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A comparison of methods for deriving solute flux rates using long-term data from streams in the mirror lake watershed

Water, Air, and Soil Pollution

By:
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DOI: 10.1023/A:1005018030515

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Abstract

Calculation of chemical flux rates for streams requires integration of continuous measurements of discharge with discrete measurements of solute concentrations. We compared two commonly used methods for interpolating chemistry data (time-averaging and flow-weighting) to determine whether discrepancies between the two methods were large relative to other sources of error in estimating flux rates. Flux rates of dissolved Si and SO42- were calculated from 10 years of data (1981-1990) for the NW inlet and Outlet of Mirror Lake and for a 40-day period (March 22 to April 30, 1993) during which we augmented our routine (weekly) chemical monitoring with collection of daily samples. The time-averaging method yielded higher estimates of solute flux during high-flow periods if no chemistry samples were collected corresponding to peak discharge. Concentration-discharge relationships should be used to interpolate stream chemistry during changing flow conditions if chemical changes are large. Caution should be used in choosing the appropriate time-scale over which data are pooled to derive the concentration-discharge regressions because the model parameters (slope and intercept) were found to be sensitive to seasonal and inter-annual variation. Both methods approximated solute flux to within 2-10% for a range of solutes that were monitored during the intensive sampling period. Our results suggest that errors arising from interpolation of stream chemistry data are small compared with other sources of error in developing watershed mass balances.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
A comparison of methods for deriving solute flux rates using long-term data from streams in the mirror lake watershed
Series title:
Water, Air, and Soil Pollution
DOI:
10.1023/A:1005018030515
Volume
105
Issue:
1-2
Year Published:
1998
Language:
English
Publisher:
Kluwer Academic Publishers
Publisher location:
Dordrecht, Netherlands
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Water, Air, and Soil Pollution
First page:
277
Last page:
293
Number of Pages:
17