Water-quality conditions and suspended-sediment transport in the Wilson and Trask Rivers, northwestern Oregon, water years 2012–14
In October 2011, the U.S. Geological Survey began investigating and monitoring water-quality conditions and suspended-sediment transport in the Wilson and Trask Rivers, northwestern Oregon. Water temperature, specific conductance, turbidity, and dissolved oxygen were measured every 15–30 minutes in both streams using real-time instream water-quality monitors. In conjunction with the monitoring effort, suspended-sediment samples were collected and analyzed to model the amount of suspended sediment being transported by each river. Over the course of the 3-year study, which ended in September 2014, nearly 600,000 tons (t) of suspended-sediment material entered Tillamook Bay from these two tributaries.
Each year of the study, the Wilson River transported between 80,300 and 240,000 t of suspended sediment, while the Trask River contributed between 28,200 and 69,900 t. The suspended-sediment loads observed during the study were relatively small because streamflow conditions were routinely lower than normal between October 2011 and September 2014. Only one storm had a recurrence interval between a 2- and 5-year event. Every other storm produced streamflows equivalent to what would be classified as a 1- or 2-year event. Because most sediment moves during high flows, the lack of heavy rainfall and elevated streamflows muted any high sediment loads.
Along with assessing suspended-sediment transport, the U.S. Geological Survey also monitored instream water quality. This monitoring was used to track instream conditions and relate them to water temperature, dissolved oxygen, and sedimentation issues for the Wilson and Trask Rivers. Stream temperatures in the Wilson and Trask Rivers exceeded the temperature standard for cold-water habitat. Water temperatures at both streams exceeded the standard for more than 30 percent of the year, as stream temperatures increased above the seasonal 13 degrees Celsius (°C) (seasonal core cold-water habitat) and 16 °C (salmon and steelhead [Oncorhynchus mykiss] spawning) thresholds. Conversely, dissolved oxygen concentrations rarely decreased to less than the absolute water-quality criterion of 8 milligrams per liter for cold-water streams.
Results from this study will provide resource managers insight into the seasonality of water-quality conditions and the extent of suspended-sediment transport in the Wilson and Trask Rivers. The data are useful for establishing a baseline and for maintaining best-use land management practices and possibly for aiding in prioritization of restoration actions for both rivers and their respective watersheds.
Sobieszczyk, Steven, Bragg, H.M., and Uhrich, M.A., 2015, Water-quality conditions and suspended-sediment transport in the Wilson and Trask Rivers, northwestern Oregon, water years 2012–14: U.S. Geological Survey Scientific Investigations Report 2015-5109, 32 p., http://dx.doi.org/10.3133/sir20155109.
ISSN: 2328-0328 (online)
Table of Contents
- Data Collection
- Data Analysis
- Water-Quality Conditions and Suspended-Sediment Transport
- Implications for Stream Conditions for Wilson and Trask Rivers
- Summary and Conclusions
- References Cited
- Appendix A. Wilson River Suspended-Sediment Concentration Record
- Appendix B. Trask River Suspended-Sediment Concentration Record
- Appendix C. Troubleshooting Instream Monitors
Additional publication details
|Publication Subtype||USGS Numbered Series|
|Title||Water-quality conditions and suspended-sediment transport in the Wilson and Trask Rivers, northwestern Oregon, water years 2012–14|
|Series title||Scientific Investigations Report|
|Publisher||U.S. Geological Survey|
|Publisher location||Reston, VA|
|Contributing office(s)||Oregon Water Science Center|
|Description||vi, 32 p.|
|Time Range Start||2011-10-01|
|Time Range End||2014-09-30|
|Other Geospatial||Trask River, Wilson River|
|Online Only (Y/N)||Y|
|Additional Online Files (Y/N)||N|