Document Type

Thesis

Date of Degree Completion

Spring 2026

Degree Name

Master of Science (MS)

Department

Geological Sciences

Committee Chair

Dr. Lisa Ely

Second Committee Member

Dr. Carey Gazis

Third Committee Member

Dr. Jennifer Lipton

Abstract

The West Fork Teanaway (WFT) River in Kittitas County, WA is an entrenched bedrock river channel with disturbed floodplain geomorphology and degraded riparian ecology. Two stream restoration approaches, “stage 0” valley bottom reset and engineered logjam installation, will be installed at the WFT in summer 2026 by collaborators at the Washington State Department of Fish and Wildlife and Mid-Columbia Fisheries Enhancement Group. The objective of this study was to constrain the pre-restoration geomorphic and hydrologic conditions of the WFT. The WFT has an unconsolidated floodplain aquifer of predominantly coarse-grained fluvial deposits. Monitoring of groundwater and surface water levels began in November 2024 and ended in May 2026. The timing of floodplain groundwater recharge and baseflow recession were determined through analysis of stable isotopes (δ18O and δ2H), groundwater hydrographs, as well as surface water hydrographs. Recharge of the WFT floodplain aquifer is sourced by surface water and occurred from October 2025 to mid-March 2026. The floodplain aquifer began baseflow into the WFT River by early June 2025 and ended by October 2025. This analysis will be used to determine hydrologic changes as a result from these restoration approaches through future post- restoration monitoring of the WFT study area.

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