M. Amghar, A. Watt, C. Thorstensen
The future effects of climate change on water resources in the southeast Queensland and other parts of Australia will depend on trends in both climatic and non-climatic factors. Evaluating these impacts is challenging because water availability, quality and streamflow are sensitive to changes in temperature and precipitation. Other important factors include increased demand for water caused by population growth, changes in the economy, development of new technologies, changes in catchment characteristics and water management decisions. In Southeast Queensland, concern for climate change has increased in recent years with research on global climate change applied to part of Southeast Queensland and it has become apparent that the region’s climate has changed in recent times. Studies have shown that Southeast Queensland’s climate has been variable over history and in the present, is experiencing continuing sea level rise, and may experience
significant climate warming. The potential effects of climate change on coastal erosion, water availability, flood control, and general water management issues have been raised and widely discussed from a variety of perspectives.
This paper presents results of an integrated economic-engineering resource assessment optimisation model of Seqwater’s water supply system illustrating the value of optimisation modelling for providing an integrated approach needed to manage a complex multipurpose water system. Overall, the approach has its own limitations, but provides useful insights on the potential for operating the current or proposed infrastructure for different future conditions.
Keywords: Brisbane Water supply, Moreton, water resource plan, optimisation, environmental flows.
Shane Papworth, Stuart Richardson, David Dreverman, Mel Jackson
A prominent element of the operational environment of a dam is its interaction with the community.The management of public recreational use of irrigation storages is an increasing challenge for Goulburn-Murray Water and the Murray Darling Basin Authority. The upper Murray storages have been significantly affected by the unprecedented low water resource availability which has caused an increasing conflict between the primary use of the dam to supply irrigation water and the secondary benefit of recreation and tourism use by the local communities. Many difficult management issues (media, community relations, political interest) arise from the local community, rather than just from operation of the dam itself.
An increasing awareness of the dire water resource position in recent years has coincided with an ever increasing appreciation of the environmental and social impacts of recreational use. For the storages along the Murray system, effective management is further complicated by complex agency and authority responsibilities, communities and interest groups effectively ‘in competition’ for the water resource.
To better manage these issues, ‘Land and On-Water Management Plans’ have been developed for Lake Mulwala and Lake Hume. Developing the Plans has not been without controversy, but ultimately the Plans have proved to be a simple and successful means of planning for and achieving agreed land and water management outcomes. This in turn is fostering a positive spirit of cooperation and communication with communities currently under considerable stress as a result of prolonged drought.
This paper describes the process, pitfalls and learnings to come out of the development of the Land and On-Water Management Plans.
Key words: Environment, community, irrigation dams, recreational use, planning
Tariq I.H. Rahiman, Amanda Barrett, Greg Dryden, Mike Marley, Cecile Coll
In this study we present the engineering geology of complex Late Carboniferous to Early Permian silicic volcanic rocks underlying the Connors River dam site located on the Connors River, at Adopted Middle Thread Distance (AMTD) 97.7 km. The initial investigation of the site by SMEC in 1976 characterised the bedrock as simple laterally continuous layers of rhyolite and pyroclastic rocks. Engaged by SunWater Limited since October 2007, Golder Associates have utilised a range of modern investigative techniques to reveal a more intricate bedrock geological model.
Geological mapping, targeted vertical and angle geotechnical drilling and trenching reveal that the dam site foundation consists of complexly laid felsic crystalline volcanic flow deposits, volcaniclastic (pyroclastic) deposits, and mafic intrusives. Petrographical tests depict a broad range of rock types that includes rhyolite, rhyodacite, dacite, basalt, volcanic breccia, lapilli tuff and tuff. Surface structural mapping and downhole acoustic televiewer profiling reveal that defects of varying orientations have developed in the rocks mainly as a result of tectonism. The rock defects are predominantly open joints and faults, and minor bedding, flow bands, decomposed seams and veins. The permeability of the bedrock, which appears to be primarily controlled by rock defects, was assessed using the results of Lugeon tests.
Rock stratigraphy, mineralogy and texture combined with high resolution seismic tomographic imaging were used to delineate three main engineering rock units. Unit 1, the oldest, occurs on the right abutment and consists mainly of slightly weathered to fresh, high to very high strength dacites and rhyodacites. Unit 2 occupies the central area of the dam foundation and overlies Unit 1. It comprises weakly bedded, slightly weathered to fresh, high to very high strength volcaniclastic rocks. Unit 3, consisting of variably weathered, high to very high strength flow banded and autobrecciated rhyolite, is the youngest unit and it overlies and partially intrudes Unit 2. All three rock units are intruded by slightly weathered to fresh and very high strength basalt, either as dykes or sills. The rock mass properties of the rock units were evaluated based on rock strength tests and the geological strength index (GSI).
Keywords: engineering geology, dam foundation, volcanic rocks, Connors River, dam site
Jonathon Reid, Chris Kelly, Bob Wark
One of the most important aspects in the construction of an embankment dam is to be confident that the filter materials placed meet the design intent. The design methodology for filters is now well documented.
However, all too often during construction the filter material, as placed, does not comply with the specified requirements and all parties are faced with costly decisions and delays to the works to determine correction measures and whether the work completed meets the design intent. This paper shares the knowledge gained over a number of projects the authors’ have been involved in and the methods used to improve the properties of the placed filters taking into account some of the practicalities of having these materials produced and placed in a commercial environment
Keywords: filters, specifications, manufacturing, construction, quality assurance.
Gavan Hunter and James Toose
Hinze Dam, an extreme hazard storage, is under the authority of Seqwater (Southeast Queensland) and is the principal potable water storage supplying the Gold Coast. The Stage 3 raise, presently under construction, involves raising the embankment almost 15m to a maximum height of 80m.
The central core earth and rockfill embankment is founded on competent greywacke rock within the valley floor and left abutment. On the right abutment it is founded on extremely weathered greywacke and rockfill stability berms were constructed upstream and downstream on this weak foundation.
Key issues for the design of Stage 3 embankment raise on the right abutment were: 1/ removal of the existing downstream stability berm and deep excavation at the toe of the Stage 2 embankment to connect into the blanket filters under the downstream shoulder; 2/ the soil strength properties of the weathered greywacke foundation and the presence of pre-sheared defects with strength properties significantly below the strength of the soil mass; and 3/ undertaking the works while the reservoir remained in operation and close to full supply level.
It was not possible to undertake large scale excavation at the downstream toe of the right abutment as the factor of safety for the excavation condition was below the design criterion for slip surfaces extending back to the upstream shoulder. The innovative design solution was for a staged excavation and back fill operation up the right abutment. In this ay the stability requirements were achieved by a 3-dimensional buttressing support and reduced the time that critical excavation sections were exposed.
The construction risk is being managed under a dam safety management plan. Key elements of this plan include instrumentation monitoring and increased surveillance for early detection of a potential incident, a series of trigger levels and responses to these levels, a clear hierarchy of contacts and adequate preparation for a dam safety emergency (including materials, personnel and equipment).
The embankment construction is presently in progress. The most critical sections have been successfully completed without incident and displacements are within the predicted range. Communication and planning within the Alliance between the designers and constructors has been a key element in the successful construction works to date.
Keywords: construction risk, embankment design, embankment construction, dam safety management
Khanh (Ken) Nguyen, Peter Allen
There is community concern regarding the potential for dams to fail and threaten lives. In Queensland, the Water Supply (Security and Reliability) Act 2008 provides for the regulation of dams whose failure could cause loss of life. Other consequences of dam failure such as interruption of services, economic loss and damage to the environment would also be of paramount importance for the safety management of our dams in the current climates of change.
In 2003, the Bureau of Meteorology (BoM) revised the Probable Maximum Precipitation (PMP) estimates for both short and long durations of extreme rainfalls for northern Australia. As a consequence, the majority of cases resulted in a significant increase of extreme flood estimates for many river catchments in Queensland. Subsequent studies by the BoM have investigated the potential impact that climate change might have on PMP estimation.
This paper examines the current progress of the Queensland Spillway Upgrade Program, by discussing the current regulatory environment and identifying a number of hydrological issues which may require further investigation for Queensland conditions.
Keywords: Spillway Upgrade, Acceptable Flood Capacity, Flood Discharge Capacity.