Investigation of hydroacoustic flow-monitoring alternatives at the Sacramento River at Freeport, California: results of the 2002-2004 pilot study

The Sacramento River at Freeport is a tidally affected channel approximately 620 feet wide located at the northern boundary of the Sacramento?San Joaquin River Delta, California. In 1978, an acoustic velocity meter was installed at Freeport to monitor the flow. The acoustic velocity meter was calibrated successfully and has been used continuously since that time. Although the calibration has been extremely stable, an increasing number of maintenance problems prompted a search for alternatives to monitor discharge at this location. Two sideward-looking acoustic Doppler velocity meters were tested in a pilot study from 2002-2004: a short-range system and a long-range system. The pilot study was conducted over a wide range of hydrologic conditions and both sideward-l-ooking acoustic Doppler velocity meters have performed well at this location and have been calibrated successfully. As of February 2004, the short-range system had a robust calibration and a higher data-recovery rate, therefore, it was selected as the primary replacement of the acoustic velocity meter, with the long-range system providing real-time data redundancy to minimize data loss.