Streamflow Measurements Using Salt Dilution Techniques
Salt dilution is a proven method of measuring stream discharge that is widely used around the world but seldom within the U.S. Geological Survey (USGS). This technique is useful at sites where mid-section, ADCP, flume, and volumetric measurement techniques cannot be effectively conducted due to high turbulence, high velocities, and inadequate cross sections. The South Atlantic Water Science Center (SAWSC) formed a team of scientists to demonstrate the use of the salt dilution slug injection method to measure streamflow and to make comparisons indicating agreement with traditional discharge measurement methods. The Scientists Using Salt Hydrometric Instruments (SUSHI) team continues to investigate equipment and methods for conducting salt dilution measurements within the USGS streamgaging program.
Goal:
The SUSHI team proposes to learn the salt dilution measurement technique, purchase modern equipment manufactured to simplify the field data collection and analysis process, and gain experience with the technique and equipment. These techniques will then be applied at numerous streamgages throughout SAWSC and the USGS that have stable ratings and conditions allowing for comparisons against concurrent traditional discharge measurements. At the end of the project, the team will have the training and experience necessary to train technicians within the SAWSC as well as throughout the USGS. Workflow documents, field notes, equipment information, references, and all salt dilution information gathered or created by the SUSHI Team will be presented in the internal Salt Dilution SharePoint Site for internal USGS users to help establish this method in offices throughout the USGS.
The SUSHI Team will be coordinating their work along with training and collaboration with the USGS Hydrologic Networks Branch, the Swedish Meteorological and Hydrological Institute (SMHI), the Water Survey of Canada, and the International Hydrometry Group. Techniques and methods used in this project will be thoroughly documented and derived from Rantz and others (1982) and Kilpatrick & Cobb (1985) as well as from standard operating procedures and workflows developed by the British Columbia SMHI, the New Zealand National Institute of Water and Atmospheric Research (NIWA), the World Meteorological Organization (WMO), and the ISO-9555-1:1994 Standard.
The main goal of this project is to determine the applicability of the salt dilution method for measuring stream discharge at sites within the SAWSC and to make the SAWSC a center of excellence on this technique. Gaining experience with this discharge measurement method will contribute to the quality of foundational data collected within the SAWSC, which will in turn improve the understanding of water availability within the SAWSC. This will further allow the SAWSC to better meet the needs of cooperators, public utilities, and drought management agencies.
During field data collection activities, the SUSHI Team takes all possible precautions to ensure that the potential environmental impacts of performing salt dilution discharge measurements are minimized. Efforts are made to ensure chloride levels in the stream do not rise above EPA recommended chronic and acute criterion concentrations for aquatic life. A specific amount of lab grade NaCl is selected based on the rated discharge in order to raise the downstream specific conductance by no more than 10 microsiemens/cm. The amount added to streams during these measurements is never greater than 1kg NaCl per cubic meter per second of flow. The prescribed amount of salt is pre-diluted before pouring into the stream to a maximum concentration of 10% NaCl. This solution is poured into rapidly flowing water to ensure fast dispersion of the solution. While pouring, technicians are careful not to pour fast enough to disturb the strembed materials. Multiple conductance sensors are placed upstream and downstream of the stream reach to ensure that quality salt dilution discharge measurements can be acquired while maintaining minimal impact on the aquatic environment.
Deliverables:
- Preparation of SAWSC quality assurance (QA) Plan for Salt Dilution Discharge Measurements. The QA Plan will be submitted for approval to the SAWSC Specialists.
- Internal Salt Dilution SharePoint Site.
- Workflow documents created during the 2022 Program Development Challenge outlining instrument-specific procedures and methods used (these will be incorporated into the QA Plan where appropriate).
- Salt dilution measurement comparisons with more common measurement techniques as well as between salt dilution systems.
- Poster and presentations at USGS National Water Data Workshops.
- Creation of electronic salt dilution field notes (pdf) as well as continuing to work with Hydrologic Networks Branch on the development of the SUSHI Salt Dilution Field Note Python Application.
USGS References:
Rantz, S.E., and others, 1982, Measurement and computation of streamflow—Volume 1: Measurement of stage and discharge: U.S. Geological Survey Water-Supply Paper 2175, 284 p. plus an index. (https://pubs.usgs.gov/publication/wsp2175)
Kilpatrick, F. A., & Cobb, E. D. (1985). Measurement of discharge using tracers (p. 52). Washington, DC, USA: Department of the Interior, US Geological Survey. (https://pubs.usgs.gov/publication/twri03A16)
Buckeye Creek Below Buckeye Lake Near Cannon Gap, NC, used for creating rating curve using salt dilution. (Gage 0347927164)
Other References (Introduction to Salt Dilution)
- Introduction to salt dilution gauging for streamflow measurement: Part 1 - Moore 2004
- Introduction to Salt Dilution Gauging for Streamflow Measurement Part IV - Hudson & Fraser 2005
- Slug Injection Using Salt in Solution - Moore 2005
- Quantifying the Relation Between Electrical Conductivity and Salt Concentration for Dilution Gauging Via Dry Salt Injection - Richardson, Sentlinger, Moore, Zimmermann 2017
- Refinement of tracer dilution methods for discharge measurements in steep mountain streams - Richardson 2015
- Manual of British Columbia Hydrometric Standards - Salt Dilution, p. 81; Field Note, Appendix V, p. 151
- Computerized streamflow measurement using slug injection - Kite 1993
- Use of Tracer Injections to Measure Discharge and Quantify Pollutant Loading - Carey 2001
Other References (Environmental Impact)
- Major Ion Toxicity to Glochidia of Common and Imperiled Freshwater Mussel Species - Bringolf, Raines, Ratajczak, Haskins 2022
- The effect of road deicing salt on the drift of stream benthos - Crowther, Hynes 1977
- Priority Substances List Assessment Report (Road Salts) - 2001
- Ambient Water Quality Criteria for Chloride-1988
- Assessing the toxicity of sodium chloride to the glochidia of freshwater
mussels: Implications for salinization of surface waters - Gillis 2011 - Benighn Use Of Salt Slugs On Aquatic Macroinvertibrates: Measuring
Discharge With Salt During An Aquatic Ecologhy Study - Muehlbaur, Duncan, Doyle 2011 - The use of salt dilution gauging techniques: ecological considerations and insights - Wood, Dykes 2001
Salt dilution is a proven method of measuring stream discharge that is widely used around the world but seldom within the U.S. Geological Survey (USGS). This technique is useful at sites where mid-section, ADCP, flume, and volumetric measurement techniques cannot be effectively conducted due to high turbulence, high velocities, and inadequate cross sections. The South Atlantic Water Science Center (SAWSC) formed a team of scientists to demonstrate the use of the salt dilution slug injection method to measure streamflow and to make comparisons indicating agreement with traditional discharge measurement methods. The Scientists Using Salt Hydrometric Instruments (SUSHI) team continues to investigate equipment and methods for conducting salt dilution measurements within the USGS streamgaging program.
Goal:
The SUSHI team proposes to learn the salt dilution measurement technique, purchase modern equipment manufactured to simplify the field data collection and analysis process, and gain experience with the technique and equipment. These techniques will then be applied at numerous streamgages throughout SAWSC and the USGS that have stable ratings and conditions allowing for comparisons against concurrent traditional discharge measurements. At the end of the project, the team will have the training and experience necessary to train technicians within the SAWSC as well as throughout the USGS. Workflow documents, field notes, equipment information, references, and all salt dilution information gathered or created by the SUSHI Team will be presented in the internal Salt Dilution SharePoint Site for internal USGS users to help establish this method in offices throughout the USGS.
The SUSHI Team will be coordinating their work along with training and collaboration with the USGS Hydrologic Networks Branch, the Swedish Meteorological and Hydrological Institute (SMHI), the Water Survey of Canada, and the International Hydrometry Group. Techniques and methods used in this project will be thoroughly documented and derived from Rantz and others (1982) and Kilpatrick & Cobb (1985) as well as from standard operating procedures and workflows developed by the British Columbia SMHI, the New Zealand National Institute of Water and Atmospheric Research (NIWA), the World Meteorological Organization (WMO), and the ISO-9555-1:1994 Standard.
The main goal of this project is to determine the applicability of the salt dilution method for measuring stream discharge at sites within the SAWSC and to make the SAWSC a center of excellence on this technique. Gaining experience with this discharge measurement method will contribute to the quality of foundational data collected within the SAWSC, which will in turn improve the understanding of water availability within the SAWSC. This will further allow the SAWSC to better meet the needs of cooperators, public utilities, and drought management agencies.
During field data collection activities, the SUSHI Team takes all possible precautions to ensure that the potential environmental impacts of performing salt dilution discharge measurements are minimized. Efforts are made to ensure chloride levels in the stream do not rise above EPA recommended chronic and acute criterion concentrations for aquatic life. A specific amount of lab grade NaCl is selected based on the rated discharge in order to raise the downstream specific conductance by no more than 10 microsiemens/cm. The amount added to streams during these measurements is never greater than 1kg NaCl per cubic meter per second of flow. The prescribed amount of salt is pre-diluted before pouring into the stream to a maximum concentration of 10% NaCl. This solution is poured into rapidly flowing water to ensure fast dispersion of the solution. While pouring, technicians are careful not to pour fast enough to disturb the strembed materials. Multiple conductance sensors are placed upstream and downstream of the stream reach to ensure that quality salt dilution discharge measurements can be acquired while maintaining minimal impact on the aquatic environment.
Deliverables:
- Preparation of SAWSC quality assurance (QA) Plan for Salt Dilution Discharge Measurements. The QA Plan will be submitted for approval to the SAWSC Specialists.
- Internal Salt Dilution SharePoint Site.
- Workflow documents created during the 2022 Program Development Challenge outlining instrument-specific procedures and methods used (these will be incorporated into the QA Plan where appropriate).
- Salt dilution measurement comparisons with more common measurement techniques as well as between salt dilution systems.
- Poster and presentations at USGS National Water Data Workshops.
- Creation of electronic salt dilution field notes (pdf) as well as continuing to work with Hydrologic Networks Branch on the development of the SUSHI Salt Dilution Field Note Python Application.
USGS References:
Rantz, S.E., and others, 1982, Measurement and computation of streamflow—Volume 1: Measurement of stage and discharge: U.S. Geological Survey Water-Supply Paper 2175, 284 p. plus an index. (https://pubs.usgs.gov/publication/wsp2175)
Kilpatrick, F. A., & Cobb, E. D. (1985). Measurement of discharge using tracers (p. 52). Washington, DC, USA: Department of the Interior, US Geological Survey. (https://pubs.usgs.gov/publication/twri03A16)
Buckeye Creek Below Buckeye Lake Near Cannon Gap, NC, used for creating rating curve using salt dilution. (Gage 0347927164)
Other References (Introduction to Salt Dilution)
- Introduction to salt dilution gauging for streamflow measurement: Part 1 - Moore 2004
- Introduction to Salt Dilution Gauging for Streamflow Measurement Part IV - Hudson & Fraser 2005
- Slug Injection Using Salt in Solution - Moore 2005
- Quantifying the Relation Between Electrical Conductivity and Salt Concentration for Dilution Gauging Via Dry Salt Injection - Richardson, Sentlinger, Moore, Zimmermann 2017
- Refinement of tracer dilution methods for discharge measurements in steep mountain streams - Richardson 2015
- Manual of British Columbia Hydrometric Standards - Salt Dilution, p. 81; Field Note, Appendix V, p. 151
- Computerized streamflow measurement using slug injection - Kite 1993
- Use of Tracer Injections to Measure Discharge and Quantify Pollutant Loading - Carey 2001
Other References (Environmental Impact)
- Major Ion Toxicity to Glochidia of Common and Imperiled Freshwater Mussel Species - Bringolf, Raines, Ratajczak, Haskins 2022
- The effect of road deicing salt on the drift of stream benthos - Crowther, Hynes 1977
- Priority Substances List Assessment Report (Road Salts) - 2001
- Ambient Water Quality Criteria for Chloride-1988
- Assessing the toxicity of sodium chloride to the glochidia of freshwater
mussels: Implications for salinization of surface waters - Gillis 2011 - Benighn Use Of Salt Slugs On Aquatic Macroinvertibrates: Measuring
Discharge With Salt During An Aquatic Ecologhy Study - Muehlbaur, Duncan, Doyle 2011 - The use of salt dilution gauging techniques: ecological considerations and insights - Wood, Dykes 2001