Richard R. Davidson, Roger Vreugdenhil and Mark Foster
Significant cracking was observed on the crest of the main embankment at Lake Eppalock for many years, but in recent years increasing movement upstream during low reservoir levels indicated a progressively deteriorating stability situation. Investigations also revealed cohesive filter material that would allow a crack to propagate. A fast-tracked remedial works program was completed in 1999 to rebuild the highly vulnerable upper rockfill shells and filters, both upstream and downstream. To manage construction risk, the works were carried out directly by G- MW with innovations in removal, protection and replacement of the downstream shoulders, and placement of a new multi-zone filter.
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Now showing 1-12 of 27 2964:
B. S. Sherman
Many large Australian dams currently lack selective withdrawal capabilities and release water mainly from deep within the hypolimnion. Deep-water releases coupled with the strong thermal stratification typical of Australian reservoirs results in discharge temperatures 10 °C or more colder than would normally be expected. Cold water pollution has impacted more than 1000 km of river habitat in Australia where it is known to impair spawning, feeding and survival of many native fishes.
This report reviews alternative approaches for the mitigation of cold water pollution below dams. The underlying theory and practical limitations of operation as well as field experience (including cost) with each of the methods are discussed. Two methods in particular, suface pumps and submerged curtains, appear to offer cost-effective alternatives to the expensive retrofitting of dams with multi-level outlet structures (estimated to cost $5-35m per dam for major dams in NSW). These methods are predicted to be capable of increasing discharge temperatures by 4-10 ° throughout the range of irrigation releases without any redirection of flows, i.e. hydropower releases can be maintained at present levels. This holds the promise of restoring more desirable temperatures over hundreds of kilometres of river.
Glen Hobbs and Danny Azavedo
Recent years have seen a growing awareness and understanding of the factors that contribute to the reliability of spillway gates and the incorporation of reliability data into overall dam risk studies.
The study of a number of spillway gate failures shows that no one component or incident leads to gate failure, but rather a combination of factors have resulted in gate failure. A rigorous reliability assessment should consider all factors, not only the equipment condition and performance but the complete system, from the receipt of data through to the actuation of the gates. It should take into account issues such as human factors, poor design, maintenance history and policy. Unfortunately one of the main hindrances to quantifying gate reliability is the lack of information on spillway gate equipment and system performance and failures.
This paper considers a number of gate failures, then looks at some of the tools of reliability assessment and the role of human factors in gate reliability.
The paper then discusses a recent study of four gated dams. For this study a systems approach was adopted and human factors were considered. The results compare favourably with other similar critical structures, and show that for these well designed and maintained structures human factors are the limiting criteria in multiple gate operations. The study also shows that the probability of opening all the spillway gates at a dam improves with time (2-4 hours) during the flood operation, and it is considered that time based reliability provides a more meaningful and useful assessment of overall spillway gate reliability.
B. A. Cole
In October 2000 ANCOLD published a history of dam technology in Australia covering the 150 years in which large dams have been constructed in this country. The paper describes how this project began, the search for authors, the way the authors tackled their tasks, the peer reviews which resulted in additional chapters being written, and the archive searches for interesting photographs to illustrate the text. All this was accomplished by dam engineers including the editor. Then follows an account of the professional publication process: sub-editing, desktop publishing, proof-reading, the preparation of an index, the cover design and the printing process. Some conclusions are drawn from this first experience of book publishing.
R. E. Saunders, J. Roberts, B. W. Omundson
Ross River Dam is located immediately upstream of the twin cities of Townsville and Thuringowa. The population at risk from failure of the dam is approximately 110,000. A recently completed risk assessment has confirmed earlier studies that the dam does not satisfy current safety criteria and presents high risk levels in a number of areas. Importantly, the risk assessment has enabled the extent of these risks to be clearly identified. This paper summarises the risk assessment highlighting notable methodologies employed and the key findings of the study.
The entire historical record of rainfall archives held by the Bureau of Meteorology over the region of Australia affected by tropical storms has been examined and the extreme storms have been extracted. From this database, we account for site specific effects (moisture and topography) from each of the storms, allowing us to compare storms amongst each other. This then allows us to construct a theoretical maximum precipitation in a generalised sense. By then returning the site specific information for a particular region, we can infer the probable maximum precipitation at this location.