Quantifying the Relation Between Electrical Conductivity and Salt Concentration for Dilution Gauging Via Dry Salt Injection

  • Mark Richardson University of British Columbia, Vancouver, BC V6T 1Z4 Current affiliation: US Army Corps of Engineers, St. Paul District, St. Paul, MN http://orcid.org/0000-0001-9191-9087
  • Gabe Sentlinger Aquarius R&D Inc. and Fathom Scientific Ltd., Bowen Island, BC V0N 1G2
  • R.D. (Dan) Moore University of British Columbia, Vancouver, BC V6T 1Z4
  • André Zimmermann (1) University of British Columbia, Vancouver, BC V6T 1Z4 (2) Northwest Hydraulic Consultants, North Vancouver, BC V7M 3G3
Keywords: dilution gauging, hydrometry, salt dilution, streamflow measurement

Abstract

Salt dilution is a popular approach used for discharge measurement. This research focused on the procedure for determining the calibration factor (CFT) that is used to convert measured temperature corrected electrical conductivity to salt concentration for injection using dry salt. It is important to document the uncertainty in CFT because it contributes directly to uncertainty in the calculated discharge. Based on laboratory trials, it was found that the calibration should be performed as close to in situ stream temperature as possible to minimize errors. The discharge measurement and calibration procedure should be performed with the same probe to minimize uncertainty. Distilled water can be used instead of stream water for a calibration solution if an analytical correction is applied to account for differences in ionic composition of the water. The calibration factor can be determined with an uncertainty of less than ± 1% under “best-case” conditions, and the uncertainty may be as high as ± 4% under less favourable conditions. If calibration is not performed, CFT can be estimated from the relation between CFT and background temperature-corrected electrical conductivity (ECBG) with an uncertainty of about ± 2%, or estimated as a set value of 0.486 mg·cm·μS-1·L-1 with an uncertainty of about ± 2.8% for a properly calibrated probe. More testing should focus on streams with ECBG > 500 μS·cm-1, which were not well represented in this study.

Author Biographies

Mark Richardson, University of British Columbia, Vancouver, BC V6T 1Z4 Current affiliation: US Army Corps of Engineers, St. Paul District, St. Paul, MN

Department of Geography

[all relevant research performed during time at University of British Columbia, hence why it is listed first]

Gabe Sentlinger, Aquarius R&D Inc. and Fathom Scientific Ltd., Bowen Island, BC V0N 1G2
[none]
R.D. (Dan) Moore, University of British Columbia, Vancouver, BC V6T 1Z4
Department of Geography
André Zimmermann, (1) University of British Columbia, Vancouver, BC V6T 1Z4 (2) Northwest Hydraulic Consultants, North Vancouver, BC V7M 3G3

(1) Department of Geography

(2) [none]

Published
2017-10-11