Model Archive Summary for Suspended-Sediment Concentration at station 11501000, Sprague River near Chiloquin, OR WY 2008-2017 revision and computation for WY 2008-2020

This model archive summary (MAS) documents the revision of suspended sediment concentration (SSC) unit and daily values computed from WY 2008-2017, and the additional computation of SSC unit values from WY 2018-2020 using a new log-transformed regression model with SSC samples from the period of record at this site. The new, revised model computes SSC unit values for WY 2008-2020. This model supersedes all prior models for this site. Prior approved models were simple linear, non-transformed regressions with turbidity as the explanatory variable. Evaluation of 90 percent prediction intervals after the records were approved showed that negative values were being reported during periods of low turbidity. As a result, prior approved time periods are being revised with the log-transformed model documented in this MAS. These time periods have been flagged as “revised” in the USGS National Water Information System [NWIS], and a revision statement is documented in Aquarius. Prior approved time periods that will be “revised” include WY 2013-2017. This MAS includes additional approval of WY 2008-2013 data, which were not previously approved, but were computed with the prior models. Implementing the new, revised model described in this MAS completes SSC for the period of record where turbidity data and SSC samples were collected, covering WY 2008-2020.