The effects of sample scheduling and sample numbers on estimates of the annual fluxes of suspended sediment in fluvial systems

Arthur J. Horowitz, Robin T. Clarke, Gustavo Henrique Merten

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

Since the 1970s, there has been both continuing and growing interest in developing accurate estimates of the annual fluvial transport (fluxes and loads) of suspended sediment and sediment-associated chemical constituents. This study provides an evaluation of the effects of manual sample numbers (from 4 to 12year-1) and sample scheduling (random-based, calendar-based and hydrology-based) on the precision, bias and accuracy of annual suspended sediment flux estimates. The evaluation is based on data from selected US Geological Survey daily suspended sediment stations in the USA and covers basins ranging in area from just over 900km2 to nearly 2millionkm2 and annual suspended sediment fluxes ranging from about 4Ktyear-1 to about 200Mtyear-1. The results appear to indicate that there is a scale effect for random-based and calendar-based sampling schemes, with larger sample numbers required as basin size decreases. All the sampling schemes evaluated display some level of positive (overestimates) or negative (underestimates) bias. The study further indicates that hydrology-based sampling schemes are likely to generate the most accurate annual suspended sediment flux estimates with the fewest number of samples, regardless of basin size. This type of scheme seems most appropriate when the determination of suspended sediment concentrations, sediment-associated chemical concentrations, annual suspended sediment and annual suspended sediment-associated chemical fluxes only represent a few of the parameters of interest in multidisciplinary, multiparameter monitoring programmes. The results are just as applicable to the calibration of autosamplers/suspended sediment surrogates currently used to measure/estimate suspended sediment concentrations and ultimately, annual suspended sediment fluxes, because manual samples are required to adjust the sample data/measurements generated by these techniques so that they provide depth-integrated and cross-sectionally representative data.

Original languageEnglish (US)
Pages (from-to)531-543
Number of pages13
JournalHydrological Processes
Volume29
Issue number4
DOIs
StatePublished - Feb 15 2015

Keywords

  • Annual fluxes
  • Monitoring programmes
  • Rating curves
  • Sample numbers
  • Sample scheduling
  • Suspended sediment

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