Hell's Canyon RiverCat Discharge Measurements

SonTek/YSI hydrologist John Sloat (bow) and Idaho Power Company engineer Pete Vidmar (helm) shoot Granite Rapids on the way to the measurement site at Johnson Bar on the Snake River in Hell's Canyon.

June 12-14, 2001 - Adventurous personnel from Idaho Power Company and SonTek/YSI braved class IV rapids to make RiverCat discharge measurements using a kayak on the Snake River at Johnson Bar gauging station. This station is about 18 miles downstream of Idaho Power Company's Hell's Canyon Hydroelectric Dam.

The Johnson Bar gauging station is designated by the Federal Energy Regulatory Commission (FERC) as a minimum flow and ramp rate compliance site. Idaho Power Company has recently assumed operation of this gauging station in a continued effort that began in 1996 to reduce costs. Idaho Power Company currently maintains a network of over 20 of their own gauging stations, including nine on the main stem of the Snake River. They have also been involved in the installation and maintenance of additional gauges for other organizations in a revenue generating effort since 1998.

Onshore technicians Stan Pierce and Jim Hulme observe telemetered data from the RiverCat using the RiverSurveyor data collection software program at Johnson Bar on the Snake River.

Historically, attempts to develop stage-discharge rating curves for the Johnson Bar site required massive efforts just to get metering equipment to the site and set up for data collection. Even though provisional ratings at Johnson Bar had been developed, compliance monitoring for minimum flow downstream of the dam has been reported using data from the Snake River below the Hell's Canyon Dam gauging station, which is about one-half mile downstream of the dam.

As part of a strategic effort to improve the existing stage-discharge rating at Johnson Bar, Idaho Power Company had the creative idea to use a SonTek/YSI RiverCat attached to a hard-shell kayak, which is then paddled across the river to get quick and accurate discharge measurements. This simple idea was effective, and the results of the measurements were excellent. This design also eliminated the need to navigate high-powered jet boats to the site just for the purpose of transecting a profiler across the river.

Idaho Power Company's RiverCat/kayak setup on the Snake River

Pete Vidmar (Idaho Power Company) paddles the RiverCat across the Snake River

Measurements were collected over a two-day period at flow rates between 7,500 and 13,000 cfs with surface velocity often exceeding 9 ft/s. Each measurement took less than five minutes, minimizing the effect of possible flow fluctuations. The RiverCat proved itself once again as a useful tool for measuring discharge even at the most challenging and dynamic sites.

• RiverCat
• RiverSurveyor ADP