Across Australia, recreation usage around dams is growing rapidly. There is also increasing public expectation around the facilities provided and the activities that can be undertaken.
While dams create many benefits, they also have inherent risks associated with them. The risks associated with public access include public and staff safety, water quality, pollution, environmental degradation, bushfires, water availability, dam & power generation operations, and financial.
In 2016 the Victorian government released “Water for Victoria”, a strategy for managing increasingly valued water resources and a growing population. This strategy recognises the importance of recreational enjoyment of waterways and commits water corporations to continuing to maintain infrastructure and facilities to support recreational objectives at their water storages. Water for Victoria also commits water corporations to consider recreational user objectives in the way water storage and supply is managed. However, this must be within legislative requirements to meet the needs of water entitlement holders and with awareness of the realities of dry conditions and climate change.
For the last 10 years, Goulburn Murray Water has been progressively rolling out Land & on Water Management Plans and setting up Land & on Water Implementation Committees. These committees provide a forum for liaison with local government, other statutory authorities, as well as interested environmental, heritage, indigenous, commercial and recreation groups. The groups aim to understand the concerns and requirements of all parties, take appropriate action, which may involve educating communities where some of their desired actions are not achievable.
While this approach has been successful, the growth in social media and the emergence of groups outside of the Land & on Water process has meant that consultation has had to be extended to include self-identifying, special interest groups. This has involved the development of separate groups at Dartmouth and Lake Eppalock to educate and work through the issue at hand, developing appropriate actions, which are accepted and implemented by all parties.
This paper will review the Goulburn Murray Water Land & on Water process, and consider two cases studies, namely the “Save Lake Eppalock” community driven campaign and the provision of fishing access on Dartmouth regulating pondage.
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On February 7, 2017, the gated service spillway (also known as the Flood
Control Outlet or FCO Spillway) at Oroville Dam was being used to release water
to control the Lake Oroville level according to the prescribed operations plan.
During this operation, the service spillway’s concrete chute slab failed, resulting
in the loss of spillway chute slab sections and deep erosion of underlying
foundation materials. Subsequently, as the damaged service spillway was
operated in an attempt to manage multiple risks, the project’s free overflow
emergency spillway was overtopped for the first time since the project was
completed in 1968. Significant erosion and headcutting occurred downstream of
the emergency spillway’s crest structure, leading authorities to evacuate about
188,000 people from downstream communities.
In the face of potential future climate change, it is important that reservoir asset owners and operators consider what such change could mean for the integrity and operations of their assets. This must be developed as an integral part of risk-based management, with a systematic consideration of the uncertain future implications of climate change and their potential consequences.
Systematic assessment of the consequences of potential climate related events/loads should be included as an integral component of a risk-based approach to dam safety management. The magnitude of potential consequences can be used to inform the prioritisation and management responses to these conditions, regardless of probability of occurrence. Designing to accommodate exceedance events is an important response in this process.
The adaptive management process provides a framework within which the implications of uncertain future conditions and risks can be systematically identified and managed, forming the basis of agreeing a defined ‘pathway’ for monitoring and implementation of management actions. The concept of Adaptation Pathways can be utilised for reservoir adaptation, setting out the long-term risk informed process to manage operations and risks.
Since publication in 2003, the ANCOLD Guidelines for Risk Assessment have reached broad acceptance and use in Australia. In practice, dam owners use the principles of risk assessment to drive business investment decisions. As the guidelines undergo revision, it is timely to assess whether our practices need to evolve to more holistically consider all types of consequences, rather than our current focus on loss of life, in decision-making. This paper aims to prompt dam owners and consultants alike to re-assess our focus on loss of life in risk assessment decision-making, and whether we should more meaningfully consider alternative or broader indicators.
An industry survey was undertaken which found that large dam owners are generally happy with the current system of dam safety decision making. However, the survey responses did identify difficulties in relation to justifying investment below the limit of tolerability that are subject to ALARP principles. In a small number of cases, dam owners found it difficult to justify investment when life safety was not important.
Building on the industry survey and subsequent discussions with practitioners, this paper discusses how the current approach to risk based decision making may result in sub optimal decision making. Further it is discussed how there is an important role that economics should play in providing a universally accepted framework for assessing trade-offs and providing consistent evidence to support decision making.
Junction and Clover Dams are central spillway slab-and-buttress dams located in Victoria. Previous safety reviews and assessments of the dams concluded that neither dam met modern dam design standards and remedial works were recommended, including infilling the slab-and-buttress dams with mass concrete to sustain seismic loadings. These conclusions were based largely on the assessed seismic hazard at the site, the results of response spectrum analyses and observed conditions of the dams including alkali-aggregate reaction of the concrete. AECOM used current seismic hazard assessment techniques, conducted concrete investigations and testing, assessed long term surveillance monitoring results and used modern finite element techniques to demonstrate that no upgrade works were required at either dam resulting in a significant saving for AGL.
Dams leak! But only some of the leaks require investigation and remediation. When they do, finding the pathway of the leak becomes an expensive and slow process, often characterised by drilling “trial and error” boreholes that further impair the integrity of the structure. A much better alternative is to collect specialised data with highly sensitive instruments along all relevant points, map the data using the latest groundwater geophysics technology or hydrogeophysics technology, create 3D models of the subsurface including the flow path of the leak in question, and finally use software filters and algorithms to predict ongoing effects of the water problem. In this paper three case studies are presented including the Bartley Dam, King George Dam, and the Samanalawewa dam. All of the dams had leaks that concerned the dam owners. The method was applied to determine the location of the seepage paths passing through the dam. Remediation was completed at the Bartley Dam and King George Dam confirming the results from the method. And there are plans for remediation at the Samanalawewa dam. The method saved the clients a significant amount of money because they had a focused remediation. Knowing the dam has been repaired and there are no other leaks provides peace of mind to the dam owners.