Calculating sediment trapping efficiencies for reservoirs in tropical settings: a case study from the Burdekin Falls Dam, NE Australia
Journal Publication ResearchOnline@JCUAbstract
The Brune and Churchill curves have long been used to predict sediment trapping efficiencies for reservoirs in the USA which typically experience winter and spring-dominant runoff. Their suitability for reservoirs receiving highly variable summer-dominant inflows has not previously been evaluated. This study compares sediment trapping efficiency (TE) data with the predictions of the two established curves for the Burdekin Falls Dam, a large reservoir in northern tropical Australia which receives highly variable summer-dominant runoff. The measured TE of the reservoir ranged between 50% and 85% and was considerably less than estimates using the Brune and Churchill curves over the 5 year study period. We modified the original equations so that daily trapping can be calculated and weighted based on daily flow volumes. This modification better accounts for shorter residence times experienced by such systems characterized by relatively high intraannual flow variability. The modification to the Churchill equation reasonably predicted sediment TEs for the Burdekin Dam for four of the five monitored years and over the whole monitoring period. We identified four key sediment particle classes: (1) <0.5 µm which exclusively passes over the dam spillway; (2) 0.5–5.0 µm which, on average, 50% is trapped in the reservoir; (3) 5.0–30 µm most (75%) of which is trapped; and (4) >30 µm which is almost totally (95%) trapped in the dam reservoir. We show that the modification to the Churchill equation has broader application to predict reservoir TE provided that daily flow data are available.
Journal
Water Resources Research
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N/A
Volume
49
ISBN/ISSN
1944-7973
Edition
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Issue
2
Pages Count
13
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Publisher
Wiley-Blackwell
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EISSN
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DOI
10.1002/wrcr.20117