University of Alaska, Institute of Water Resources
Abstract
Bedrock of the Caribou-Poker Creeks Research Watershed dissolves incongruently
with a first-order rate constant of about 5 x 10-6 day-1 at 5° C. The
resulting solution is potassium-calcium-magnesium rich. The soil-plant environment
acts on this solution through sorption of potassium and by evapotranspiration
to yield a solution that is relatively depleted in potassium and
enriched in calcium and magnesium, but with the same molar ratio of Ca:Mg as
the fluid from the rock dissolution. This fluid from the soil-plant reservoir
is the dominant contributor of ions to stream waters.
Using the discriminant functions obtained by multiple discriminant
analysis
DPKR = 0.572Si02 + 0.240Ca + 2.89Mg - 0.384Na + 0.452N03 - 9.18
DCRB = 0.913Si02 + 0.042Ca + 1.28Mg + 1.17Na + 4.63N03 - 7.27,
the waters of Caribou Creek and Poker Creek can be distinguished on the basis
of chemical composition. In general, Poker Creek waters are slightly more
concentrated than Caribou Creek waters.
On the average, 1.4 x 10^13g H20/year leaves the watershed as surface
water. At an average calcium concentration of 14 ppm for the water, 0.1% for
the bedrock, and a watershed area of 46 mi^2, this flow corresponds to a maximum
loss of about 17 metric tons of rock per hectare per year