Improving, demonstrating and evaluating the benefits of environmental management of stressed rivers

The Living Murray is the most substantial attempt in Australia to improve ecological outcomes from increased environmental water allocations and other works, but there are other examples too that deserve attention. The intergovernmental agreement to invest $500 million to recover additional water for environmental benefit has focussed attention on the need to identify, demonstrate and maximise the outcomes that can be achieved from the additional water and to recover it in the most cost effective way. Similar issues will be raised in other systems where there is pressure on water resources and degradation of stressed ecosystems.

The debate is moving from establishing the impacts of altered flow regimes to predicting the outcomes of future managed flows and to designing optimal flow allocations and associated structural works. This requires greater precision in our ability to predict future responses of ecosystem assets. The MDBC, for example, has analysed the last ten years of flows along the River Murray to examine how an increased environmental allocation could best be used. The results show several key points. The amounts allocated are only sufficient to slightly modify natural flood events by either extending their duration or increasing their peak height. Allocations to individual ecosystem assets will have to be made actively to use opportunities that present themselves at short notice, but such opportunities might occur only three times a decade. The flows are likely to have relatively little effect on allocations to agriculture in dry years, as no environmental allocations could be made as no significant benefits could be gained.

Because the changes that can be made are subtle, there is relatively little knowledge of the benefits of particular choices in the allocation. For example, the relative merits of increasing the peak or extending the recession of a flood to meet particular aims are not clear. This does not mean that the environmental allocations are unlikely to be beneficial. There are many thresholds inherent in the river system where there is likely to be a sharp increase in benefit once a flow threshold is crossed. The most obvious of these is the threshold for flow to go overbank, or reach levels that commence to fill wetlands. Allocations that allow floods to cross these thresholds and remain over them are likely to have greatest benefit.

Previous work on the benefits of environmental flows in the Murray, essentially captured in the Murray Flows Assessment Tool, is of insufficient resolution to predict the precise benefits of particular flow allocation decisions or structural works. Some ecosystem elements are relatively well known, such as the requirements for bird breeding, but others are poorly understood, such as the response of wetland macrophytes. The design of works and environmental flow allocations requires a disciplined process of hypothesis setting, testing and evaluation. In setting these precise hypotheses of outcomes it will become clear that there are aspects of ecosystem assets, and their link to flow regimes, that are poorly understood and which inhibit our ability to design environmental management regimes and predict their benefits. In several cases these knowledge gaps can be researched independently of the actual allocation of environmental water or other works.

In all cases there is a need to not only improve prediction but also to monitor and evaluate the benefits; to test with real system management the hypotheses that are raised. This is required to ensure effective adaptive management and to demonstrate that outcomes have been achieved. The monitoring and evaluation work will need to react quickly to opportunities that are presented at short notice. It will require quite direct and mature relationships between environmental managers, including the MDBC, and researchers. Resources should be available from managing authorities for this work and while essential it is not a niche that is met well by this research program. The most significant role for this program will be to capture lessons from leading examples of monitoring and evaluation in management, and communicate these to other jurisdictions.

Projects

Publications and Resources

Type	Title	Product Number	Publication Year
General Information | Fact Sheet	Water Allocation to the River Murray wetlands	PN30309