Characterization and Quantification of Salinity Loads from Blacks Fork above Smiths Fork near Lyman, Wyoming

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The Blacks Fork is a stream that contributes a salinity load to the Colorado River Basin. In order to quantify the salinity load, collection of continuous streamflow and specific conductance data, and monthly sampling for total-dissolved solids will occur from April 2018 through September 2019. Calculations of monthly and annual salinity loading from the Blacks Fork will be published in 2020.

The Blacks Fork is a stream in Wyoming that starts in the Uinta Mountains and flows in a U-shaped path to Flaming Gorge Reservoir, becoming a tributary to the Green River in Wyoming. Application of irrigation water to fields located on top of some geologic materials, such as shales, allows infiltrating water to dissolve salts from the rocks. These dissolved minerals increase the salinity of Blacks Fork and nearby streams from surface-water irrigation return flows and baseflow from groundwater. 

Previous investigations of the salinity of the Blacks Fork, downstream of the Smiths Fork, have found that the Blacks Fork does contribute salinity to the Colorado Basin. In order to determine the contribution from the Blacks Fork upstream of the Smiths Fork,

  • a streamgage (site 09219200) has been installed and will begin collecting continuous streamflow and specific conductance begining in April 2018.
  • Monthy water samples for total-dissolved solids analysis will be collected from April 2018 through September 2019. 
  • Using methods described in Clark and Davidson, 2009, a regression equation between the total-dissolved solids concentrations and continuous specific conductance will enable continuous total-dissolved solids concentrations to be calculated and salinity loads will be determined for the 2018 and 2019 irrigation seasons.

Additionally, samples will be collected at a total of seven sites during three samples events in both 2018 and 2019 irrigation seasons to describe the water-quality changes in the Blacks Fork as it flows downstream approximately 35 miles from the outlet of Meeks Cabin Reservoir to the Blacks Fork above Smiths Fork streamgage.

These data will help the Colorado River Basin Salinity Forum members determine areas of the Blacks Fork drainage basin that are contributing the highest salinity loads to the system.