1. Comparison of Cations in Three Lakes
Green Lakes Basin, CO

2. Green Lakes Basin, CO Red rectangles = sampling locations
Continental Divide
Red rectangles = sampling locations
Blue arrows = direction of stream flow

3. 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?

4. Calcium Site X2 calc. X2 crit. Reject? GL1 458.2459 429.6325 yes GL4
GL5
1.70E+005
Comparison
t calc.
t crit.
Reject?
f calc.
f crit.
GL1 v. GL4
1.9624
yes
1.9473
1.1624
GL4 v. GL5
8.8542
2.1819
1.1649
GL5 v. GL1
1.9630
4.2489
1.1821

5. Magnesium Site X2 calc. X2 crit. Reject? GL1 9.53E+003 429.6325 yes
GL5
3.80E+003
Comparison
t calc.
t crit.
Reject?
f calc.
f crit.
GL1 v. GL4
1.9624
yes
3.9011
1.1624
GL4 v. GL5
2.4267
1.1649
GL5 v. GL1
1.9630
1.6076
1.1821

6. Sodium Site X2 calc. X2 crit. Reject? GL1 1.35E+007 429.6325 yes GL4
GL5
1.01E+003
Comparison
t calc.
t crit.
Reject?
f calc.
f crit.
GL1 v. GL4
1.9624
yes
1.9963
1.1624
GL4 v. GL5
3.1584
1.1649
GL5 v. GL1
1.9630
1.5821
1.1821

7. Potassium Site X2 calc. X2 crit. Reject? GL1 1.03E+016 429.6325 yes
GL5
1.33E+016
Comparison
t calc.
t crit.
Reject?
f calc.
f crit.
GL1 v. GL4
1.9624
yes
2.8265
1.1624
GL4 v. GL5
2.0048
1.1649
GL5 v. GL1
1.9630
1.4099
1.1821

8. 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