Hydrogeochemistry of the Caribou-Poker Creeks Research Watershed

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.