Date of Award:

12-2017

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Watershed Sciences

Department name when degree awarded

Watershed Science

Committee Chair(s)

Sarah Null

Committee

Sarah Null

Committee

Brett Roper

Committee

Bethany Neilson

Abstract

Water temperature is an important variable for aquatic ecosystems. Salmonid population numbers and distribution are heavily influenced by stream temperature, and there is growing concern about the health of salmonid populations with anticipated climate change. Managers are looking to efficiently evaluate options to maintain stream temperatures needed by salmonids. This study evaluated and compared stream temperature restoration alternatives in two streams with warm temperatures using stream temperature monitoring and modeling.

The first study identified pockets of cold water that are important to native fish species in Nevada’s Walker River. Comparison of monitoring results with existing basin-scale model outputs identified two habitat features, beaver dams and irrigation return flow channels, that maximize stream temperature variability. Restoration should maintain and enhance these features, although different restoration approaches may be needed at different locations. This study may provide guidance for the interpretation of stream temperature results from other basin-scale models.

The second study quantified stream temperature effects of wildfire and restoration plantings in Oregon’s Meadow Creek with current and projected mid-21st century climate. A stream temperature model developed and applied using Heat Source found restoration eliminated days above the lethal threshold (25 °C) for salmonids and decreased the number of days exceeding spawning criteria during spawning periods. Days exceeding salmonid spawning (13 °C) and rearing (18 °C) thresholds were reduced by all vegetation restoration scenarios, but elimiated by none. Results highlights the importance of the length and location of restoration, which can maximize pockets of cold water for salmonids or alleviate the impact of warm water sections.

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