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Date Permissions Signed

6-15-2018

Date of Award

Summer 1993

Document Type

Masters Thesis

Degree Name

Master of Science (MS)

Department

Geology

First Advisor

Babcock, R. Scott (Randall Scott)

Second Advisor

Matthews, Robin A., 1952-

Third Advisor

Suczek, Christopher A., 1942-2014

Abstract

The Upper Bagley watershed was monitored from April to November, 1992. The watershed is described as a series of chemically distinct subsystems: 1) the snowpack, 2) soil solutions, and 3) surface water. The hydrogeochemical interactions between these subsystems were investigated in the Upper Bagley watershed. Chemical analyses of these fluids were used to identify how soil solutions vary from water derived from the snowpack and what impact soil solutions have on surface-water chemistry.

Water-ice interactions alter the snowpack chemistry, enriching the melt in calcium, magnesium, sodium, chloride, and sulfate that accumulate at the surface of ice crystals. The melt from the Upper Bagley watershed is enriched in calcium and sodium by a factor of three and in magnesium by a factor of six relative to snow concentrations. Chloride and sulfate concentrations are up to four times greater in the melt fraction. Nitrate does not become concentrated in the melt fraction since the equilibrium of nitrate in the snowpack is controlled in part by denitrification.

Soils in the Upper Bagley watershed are Entisols, or primitive soils. Two soils types were defined on the basis of clay content and the ability of the soil to support vegetation. Soil I, a clay loam that originates from glacial till and volcanic ash, is composed of montmorillonite, inorganic colloids, and organic acids. This soil supports vegetation dominated by heather and sedge. Soil II, a gravelly sand loam derived from andesite with sparse vegetation, is primarily andesine and inorganic colloids. Pore fluids from these soils are chemically distinct. Pore fluids from Soil I (Pore Fluid I) have greater ion concentrations that those from Soil II (Pore Fluid II). Pore Fluid I is dominated by calcium and sulfate and is more acidic than Pore Fluid II, which is dominated by sodium.

The chemical composition of surface water in the Upper Bagley watershed reflects the mixing of fluids derived from snow and soil solutions. End-Member Mixing Analysis suggests that solutions from the inlet, outlet, and lake are a mixing product between four end-members: 1) the relatively dilute snow and melt, 2) surface water that has leached cations from vegetation, 3) Pore Fluid I, and 4) Pore Fluid ll. When plotted against chloride concentrations, calcium, magnesium, and sulfate provide evidence for the mixing of fluids in the Upper Bagley watershed. Processes other than simple mixing also influence the chemistry of the Upper Bagley watershed. Nitrate and alkalinity concentrations for the fluids do not provide evidence for interaction between fluids. The equilibria of these ions are more strongly affected by biological transformations (nitrate) and gas exchange with the atmosphere (alkalinity).

Normalized mixing analysis was used to indicate individual sample clusters that do not demonstrate simple mixing. Ions were normalized for chloride and plotted against each other. Plots of calcium, magnesium, and sulfate normalized to chloride are strongly linear because the equilibria of these ions are controlled in part by mixing. Correlation of the data clusters that diverge from the linear plot pattern with field conditions at the time of collection indicates that redox reactions and aerosol deposition also control the chemical equilibria of the watershed.

Type

Text

Keywords

Hydrogeochemical interactions, Watershed studies

Publisher

Western Washington University

OCLC Number

1083218606

Subject – LCSH

Mountain ecology--Washington (State)--Mount Baker National Recreation Area; Biogeochemistry--Washington (State)--Mount Baker National Recreation Area; Hydrogeology--Washington (State)--Mount Baker National Recreation Area

Geographic Coverage

Mount Baker National Recreation Area (Wash.); Upper Bagley Watershed (Wash.)

Format

application/pdf

Genre/Form

masters theses

Language

English

Rights

Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this thesis for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.

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