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Post D.A.,CSIRO | Chiew F.H.S.,CSIRO | Teng J.,CSIRO | Viney N.R.,CSIRO | And 6 more authors.
Journal of Hydrology | Year: 2012

This paper describes a robust methodology for determining current surface and groundwater availability and use, as well as future changes due to climate and landuse changes. It is based on the methodology developed by CSIRO to deliver on four large-scale water availability assessments conducted in the Murray-Darling Basin, Northern Australia, south-west Western Australia, and Tasmania. It will focus on the application of the technique and results from Tasmania, providing a representative example of the approach used. The genesis of this work was the explicit desire by Australian State and Commonwealth governments to use the outputs of these water availability assessments for assisting the formation of state and federal government water policy. For example, the results of the work have already been utilised as a key technical input to decision making on funding for proposed irrigation projects in Tasmania. Outputs from the other three study areas have been used to assist in developing a water resources plan for the Murray-Darling Basin, to guide infrastructure development in northern Australia, and to plan for reductions in water availability due to climate change in south-west Western Australia.The methodology assesses current water availability through the application of rainfall-runoff and river models, and recharge and groundwater models. These were calibrated to streamflow records and groundwater levels, and parameterised using estimates of current surface and groundwater extractions and use. Having derived an estimate of current water availability, the impacts of future climate change on water availability were determined through deriving projected changes in rainfall and potential evaporation from 15 IPCC AR4 global climate models. The changes in rainfall were then dynamically downscaled using the CSIRO-CCAM model over the study area (50,000km 2). The future climate sequence was then derived by modifying the historical 84-year climate sequence based on these changes in rainfall and potential evaporation. This future climate sequence was then run through the rainfall-runoff, river, recharge and groundwater models to give an estimate of water availability under future climate. The impacts of landuse changes were derived by modifying the parameters and inputs/outputs of each of the models as appropriate.Results for Tasmania indicate that historical average surface water availability across the study area is 21,815. GL/year. Of this, 636. GL/year is currently extracted for use. Historical groundwater development in Tasmania has been largely unregulated and unmetered, however current extraction is estimated to be only 38. GL/year. In some intensive irrigation areas, the modelling has demonstrated that current and future groundwater extraction will reduce baseflow in connected streams. By 2030, rainfall is projected to decrease by an average of 3% over the study area. This decrease in rainfall and concurrent increase in potential evaporation leads to a decrease in runoff and, to a lesser extent recharge, leading to a reduction in surface water availability of 5% by 2030. Results from this study are being used by the Tasmanian and Australian governments to guide decisions on the development of a sustainable irrigated agriculture industry in Tasmania. © 2011.

Ling F.L.N.,Entura | Robinson K.A.,Entura | Bennett J.C.,CSIRO
Hydrology and Water Resources Symposium 2014, HWRS 2014 - Conference Proceedings | Year: 2014

Simulations of storage behaviour under future climate are an important component of planning for irrigation, hydro-electricity and water supply systems. The methods used for developing future climate projections of storage commonly include modelling inflows to the storages under future climate with a rainfall-runoff model. The rainfall and evaporation inputs to these models are adjusted for future climate using a variety of methods, which are dependent upon the availability of global climate model (GCM) and regional climate model (RCM) data. In this paper we compare future projections of storage reliability for storages of differing sizes used for irrigation, water supply and hydro-electric power generation. The future projections are developed using inflows generated by the SIMHYD hydrologic model. Rainfall and evaporation inputs for future climate are generated using different methods including: direct use of bias-corrected RCM outputs, application of a simple seasonal scaling factor to historic data, and quantile scaling of daily historic input values. The results show that the method used to derive future rainfall and evaporation inputs to the hydrologic model can have an impact on projections of storage reliability under climate change. In particular, simple scaling of historic rainfall and evaporation time-series does not capture the increased variability that is often a characteristic of future climate projections derived using dynamical downscaling of GCMs, which can have a marked effect on projected reliability of smaller storages.

Ross M.,Entura | Byleveld S.,Hydro Tasmania
The Art and Science of Water - 36th Hydrology and Water Resources Symposium, HWRS 2015 | Year: 2015

SCADA systems and telemetry systems have typically held two different roles within water management organisations. SCADA usually revolves around the real-time operation of assets, while telemetry lends itself more to analytical applications. With an increasingly mobile workforce, organisations are trying to find ways of empowering workers to do more with less; to have real-time visibility of their assets on the go; and to more easily leverage data to make optimising assets easier. None of these goals have historically been easy with legacy approaches to data management. The Tarraleah hydropower station's first three turbines were commissioned in 1938. Water is supplied along two canals where it takes two hours for the water to travel the full length. Tuning the flow into the canal is critical to maximise the availability of water to the power station, and operating an asset at maximum levels needs careful consideration for safety and reliability reasons. While man-made structures usually result in more predictable flows, plant growth in the canals can see the maximum flow rates in the canals degrade over time. Cleaning the structures is an expensive exercise, both in resource costs and through lost revenue during an outage. Hydro Tasmania has been able to increase the situational awareness of its staff by embracing the latest technology to federate SCADA, telemetry and manually read data into a single online interface. Staff have a live view of the canals on their iPads allowing them tune the canal for maximum efficiency, and can easily step into a historical view to see how the characteristics of the canal have changed over time. Simplifying the access to data is helping increase the return on investment through reduced costs, and makes it easier to maximise the day to day operational efficiency of the canals. © 2015, Engineers Australia. All rights reserved.

Pokhrel P.,Entura | Ling F.L.N.,Entura | Cohen W.J.,Entura
The Art and Science of Water - 36th Hydrology and Water Resources Symposium, HWRS 2015 | Year: 2015

Continuous simulation models have found limited application for design flood estimation despite being conceptually attractive. This study, as part of Australian Rainfall and Runoff (ARR) revision, explored the suitability of continuous simulation models for design flood estimation on natural catchments. The ability of continuous simulation models to reproduce design flood quantiles as well as hydrograph behaviour was investigated in 5 catchments under 4 different calibration scenarios and 3 rainfall-runoff models. The scenarios included calibration to: all available record (Scenario 1), a shorter subset of the record (Scenario 2), the larger events (Scenario 3) and the observed flood frequency curve (Scenario 4). For each scenario, the ability of the model to reproduce the observed flood frequency curve (FFC) and the observed hydrograph were tested. The best reproduction of the hydrograph shape and volume was achieved by Scenario 1 and the best reproduction of the observed FFC was obtained by Scenario 4. In four out of the five catchments it was not possible to obtain good fit to both the hydrograph and the observed FFC, indicating that there is a "trade off" between the matching the general hydrograph shape and the FFC. © 2015, Engineers Australia. All rights reserved.

Pokhrel P.,Entura | Robinson K.,Entura | Ling F.L.N.,Entura | Peterson J.,Entura
The Art and Science of Water - 36th Hydrology and Water Resources Symposium, HWRS 2015 | Year: 2015

The natural inflow series to reservoirs are usually derived using storage volume difference approaches, based on the measured lake levels. However, lake level sensors are often susceptible to errors introduced from various sources (eg. fluctuations by wave actions), resulting in hydrographs that contain large randomly oscillating noise. The common approach for removing such oscillatory noise is to use moving average filtering (MA) or filtering methods based on Fourier analysis (FR). However, while the MA can provide good information on the hydrograph recession, it fails to effectively retain crucial information about the peaks. Similarly, FR integrates signal over the entire temporal domain such that it is difficult to separate out the signal from noise; especially where the Fourier spectra overlap. Another alternative is to filter the signal in the wavelet domain such that it retains both spectral and temporal information. Wavelet filters are becoming popular in electronic signal processing. The common approach is to remove (or manipulate) the wavelet coefficients that correspond to low spectral power by applying a fixed threshold over the entire time-spectral domain. We propose a wavelet based denoising algorithm, that utilizes the strengths of moving average and the wavelet based hard thresholding approach and corrects for large deviations in the local variance. The method allows inclusion of prior information, in the form of inflow magnitude, to further improve the denoising performance. We compare the proposed denoising method against the MA, FR and the wavelet based "universal" (WU) thresholding approach. We show that the proposed method is capable of providing a closer representation of the peaks of the hydrographs compared to the other methods and also preserves general hydrograph characteristics. © 2015, Engineers Australia. All rights reserved.

Cohen W.J.,Entura | Birch E.,Hydro Tasmania | Ling F.L.N.,Entura | Pokhrel P.,Entura
The Art and Science of Water - 36th Hydrology and Water Resources Symposium, HWRS 2015 | Year: 2015

The Monte Carlo method of design flood estimation is widely accepted as being a rigorous approach to modelling flood frequency of dams, as it can include representative distributions of storm, catchment, and storage characteristics. These include temporal patterns, antecedent catchment conditions, and starting lake storage level. The Monte Carlo method also allows for analysis of other model variables, such as hydrograph timing. Flood frequency of the outflow peak discharges is not the only variable of interest when modelling design floods dams and reservoirs. Also of importance is the time of the storage to rise from a series of warning levels in order to assist with planning for downstream flowing. A catchment and storage model for the dam has been developed, and adapted to Monte Carlo analysis. The suitability of this approach to determining warning times has been assessed. Tens of thousands of design event simulations of the model were executed, with a number of variables recorded for each simulation including peak inflow, peak outflow, peak storage level, and time to reach a given target level from a range of start trigger levels. An attempt was made to fit a statistical distribution to scenario rise times, with mixed results. The scenario rise times were used as qualitative information to guide further investigations, and could also be used for sensitivity analysis to determine parameters critical to short warning times. © 2015, Engineers Australia. All rights reserved.

Nikolic Z.,Serbian Institute of Technical Sciences | Shiljkut V.M.,Electricity Distribution Company Elektrodistribucija Beograd | Nikolic D.,Entura
Journal of Renewable and Sustainable Energy | Year: 2013

This paper proposes a hybrid autonomous electricity supply system for monasteries as a specific type of load. Chilandar monastery (Mount Athos, Greece) was presented as a case study. Taking into consideration specific location, historical significance, present and future needs of the monastery, and peculiar life style of its inhabitants, a new hybrid system for 400 kWh daily energy consumption and 80 kW peak load have been designed, proposed and elaborated here. It is based on combined use of three new diesel aggregates and a field of photovoltaic panels. Paper further outlines the methodology for selection and sizing up of power generating sources and other equipment. The primary goal for the new system was the reduction of diesel fuel and operational costs. Finally, cost-benefit analysis results of the proposed hybrid system are presented as well. © 2013 AIP Publishing LLC.

Herweynen R.,Entura
Dams and Reservoirs under Changing Challenges - Proceedings of the International Symposium on Dams and Reservoirs under Changing Challenges - 79 Annual Meeting of ICOLD, Swiss Committee on Dams | Year: 2011

The integrity of post-tensioned anchors is a significant dilemma facing dam safety engineers worldwide. Hydro Tasmania, the largest dam owning authority in Australia, has seven major dams which were designed and constructed in the 1950-70s with fully grouted, post-tensioned anchors. The method used was leading edge in its day, and enabled significant savings in concrete. However, these anchors only defence against corrosion was the grout column, rather than the two barriers that modern permanent anchors have. In 1999, Hydro Tasmania commenced its dam portfolio risk assessment, which highlighted safety deficiencies with Catagunya dam due to the unknown integrity of its post-tensioned anchors. It was recognised that this was potentially a bigger issue than just Catagunya dam. Rather than abandon all of these anchors as other dam owners have done, due to their lack of conformance to current standards, Hydro Tasmania endeavoured to develop an investigation program to assess their integrity. The investigation and assessment undertaken at Catagunya dam indicated the likelihood that some corrosion of the anchors was occurring; as a result a decision was made in 2004 to cease reliance on the anchors, and in 2009-10 major upgrade works occurred. This paper presents the Catagunya dam journey, providing other dam owners with this knowledge. © 2011 Taylor & Francis Group.

Vaughan D.,Entura | Rooney B.,Entura | Adamczewski G.,Entura
44th International Conference on Large High Voltage Electric Systems 2012 | Year: 2012

IEC 60865-1: 1993-09 Short Circuit Currents - Calculation of effects [2] covers a method to determine short-circuit forces for bundled conductors in substations. The standard is specifically written around bundled conductors of a circular configuration ( and even spacer distribution across the span. This paper describes methods and considerations for calculating pinch forces due to short circuit currents on conductor spans at low tension (< 1.5 kN) and short spans (< 10 m) with uneven spacer distribution along the span in a flat bundle configuration. It is intended for readers with some familiarity with IEC 60865 - 1 and the physics of conductor suspension. The paper describes the analysis undertaken to determine why design practices such as short spacer intervals, reduced span tensions and closer sub-conductor spacing are effective in reducing the short-circuit forces experienced by switchyard equipment. The findings of this analysis suggest a number of design practices which either eliminate ambiguity in application of IEC 60865-1 [2] or allow a more correct calculation of short-circuit forces by adjusting the assumptions within IEC 60865-1 [2]. Included is a discussion around the acceptability of applying these techniques and that the adjustments considered are a legitimate application of IEC 60865-1 [2]. In summary, the paper presents the approach that Entura has adopted to optimise substation layouts and mitigate the forces acting on existing equipment based on detailed modelling and examination of IEC 60865 and the physics of bundled conductors under short-circuit conditions.

Blanksby C.,Entura | Bennett D.,Entura | Langford S.,Entura
Solar Energy | Year: 2013

To assist in site identification for development of solar energy facilities in Australia, relevant spatial data were drawn from a range of sources. Along with infrastructure and development constraints, spatial solar irradiance estimates were a key requirement. Existing estimates, derived from satellite observations, were found to include significant bias when compared to ground station observations, likely due to the difference in measurement (spatial average for satellite and point location for ground station). Rather than revert to reprocessing the original data, post-processing corrections were developed to compensate for this bias.Investigations were also made into the influence of aerosols on the satellite estimates (aerosols were not included in the existing model), and whether any spatial bias existed in the satellite estimates. In both cases, no evidence was found to indicate that improvements in the data were possible by including these effects. © 2012 Elsevier Ltd.

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