A C Mostert, D J Hagen, P C Blersch
The changes in flood operations since the 2006 flood, covering weather monitoring, hydrological flood station monitoring, and downstream monitoring, are discussed in detail in the paper.
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Now showing 1-12 of 39 2978:
Suraj Neupane, Paul Southcott, and Tung Hoang
Conglomerate Dam has multiple cracks along the asbestos cement outlet conduits running through the embankment. The reservoir level has been maintained at 2m below the full supply level to reduce the amount of seepage, emerging on the downstream face, until the conduits are repaired and protect the embankment from slope instability and piping. Several methods were investigated under an options study to determine the most suitable internal lining method. Slip lining with polyethylene pipe was found to be the most suitable method in terms of technology as well as cost.
JN Rossouw, AHM Görgens and PC Blersch
Shallow lakes or reservoirs generally exist in either of two stable states; a clear water state dominated by rooted water plants, or a turbid state dominated by free floating algae. A dramatic event can switch a shallow reservoir from one state to another. Voëlvlei Dam, a relatively shallow off-channel storage reservoir in the Berg River catchment, South Africa, switched from a stable, clear water system to a turbid, algal dominated system when it was severely drawn down during a drought in the mid-2000s.
It appears that there is tipping point beyond which a shallow reservoir can switch from one stable state to another and that there are buffers that maintain it in a specific state. Voëlvlei Dam is a good example of what such a switch might be (low water levels and high wind mixing) and what buffers (change to bottom-feeding fish species) may maintain it in the new state. It is only by understanding the hydrodynamic behaviour of a shallow reservoir that one can predict what these switches and buffers could be. Complex hydrodynamic modelling and comprehensive fish monitoring will facilitate more informed decision making and better management of reservoirs.
This paper describes the mechanisms that lead to the switch and how it can be prevented by developing an understanding of the hydrodynamic behaviour of shallow reservoirs through hydrodynamic water quality modelling.
Stephen Newman, Rod Jacobs, and Dr John Yeates
Independence Group (IGO) is assessing the feasibility of re-commissioning a closed copper-zinc mine in Victoria. Due to the acid producing potential of the mine tailings if exposed to oxygen they are to be contained in a saturated condition not only during the life of the mine but well beyond closure and effectively in perpetuity. The tailings are to be stored in a saturated condition underground in the mining void however due to the limited volume available approximately half of the tailings produced over the mine life will require containment in a purpose built surface Tailings Storage Facility that would need to perform as a water retaining structure.
This paper describes key challenges with tailings management including demonstrating the viability of maintaining permanent saturation of the tailings and the long term integrity of the structure. Excessive poor quality seepage, piping and other failure modes have also been considered in the long term design of the closed Tailings Storage Facility. A surveillance program to provide early identification of potential issues has also been developed.
The design is consistent with ANCOLD guidelines and used a risk based approach to assess key issues associated with the extended design life.
Marius Jonker and Dr Radin Espandar
This paper provides a summary of the current state of practice for arch dam design criteria that have been adopted by some international dam organizations, and where relevant, compares that with the criteria provided in the updated ANCOLD Guidelines on Design Criteria for Concrete Gravity Dams, with the view to provide a basis for consistent and unified design criteria for arch dams in Australia.
The paper draws on the authors’ experience with arch dams, including recent experience with a number of arch dam safety reviews in Australia, their past experience with arch dams over 200 m height, as well as their involvement with the development of the mentioned updated ANCOLD Guidelines.
Since the last arch dam was constructed in Australia, a number of international publications have been released on arch dam design practices, providing general information and guidance for the design of new dams and evaluation of the safety and structural integrity of existing arch dams. This paper compares these publications and proposes criteria that are aligned with the ANCOLD gravity dam guidelines.
Paul Southcott, Tony Harman
This paper addresses structural behaviour of the Rowallan spillway walls and the learning that can be derived from this in the design of critical retaining walls in dams and how this can be applied both to remedial works and new work. The authors propose design criteria suitable for retaining walls in high hazard dams.