From 2008 to 2012, the U.S. Geological Survey, in cooperation with the U.S. Army Corps of Engineers, Walla Walla District, developed an acoustic backscatter surrogate (model 1.0) for estimating real-time suspended-sediment concentration and loads at Clearwater River at Spalding, ID (USGS ID: 13342500) using a horizontally-mounted 3000kHz acoustic Doppler velocity meter (ADVM). This study is a continuation of the 2008 to 2012 acoustic backscatter surrogate study using samples collected since 2015 to validate the continued use of model 1.0. Sample data collected in 2015 to 2018 show a deviation from model 1.0 when backscatter data from the ADVM, after correction for acoustic losses, is greater than 65.7 decibels. The model archive summary documents acoustic backscatter surrogate model 2.0 for the real-time calculation of suspended-sediment concentration at Clearwater River at Spalding, ID (USGS ID: 13342500). Model 2.0 is in effect from March 24, 2015 to September 30, 2019 (end of the study). The methods used in the study follow U.S. Geological Survey protocols as referenced in relevant Office of Surface Water/Office of Water Quality Technical Memoranda and U.S. Geological Survey Techniques and Methods reports.
