A vision for future hydrologic modelling to support Victoria's evolving water resource management

Abstract

The development and management of Victoria's water resources has undergone major changes as the supply system was developed, entitlements and property rights were established and diversions grew. The growth of diversions, particularly within the Murray-Darling Basin, was not sustainable. These changes were major drivers of the process of water reform which was begun in 1994. The impact of the water reform on Victoria's water supply systems has been important and created many opportunities to sustainably manage water resources. These included a cap (or limit) on diversions, the separation of entitlements from land, the establishment of a water market, improved efficiency in water use and the recent Murray-Darling Basin Plan water recovery to better protect the environment. These water reforms have resulted in water supply systems becoming far more complex to manage, operate and meet compliance. For example, the local irrigation areas had a defined boundary prior to water reform. There was fixed number of licences attached to the land and allocations to those licences. Now, water that may once have been used for irrigation in one irrigation area may be traded and used for consumptive as well as non-consumptive purposes in other areas within a connected system or vice versa, for example the southern connected Murray-Darling Basin and Melbourne system. As the regulatory framework has evolved over the past twenty-five years, so too has water demand patterns of all users. For irrigators, this has included adapting irrigation practices to manage their water entitlement usage, manage their risk and improve their water use efficiency. Victoria has also invested significantly in the modernisation of the irrigation distribution system itself to minimise distribution losses and recover water. Urban use has changed with improved water efficiencies and alternative sources of supply such as storm water, rainwater tanks and recycled water. New environmental entitlements have been created to deliver environmental outcomes. There are delivery capacity constraints to consider as competing water demand patterns change including both consumptive use as well as the large-scale delivery of environmental water. Throughout the process of water reform, hydrologic modelling has been continuously developed to cope with real world changes and played a key role to inform policy and compliance framework. Moving forward, modern software tools and technology are required to meet water industry needs to model the system as it is now and may be in the future. Victoria contributed to the development of the National Hydrological Modelling Strategy (NHMS) to plan for its modelling requirements. The NHMS ensures that Australia's hydrologic modelling capability, community and software is ready to meet the priority hydrological modelling needs of Australian governments. Source is a modelling tool that has been developed within the NHMS. Victoria has implemented Source in many valleys including the foundational model of Goulburn, Broken, Campaspe, Coliban and Loddon system, and is developing Source models for other parts of Victoria. Looking forward, there is a need and an opportunity for the hydrological models to be applied in a transparent, repeatable and defensible way for a wide range of applications with different purposes such as: (i) a planning model to support water management practices including assessing alternatives sources for urban water supply, catchment modelling of climate change and land use change, (ii) an operational model which may input live climate and streamflow data feeds for flow and demand forecasting, (iii) a tool for compliance which at a basin or state level requires modelling, (iv) environmental flow delivery, flooding issues, delivery capacity and salinity assessments, and (v) a planning as well operational tool to manage the movement of water through the water grid across the jurisdictions to meet competing water demand. Source, a modern software, provides a platform for ongoing development and improvement to meet modelling needs across Australia. Challenges for future modelling, including representing complex interconnected systems, water trade, environmental requirements and accounting of water across all water users in a system with no boundaries and a continuously changing landscape. It is expected that the next generation of hydrological models, that leverage the Source software will provide a mechanism to explicitly or implicitly support analysis of a wide range of impacts of water management.