Suspended sediment concentration in Alpine glacial meltwaters

Peters, R 2017, Suspended sediment concentration in Alpine glacial meltwaters , MSc by research thesis, University of Salford.

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Suspended sediment concentration in meltwaters draining from Alpine glaciers vary considerably both diurnally and seasonally. In order to characterise sediment variability, sub-daily close-interval sampling measurements of suspended sediment concentrations are usually undertaken. In close-interval sampling, concentrations are assessed in small volumes of water (< 250 ml). Suspended sediment concentrations can be determined instantaneously and continuously using photoelectric sensors on volumes of ~1-2 ml meltwaters. However, according to the nature of the sediment in suspension, occasional larger particles amongst the general silt fraction contribute to the weight of sediment in a sample. Suspended sediment concentration in meltwater in the Gornera, the only melt-stream draining from Gornergletscher, Wallis, Switzerland, during the summer ablation season of 1982, were assessed using three methods, with differing sampling intervals in time, with differing volumes of meltwater. Meltwater samples of < 200 ml were collected hourly by a Manning S-4050 automatic liquid pump sampler, and filtered for gravimetric determination of sediment content. This is the original method of collection and data for all three methods was calibrated into kg/ day. This method correlates positively with discharge as the R2 measured 0.16, and the p-value was also lower than the alpha (p= <0.00) meaning the correlation is statistically significant. Photoelectric measurements were determined continuously with a Partech 740 suspended sediment monitor, and were extracted during hourly intervals. This method did not correlate with discharge because even though the R2 is strong (0.76), the p-value is higher than the alpha, meaning correlation is not statistically significant. Large samples of 50 L were collected once a day by a large aluminium cone, with the height of the settled sediment cone being recorded. This method did not correlate with discharge because the R2 was non-existent (0.00) and p-value was higher than the alpha (p= <4.23), meaning the correlation is not statistically significant. Close interval methods proved to be most representative as they show more temporal variation, however, sediment cones show less variation due to once a day samples being collected. The Manning method proved to show most diurnal variation meaning it is most representative, other methods seem to underestimate values or seem to be limited.

Item Type: Thesis (MSc by research)
Schools: Schools > School of Environment and Life Sciences
Depositing User: Richard Peters
Date Deposited: 23 Feb 2018 15:28
Last Modified: 27 Aug 2021 20:45

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