Water-quality conditions (including temperature) in the Willamette River and many of its adjacent off-channel features, such as alcoves and side channels, were monitored between river miles 67 (near Salem, Oregon) and 168 (near Eugene, Oregon) during the summers of 2015 and 2016. One or more parameters (water temperature, dissolved oxygen, pH, specific conductance, and [or] water depth) were continuously measured at sites in the main channel (9 sites in 2015; 5 sites in 2016) and select off-channel features (20 features in 2015; 22 features in 2016). This study was initiated in reaction to the unusually warm, dry weather and resulting low streamflows that occurred in the Pacific Northwest in 2015 and the need for flow managers to understand the effects of streamflow on water-quality conditions in off-channel features of the Willamette River. Field monitoring was focused on documenting water-quality conditions during low summer streamflows and during fluctuations in streamflow, including when side channels became alcoves and reconnected to become side channels again.
Water in the main channel of the Willamette River upstream from river mile 50 near Newberg typically is well mixed during summer, with warm water temperatures (greater than 18 degrees Celsius) and high dissolved-oxygen concentrations (often greater than 7.7 milligrams per liter). During low summer flows, a diverse suite of off-channel features exists adjacent to the main channel of the Willamette River. Despite temporal and spatial variability within individual features, comparison of continuous water-temperature data between the main channel and off-channel features indicated that some off-channel features were consistently cooler than the main channel, some were consistently warmer than the main channel, and others frequently fluctuated between warmer or cooler than the main channel. Site-specific characteristics including upstream connection, depth, and presence or absence of aquatic or riparian vegetation were factors that seemed to affect the water quality of a feature.
Results from this study showed a relation between the geomorphology, hydrology, ecology, and water quality of an off-channel feature. Data confirmed that many features that can be classified as cold-water refuges based on water-temperature standards also contained low concentrations of dissolved oxygen that may not be suitable for sensitive fish species. A simplified site classification scheme is proposed that links water-quality conditions in measured off-channel features with site-specific characteristics and summer streamflows. The site classification scheme was extended to create a theoretical process matrix that relates measured water-quality conditions to a list of the processes and site-specific characteristics that could create those conditions.
|Title||Temperature and water-quality diversity and the effects of surface-water connection in off-channel features of the Willamette River, Oregon, 2015–16|
|Authors||Cassandra D. Smith, Joseph F. Mangano, Stewart A. Rounds|
|Publication Subtype||USGS Numbered Series|
|Series Title||Scientific Investigations Report|
|Record Source||USGS Publications Warehouse|
|USGS Organization||Oregon Water Science Center|
Continuous temperature measurements to assess upstream connection of off-channel features of the middle and upper Willamette River, Oregon, Summer, 2016
Water surface elevations recorded by submerged water level loggers in off-channel features of the middle and upper Willamette River, Oregon, Summer, 2016
Point measurements of temperature and water quality in main-channel and off-channel features of the Willamette River, 2015-2016
Continuous temperature measurements to assess upstream connection of off-channel features of the middle and upper Willamette River, Oregon, Summer, 2016Temperature loggers were placed on the ground (n=4) and hung in the air (n=2) near the upstream connection point of four Willamette River off-channel features (side channels and alcoves) to assess timing and discharge conditions when these four off-channel features were inundated at the upstream end with flow from the main channel. Temperature readings indicate that the upstream end of an off-chan
Water surface elevations recorded by submerged water level loggers in off-channel features of the middle and upper Willamette River, Oregon, Summer, 2016Water surface elevations within seven Willamette River off-channel features (OCF; alcoves and side channels) were measured using submerged pressure transducers. Transducers were installed from late May through mid-October, 2016, when discharge of the Willamette River was between approximately 5,500 and 45,000 cubic feet per second at Salem, Oregon (USGS gage 14191000) and 3,500 to 17,500 cubic fee
Point measurements of temperature and water quality in main-channel and off-channel features of the Willamette River, 2015-2016Water quality point measurements were collected by the US Geological Survey within the main channel Willamette River and its off-channel features in the summer and autumn of 2015 and 2016. All measurements include location, time, temperature, and depth below water surface, while most also include specific conductivity, dissolved oxygen, and pH.