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COMPUTING TIME-SERIES SUSPENDED-SEDIMENT CONCENTRATIONS AND LOADS FROM IN-STREAM TURBIDITY-SENSOR AND STREAMFLOW DATA

Guidelines and procedures for estimating time series of suspended-sediment concentration and loading as a function of turbidity and streamflow data have been published in a U.S. Geological Survey Techniques and Methods Report, Book 3, Chapter C4. The concepts, statistical procedures, and techniques used to maintain a multiyear suspended sediment time series and to prepare sediment data for public dissemination are described. Procedures for comparing computed suspended-sediment concentrations to water-quality criteria and assessing the frequency of exceeding criteria are included. Specific examples of the method used in Kansas and Missouri are provided.

The method for computing suspended-sediment concentration and loads using turbidity sensors is primarily for nephelometry, but also can be used for optical backscatter. Because an in-situ turbidity sensor is capable of measuring turbidity instantaneously, a turbidity time series can be recorded and related directly to time-varying suspended-sediment concentrations. Depending on the suspended-sediment characteristics of the measurement site, this method can be more reliable and, in many cases, a more accurate means for computing suspended-sediment concentrations and loads than traditional U.S. Geological Survey computational methods.

A spreadsheet and user manual to develop a single or multiple linear regression model using SSC, turbidity, and streamflow data can be downloaded here (Turbidity Sediment Spreadsheet and User Manual). The macros in this spreadsheet allow the user to paste their data in and interactively develop regression models that can then be used to compute SSC and SSL. The methods discussed in T&M 3C4 are used in the spreadsheet.

Additional Information:

• Daily-value suspended-sediment data collected by the USGS from 1930 through September 30, 1994, are available to the public on-line at http://webserver.cr.usgs.gov/sediment. These and subsequent daily-value USGS suspended-sediment data are entered into the NWISWeb data base as the data become available.

Other Links:

• Chapter 6.7 Turbidity of the USGS National Field Manual for the Collection of Water-Quality Data (TWRI Book 9).
• Daily-value suspended-sediment data collected by the USGS from 1930 through September 30, 1994, are available to the public on-line at http://webserver.cr.usgs.gov/sediment/.
• Guidelines and Standard Procedures for Continuous Water-Quality Monitors: Station Operation, Record Computation, and Data Reporting, 2006, Wagner and others.
• Computation of fluvial-sediment discharge, by George Porterfield: USGS—TWRI Book 3, Chapter C3. 1972.
• Field methods for measurement of fluvial sediment, by T.K. Edwards and G.D. Glysson: USGS—TWRI Book 3, Chapter C2. 1999.
• Kendall-Theil Robust Line (KTRLine—version 1.0)—A Visual Basic Program for Calculating and Graphing Robust Nonparametric Estimates of Linear-Regression Coefficients Between Two Continuous Variables, by Gregory E. Granato.