Statistical Analysis of Trends in the Red River Over a 45 Year Period

Table 3.5: Flow Adjusted Seasonal Mann-Kendall Test for Trend Results.
Station Slope (units/year) p-value
Calcium, dissolved (mg/l)
1. 0.1710 < 0.001
2. n/a n/a
3. n/a n/a
Sodium, dissolved (mg/l)
1. 0.2580 < 0.001
2. n/a n/a
3. n/a n/a
Potassium, dissolved (mg/l)
1. 0.0460 < 0.001
2. n/a n/a
3. n/a n/a
Magnesium, dissolved (mg/l)
1. 0.3567 < 0.001
2. n/a n/a
3. n/a n/a
slopes at all three monitoring stations and an extremely large slope at the south
floodway monitoring station and specific conductivity produced an increasing significant
slope at the Emerson station and insignificant slopes at the south floodway
and Selkirk monitoring stations. Certain constituents were also weighted for flow
and trends re-examined using this non-parametric method. Flow adjusting data
shows how streamflow relates with the constituents and by flow adjusting we can
remove flow effects. Slopes from the four constituents selected increased slightly
and remained significant. The question is how one would handle such increases; if
the slope is only increasing slightly relative to others with large increases the latter
should be looked at and evaluated first. Although the slopes are significant, the
p-values given in Table 3.4 and Table 3.5 are that of Kendall’s τ.
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