"The Drying of Dry Creek: A Paired Catchment Experiement Assessing Non-" by Elizabeth Crowther

Publication Date

12-2023

Date of Final Oral Examination (Defense)

August 2023

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Hydrologic Sciences

Department Filter

Geosciences

Department

Geosciences

Supervisory Committee Chair

James McNamara, Ph.D.

Supervisory Committee Member

Sarah Godsey, Ph.D.

Supervisory Committee Member

Anna Bergstrom, Ph.D.

Abstract

Intermittent streams make up the majority of waterways in the United States and are becoming more common in a changing climate, yet they lack stream gaging and habitat data compared to their perennial counterparts. Headwater streams in the western US can be classified as intermittent through seasonal contraction of flowing streams. Although small, they provide critical habitat for fish species and contribute to larger downstream systems. Predictive models, such as the Probability of Stream Permanence (PROSPER) model, have been created to map dry and intermittent reaches at the regional scale, yet they lack large-scale spring data sets as inputs for their model. Field mapping of these headwater springs improves the accuracy of these models and enhances water management decisions in the western US.

Active stream channel networks within intermittent headwater streams expand and contract within geomorphic channel networks in response to climatic conditions. Relationships between the networks depend on watershed structural characteristics, including underlying geology, climate, and topography. The expansion and contraction of flowing stream networks are proposed to be visible representations of their geomorphologic conditions. However, the surface channel network can differ from the assumed geomorphic drainage density. Stable springs can contribute to higher stream permanence in headwater streams and create a more stable flowing stream network across seasons. To further understand how groundwater characteristics influence surficial water expressions, a controlled paired watershed experiment was conducted to relate active channel network mapping to stable spring input concentrations. Predicting stream behavior in low-flow conditions can improve water resource management practices and mapping of critical aquatic habitat in headwater catchments. Drying patterns in the Dry Creek Experimental Watershed (DCEW) offer a unique opportunity to assess connectivity in spring-fed and non-spring-fed catchments with similar geologic and topographic profiles. To assess active stream network stability, flowing streams were mapped and discharge measurements were made at high-flow, low-flow, and fall ‘re-wetting’ conditions. Active stream networks at low-flow conditions were then compared to the PROSPER models wet/dry predictions. Geomorphic and hydrologic analysis was also conducted to assess climatic and topographic controls on stream permanence.

Active stream mapping results showed that the spring-fed catchment was more stable than the non-spring-fed catchment throughout the 2021 water year. Over a 15-year record, the spring-fed catchment had higher annual volumes and more stable annual flows. When assessing topographic and geomorphic metrics across both catchments, the spring-fed catchment had slightly higher slopes and elevation, which could potentially contribute to more perennial behavior. Compared to the mapped network, the PROSPER model overpredicted dry conditions in the spring-fed catchment, whereas it under- and overpredicted dry conditions in the non-spring-fed catchment, depending on the water year. Our findings concluded that springs are a driver of stream permanence in headwater streams, challenging the predominance of topographic and climatic controls on stream permanence. The presence of springs led to an over-prediction of dry conditions in regional intermittent stream datasets and models. These findings will assist in defining Dry Creek stream expansion-contraction dynamics and improve active drainage network predictive models.

DOI

https://doi.org/10.18122/td.2158.boisestate

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