Paired geochemical tracing and load monitoring analysis for identifying sediment sources in a large catchment draining into the Great Barrier Reef Lagoon
Journal Publication ResearchOnline@JCUAbstract
While sediment tracing has been typically applied to identify sediment sources that are difficult to measure by gauging (monitoring), it can also be useful in estimating relative sediment yields from gauged river catchments. The major and trace element composition of river sediments from eleven locations in the 130000 km2 Burdekin River catchment, northeastern Australia was analysed to examine relative contributions from upstream source areas in the 2011/12water year. Sediment tracing results are compared against estimates derived fromsediment load monitoring at three locations. Comparisons show that there is good agreement between tracing results and monitoring data at one of the tributary confluences. At the second site, notable contrastswere found between the load estimates from the monitoring and tracing data. At this site a large impoundment occurs between the upstream sampling/gauging sites for source sediments and the downstream sampling/gauging sites for target sediments. The contrast is likely caused by temporal variations in particle size distributions of suspended sediment fromeach river and differential trapping efficiencies in the impoundment for sediment derived fromthe different tributaries. In the absence of the detailed particle size data and trapping efficiency estimates, sediment tracing provides the unique opportunity to elucidate source contributions of the finer fractions of suspended sediment. At a third site, where there were recognised measurement gaps in the monitoring data during large discharge events, the relative load estimates fromthe tracing data provided a means of constraining the recognized uncertainty of monitored load estimates.We conclude that sediment tracing can be used as a valuable adjunct to monitoring data particularly in remote, large and data-sparse catchments. Both tracing results and monitoring data showthat the Upper Burdekin River and Bowen-Bogie Riverswere the dominant source of the b10 μm sediments being delivered to the GBR lagoon from the Burdekin River catchment in the 2011/12 water year. More substantial contribution from the Belyando-Suttor Rivers indicated by the tracing results than the monitoring data is attributed to preferential delivery of the 1–10 μm sediments through the impoundment and has uncovered a knowledge gap in sediment budgets in the catchment.
Journal
Geomorphology
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Volume
266
ISBN/ISSN
1872-695X
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Pages Count
12
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Publisher
Elsevier
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DOI
10.1016/j.geomorph.2016.05.008