Comparison of Cations in Three Lakes

Green Lakes Basin, CO

Green Lakes Basin, CO

Red rectangles = sampling locationsBlue arrows = direction of stream flow

Continental Divide

Methods

Look at concentrations of Ca2+, Mg2+, Na+, and K+ from 1982 to 2006.

F-test – are the variances the same? T-test – are the means the same? χ2 test – are the distributions normal?

Calcium

Comparison t calc. t crit. Reject? f calc. f crit. Reject?

GL1 v. GL4 59.3444 1.9624 yes 1.9473 1.1624 yes

GL4 v. GL5 8.8542 1.9624 yes 2.1819 1.1649 yes

GL5 v. GL1 64.1980 1.9630 yes 4.2489 1.1821 yes

Site X2 calc. X2 crit. Reject?

GL1 458.2459 429.6325 yes

GL4 3.91E+013 658.0936 yes

GL5 1.70E+005 435.9879 yes

Magnesium

Comparison t calc. t crit. Reject? f calc. f crit. Reject?

GL1 v. GL4 19.0031 1.9624 yes 3.9011 1.1624 yes

GL4 v. GL5 12.0963 1.9624 yes 2.4267 1.1649 yes

GL5 v. GL1 41.7364 1.9630 yes 1.6076 1.1821 yes

Site X2 calc. X2 crit. Reject?

GL1 9.53E+003 429.6325 yes

GL4 1.53E+015 658.0936 yes

GL5 3.80E+003 435.9879 yes

Sodium

Comparison t calc. t crit. Reject? f calc. f crit. Reject?

GL1 v. GL4 47.2662 1.9624 yes 1.9963 1.1624 yes

GL4 v. GL5 10.5802 1.9624 yes 3.1584 1.1649 yes

GL5 v. GL1 17.7345 1.9630 yes 1.5821 1.1821 yes

Site X2 calc. X2 crit. Reject?

GL1 1.35E+007 429.6325 yes

GL4 1.73E+017 658.0936 yes

GL5 1.01E+003 435.9879 yes

Potassium

Comparison t calc. t crit. Reject? f calc. f crit. Reject?

GL1 v. GL4 10.1557 1.9624 yes 2.8265 1.1624 yes

GL4 v. GL5 10.9637 1.9624 yes 2.0048 1.1649 yes

GL5 v. GL1 25.8235 1.9630 yes 1.4099 1.1821 yes

Site X2 calc. X2 crit. Reject?

GL1 1.03E+016 429.6325 yes

GL4 8.45E+008 658.0936 yes

GL5 1.33E+016 435.9879 yes

Conclusions Green Lakes 1, 4, and 5 have different

cation chemistries– Variances and means are not the same

– None of the data are normally distributed GL4 has higher concentrations than GL5

– Inputs from hillslopes and from GL5 GL1 is the most different of the three

– Ca2+ and Na+ concentrations are much higher

– Possibly a different rock type