Title

Analysis of surface water-groundwater interaction in North Kittitas County, WA

Presenter Information

Trent Hartman

Document Type

Oral Presentation

Location

SURC Ballroom C/D

Start Date

16-5-2013

End Date

16-5-2013

Abstract

Kittitas County, Washington, is part of the larger Yakima Basin area which boasts a thriving agriculture industry that is heavily reliant on surface water for irrigation. Because surface water in the basin is in such high demand, there has been an ongoing discussion about how to supply water for its many uses in this arid region. Artificial recharge of aquifers in north Kittitas County during high spring flows has been suggested as a means of increasing flow in-stream for irrigation purposes as well as increasing base flow levels for endangered fish species at critical low periods. To assess the feasibility of these techniques locally, the groundwater-surface water relationships were investigated using geochemical analysis. Surface and groundwater samples were collected and underwent major anion, 18O/16O stable isotope, and trace element analysis. Preliminary data suggests the absence of nitrate in deep groundwater from Cooke Canyon and relatively low but measurable levels within most moderate depth wells of the Ellensburg formation. Measurable nitrate levels in these moderate depth wells are presumed to be the result of small amounts of seepage from irrigation runoff. Elevated sulfate levels were measured in one sample from the deep, basalt aquifer in Cooke Canyon and a single shallow sample from the Ellensburg formation. These increased sulfate concentrations are attributed to ion exchange between specific aquifer materials and groundwater. 18O/16O ratios similar to generally accepted values for local irrigation canal water were measured in the single shallow sample collected from the Ellensburg formation indicating a large amount of direct recharge of the aquifer by nearby KRD canals. Similarities between isotopic signatures of groundwaters collected from wells finished in the sedimentary basin fill and those that extend into the deeper basalt aquifer suggest some degree of mixing between the two aquifers.

Poster Number

60

Faculty Mentor(s)

Carey Gazis

Additional Mentoring Department

Geological Sciences

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May 16th, 8:20 AM May 16th, 10:50 AM

Analysis of surface water-groundwater interaction in North Kittitas County, WA

SURC Ballroom C/D

Kittitas County, Washington, is part of the larger Yakima Basin area which boasts a thriving agriculture industry that is heavily reliant on surface water for irrigation. Because surface water in the basin is in such high demand, there has been an ongoing discussion about how to supply water for its many uses in this arid region. Artificial recharge of aquifers in north Kittitas County during high spring flows has been suggested as a means of increasing flow in-stream for irrigation purposes as well as increasing base flow levels for endangered fish species at critical low periods. To assess the feasibility of these techniques locally, the groundwater-surface water relationships were investigated using geochemical analysis. Surface and groundwater samples were collected and underwent major anion, 18O/16O stable isotope, and trace element analysis. Preliminary data suggests the absence of nitrate in deep groundwater from Cooke Canyon and relatively low but measurable levels within most moderate depth wells of the Ellensburg formation. Measurable nitrate levels in these moderate depth wells are presumed to be the result of small amounts of seepage from irrigation runoff. Elevated sulfate levels were measured in one sample from the deep, basalt aquifer in Cooke Canyon and a single shallow sample from the Ellensburg formation. These increased sulfate concentrations are attributed to ion exchange between specific aquifer materials and groundwater. 18O/16O ratios similar to generally accepted values for local irrigation canal water were measured in the single shallow sample collected from the Ellensburg formation indicating a large amount of direct recharge of the aquifer by nearby KRD canals. Similarities between isotopic signatures of groundwaters collected from wells finished in the sedimentary basin fill and those that extend into the deeper basalt aquifer suggest some degree of mixing between the two aquifers.