An Investigation of Spatial and Temporal Variability in Several of Montana's Reference Streams: Working Toward a More Holistic Management Strategy

Water temperature is a physical property that fundamentally affects stream ecology and is considered an important water quality parameter from scientific and legal view points. On global, catchment and reach scales, anthropogenic activities have substantially altered natural stream temperature regimes, impairing these systems’ ability to maintain ecological integrity. Thermal degradation often can be attributed to a variety of human activities, and global climate change, which has been accelerated by the demands of an exponentially expanding human population, will play a central role in defining stream temperature regimes in the future. Natural spatial and temporal variability in stream temperatures adds to the complexity of regulating thermal pollution and restoring natural conditions of stream ecosystems. As such, managers would benefit from a comprehensive understanding of the thermal dynamics and primary drivers, including air temperature, of the thermal energy budgets in unaltered, or reference, streams. In this study, a random coefficient regression model was developed and used to analyze variability in summer daily average water temperatures and the relationship between summer daily average air and water temperatures of thirty-six of the Montana Department of Environmental Quality’s reference streams. These streams represent four of Montana’s seven Level III ecoregions: Middle Rockies, Northern Rockies, Northwestern Glaciated Plains, and Northwestern Great Plains. Variability in stream temperatures between ecoregions, between streams within ecoregions, and the air-water temperature relationship were primary considerations. This model indicates that there is not significant variability between ecoregions in Montana’s reference stream temperatures and in the air-water temperature relationship. Alternately, the model indicates that there is significant variability between streams within each ecoregion in reference stream temperatures and the air-water temperature relationship. Equations representing the expected daily average water temperatures of reference streams, given values of daily average air temperature with zero and one-day lag, are also presented. Finally, the management implications of this predictive model are discussed, and a holistic approach is recommended for developing thermal regime-based stream temperature standards, which are critical for the restoration and maintenance of ecological integrity, based on ‘natural’ conditions in reference streams.

Name thesis:degree_name

Master of Science (MS)

Grantor dc:publisher

University of Montana

Year

2009

Author dc:creator

• Makarowski, Kathryn Elizabeth

• ecoregion
• restoration
• stream management
• stream temperature
• temperature regime
• thermal variability

Repository record dc:identifier

https://scholarworks.umt.edu/etd/140

OAI identifier oai:identifier

oai:scholarworks.umt.edu:etd-1159