Tobacco River Stream Assessment and Restoration Recommendations
by
Jeffrey W. Dunn
B.S., Montana State University, 1998
presented in partial fulfillment
of the requirements for a degree of
Master of Science
The University of Montana
October 2002
ABSTRACT: The Tobacco River flows through the town of Eureka in northwestern Montana. Historically, Eureka applied treated wastewater to a privately owned hay field beside the river. Recently, the town of Eureka obtained a permit to discharge directly to the river, and wastewater was discharged into the river in May and June of 2001 and again in March and April of 2002. Wastewater is stored in a lagoon at other times.
This study reports on current stream morphology, riparian conditions, and late summer instream nutrient levels along the Tobacco River and provides some recommendations for streambank stabilization at the land application site.
Water samples were taken in July and August 2001, when discharge was not occurring. Sampling sites bracketed the land application site and the discharge pipe. At the time of sampling, nutrient levels were at or below standards and targets adopted for the Clark Fork River and Flathead Lake. The ratio of nitrogen to phosphorus suggests that phosphorus is in shorter supply than nitrogen and likely limits the growth of river bottom algae. Since phosphorus is better trapped by land application than nitrogen, discharging wastewater to the river will likely increase the amount of phosphorus in the Tobacco River. This may result in an unacceptable increase in algae levels, especially if discharge continues throughout the growing season. Hence, the decision to abandon land application should be reconsidered. Wastewater could be stored or land applied during the growing season, and direct discharged only during winter and/or spring high flows.
Based on the width of the riparian zone in less disturbed reaches, I propose that the riparian corridor along the land application site be revegetated with native woody species to a width of 60 meters. This should reduce the rate of streambank erosion and the loss of nutrients from the land application site to the river.
Table of Contents
Abstract
Acknowledgements
Table of Contents
List of Tables
List of Figures
List of Appendices
Introduction
Study Design
Methods
Channel Morphology
Cross-section Measurements
Longitudinal Profile
Stream Classification
Discharge
Riparian Assessment
Instream Analyses
Water Samples for Nutrients
Attached Algae (Periphyton) Samples
Maps
Results and Discussion
Channel Morphology
Polygon Descriptions
Cross-section Measurements
Wetted width
Bankfull width
Width-to-depth ratio
Channel substrate
Bank angle and canopy cover
Longitudinal Profile
Riffle-pool sequences
Pool spacing
Eroding banks
Channel stage
Slope and sinuosity
Stream Classification
Discharge
Riparian Assessment
Community and Habitat Types
Riparian Cross-sections
Health Scores
Biodiversity
Noxious Weeds
Instream Analyses
Water Samples for Nutrients
Total per-sulfate nitrogen
Total phosphorus
Soluble nitrogen
Soluble reactive phosphorus
Water clarity
Attached Algae (Periphyton) Samples
Conclusions and Recommendations
Channel Morphology
Riparian Vegetation
Nutrient and Algae Levels
Table 1. Water quality sample sites proceeding downstream
Table 2. Pools, riffles, and glides (length in meters)
Table 3. Slope and sinuosity
Table 4. Land coverage of riparian vegetation
Table 5. Lotic wetland health assessment
Table 6. Health scores
Table 7. Plants species
Figure 1. Tobacco River watershed and sample sites
Figure 2. Overview of the study reach
Figure 3. Photographs
Figure 4. Wetted width
Figure 5. Bankfull width
Figure 6. Bankfull width and wetted width along the study reach
Figure 7. Channel substrate
Figure 8. Pool spacing
Figure 9. Channel stage
Figure 10. Flow duration curve
Figure 11. Flood frequency curve
Figure 12. Riparian vegetation types
Figure 13. Percent coverage by riparian communities
Figure 14. Riparian zone widths
Figure 15. Total per-sulfate nitrogen
Figure 16. Total phosphorus
Figure 17. Nitrates/nitrites (soluble nitrogen)
Figure 18. Soluble reactive phosphorus
Figure 19. Chlorophyll a concentrations
Figure 20. Ash free dry weight of algae
Figure 21. Streambank stabilization with willow plantings
Figure 22. Riparian restoration proposal
Appendix A. Literature review
Appendix C. Lotic wetland health assessment field score sheet
Figure 1. The Tobacco River Watershed and an overview of the sample sites (Natural Resource Information System, 2002).
Overview of Water Quality Sample Sites and
the Land Application Site
Figure 2. Overview of the Tobacco River study reach showing polygons, transects, and sample sites presented at bankfull flow.
Photo 3: Polygon 1, Transect 10, Photo 4: Polygon 1, Transect 12, upstream downstream view showing the view showing the “reference condition.”
“reference condition.”
Photo 5: End of Polygon 1, start of Photo 6: End of Polygon 1, start of Polygon 2, Transect 14, upstream view. Polygon 2, Transect 14, downstream view.
Photo 7 (series): Polygon 2, Transects 19-23, showing an overview of the land application site along with erosion upstream and downstream of the bridge.
Photo 8: Erosion below Transect 20. Photo 9: Deep pool at Transect 20
formed by LWD and autobody rip-rap.
Photo 10: Erosion above Transect 23. Photo 11: Autobody rip-rap “stabilizing”
the streambank below Transect 23.
Photo 12: End of Polygon 2, Start of Photo 13: End of Polygon 2, start of
Polygon 3, Transect 26, upstream view. Polygon 3, Transect 26, downstream view.
Photo 14: Polygon 3, Transect 31, Photo 15: Outlet of effluent discharge pipe,
eroding Reed Canarygrass. around the bend from Transect 34.
Photo 16: End of Polygon 3, Transect 34, Photo 17: End of Polygon 3, Transect 34,
upstream view. downstream view.