Discharge of acidic drainage from mining operations or acid sulphate soils can create severe environmental impacts if not managed appropriately. We tested different hydro-geochemical models to predict pH and dissolved Al, Fe and Mn concentrations and speciation following discharge and mixing of acid drainage into receiving waters; (1) an end member mixing approach using the geochemical model PHREEQC could accurately predict (r(2) > 0.9) pH and dissolved metal concentrations at various dilutions over a pH range of 2-7, (2) dissolved inorganic and organic, and solid phase, Al and Fe speciation could be predicted using the geochemical model Visual MINTEQ (at 10% dilution), although poorer results were observed for Mn and drainage mixtures with lower metal concentrations, (3) PHREEQC gave similar results to a 3-D hydro-biogeochemical model (ELCOM-CAEDYM) when tested on a small-scale, and (4) ELCOM-CAEDYM successfully predicted dissolved metal concentrations (r(2) >= 0.8), and to some extent pH (r(2) = 0.2), over a 5 month period in a 90 km reach of the River Murray (South Australia) with over ten acid drainage discharges. The 3-D model was also used to assess river management scenarios and this highlighted a risk for dissolved Mn exceeding (aesthetic) drinking water guidelines in the river water at low flows. Limitations of the various models are discussed and we conclude that geochemical modelling is a useful tool to predict water quality impacts following discharge of acidic drainage to natural waters. (C) 2015 Elsevier Ltd. All rights reserved.

Operators and managers of water resources have a responsibility to make reliable decisions in response to a broad range of drivers, from strategic planning requirements to unforeseen or unusual events. These decisions are made with varying levels of uncertainty. To increase their certainty in the management of its drinking water reservoirs Melbourne Water (MW) have implemented a real-time decision support tool. The Aquatic Real-time Management System (ARMS) utilises historical and real-time field data and numerical models for reporting, analysing and assessing reservoir conditions with improved certainty. The three-dimensional hydrodynamic model ELCOM is configured for six of MW’s nine major drinking water reservoirs, and each reservoir model has undergone performance checks commensurate with the available field data. Field instruments record up-to-the-minute observations that are remotely acquired by ARMS and automatically applied to the models to execute real-time simulations and scenario forecasting. The ability to run models in real-time allows the user to forecast a range of scenarios and compare possible outcomes, thereby reducing uncertainty in decisions relating to the operational management of reservoirs. The ARMS Graphic User Interface (GUI) was tailor-made to MW’s specific needs. Time series of an observed or modelled variable may be plotted against reporting criteria and presented to the operator for quick assessment. Customisation of ARMS is a major advantage. All MW’s discrete and continuous data sources may be imported, configured and analysed, streamlining use and interrogation of data. Custom plotting allows efficient communication of key information and model output to operators and managers. Data gaps are filled using basic algorithms there-by minimising downtime. The on-going integration of field data, model output, reporting criteria, error analysis and gap identification in ARMS has been applied successfully at MW to investigate the fate and transport of post-fire debris flow in Upper Yarra Reservoir, and to conduct scenario analysis for complex operational decision-making, for example, assessing the dilution rate of desalinated water in Cardinia Reservoir. The components of MW ARMS are continually improved and updated, such as improving model performance and customising GUI functions. In-house capability is built through training in the use of MW ARMS and interpretation of output.

Australia's surface drinking water resources are commonly comprised of multiple interconnecting dams with numerous users and various water quality priorities. Managing such systems is challenging and requires innovative methods to make use of complex database systems and therefore enable optimal decision-making. Decision support systems are designed to assist decision makers, managers and operators access relevant information and make informed short and long term operational and strategic decisions through the use of data, tools and knowledge.The Sydney Catchment Authority (SCA) is responsible for the provision of water to Sydney Water Corporation for treatment and distribution of drinking water to more than four million people in Sydney, the Blue Mountains and the Illawarra, and supply to Southern Highlands, Goulburn, and Shoalhaven communities. The water supply storages comprise 2600 GL across 10 major (plus 6 minor) water storage dams. Of these, Lake Burragorang, the Shoalhaven Scheme and Prospect Reservoir account for 81% of the SCA water storage capacity. These systems have multiple water users and varying water quality issues. A key concern in Warragamba Dam is flood inflow dynamics and the load of catchment contaminants that can lead to outlet water quality problems, including blue-green algae. The Shoalhaven Scheme, comprised of Lake Yarrunga, Fitzroy Falls Reservoir and Wingecarribee Reservoir, is managed with respect to hydroelectric power transfers, recreational use and downstream impacts.To manage the multiple dimensions of the storage network, a customised innovative tool is used for water supply planning and operations. The Sydney Catchment Authority Reservoir Management System (SCARMS) integrates observational data and validated catchment, hydrodynamic and water quality models into a decision support system. Five major SCA storages (Warragamba Dam, Tallowa Dam, Fitzroy Falls Dam, Wingecarribee Dam and Prospect Dam) are currently integrated into SCARMS.SCARMS integrates an extensive supply of both real-time and historical data sources for the five storages. Real-time data sources include stream flow rates and properties, in-lake meteorology and in-lake water column temperature and water quality. Historical data sources include routine physical, chemical and biological monitoring data collected by SCA over the past 40 years. All relevant data are integrated into SCARMS and are processed, quality assessed and visualised. The data are used to drive and validate coupled three-dimensional hydrodynamics and water quality models (The Estuary, Lake and Coastal Ocean Model, ELCOM, and the Computational Aquatic Ecosystems Dynamics Model, CAEDYM). The integration of field data and numerical models allows a combination of real-time, forecast and hindcast simulations of reservoir conditions to be conducted on an ongoing basis. Collation of the field data and model scenario output in a user-friendly interface provides decision support for daily operations and long-term strategic planning. Customised reports can be generated to communicate knowledge to the range of operators, managers and selected stakeholders.This data, model and knowledge package is housed at SCA and demonstrates successful innovations in collating a range of necessary tools into a seamlessly linked and customised decision support system for the management of large-scale water resource systems.

Physical characteristics of a hypolimnetic oxygenator known as a Water Environmental Preservation System (WEP), were investigated through field tests carried out in Sanbe Reservoir, Japan. Field data showed that the oxygen‐rich intrusion traveled at nearly the same height as the outflow opening of the device. The thickness of the intrusion, travel time and other important values were derived from the field data. The results showed the flow to be similar to that of an intrusion emanating from a bubble plume after the plunging point and was controlled by an inertia‐buoyancy force balance. The intrusion from the oxygenator was successfully simulated with a three‐dimensional hydrodynamic and water quality simulation model (ELCOM‐CAEYDM) including a simple integral model for the oxygenator.

Hydrostatic and non-hydrostatic models were used to simulate the generation of internal surges and associated soliton-like trailing waves from the non-linear steepening of low-frequency basin-scale waves. Results confirmed that the process cannot be modelled using the hydrostatic approximation. A grid-switching strategy was developed to reduce the simulation run-time of the non-hydrostatic model; a low-resolution grid using a hydrostatic computation of the flow field is dynamically switched to a high-resolution grid in the region of propagation of the leading internal surge, using a non-hydrostatic computation of the flow field. The strategy takes advantage of the small time scale required for non-hydrostatic effects to become important such that a high-resolution grid is invoked only when and where these effects become large. Run-time reduction, conservation of the interpolation scheme involved in the grid switching and strategies for field scale studies were addressed. In relation to the laboratory experiments, the grid-switching strategy predicted the phase speed and the amplitude of the leading internal surge similarly to the uniform-grid models, however, the trailing soliton-like waves lost some of their signature. All non-hydrostatic models predicted the features of the energy flux path between low- and high-frequency waves.

Physical characteristics of a hypolimnetic oxygenator known as a Water Environmental Preservation System (WEP), were investigated through field tests carried out in Sanbe Reservoir, Japan. Field data showed that the oxygen-rich intrusion traveled at nearly the same height as the outflow opening of the device. The thickness of the intrusion, travel time and other important values were derived from the field data. The results showed the flow to be similar to that of an intrusion emanating from a bubble plume after the plunging point and was controlled by an inertia-buoyancy force balance. The intrusion from the oxygenator was successfully simulated with a three-dimensional hydrodynamic and water quality simulation model (ELCOM-CAEYDM) including a simple integral model for the oxygenator.

Results from a three-dimensional hydrodynamic model of a stratified lake show that the computed structure of the pycnocline changed rapidly due to numerical diffusion, thus altering the vertical mixing dynamics and introducing a positive feedback that quickly drives model predictions off course. To negate the numerical diffusion a pycnocline filtering method is proposed that assimilates high-resolution thermistor chain data and adaptively adjusts to minimize the discrepancy between observed and computed temperatures. The adaptive pycnocline filter ensures that the computed temperature gradients in the metalimnion at the position of the thermistor chain remain within the bounds of the measured values so the computation preserves the spectrum of internal wave motions that trigger diapycnal mixing events in the deeper reaches of the lake.

Analogous to flood forecasting systems, an automated real-time system has been developed for reservoirs, estuaries, and coastal regions, called ARMS (Aquatic Real-time Management System). ARMS is a short-term decision support system to aid in the management of crisis events through integration of real-time data and numerical modeling. ARMS relies on a three-dimensional hydrodynamics model (ELCOM) coupled to a biochemical model (CAEDYM). Such numerical models are complex and time consuming to utilize, and are of limited use `during' crisis events (i.e. spills, floods, algal blooms). To overcome these modeling limitations ARMS has a high degree of automation to access real-time data, to perform quality checks, to fill data gaps intelligently, to update simulation inputs, and to run simulations up to the current conditions (i.e. nowcast simulations). The entire model domain is saved after the final time step of a nowcast simulation to serve as the initial conditions for subsequent nowcast and forecast simulations. Hence, simulations require no 'spin up' of circulation patterns and biochemical gradients in a water body. ARMS has been applied in field research and operational water supply contexts. ARMS served to optimize data collection during a field experiment in Lake Victoria, Kenya through identification of tidal-like dynamics that guided early adjustments to the field program. ARMS is currently operational on a major water supply reservoir for Sydney, Australia as a tool to minimize risk of microbial contamination during floods. The potential effect of floods on the reservoir is forecast for I month each day to provide an early warning system, useful for short term operational decisions to manage optimal water quality during such events.

A coupled three-dimensional hydrodynamics and two-dimensional underflow model is adapted to provide simulation of plunging inflows in reservoirs. The new approach accounts for the effect of the barotropic term prior to the plunge point of the inflow. Simulations of plunging flows in constant width and constant slope channels are conducted and the resulting plunge depths are in agreement with prior empirical models. Simulation of a previously measured underflow in Wellington Reservoir (Australia) demonstrates the model application to a plunging inflow in a natural water body and good agreement between field and model results.

A separate underflow model is coupled to the three-dimensional (3D) estuary and lake computer model. The underflow equations are solved on a two-dimensional (2D) grid underlying the 3D model grid. The underflow model entrains ambient water whose properties are given by the fluid properties of the bottom boundary cells in the 3D model. This new approach allows improved representation of underflow effects in z-coordinate models by reducing numerical convective entrainment. An idealized case is used to illustrate the benefits of the underflow model. Comparisons of model results and field data for a saline underflow event in Lake Ogawara and a cold-water underflow in Lake Kinneret demonstrate improved model capability in representing underflow events that are thin compared to the vertical grid scale.

The Swan River estuary, Western Australia, has undergone substantial hydrological modifications since pre-European settlement. Land clearing has increased discharge from some major tributaries roughly 5-fold, while weirs and reservoirs for water supply have mitigated this increase and reduced the duration of discharge to the estuary. Nutrient loads have increased disproportionately with flow and are now approximately 20-times higher than pre-European levels. We explore the individual and collective impacts of these hydrological changes on the Swan River estuary using a coupled hydrodynamic-ecological numerical model. The simulation results indicate that despite increased hydraulic flushing and reduced residence times, increases in nutrient loads are the dominant perturbation, producing increases in the incidence and peak biomass of blooms of both estuarine and freshwater phytoplankton. Changes in salinity associated with altered seasonal freshwater discharge have a limited impact on phytoplankton dynamics.

Under certain tidal conditions, a saline underflow originating in the Pacific Ocean moves into Lake Ogawara, Japan. The underflow consists of a uniform saline bottom layer that is slightly warmer than the ambient and an interfacial shear layer in which the velocity and density are decreased. Within the experimental area the underflow is confined to a channel approximately 1 km wide and is essentially two-dimensional. The underflow had a bulk Richardson number, defined in terms of the mean properties, between 1 and 2. The rate of entrainment into the bottom layer was calculated using two distinct methods. The first method used the change in the maximum salinity of the underflow measured at two stations along the path of the underflow to infer the amount of ambient water entrained. The second method made direct measurements of vertical mass fluxes with a profiler. The agreement between the two methods was excellent. The measured entrainment coefficients were consistent with the derived entrainment law. The turbulent structure of the flow was mapped for a 3 h quasisteady period of the flow. Turbulence is predominantly generated on the bottom boundary and is transported vertically to the density interface, where it leads to mixing.