35 49 37 26 
Spring 88 91 
Summer 16 65 46 11 
Fall 14 42 43 30 
1994–2011 51 75 17 11 
Spring 91 95 
Summer 10 53 31 19 
Fall 51 77 17 12 

aQmin, Q25, Q50, Q75, and Qmax are five quartiles (respectively, minimum, first quartile, second quartile/mean, third quartile, and maximum) of the mean annual streamflows from 1960 to 2011. Qmin = 0.20 m3 s–1; Q25 = 0.65 m3 s–1; Q50 = 0.96 m3 s–1; Q75 = 1.38 m3 s–1; and Qmax = 4.02 m3 s–1.

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