Geochemistry of the Birch Creek Drainage Basin, Idaho

Department of the Interior, U.S. Geological Survey

Prepared in cooperation with the

U.S. Department of Energy


U.S. Geological Survey Water-Resources Investigations Report 03-4272


By Shawn A. Swanson, Jeffrey J. Rosentreter, Roy C. Bartholomay, and LeRoy L. Knobel


Idaho Falls, Idaho

March 2004


This report is available as a pdf.


The U.S. Survey and Idaho State University, in cooperation with the U.S. Department of Energy, are conducting studies to describe the chemical character of ground water that moves as underflow from drainage basins into the eastern Snake River Plain aquifer (ESRPA) system at and near the Idaho National Engineering and Environmental Laboratory (INEEL) and the effects of these recharge waters on the geochemistry of the ESRPA system. Each of these recharge waters has a hydrochemical character related to geochemical processes, especially water-rock interactions, that occur during migration to the ESRPA. Results of these studies will benefit ongoing and planned geochemical modeling of the ESRPA at the INEEL by providing model input on the hydrochemical character of water from each drainage basin.

During 2000, water samples were collected from five wells and one surface-water site in the Birch Creek drainage basin and analyzed for selected inorganic constituents, nutrients, dissolved organic carbon, tritium, measurements of gross alpha and beta radioactivity, and stable isotopes. Four duplicate samples also were collected for quality assurance. Results, which include analyses of samples previously collected from four other sites, in the basin, show that most water from the Birch Creek drainage basin has a calcium-magnesium bicarbonate character.

The Birch Creek Valley can be divided roughly into three hydrologic areas. In the northern part, ground water is forced to the surface by a basalt barrier and the sampling sites were either surface water or shallow wells. Water chemistry in this area was characterized by simple evaporation models, simple calcite-carbon dioxide models, or complex models involving carbonate and silicate minerals. The central part of the valley is filled by sedimentary material and the sampling sites were wells that are deeper than those in the northern part. Water chemistry in this area was characterized by simple calcite-dolomite-carbon dioxide models. In the southern part, ground water enters the ESRPA. In this area, the sampling sites were wells with depths and water levels much deeper than those in the northern and central parts of the valley. The calcium and carbon water chemistry in this area was characterized by a simple calcite-carbon dioxide model, but complex calcite-silicate models more accurately accounted for mass transfer in these areas.

Throughout the geochemical system, calcite precipitated if it was an active phase in the models. Carbon dioxide either precipitated (outgassed) or dissolved depending on the partial pressure of carbon dioxide in water from the modeled sites. Dolomite was an active phase only in models from the central part of the system. Generally the entire geochemical system could be modeled with either evaporative models, carbonate models, or carbonate-silicate models. In both of the latter types of models, a significant amount of calcite precipitated relative to the mass transfer to and from the other active phases. The amount of calcite precipitated in the more complex models was consistent with the amount of calcite precipitated in the simpler models. This consistency suggests that, although the simpler models can predict calcium and carbon concentrations in Birch Creek Valley ground and surface water, silicate-mineral-based models are required to account for the other constituents. The amount of mass transfer to and from the silicate mineral phases was generally small compared with that in the carbonate phases. It appears that the water chemistry of well USGS 126B represents the chemistry of water recharging the ESRPA by means of underflow from the Birch Creek Valley.

Table of Contents



Purpose and scope

Geohydrologic setting


Guidelines, methods, and quality assurance

Sample containers and preservatives

Sampling locations and sample collection

Guidelines for interpreting results of analyses

Quality assurance

Evaluation of quality assurance data

Results of analyses

Cations, anions, and silica

Selected inorganic constituents


Dissolved organic carbon


Gross alpha- and gross beta-particle radioactivity

Stable isotopes


Solid phase description

Ion distribution

Hydrochemical facies

Thermodynamic considerations

Plausible chemical reactions

Dissolution or precipitation of calcite

Dissolution of dolomite

Dissolution of gypsum

Dissolution of olivine

Dissolution of diopside

Dissolution of labradorite

Dissolution of potassium feldspar

Dissolution of illite

Cation exchange

Geochemical modeling

Summary and conclusions

Selected references

For additional information write to:

U.S. Geological Survey

INEEL, MS 1160

P.O. BOX 2230

Idaho Falls, ID 83403


Copies of this report can be purchased from:

U.S. Geological Survey

Information Services

Building 810

Box 25286, Federal Center

Denver, CO 80225-0286

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