Dr Judy Henderson
Against a background of several decades of increasingly polarised and acrimonious debate, the World Commission on Dams (WCD) was established in 1998 with a two year mandate to review the development effectiveness of dams, assess alternatives for water resources and energy development and develop internationally acceptable criteria and guidelines for future decision- making. This report discusses the role of large dams in development and the challenges of water resource management in the future. T the work program of the WCD is outlined and progress to date on fulfilling its mandate.
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Brian Haisman, Clarke Ballard and Neville Garland
In early 1997 the Murray-Darling Basin Ministerial Council instigated a review of the operations of its primary reservoirs, the Hume and Dartmouth Dams, in response to concerns of floodplain communities below the dams, coupled with changing community values in relation to the in-stream environmental effects of dams. The review, completed in May 1999, achieved a consensus between parties advocating what are on the surface irreconcilable objectives for the management of the water resource. Foremost competing objectives were flood mitigation, consumptive water use, and environmental health of the river system, plus subsidiary objectives related to recreation, hydro-electric generation, salinity management, tourism and the like. The keys to success were firstly, creation of a community-based Reference Panel which took on a steering role coupled with extensive consultation, and secondly a determination to describe situations wherever possible by means of factual information. The paper describes the identification and evaluation of issues, the consensus building process, the intensive hydrology and economic modelling undertaken, and the development of a comprehensive set of flow parameters which could be viewed as surrogates for environmental outcomes. Conclusions and recommendations are drawn for future reviews of similar dams.
A strategy designed to ensure that an existing dam continues to perform effectively will include:
This paper will explore each of these issues and how they may be applied to dams in a variety of situations. These situations include water supply reservoirs, flood retarding basins, levees and wastewater lagoons. While each situation is different, the underlying principles will remain consistent. The range of situations encountered by Victorian Water Authorities provides the inspiration for the development of an efficient approach to the management of the safety of dams.
Peter Quinlan and Sergio Giudici
The Hydro Electric Corporation (HEC) owns and manages 54 large and referable dams across Tasmania. Monitoring, data storage and data utilisation techniques have evolved significantly over the years as the dams have aged and as instrumentation, communication and data management technologies have advanced. This paper describes the development of the HEC’s ‘Asset Safety Evaluation Tool’ (ASET) for acquisition, management and interpretation of data relating to dam safety management. The paper also provides examples of how ASET has been applied within the HEC to demonstrate how the primary functional development goals of robustness and practicality have been achieved.
Andrew Day, Rod Bridges and Corrado Fabbri
A joint venture between Astaldi SpA of Italy and Thiess Contractors Pty Ltd of Australia (ATJO) has just completed a 95m high roller compacted concrete (RCC) dam on the island of Sulawesi in Indonesia. The dam which includes 528,000m’ of RCC was completed in September 1999 and will provide hydro-electric power for a nearby nickel smelting operation.
One of the largest RCC dams built in the region in recent times, the construction presented a number of unique challenges in particular placing techniques to cope with the heavy rainfall in the area as well the logistics to this remote location. Other aspects which are addressed in the paper include production rates, RCC placing systems (Rotec), dam formwork systems, aggregate sources, RCC mixes and waterproofing (membrane).
After early problems with the river diversion, the works were accelerated and completed to a very tight program. To enable dam construction to commence prior to river diversion the wall was advanced as a series of separate monoliths which led to a number of RCC placing innovations.
Douglas Gallacher, Richard Doake and Debbie Hay-Smith
Damage to the rip-rap protection on the upstream face of Megget Dam has occurred since first filling in 1983 and independent wind-wave investigations have demonstrated that waves exceeded anticipated wave heights. Value Planning Studies for alternative schemes to upgrade the rip-rap protection indicated that bituminous grouting was the preferred option and its satisfactory performance was proved by site trials during May 1997. The bituminous grouting works were carried out in two stages with a break over the winter season. The upper part of the face was completed over a 12 week period (September to early November 1997) and the grouting works for the remaining area was completed over a 24 week period (mid April to early October 1998).