As one of Australia’s largest dam owners, Hydro Tasmania maintains a comprehensive Dam Safety Program. The Program makes use of industry Guidelines in combination with complementary processes to form a decision framework. This framework drives dam improvement initiatives, one of which is the development and operation of survey and instrumentation programs. It is Hydro Tasmania’s belief that the ANCOLD Guidelines on Dam Safety Management currently provide adequate descriptive guidance with regards to survey and instrumentation and it is questionable if more prescriptive Guidelines are prudent or required. Hydro Tasmania believes that a Guideline presenting a decision framework from which targeted Survey, instrumentation and inspection programs and other initiatives can evolve would be a welcomed document to the Australian dams community.
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Janice H. Green and Jeanette Meighen
The Probable Maximum Precipitation (PMP) is defined as ‘the theoretical greatest depth of
precipitation that is physically possible over a particular catchment’. The PMP depths provided by
the Bureau of Meteorology are described as ‘operational estimates of the PMP’ as they represent the best estimate of the PMP depth that can be made, based on the relatively small number of large events that have been observed and our limited knowledge of the causative mechanisms of extreme rainfalls.
Nevertheless, the magnitudes of the PMP depths provided by the Bureau are often met with scepticism concerning their accuracy when compared to large rainfall events which have been observed within catchments and which are, typically, only 20% to 25% of the PMP estimates. The recent increases in the PMP depths, resulting from the revision of the Generalised Tropical Storm Method (GTSMR), have served only to entrench this cynicism.
However, analyses of the magnitudes of the storms in the databases adopted for deriving PMP depths show that these observed storms constituted up to 76% of the corresponding GTSMR PMP depths and up to 80% of the Generalised Southeast Australia Method PMPs for the storm location. Further, comparisons of the PMP depths to large storms observed in similar climatic regions around the world indicate that the PMPs are not outliers.
The results of these analyses are presented for a range of catchment locations and sizes and storm durations and demonstrate that the PMP estimates provided by the Bureau of Meteorology are reasonable and are not unduly large.
The paper describes the methodology, operative techniques and organizational aspects that are used for dam safety assessment procedures. Kelag owns 15 larger dams with wall heights up to 110 m. It is necessary to monitor the aging of the structures and to check all safety equipment regularly. The manned control centre is situated at the KELAG Headquarter in Klagenfurt, which is the capital of Austria’s southern-most Province, Carinthia. KELAG is the principal electricity supplier in Carinthia, and owns several reservoirs in the Austrian Alps. The whole hydropower system has a capacity of 434 MW with an annual production of 1000 GWh. During the last century KELAG employees designed, supervised and constructed most of the structures in cooperation with the authorities. Most of the rock-fill dams have a bituminous concrete sealing on the upstream face. KELAG owns one concrete arch dam with a height of 30 m. A pendulum monitors the movement of the dam crest. This information is transmitted to both the power house and the manned control centre in Klagenfurt. Seepage is monitored at all rock-fill dams. In case of an alarm a skilled engineer has to be informed by the staff of the manned control centre. This dam safety engineer starts to check the reasons on site and manages the emergency action plan. Data has been collected since 1998 and special software is used to handle this information, carry out interpretation and safety assessments. One aim of data collection is to develop a decision support system performing online evaluation, explanation and interpretation of dam behaviour. Normally, once a year geodetic measurements are carried out at all dams.
KELAG’s experience gained in the use of automatic monitoring and risk assessment of dams is covered in this paper. The monitoring systems show the state of the structures and those showing anomalous situations requiring human intervention can be identified as soon as possible. Although the repercussions of the free market system have led to substantial staff reductions, the quality of dam surveillance has had to remain unaffected. Dam safety is guaranteed by new types of instrumentation, data transmission and data assessment. A special software has to be updated constantly.
Michael Somerford, Alex Gower
The Water Corporation is the principal dam owner in Western Australian with a portfolio of 95 dams. In the absence of dam safety legislation in Western Australia the Corporation has adopted a policy of self regulation. This paper presents how the Corporation’s dam safety policy has been implemented with respect to dam instrumentation and monitoring. It includes a summary of the type of instruments used and experiences with automated data collection systems. The paper concludes that the Corporation does not see a need for a dam instrumentation guideline, however a document summarising current Australian practices and experiences would be of value.
A. Uromeihy, P.G. Ranjith
In response to increasing potable water need and in order to control and collect precipitations, many dams have been constructed and many more are under construction in Iran. Due to the complex geology of the country, many of the dam sites face serious geological problems both during construction and in operation phases. The most predominant types of problems are water leakage and sediment deposition in the reservoirs. In order to define and classify the type of problem with regards to geological condition, the country is divided into eight zonesin whicheach zone demonstrates similar problem on the dam site location. It is found that the water leakage is related directly to either the presence of soluble carbonate rocks in the abutment or the presence of thick permeable material in the foundation. It is also shown that the sediment deposition in the reservoir is related to many factors but the geology of the watershed area has a major effect. Therefore it can be concluded that the geology has a great role in the construction of dams.
Karen Soo Kee
Strategic resource management has never been more important than it is today with the aging of the “baby boomers” and their ongoing exodus from the workforce. The vacancies they leave in professions such as engineering are just beginning to be felt and will exponentially escalate over the next few years. Specialised professions such as dam engineering and related professions will be hit the hardest as the knowledge and skills learnt over decades are depleted.
The lack of skilled staff and in fact the lack of interest of young engineers in entering the dam industry is one of the critical challenges for today. How do we attract professional staff into the field of dam safety before the exodus creates a “black hole” that can never be filled? And how can we ensure the knowledge transfer from existing skilled staff to newer staff to retain expertise within the industry?
Another issue for resource management is that tomorrow’s workers, the “X &Y generations”, will be unlike the current and previous generations of workers. These workers will be less likely to have a mortgage, will have fewer children and be more interested in lifestyle, not career. They will be extremely confident, well-educated and very mobile. The future will be a sellers market. The challenge here will not only be to attract and recruit talented workers but also to retain them.