Meeting Environmental Outcomes – A Planning Framework - Water and Agriculture: Sustainability, Markets and Policies - page 193

fauna, reflecting the variety of geology and landforms, altitudes and climates across the
catchment. The Murrumbidgee River catchment is also home to sites of international
ecological significance, including the Fivebough and Tuckerbil Swamps and the
Lowbidgee Wetlands (Murrumbidgee Catchment Management Authority 2005).
As part of a National Land and Water Audit, Norris et al. (2001) calculated an index
of hydrological disturbance for all rivers in the southern Murray Darling Basin. The index
rated the rivers on a scale of 0 to 1 from extremely disturbed to undisturbed. Of the
twelve river basins assessed, the Murrumbidgee River was estimated to be the most
disturbed (hydrologically modified) category, with an index value of 0.41. The
Murrumbidgee River is a highly regulated river, with two major storages, a number of
smaller weirs and a network of irrigation delivery channels designed to meet irrigator
demand. Diversions for irrigation are significant and, as a result, end-of-system flows are
considerably less than they would have been under natural conditions (Crabb 1997). In
addition, seasonal patterns of flow have shifted, with high releases during summer and
autumn, and low flows during winter and spring while storages are replenished.
The Murrumbidgee River, as with most rivers and streams in the southern Murray
Darling Basin, is a working river — a term coined by Dr Dedee Woodside to describe a
river that has been harnessed for human purposes but which nonetheless should be
afforded resources, including hydrological resources, to maintain its ecological 'health'
indefinitely (Hillman et al. 2003). While the re-creation of natural or predevelopment
high flow conditions on a working river may not be possible or desirable, the restoration
of some aspects of stream ecology by more closely re-creating the frequency, timing and
duration of naturally-occurring high flow events is seen as an essential element of water
management (Murray-Darling Basin Commission 2005).
Data from the New South Wales Government Department of Natural Resources
Integrated Quantity Quality Model (IQQM) were analysed to understand the changes that
have occurred with the development of large-scale storage and delivery infrastructure to
support irrigation on the Murrumbidgee River. IQQM is a daily time step hydrologic
modelling tool that was developed by the New South Wales Government Department of
Natural Resources, with collaborative assistance from the Queensland Government
Department of Natural Resources. It is intended for use in investigating the impacts of
water resource management policies or policy changes on stakeholders and
environmental outcomes. IQQM is designed to be capable of addressing water quality
issues as well as water quantity issues. It can also be used to investigate new water
resource developments or modifications to existing developments.
Some of the major processes that are simulated include:
flow routing in rivers and irrigation channels, including branches, loops and tributaries;
storage operation;
irrigation; and
wetland and environmental flow requirements.
In this paper, the model has been used to simulate two flow regimes from the
Murrumbidgee River for the period from 1900 to 1999. The first, referred to as natural
conditions, is without existing storage and delivery infrastructure and consumptive
demands. The second is with current infrastructure, consumptive demands and agreed