Estimating the suspended sediment loads of rivers in the LOIS study area using infrequent samples

Abstract

Abstract:A central objective of the LOIS Community Research Programme is to provide estimates of the land±ocean¯ux of suspended sediment from the LOIS study area. While high frequency (15-minute interval) suspended sediment concentration data are recorded within the programme at six tidal limit sites, infrequent (weekly± monthly) sampling undertaken by the Harmonized Monitoring (HM) Programme provides additional concentration data for 23 tidal limit sites in the LOIS study area. In order that these infrequent data can be used to generate sediment¯ux estimates, the accuracy and precision of 22 load estimation procedures are assessed in the context of sampling frequency (weekly, fortnightly and monthly) and basin scales representative of the LOIS study area. Sampling frequency is demonstrated to exert a signi®cant in¯uence on the precision of the individual procedures, with precision being inversely related to sampling frequency. Accuracy is less clearly in¯uenced by sampling frequency, although dierent procedures were identi®ed as being the most accurate at the three sampling frequencies. Basin scale is shown to exert a signi®cant in¯uence upon accuracy and precision, with the performance of the load estimation procedures being inversely related to basin scale. For one interpolation procedure, an error correction procedure is developed, based on the strong relationship identi®ed in this study between the error associated with individual¯ux estimates and the ratio of mean sampled discharge to the mean discharge obtained from the high frequency record. This relatively high resolution error correction method is applied to HM data from eight tidal limit sites in the LOIS area, and corrects the initial annual load estimates to provide values that are considered to be more representative of rivers from the LOIS study area.

Influence of Sampling Frequency on Estimation of Annual Total Phosphorus and Total Suspended Solids Loads1

“…In addition to a greater bias in load estimates at Paradise than Mendon, there was a greater degree of underestimation of loads at Paradise than at Mendon. This is consistent with studies that found loads tend to be underestimated on smaller rivers more so than larger rivers (Kronvang and Bruhn, 1996; Phillips et al. , 1999).…”

Temporal variability of suspended sediment transport and rating curves in a Mediterranean river basin: The Celone (SE Italy)

“…Generally, this is a power function derived by a log-transformed leastsquares regression (linear, Eq. (2); or second-order polynomial) where the discharge (Q) is the independent variable (Phillips et al, 1999) and SSC (C) is the dependent variable.…”

Optimal estimation of suspended‐sediment concentrations in streams

“…In particular, off-line root mean square errors showed a slight tendency to decrease with increasing median discharges. Although the number of sites analysed is thought to be too small to provide conclusive results, the finding is consistent with results by Phillips et al (1999), who indicated that the accuracy and precision of the estimators that they evaluated declined with a reduction in drainage area. No relation between model errors and sediment characteristics was detected.…”