NSW Office of Water

Wollongong, Australia

NSW Office of Water

Wollongong, Australia
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Reinfelds I.V.,NSW Office of Water | Walsh C.T.,Australian Department of Primary Industries and Fisheries | Walsh C.T.,University of Wollongong | Van der Meulen D.E.,Australian Department of Primary Industries and Fisheries | And 2 more authors.
River Research and Applications | Year: 2013

The migratory response and behaviour of catadromous Australian bass with regard to hourly mean river flows and water temperatures was assessed over 15months. Fish movement was assessed using a 75-km passive acoustic telemetry array in the regulated Shoalhaven River below Tallowa Dam, NSW, Australia. The majority (62%) of downstream pre-spawning migrations from freshwater to estuarine habitats were stimulated by a series of flow pulses from April to September, but a proportion of fish (38%) commenced downstream migrations under regulated baseflow conditions after a sustained decrease in water temperature to below 15°C in late autumn. Equal numbers of fish undertook post-spawning upstream return migrations during flow pulses and during regulated baseflow conditions, with regulated baseflow migrants exhibiting a preference for dusk-dawn passage through freshwater pool-riffle sequences. The median magnitude of flow pulses at the time of commencement of downstream and upstream freshwater migrations by Australian bass was not large, equivalent to natural (in the absence of river regulation) flows equalled or exceeded for 56% and 48% of time, respectively. There was no evidence for increased numbers of migrants with increasing flow pulse magnitude, with individual fish ignoring some flow pulses but responding to subsequent events. In regulated rivers, the release of more frequent flow pulses with peak magnitudes approximating the natural 50th flow duration percentile may be more effective in stimulating greater numbers of Australian bass to undertake pre-spawning and post-spawning migrations between freshwater and estuarine habitats than the release of a single, larger event. The propensity of Australian bass to also undertake spawning migrations under regulated baseflow conditions emphasizes the need for provision of baseflow regimes in regulated rivers that can facilitate migrations by large bodied fishes. © 2011 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.

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.

Walsh C.T.,Australian Department of Primary Industries and Fisheries | Walsh C.T.,University of Wollongong | Reinfelds I.V.,NSW Office of Water | Gray C.A.,Australian Department of Primary Industries and Fisheries | And 3 more authors.
Ecology of Freshwater Fish | Year: 2012

Understanding movement patterns and habitat utilisation is critical for the management of diadromous fishes. An acoustic telemetry array was used to monitor 33 estuary perch, Macquaria colonorum and 39 Australian bass, Macquaria novemaculeata in the freshwater and estuarine reaches on the Shoalhaven River, south-east Australia. On average, tagged M. novemaculeata were detected for a considerably shorter period than M. colonorum, and evidence suggested that fishing pressure may have impacted on their survival. Macquaria colonorum displayed significant shifts in seasonal and size-related habitat use, with fish predominantly residing in deep (>5m) areas within the middle (mesohaline) reaches of the estuary during the austral spring to autumn months. In winter, M. colonorum individuals made frequent downstream migrations, often to localised areas, within the lower estuary (LE). In contrast, M. novemaculeata were distributed in shallow (<2m) habitats throughout the year, within the upper (oligohaline) estuarine reaches of the river, as well as in fresh water. Like M. colonorum, M. novemaculeata made extensive downstream and upstream movements, often coincident with reproductive behaviour, water temperature and increased freshwater inflows. It is postulated that the high site fidelity and repetitive homing displayed by both species is influenced by ontogenetic behaviour and prey availability. Furthermore, the extent of instream distribution by both species, and the lack of observed annual spawning migrations by some M. novemaculeata individuals, indicates the once considered 'catadromous' life cycle of these fishes may not be obligatory. A management approach is recommended to ensure that both these species are not over-exploited within a portion of their instream range, thus maintaining their full reproductive potential. © 2011 State of NSW.

Vaze J.,NSW Office of Water | Vaze J.,Water Cooperative Research Center | Teng J.,NSW Office of Water | Teng J.,Water Cooperative Research Center | Spencer G.,NSW Office of Water
Environmental Modelling and Software | Year: 2010

Topography is an important land-surface characteristic that affects most aspects of the water balance in a catchment, including the generation of surface and sub-surface runoff; the flow paths followed by water as it moves down and through hillslopes and the rate of water movement. All of the spatially explicit fully distributed hydraulic and hydrological models use topography (represented by the DEM of the area modelled) to derive bathymetry. DEM is also used to derive some other key information critical in fully distributed hydraulic and hydrological models.With high-resolution DEMs such as LiDAR (Light Detection and Ranging) becoming more readily available and also with the advancements in computing facilities which can handle these large data sets, there is a need to quantify the impact of using different resolution DEMs (e.g. 1 m against 10 m or 25 m) on hydrologically important variables and the loss of accuracy and reliability of the results as we move from high resolution to coarser resolution.The results from statistical analysis carried out to compare field survey elevations with the LiDAR DEM-derived elevations, show that there are small differences between the two data sets but LiDAR DEM is a reasonably good representation of the actual ground surface compared to other commonly used DEMs derived from contour maps.The results from the analysis clearly show that the accuracy and resolution of the input DEM have serious implications on the values of the hydrologically important spatial indices derived from the DEM. The result also indicates that the loss of details by re-sampling the higher resolution DEM to coarser resolution are much less compared to the details captured in the commonly available coarse resolution DEM derived from contour maps. Topographic indices based on contour derived DEMs should be used with caution and where available, the higher resolution DEM should be used instead of the coarse resolution one. © 2010 Elsevier Ltd.

Mitrovic S.M.,Nsw Office of Water | Mitrovic S.M.,University of Technology, Sydney | Lorrainehardwick,Nsw Office of Water | Forughdorani,Nsw Office of Water
Journal of Plankton Research | Year: 2011

The growth of planktonic cyanobacteria in a weir pool on the Lower Darling River, Australia, downstream of the major regulated Menindee Lake system was examined. Blooms of the saxitoxin producing freshwater cyanobacterium Anabaena circinalis occurred for two summers out of four studied. Large cell numbers of other cyanobacteria including Aphanizomenon, Planktolyngbya and Merismopedia also occurred during the same summer periods as the Anabaena blooms. The growth events also coincided with periods of improved light climate. Flow releases from the regulated Menindee Lakes System were assessed for their ability to either suppress bloom development or to mitigate pre-existing blooms over this period. A discharge of 300 ML/day (flow velocity of 0.03 m/s) was found to be sufficient to prevent prolonged periods of persistent thermal stratification, which also suppressed the development of A. circinalis blooms. A flow release of 3000 ML/day was effective at removing an established cyanobacterial bloom, and total cyanobacterial numbers declined from over 100 000 to <1000 cells/mL within a week. In two summers without blooms, higher flows and decreased light availability prevented the development of cyanobacterial blooms. Flow releases were effective at mitigating cyanobacterial growth through either the suppression of persistent thermal stratification or through dilution and translocation of cells. Greater discharges also increased turbidity, which diminished the growth of cyanobacteria through reduced light availability under the mixed conditions, which also reduced the ability for surface migration through buoyancy regulation. The volume of water required for different management strategies varied and is considered in terms of environmental allocations. © The Author 2010.

Reinfelds I.,NSW Office of Water | Williams S.,NSW Office of Water
River Research and Applications | Year: 2012

Reduced mixing of deep pools attributable to river regulation and downstream flow suppression can lead to an increase in the magnitude, frequency and duration of thermal stratification in riverine pools over summer. This study monitored hourly temperature profiles with five thermistor loggers in a 15m deep natural pool over 12 months from May 2005. Detailed bathymetric and topographic survey data and HEC-RAS hydraulic modelling of layer Richardson numbers were used to extend thermistor observations of flow-related stratification breakdown in this single deep pool to a 20km long pool-riffle dominated river reach below the dam. Reach-wide breakdown of persistent thermal stratification in deep pools over spring and summer was likely to be achieved by a flow rate of 3000MLday -1. This flow rate approximates the long-term mean annual natural flow (2860MLday -1) and the 16th flow duration percentile (mean daily flows equalled or exceeded for 16% of time), indicating that thermal stratification of the deepest pools in the Shoalhaven River is a common, natural phenomenon not solely attributable to river regulation. Should reasonably consistent hydraulic geometry relationships exist between low salinity rivers in similar climatic, hydrologic and geomorphic settings, then we suggest that the mean annual natural flow is likely to achieve widespread breakdown of thermal stratification across lengthy reaches of similar pool-riffle sequence rivers elsewhere. Hourly mean wind speeds of up to 65kmh -1 recorded at an automated weather station 25km from the study site were found to suppress of the degree of thermal stratification in the study pool but did not achieve deep mixing of persistent seasonal thermoclines. Large, rapid and sustained air temperature decreases associated with the passage of cold fronts across southeastern Australia in summer were found to be more effective than wind and achieved mixing to depths of at least 4.2m. © 2011 John Wiley & Sons, Ltd.

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.

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..

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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