The Umpqua River Basin is a major coastal fishery resource in Oregon and water temperature is a key management issue.  Summer water temperatures in the lower part of the system frequently exceed 80 °F.

In the summer of 2002, Oregon DEQ contracted with Watershed Sciences, LLC of Corvallis to conduct airborne thermal infrared (TIR) remote sensing surveys in the Umpqua Basin.  One of the outputs from this project was a profile of the surface temperature of the river thalweg based on samples from the TIR imagery.

(Click on the figures for large view)

The chart shows the results of this sampling for a portion of the river.  The variability of the data was of special interest since the low temperature areas could be associated with substantial cold-water inflow from the river bed that would be beneficial to the fishery resource.  

2008 Work

In 2008 the Partnership for the Umpqua Rivers Watershed Council (PUR) conducted water quality sampling on about 24 river miles between Mill Creek and Elkton. Intensive bottom sampling did not detect significant cold-water inflow. The results of this work is reported on the 2008 Report page.

The 2008 results indicated that more time-series data of the thalweg temperature was needed to fully characterize the longitudinal temperature profile of the river.

2009 Work

In the summer of 2009 PUR initiated a synoptic study of the dynamic response of the thalweg temperature of the river by deploying 33 temperature dataloggers in 33 miles of the river between Elkton and Wolf Creek..The TIR chart (above) and the map show the location of the monitoring points.  Cross section data was measured at two sites  - indicated by the red slash lines on the map.  [Pictures of the monitoring sites are available in the table]

Thalweg Temperature data was recorded at all of the sites 30 minute intervals between 7/10 -9/2/2010.  The chart shows a 3D representation of the data for a two-day interval. 

These two charts show representative synoptic temperature profiles for three different dates.  The chart with the yellow background includes the median TIR data that was obtained between 15:00 and 16:00 on 7/23/2002.  An animation of all the data for three 48-hour periods during the study can be viewed on the link.[View Movie Clip on YouTube] 

Initial Comments:

1.  The uneven response over time suggests that the temperature response at each site is strongly influenced by local conditions.

2.  The observed variability during the 15:00 time period appears to be consistent with the 2002 TIR data.

3.  Based on our 2008 work, the variability is more likely driven by differences in solar loading rather than cold-water influences.

On going work:

1. Characterize the effective influence zone for each site.

2. Attempt to correlate differences in solar input with the observed response.  Data from the TIR imagery and geospatial radiation loading will be used. 

3. Develop the cross-section data.

4. Compare response of the loggers between start time and end of study to test for embedded effects.

Power Point  of Sample Work (7mb)

 Acknowledgements:

This project was funded in part by an Oregon NPS Implementation 319 Grant.

Thanks to Vince Fox, a master river boatman, who made the impossible possible.  Special thanks goes to Sandy Lyon of the PUR Watershed Council for her encouragement and support.  This project would not have happened without her.

Obtaining synoptic data from the thalweg of a large rive is problematic to say the least.  We are grateful for the assistane of Alan Bunce who enabled the retrieval of the concrete blocks by snorkel diving in swift current to depths exceeding 20 feet.