Tm Daniell

The vulnerability of water supply catchments to bushfires: impacts of the January 2003 wildfires on the Australian Capital Territory

Abstract Eastern Australia has been swept by landscape scale bushfires throughout the Holocene period. In January 2003, major bushfires burnt through the Australian Capital Territory (ACT). They devastated parts of the national capital, Canberra, and almost all the Cotter catchment, a normally pristine source in its upper catchment for ACT drinking water. Intense, local thunderstorms following the fires, estimated to be a 1 in 400 year event, moved large sediment loads from steep, denuded slopes into the supply reservoirs, Corin, Bendora and Cotter dams. Bushfires in Melbourne’s water supply catchments in 1939 produced large decreases in yield that persisted for 50 years as mountain ash forests regrew. The Cotter fires raised concerns over yield decline and short and long term water quality impacts. In this paper, preliminary impacts on water yields and water quality are analysed for Bendora dam and its catchment. Major landscape scale bushfires in the Cotter catchment over the last 150 years have been associated with severe droughts mostly related to positive phases of the Pacific Decadal Oscillation and El Nino events. Our preliminary, non-parametric, yield analysis shows no significant changes in annual upper catchment yield following the fires. Before the 2003 fires, water quality in the storage was excellent, although annual build up in iron and manganese and turbidity occurred at the bottom of the reservoir. The 2003 fires caused unprecedented increases in turbidity, iron and manganese, by up to thirty times previous events in the upper catchment storages. These increases caused disruptions to water supply and resulted in the construction of a major water filtration plant to address turbidity and other water quality problems. While natural revegetation in the upper Cotter has lead to improvements in water quality, the area of former pine plantations in the lower Cotter continues as a major sediment source.

An improved genetic algorithm for rainfall-runoff model calibration and function optimization

The standard binary-coded genetic algorithm (GA) has been improved using the three strategies of automatic search space shifting to achieve hill-climbing, automatic search space reduction to effect time-tuning, and the use of independent subpopulation searches coupled with shuffling to deal with the occurrence of multiple regions of attraction. The degrees of search space shifting and reduction are determined by the distribution of the best parameter values in the previous generations and are implemented after every specified number of generations. If the best parameter value in successive generations is clustering in a small part of the search range, a higher level of range reduction is used. The search shift is based on the deviation from the middle of the current search range of the best parameter values of a specified number of previous generations. With each independent subpopulation, a search is performed until an optimum is reached. Shuffling is then performed and new subpopulation search spaces are obtained from the shuffled subpopulations. The improved GA performs remarkably better than the standard GA with three global optimum location problems. The standard GA achieves 11% success with the Hartman function and fails totally with the SIXPAR rainfall-runoff model calibration and the Griewank function while the improved GA effectively locates the global optima. Taking the number of function evaluations used to locate the global optimum as a measure of efficiency, the improved GA is about two times less efficient, three times more efficient, and 34 times less efficient than the shuffled complex evolution (SCE-UA) method for the SIXPAR rainfall-runoff model calibration, the Hartman function, and the Griewank function, respectively. The modified GA can therefore be considered effective but not always efficient.

Turbidity-based erosion estimation in a catchment in South Australia

An erosion estimation technique was developed in this study based on turbidity and sediment sampling data in a small catchment in South Australia. Several data sets, derived from the time sequence in which the data were collected, were used to develop a number of turbidity and suspended sediment relationships. These relationships were then used to estimate erosion from the catchment. The variability in sediment load estimation using different relationships, and how these relationships impacted on load estimation, were analyzed in detail. The study estimates erosion on a storm basis using detailed sediment sampling and turbidity data. Storm sediment loads were then accumulated to derive annual load, which distinguishes this study from volume based sediment studies. The study found that large storms dominate erosion in the catchment, and erosion rate depends more on peak storm flow than other hydrological variables. A relatively low annual erosion rate from the catchment was found, which is consistent with studies in other Australian catchments. The study found that, to establish a sound relationship between suspended sediment and turbidity for a catchment, it requires extensive data collection of large as well as small storms at short time intervals, a storm-based erosion estimation approach, and a data set that is used for interpolation rather than extrapolation. Erosion estimation based on infrequent, non-storm based or extrapolated data is exposed to potentially large errors, and the results may only be relied upon as a general guide rather than serious estimation of catchment erosion.

What is sustainability and can it be measured

Abstract Existing approaches to sustainability focus on the management and use of natural resources. Some also consider financial and human resources. However, manufactured resources such as infrastructure also have a critical role in the operation of human systems. In this paper, sustainability is considered as a characteristic of a system, and a systems approach is used as the basis for understanding, and potentially measuring, sustainability. This approach highlights some important factors relating to sustainability, including: the need for the continuing management of system resources over time; the significance of interactions among systems; the importance of planning and designing systems with regard to sustainability; and the need to re-evaluate the sustainability of a system at regular intervals.

AN IMPROVED GENETIC ALGORITHM FOR CONTINUOUS AND MIXED DISCRETE-CONTINUOUS OPTIMIZATION

Abstract Modifications to the standard genetic algorithm through a finetuning strategy, a hillclimbing strategy and the use of independent subpopulations coupled with shuffling are described. The improvements obtained are demonstrated using two optimization problems; a continuous variable rainfall-runoff model calibration and a previously-studied mixed discrete-continuous optimization for cost minimization in pressure vessel manufacture. The use of independent Subpopulations and shuffling is found to considerably improve optimizations of the two problems whilst the finetuning and hillclimbing notably improve optimization in the model calibration but not the pressure vessel cost minimization. In the rainfall-runoff modelling the parameter sets obtained by the improved genetic algorithm are more consistent and seem more informative than those obtained with the standard genetic algorithm. With the pressure vessel design problem, lower costs are obtained than in previous studies.

Bushfire hydrology ― the case of leaking watersheds

Abstract A new mechanism for water yield change aftr bushfires is proposed. A simplified model for the approximate calculation of the shift in yield due to bushfires has been developed. The model describes both the short-term increase of the water yield immediately after bushfire and the long-term decrease during the following years.

Water Resources Data Collection and Water Accounting

Objective A key objective of the National Water Initiative is to establish a comprehensive system of water accounting to ensure that the overarching objective to establish a nationally compatible market, regulatory and planning based system of managing surface and ground water resources can be met. In this context, the first objective of this paper is to highlight problems with the extent and quality of Australian water data collection, access to water data and ongoing auditing of data collection and archiving processes. The second objective of the paper is to propose ways to remediate these problems.

Are Traditional Thinking and Decision-Making Techniques Adequate for Developing Sustainable Water Systems?

Abstract “The problems we have today cannot be solved by thinking the way we thought when we created them” (Einstein). Many water systems planned or constructed prior to the 1990s did not consider the concept of sustainability and were based on traditional technical thinking, analytical processes and decision-making techniques. The question now is, can we develop sustainable water systems by using the same thinking and decision making techniques? A model has been presented that develops sustainability as a journey, balancing economic, environmental and social factors in both spatial and temporal dimensions. Over time, the number, complexity, variety and interconnectedness of factors required for managing water resource projects have increased. Analytical or economic techniques are no longer sufficient or appropriate, and inputting the data into a black box for analysis would appear unnecessary.

A brave new world – expanding the remit of the Australian Journal of Water Resources

Welcome to Volume 20, Issue 1, of the Australian Journal of Water Resources! Before introducing the issue, we would like to extend our thanks to Brett Phillips for his stewardship of the journal over the past years. We would also like to thank the National Committee of Water Engineering (Engineers Australia) and the team at Taylor and Francis for the trust they have placed in us for taking the journal on the next phase of its journey. This is an exciting time as we are at the beginning of an important phase of transition for the Australian Journal of Water Resources. Over the past few months, a new and expanded editorial board has been established for the journal and the scope has been updated. The key changes are that the journal now explicitly seeks to: (1) provide an inter-disciplinary platform for water resources research, as well as policy and practice perspectives; and (2) expand its geographical scope of interest to the Australasian region, to develop improved discussion and understanding in the water communities across Australia, New Zealand and the Pacific Islands. From next year, this transition phase will continue with the first volume of the ‘Australasian Journal of Water Resources’ to be published. In preparation for this important milestone for the journal, we would welcome papers on important topics for the journal including: Indigenous perspectives and management of water from across Oceania; regional climate impacts on water resources and planning; details and implications of the Australian Rainfall and Runoff publication update; review papers of the state of knowledge in specific areas of water research and practice from, or with clear relevance to the Australasian region; and perspective pieces on upcoming challenges for water managers and policy makers across Australasia. Papers across the full range of topics as outlined in the scope will also be gratefully received. In light of these changes and the proposed future of the journal, the first paper of this issue – Is open channel flow worth the effort? by Robert J. Keller – is particularly fitting. The paper is a modified version of Robert Keller’s Henderson Oration, an Oration given by invitation of the National Committee on Water Engineering as part of their Hydraulics conference series. In it he reflects on some key components of both global open flow hydraulics history, and the recent history and practice of open flow hydraulics in both Australia and New Zealand, following his own work and that of Frank Henderson, after whom the Oration is named. Of particular note is not underestimating the importance of understanding the fundamental mechanics of flow and the assumptions, such as the values of Manning’s ‘n’ roughness coefficient and boundary and initial conditions, that are used in hydraulic modelling and design, rather than assuming that today’s computing capacity and complex models have this in hand. Particularly as misunderstandings, errors or ignorance of model assumptions can result in inadequate hydraulic designs that could have devastating consequences. He also reflects on the importance of inter-disciplinary engagement in open flow hydraulics and how the preferences and values of society have changed in recent times around the need for sustainable development, meaning that ‘environmental, social and cultural constraints must be preserved’ rather than focusing development on short-term economic development (Keller 2016). He then notes that:

When does a road become a river? Why hydrologists and water planners need to move beyond averages

At a recent Canberra Hydrological Society meeting, Phillip Prentice from Info4Eco, in the context of urban flooding, asked the question ‘when does a road become a river?’ Looking at maps of flash f...