Total dissolved gas and water temperature in the lower Columbia River, Oregon and Washington, water year 2015

Significant Findings

An analysis of total-dissolved-gas (TDG) and water-temperature data collected at eight fixed monitoring stations on the lower Columbia River in Oregon and Washington in water year 2015 indicated the following:

• All but 1 of the 85 TDG sensor laboratory checks that were performed after field deployment were within ±0.5-percent saturation of a primary standard.
• After 3–4 weeks of deployment in the river, 79 of 89 TDG sensor field checks were within ±1.0-percent saturation of a secondary standard. Nine of the field checks greater than ±1.0-percent saturation occurred at the John Day Dam tailwater station and resulted in periods of deleted TDG data at the station.
• All 90 barometric pressure field checks were within ±1 millimeter of mercury of a primary stand-ard, and all 90 water-temperature field checks were within ±0.2 degrees Celsius of a secondary standard.
• TDG data were considered complete if received in real time and within 1-percent saturation of the expected value on the basis of calibration data, replicate quality-control measurements, and comparison to river conditions at adjacent stations. For the eight monitoring stations, data completeness ranged from 71.9 to 99.8 percent.
• All quality-assurance values exceed the criteria established by the U.S. Army Corps of Engineers TDG monitoring plan. Criteria for data completeness (95-percent) were met at seven of the eight monitoring stations. Deleted data at the John Day tailwater station resulted in data completeness below criteria.