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Canberra, Australia

Aziz K.,University of Western Sydney | Rai S.,Murray Darling Basin Authority | Rahman A.,University of Western Sydney
Natural Hazards | Year: 2015

This paper focuses on the development and testing of the genetic algorithm (GA)-based regional flood frequency analysis (RFFA) models for eastern parts of Australia. The GA-based techniques do not impose a fixed model structure on the data and can better deal with nonlinearity of the input and output relationship. These nonlinear techniques have been applied successfully in many hydrologic problems; however, there have been only limited applications of these techniques in RFFA problems, particularly in Australia. A data set comprising of 452 stations is used to test the GA for artificial neural networks (ANN) optimization known as GAANN. The results from GAANN were compared with the results from back-propagation for ANN optimization known as BPANN. An independent testing shows that both the GAANN and BPANN methods are quite successful in RFFA and can be used as alternative methods to check the validity of the traditional linear models such as quantile regression technique. © 2015, Springer Science+Business Media Dordrecht.

Luo Y.,Hohai University | Khan S.,UNESCO | Peng S.,Hohai University | Rana T.,Murray Darling Basin Authority | And 2 more authors.
Mathematical and Computer Modelling | Year: 2012

The estimation of groundwater evapotranspiration (ET) helps evaluate the risk of soil salinisation and the capacity of regional water resources. This paper focused on the effect of discretisation cell size on the output uncertainty of regional groundwater evapotranspiration modelling. The study area, the Liuyuankou Irrigation System (LIS), was discretised into cell sizes of 100×100m, 200×200m, 500×500m, 1000×1000m, and 2000×2000m. Digital elevation models (DEM) at the lower resolutions were obtained by resampling the 90m Shuttle Radar Topography Mission (SRTM) DEM using an averaging algorithm. The krigged groundwater table was subtracted from the ground surface elevation to generate the groundwater depth maps for various cell sizes. For each resolution, the groundwater ET was calculated using two ET functions (linear and exponential) for each cell. Lastly, the effects of the cell size on the output of the regional groundwater ET modelling were evaluated. The results showed that lower ET rates were obtained when a coarser cell size was used due to the smothering of the surface elevations and the groundwater depths, regardless of the employed ET functions. From comparisons of the delineated area, the cell numbers, the groundwater depth maps and the simulated groundwater ET rates, a discretisation cell size of 500 m was recommended for the LIS to balance the model's accuracy and computation efficiency in groundwater ET modelling. © 2012 Elsevier Ltd.

Capon S.J.,Griffith University | Lynch A.J.J.,University of Canberra | Chessman B.C.,University of Canberra | Chessman B.C.,Center for Ecosystem Science | And 11 more authors.
Science of the Total Environment | Year: 2015

The concepts of ecosystem regime shifts, thresholds and alternative or multiple stable states are used extensively in the ecological and environmental management literature. When applied to aquatic ecosystems, these terms are used inconsistently reflecting differing levels of supporting evidence among ecosystem types. Although many aquatic ecosystems around the world have become degraded, the magnitude and causes of changes, relative to the range of historical variability, are poorly known. A working group supported by the Australian Centre for Ecological Analysis and Synthesis (ACEAS) reviewed 135 papers on freshwater ecosystems to assess the evidence for pressure-induced non-linear changes in freshwater ecosystems; these papers used terms indicating sudden and non-linear change in their titles and key words, and so was a positively biased sample. We scrutinized papers for study context and methods, ecosystem characteristics and focus, types of pressures and ecological responses considered, and the type of change reported (i.e., gradual, non-linear, hysteretic or irreversible change). There was little empirical evidence for regime shifts and changes between multiple or alternative stable states in these studies although some shifts between turbid phytoplankton-dominated states and clear-water, macrophyte-dominated states were reported in shallow lakes in temperate climates. We found limited understanding of the subtleties of the relevant theoretical concepts and encountered few mechanistic studies that investigated or identified cause-and-effect relationships between ecological responses and nominal pressures. Our results mirror those of reviews for estuarine, nearshore and marine aquatic ecosystems, demonstrating that although the concepts of regime shifts and alternative stable states have become prominent in the scientific and management literature, their empirical underpinning is weak outside of a specific environmental setting. The application of these concepts in future research and management applications should include evidence on the mechanistic links between pressures and consequent ecological change. Explicit consideration should also be given to whether observed temporal dynamics represent variation along a continuum rather than categorically different states. © 2015 Elsevier B.V.

Dutta D.,CSIRO | Chen J.,CSIRO | Penton D.,CSIRO | Bethune M.,Murray Darling Basin Authority | And 4 more authors.
Water Resources Management | Year: 2014

Different water agencies use different modeling tools for water resources planning and management. For example, different jurisdictions in Australia use a variety of river system models and these models vary considerably in approach and assumptions, including different time steps (monthly and daily), flow routing (different types of routing and no routing), ordering solution (optimization and heuristic) and representation of management and operational rules. These fundamental differences in approach make it difficult to integrate existing models of connected river systems at a basin scale. A collaborative joint venture (the eWater CRC) between research, industry and government partners has recently developed an integrated river system modelling tool called "eWater Source" to improve on the existing river system models in Australia. One of the major advances in Source is the implementation of two decision algorithms, heuristic and NetLP approaches, for water distribution modelling in the same modelling platform. This paper describes the implementation of heuristic and NetLP approaches for water delivery under management and operations rules in Source, and compares the performance of the two approaches through a case study in the Goulburn-Broken-Campaspe-Loddon (GBCL) river system in south-eastern Australia. The key performance measures used to compare the approaches include the efficiency and equity of water delivery to water users, impacts on the reliability of supply, agreement with storage operating targets, and model application run time. The results demonstrate that the heuristic approach implemented in Source can replicate the performance of the NetLP approach for a model of reasonable complexity. This is important because the run times of models with heuristic approaches are shorter than models with NetLP approaches, so this will allow more complexity to be represented than was previously practical in equivalent NetLP applications. Agreement between jurisdictions to move to the single river system modelling platform will contribute to overcoming the problems faced by river managers in Australia in transboundary river basins. © 2014 Springer Science+Business Media Dordrecht.

Chen Y.,CSIRO | Rana T.,Murray Darling Basin Authority | Abbas A.,Murray Darling Basin Authority | Buettikofer H.,CSIRO
Water Resources Management | Year: 2012

Australian irrigated agriculture utilises about 70% of all water used in the country, 21% of which is derived from groundwater. Sustainability for irrigated agriculture also depends on keeping the watertables at a safe level below the rootzone to avoid salinisation and reduction in crop yields. There is a vital need to understand groundwater and aquifer systems and their roles in the sustainability of irrigated agriculture in order to manage groundwater properly. This study builds on the previous hydrogeological and groundwater investigations of the Coleambally Irrigation Area (CIA) in New South Wales of Australia. It presents a new approach which systematically characterises regional hydrogeological environment using a three-dimensional (3-D) conceptual framework developed in ArcGIS. The 3-D hydrological conceptualisation of the CIA has integrated disparate sources of data into a coherent knowledge base for a better visualisation of hydrogeological characteristics and a comprehensive analysis of groundwater flow and aquifers. As an application example, the model was used to develop cross-sectional models of the area and to estimate regional-scale net recharge. The results have provided a basis for the numerical modelling and added values to procedures which underpin irrigation system management investment decisions through improving the understanding of hydrogeology underlying the area and creating an action-oriented dialogue among stakeholders. © 2012 Springer Science+Business Media B.V.

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