Sydney Catchment Authority

Penrith, Australia

Sydney Catchment Authority

Penrith, Australia

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Oliver T.S.N.,University of Wollongong | Rogers K.,University of Wollongong | Chafer C.J.,Sydney Catchment Authority | Woodroffe C.D.,University of Wollongong
Wetlands Ecology and Management | Year: 2012

Mangrove and saltmarsh ecosystems appear particularly vulnerable to the impacts of climate change, and their effective management will require forecasts of how these wetland habitats are likely to respond to sea-level rise through the twenty-first century. We describe a preliminary study of a small stand of mangrove and saltmarsh that involves measuring of elevation change and accretion, mapping of wetland communities, and modelling of their potential response to sea-level rise. The wetland occurs on the banks of the Minnamurra River estuary in southern New South Wales and has been the focus of several studies over recent decades. The research includes empirical measurements of sedimentation at sites in both mangrove and saltmarsh vegetation using the surface elevation table-marker horizon technique. This is a site at which mapping has been undertaken to delineate the extent of each vegetation community from a time-series of aerial photographs using geographical information systems; the gradual incursion of the mangrove, Avicennia marina, into more landward saltmarsh communities, observed over past decades for many systems in southeastern Australia, has continued into the twenty-first century. The observed patterns of change are compared with simulations of how this wetland system might respond to future sea-level rise, adopting several different approaches and the upper and lower bounds of Intergovernmental Panel on Climate Change sea-level rise projections. The model results show considerable variability in response depending on the parameters adopted. We advocate the need for the integration of these three approaches, measuring, mapping and modelling, as a basis for future management and adaptation. Our study demonstrates the considerable opportunities to refine the data input and model outputs as part of adaptive management, as more sophisticated technologies and data become available. © 2012 Springer Science+Business Media B.V.


Penev S.,University of New South Wales | Leonte D.,National Industrial Chemical Notification and Assessment Scheme | Lazarov Z.,Industrial science Group | Mann R.A.,Sydney Catchment Authority
Journal of Hydrology | Year: 2014

We discuss novel statistical methods in analysing trends in water quality. Such analysis uses complex data sets of different classes of variables, including water quality, hydrological and meteorological. We analyse the effect of rainfall and flow on trends in water quality utilising a flexible model called Mixed Data Sampling (MIDAS). This model arises because of the mixed frequency in the data collection. Typically, water quality variables are sampled fortnightly, whereas the rain data is sampled daily. The advantage of using MIDAS regression is in the flexible and parsimonious modelling of the influence of the rain and flow on trends in water quality variables. We discuss the model and its implementation on a data set from the Shoalhaven Supply System and Catchments in the state of New South Wales, Australia. Information criteria indicate that MIDAS modelling improves upon simplistic approaches that do not utilise the mixed data sampling nature of the data. © 2014 Elsevier B.V.


Upreti R.P.,Sydney Catchment Authority | Maheswaran S.,Sydney Catchment Authority
Hydrology and Water Resources Symposium 2014, HWRS 2014 - Conference Proceedings | Year: 2014

Warragamba dam receives runoff from catchment area of 9050 km2 draining into Lake Burragorang. Major rivers draining into the lake are Wollondilly, Coxs, Kowmung, Kedumba, Werriberri and Nattai. Nattai River contributes runoff from 445 km2 to Lake Burragorang. Over the years, the Sydney Catchment Authority (SCA) has used Hydrologic Simulation Program - Fortran (HSPF) developed by USGS and EPA to simulate inflows using hydrological data, topography and tributary networks and land use information. These simulated inflows are key inputs for long term water supply planning to assess the system yield, considering various parameters such as future demand, environmental demand imposed by the Water Sharing Plan and the capacity of various components of SCA's water supply network. The HSPF model requires calibration of parameters for functional units and can be onerous and involve lot of time and effort in achieving good modelling results. The exchange of modelling data across agencies has also been an issue. In recent times eWater has developed Source Catchment modelling software in partnership with federal and state government agencies which allows the use of suites of rainfall runoff models to simulate runoff from catchments. The SCA has applied the Source Catchment using Sacramento model for the Nattai River catchment and compared the results with observed and HSPF simulated flows. This paper aims to show the strength and capability of Source Catchment in calibration and verification of daily inflow data, with a good fit of volume of runoff, flow duration curve with high, moderate and low flows. It is expected that the application of Source Catchment modelling framework will improve inter-agency collaboration in catchment modelling.


Martin J.,Sydney Catchment Authority | Maheswaran S.,Sydney Catchment Authority
Proceedings of the 34th Hydrology and Water Resources Symposium, HWRS 2012 | Year: 2012

An annual occurrence in Lake Burragorang is lake turnover during winter and the associated rapid water quality changes at the water supply off-takes. It is of great interest to the Sydney Catchment Authority (SCA) to better understand the mechanisms associated with this process. In the lead up to lake turnover, there are ways to forecast the timing of this event. This paper describes some of the methods that are used by the SCA plus observations regarding the general cooling of the lake and the generation of flows from cooler upper reaches. Thermal conditions in the lake are monitored by a number of thermistor chains located throughout the lake that extends, when full, approximately 50km along 2 main tributaries, and is up to 105m deep. Meteorological conditions on the lake are provided by a LDS (Lake Diagnostic System) located approximately three km from the dam wall. Lake modelling using past or forecast meteorological conditions provides indications of when winter turnover may occur. Results from these models are compared with observed thermal conditions and sampling data to enhance the confidence in model predictions. The model predicted turnover with reasonable accuracy and provided improved understanding of lake limnological processes. © 2012 Engineers Australia.


Kibria G.,Sydney Catchment Authority | Maheswaran S.,Sydney Catchment Authority
Proceedings of the 34th Hydrology and Water Resources Symposium, HWRS 2012 | Year: 2012

The SCA is required to release environmental flows from its storages as per the Greater Metropolitan Region Water Sharing Plan (water sharing plan) administered by the NSW Office of Water. Variable environmental flow releases have commenced from all the SCA's major storages with the exception of Warragamba Dam. No decision has yet been made regarding a suitable environmental flow release regime for Warragamba. A water supply system model was developed to enable the assessment of the various potential environmental flow regimes and their impact on (i) the environment downstream of Warragamba Dam, (ii) the yield of the Sydney supply system (iii) practicalities of the releases. It is likely any future environmental flow releases will have two components, a transparent and translucent requirements, with the environmental flow release based on inflows to the dam. For example, with a 80/20 regime, inflows below the 80th percentile are released transparently and 20% of any inflow in excess of the 80th percentile is released as the translucent component. A range of potential combinations of percentiles of transparent and translucent flows have been investigated for Warragamba. The SCA uses the Wathnet Model (Generalised Water Supply Headworks Simulation using Network Linear Programming) for long-term planning and yield assessment purposes. For system yield assessment, Wathnet uses a monthly time step. For the environmental flow assessment, a daily model for the entire SCA water supply system was developed to establish daily flow regimes downstream of Warragamba Dam. The output of the model was used as an input to a downstream river model to assess the impact of the different flow regimes from environmental and river health perspectives. This paper describes the Wathnet model developed for the environmental flow regimes assessment. The model was validated against historical operating data. The key objective of the daily model is to estimate various components of the Warragamba Dam releases and these are (i) releases to supply (ii) spills, (iii) hydropower release and (iv) environmental flow releases. From the model, downstream release and spill data for 95/20, 90/10 and 80/20 environmental flow scenarios were provided as input for the downstream river model. The impact on system yield was also assessed for these scenarios. © 2012 Engineers Australia.


Jankowski J.,Sydney Catchment Authority
Biuletyn - Panstwowego Instytutu Geologicznego | Year: 2010

Water quality along the Waratah Rivulet in the Woronora Lake Catchment, New South Wales (NSW), Australia, has been monitored during the last three years by the Sydney Catchment Authority. Water quality data shows changes in chemical composition due to cracking of streambeds and rockbars, and diversion of surface water into subsurface routes in the Hawkesbury Sandstone aquifer. Water quality upstream of the longwall panels is comparable to nearly pristine water in creeks and rivers flowing in similar sandstone bedrock environments and to limited water quality data collected prior to mining. A segment of the Waratah Rivulet, where subsidence and cracking of streambeds and rockbars has occurred, is causing surface water to be redirected into subsurface fracture systems, mix with groundwater already present in the aquifer and partially reappear downstream. This subsurface flow in the shallow fractured sandstone aquifer causes the chemical composition and water quality to change as an effect of water-rock interactions. Salinity, iron, manganese and many cation and anion concentrations increase, whereas oxygen is significantly depleted. Mobilisation of barium and strontium from the rock mass indicates fast chemical dissolution reactions between the subsurface flow and carbonate minerals. Other metals mobilised include zinc, cobalt and nickel. Subsurface water partially discharges from underground receptors downstream of the area impacted by longwall mining. The discharged water is rapidly oxidised by atmospheric oxygen, causing precipitation of iron and manganese oxides/hydroxides out of solution. Hydrogeochemical modelling indicates the dominant iron minerals precipitated out from the water are in this environment goethite, lepidocrocite and ferrihydrite. The paper discusses changes in surface water and groundwater chemistry due to subsurface flow and water-rock interaction, the hydrogeochemical processes responsible for changes in water chemistry, as well as changes in water quality along the rivulet.


Jankowski J.,Sydney Catchment Authority | Knights P.,Sydney Catchment Authority
Biuletyn - Panstwowego Instytutu Geologicznego | Year: 2010

Mining-induced subsidence under surface waterways enhances surface water-groundwater interaction due to the enlargement of existing fractures, development of new fractures and the separation of bedding planes. Fracturing of streambeds and rockbars causes surface flow to divert to subsurface routes. The surface water-groundwater interaction in an undermined stream in the Southern Coalfield of New South Wales, Australia, has been assessed by analysing hydrological data including flow measurements upstream and downstream of the longwall panels. The data suggests leakage of surface water to the subsurface through fractured streambeds and rockbars. Mining-induced fracturing across the catchment is likely to have caused increased rainfall infiltration, reduced runoff, and reduced baseflow discharge, resulting in streamflow reduction and possibly loss, particularly during low flow conditions affecting the catchment's water balance. During medium and high flow conditions, the streamflow loss is relatively small in comparison to the total volume of flow in the stream, as the capacity of the subsurface system limits the volume of water that can enter subsurface routes. Streamflow reduction in mining-impacted catchments is likely to be an effect of the spatial distribution and density of fracture networks, changes in porosity and permeability of the subsurface rock mass, changes in groundwater storage capacity, modification to baseflow discharge and alteration of the hydraulic gradient near streams.


Heath J.T.,University of Sydney | Chafer C.J.,Sydney Catchment Authority | van Ogtrop F.F.,University of Sydney | Bishop T.F.A.,University of Sydney
Journal of Hydrology | Year: 2014

Wildfire is a recurring event which has been acknowledged by the literature to impact the hydrological cycle of a catchment. Hence, wildfire may have a significant impact on water yield levels within a catchment. In Australia, studies of the effect of fire on water yield have been limited to obligate seeder vegetation communities. These communities regenerate from seed banks in the ground or within woody fruits and are generally activated by fire. In contrast, the Sydney Basin is dominated by obligate resprouter communities. These communities regenerate from fire resistant buds found on the plant and are generally found in regions where wildfire is a regular occurrence. The 2001/2002 wildfires in the Sydney Basin provided an opportunity to investigate the impacts of wildfire on water yield in a number of catchments dominated by obligate resprouting communities. The overall aim of this study was to investigate whether there was a difference in water yield post-wildfire. Four burnt subcatchments and 3 control subcatchments were assessed. A general additive model was calibrated using pre-wildfire data and then used to predict post-wildfire water yield using post-wildfire data. The model errors were analysed and it was found that the errors for all subcatchments showed similar trends for the post-wildfire period. This finding demonstrates that wildfires within the Sydney Basin have no significant medium-term impact on water yield. © 2014 Elsevier B.V.


Haque M.M.,University of Western Sydney | Rahman A.,University of Western Sydney | Hagare D.,University of Western Sydney | Kibria G.,Sydney Catchment Authority
Hydrological Processes | Year: 2015

In this study, a quantitative assessment of uncertainty was made in connection with the calibration of Australian Water Balance Model (AWBM) for both gauged and ungauged catchment cases. For the gauged catchment, five different rainfall data sets, 23 different calibration data lengths and eight different optimization techniques were adopted. For the ungauged catchment case, the optimum parameter sets obtained from the nearest gauged catchment were transposed to the ungauged catchments, and two regional prediction equations were used to estimate runoff. Uncertainties were ascertained by comparing the observed and modelled runoffs by the AWBM on the basis of different combinations of methods, model parameters and input data. The main finding from this study was that the uncertainties in the AWBM modelling outputs could vary from -1.3% to 70% owing to different input rainfall data, -5.7% to 11% owing to different calibration data lengths and -6% to 0.2% owing to different optimization techniques adopted in the calibration of the AWBM. The performance of the AWBM model was found to be dominated mainly by the selection of appropriate rainfall data followed by the selection of an appropriate calibration data length and optimization algorithm. Use of relatively short data length (e.g. 3 to 6years) in the calibration was found to generate relatively poor results. Effects of different optimization techniques on the calibration were found to be minimal. The uncertainties reported here in relation to the calibration and runoff estimation by the AWBM model are relevant to the selected study catchments, which are likely to differ for other catchments. The methodology presented in this paper can be applied to other catchments in Australia and other countries using AWBM and similar rainfall-runoff models. © 2014 John Wiley & Sons, Ltd.


Haque M.M.,University of Western Sydney | Rahman A.,University of Western Sydney | Hagare D.,University of Western Sydney | Kibria G.,Sydney Catchment Authority
Water Resources Management | Year: 2014

Long term water demand forecasting is needed for the efficient planning and management of water supply systems. A Monte Carlo simulation approach is adopted in this paper to quantify the uncertainties in long term water demand prediction due to the stochastic nature of predictor variables and their correlation structures. Three future climatic scenarios (A1B, A2 and B1) and four different levels of water restrictions are considered in the demand forecasting for single and multiple dwelling residential sectors in the Blue Mountains region, Australia. It is found that future water demand in 2040 would rise by 2 to 33 % (median rise by 11 %) and 72 to 94 % (median rise by 84 %) for the single and multiple dwelling residential sectors, respectively under different climatic and water restriction scenarios in comparison to water demand in 2010 (base year). The uncertainty band for single dwelling residential sector is found to be 0.3 to 0.4 GL/year, which represent 11 to 13 % variation around the median forecasted demand. It is found that the increase in future water demand is not notably affected by the projected climatic conditions but by the increase in the dwelling numbers in future i.e. the increase in total population. The modelling approach presented in this paper can provide realistic scenarios of forecasted water demands which would assist water authorities in devising appropriate management strategies to enhance the resilience of the water supply systems. The developed method can be adapted to other water supply systems in Australia and other countries. © 2014 Springer Science+Business Media Dordrecht.

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