Continuous temperature measurements to assess upstream connection of off-channel features of the middle and upper Willamette River, Oregon, Summer, 2016

Temperature 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-channel feature is inundated when the ground temperature sensor does not match nearby air temperature readings, indicating the ground sensor is submerged by river water. Temperature loggers were installed from late May through mid-November, 2016, when discharge of the Willamette River was between approximately 5,500 and 45,000 cubic feet per second at Salem, Oregon (3,500 to 17,500 cubic feet per second at Harrisburg, Oregon). The timing and persistence of surface water connections between off-channel features and the main channel are key variables in understanding changes in temperature and water quality conditions within off-channel features.