The Drying of Dry Creek
Authors: Crowther Elizabeth 
Published: January 2025

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.