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Wollongong, Australia

Vaze J.,CSIRO | Davidson A.,NSW Office of Water | Teng J.,CSIRO | Podger G.,CSIRO
Hydrological Processes | Year: 2011

The impact of future climate on runoff generation and the implications of these changes for management of water resources in a river basin are investigated by running these changes through catchment and river system models. Two conceptual daily rainfall-runoff models are used to simulate runoff across the Macquarie-Castlereagh region for historical (1895-2006) and future (∼2030) climate based on outputs from 15 of the 23 IPCC AR4 GCMs for the A1B global warming scenario. The estimates of future runoff are used as inputs to the river system model. The mean annual historical rainfall averaged across the Macquarie-Castlereagh region is 544 mm and the simulated runoff is 34 and 30 mm for SIMHYD and Sacramento rainfall-runoff models, respectively. The mean annual future rainfall and runoff across the region are projected to decrease. The modelling results show a median estimate of a 5% reduction for SIMHYD (50% confidence interval - 11 to + 7%) and a 7% reduction for Sacramento (50% confidence interval - 15 to + 8%) in mean annual runoff under a ∼2030 climate for the region. The results from the river system modelling indicate that under the ∼2030 climate scenario, the median of general security and supplementary diversions are projected to decrease by 4% (50% confidence interval - 10 to + 5%) and 2% (50% confidence interval - 5 to + 3%) respectively for the SIMHYD inflows and 8% (50% confidence interval - 17 to + 6%) and 5% (50% confidence interval - 11 to + 3%) for the Sacramento inflows. The future annual and seasonal storage volumes for the Burrendong Dam and inflows at all major locations across the region are projected to be lower than the historical records. © 2011 John Wiley & Sons, Ltd..

Liu D.L.,Australian Department of Primary Industries and Fisheries | Liu D.L.,Charles Sturt University | Zuo H.,NSW Office of Water
Climatic Change | Year: 2012

This paper outlines a new statistical downscaling method based on a stochastic weather generator. The monthly climate projections from global climate models (GCMs) are first downscaled to specific sites using an inverse distance-weighted interpolation method. A bias correction procedure is then applied to the monthly GCM values of each site. Daily climate projections for the site are generated by using a stochastic weather generator, WGEN. For downscaling WGEN parameters, historical climate data from 1889 to 2008 are sorted, in an ascending order, into 6 climate groups. The WGEN parameters are downscaled based on the linear and non-linear relationships derived from the 6 groups of historical climates and future GCM projections. The overall averaged confidence intervals for these significant linear relationships between parameters and climate variables are 0. 08 and 0. 11 (the range of these parameters are up to a value of 1. 0) at the observed mean and maximum values of climate variables, revealing a high confidence in extrapolating parameters for downscaling future climate. An evaluation procedure is set up to ensure that the downscaled daily sequences are consistent with monthly GCM output in terms of monthly means or totals. The performance of this model is evaluated through the comparison between the distributions of measured and downscaled climate data. Kruskall-Wallis rank (K-W) and Siegel-Tukey rank sum dispersion (S-T) tests are used. The results show that the method can reproduce the climate statistics at annual, monthly and daily time scales for both training and validation periods. The method is applied to 1062 sites across New South Wales (NSW) for 9 GCMs and three IPCC SRES emission scenarios, B1, A1B and A2, for the period of 1900-2099. Projected climate changes by 7 GCMs are also analyzed for the A2 emission scenario based on the downscaling results. © 2012 Springer Science+Business Media B.V.

Vaze J.,NSW Office of Water | Teng J.,CSIRO
Hydrological Processes | Year: 2011

This paper describes the rainfall-runoff modelling for New South Wales (NSW) and Australian Capital Territory (ACT) under historical climate and the likely changes to runoff around the year 2030 for the Intergovernmental Panel on Climate Change (IPCC) SRES A1B global warming scenario. Results show that the mean annual historical rainfall and runoff, averaged over the entire region, are 516 and 55 mm, respectively. There is considerable uncertainty in the global climate modelling (GCM) of rainfall response in the region to global warming. The majority of GCMs show a decrease in the mean annual rainfall and the median estimate indicates that future mean annual runoff in the region in 2030 relative to 1990 will be lower by 0-20% in the southern parts, no change to a slight reduction in the eastern parts and higher by 0-20% in the northwest corner. Averaged across the entire region, the median estimate is a 5% decrease in the mean annual runoff and the extreme estimates range from a 14% decrease to a 10% increase in mean annual runoff. This is the first comprehensive study on the hydrological impacts of climate change done in NSW that covers the entire state. Outputs from this study are being used to underpin the hydrology for a number of major climate change impact studies that are presently underway across NSW. The results and output datasets from this study will be available through a web interface and they can be used by all state government agencies and industries in NSW to plan for and adapt to the impacts of climate change © 2010 John Wiley & Sons, Ltd.

Walsh C.T.,Australian Department of Primary Industries and Fisheries | Walsh C.T.,University of Wollongong | Reinfelds I.V.,NSW Office of Water | Ives M.C.,Australian Department of Primary Industries and Fisheries | And 3 more authors.
Estuarine, Coastal and Shelf Science | Year: 2013

Estuarine-resident fishes are highly susceptible to the effects of environmental and anthropogenic impacts on their assemblages and habitats. We investigated the distribution, movement and spawning behaviour of estuary perch, . Macquaria colonorum, in response to selected environmental variables using an acoustic telemetry array in a large tidal river in south-eastern (SE) Australia. Adult . M. colonorum were monitored for up to two years, covering two consecutive spawning periods between September 2007 and 2009. Salinity, water temperature and river flows all had a significant relationship with their estuarine distribution. In particular, large-scale movements were influenced by large freshwater inflow events and the resultant reduction in salinity levels, together with the seasonal cooling and warming trends in water temperatures associated with spawning behaviour. During the winter months, male and female . M. colonorum migrated from their upper estuarine home ranges to the lower estuarine spawning grounds in synchrony, with numbers of individual visits by both sexes consistently higher in the 'wetter' winter/spring period of 2008. Location, arrival, departure and occupation time within the spawning grounds were similar between sexes and years. Both resident and migrating . M. colonorum exhibited strong diel, and to a lesser extent, tidal behavioural patterns, with fish more likely to be detected at night and during the ebb tides. It is postulated that the effect of environmental fluctuations on the distribution and movement of . M. colonorum is influenced by behavioural mechanisms in response to osmoregulatory stress, predator-prey interactions and reproductive activity. The results also demonstrate the importance of accounting for autocorrelation inherent in telemetry data, and for developing management strategies that are more robust to the effect of future climate trends on estuarine fish populations. © 2013.

Lamontagne S.,CSIRO | Lamontagne S.,Flinders University | Taylor A.R.,CSIRO | Cook P.G.,CSIRO | And 5 more authors.
Hydrological Processes | Year: 2014

In semi-arid and arid river basins, understanding the connectivity between rivers and alluvial aquifers is one of the key challenges for the management of groundwater resources. The type of connection present (gaining, losing-connected, transitional and losing-disconnected) was assessed at 12 sites along six Murray-Darling Basin river reaches. The assessments were made by measuring the hydraulic head in the riparian zone near the rivers to evaluate if the water tables intersected the riverbeds and by measuring fluid pressure (ψ) in the riverbeds. The rationale for the latter was that ψ will always be greater than or equal to zero under connected conditions (either losing or gaining) and always lesser than or equal to zero under losing-disconnected conditions. A mixture of losing-disconnected, losing-connected and gaining conditions was found among the 12 sites. The losing-disconnected sites all had a riverbed with a lower hydraulic conductivity than the underlying aquifer, usually in the form of a silty clay or clay unit 0.5-2m in thickness. The riparian water tables were 6 to 25m below riverbed level at the losing-disconnected sites but never lower than 1m below riverbed level at the losing-connected ones. The contrast in water table depth between connected and disconnected sites was attributed to the conditions at the time of the study, when a severe regional drought had generated a widespread decline in regional water tables. This decline was apparently compensated near losing-connected rivers by increased infiltration rates, while the decline could not be compensated at the losing-disconnected rivers because the infiltration rates were already maximal there. © 2012 John Wiley & Sons, Ltd.

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