Integrated Monitoring of Environmental Flows: Assessment of predictive modelling for river flows and fish
|Integrated Monitoring of Environmental Flows: Assessment of predictive modelling for river flows and fish
River Flows in New South Wales are being restored in an effort to improve river health and sustainability under the NSW Water Reform Process. Historical development of the State’s water resources has dramatically altered the natural flow regimes in many rivers. Water managers need tools to enable them to protect the ecological needs of rivers, to restore more natural flows and to rehabilitate fish communities and other components of riverine ecosystems.
This project sought to produce a mathematical model that could predict the responses of fish communities to different environmental flow strategies in 7 regulated rivers. The development of the model had 2 stages: first, to identify and describe how current river flows differ from natural hydrological conditions; second, to assess whether the hydrological changes had affected fish communities. Based on the predictions of the mathematical model, the project aimed to recommend flow regimes that were beneficial for native fish for consideration when drafting river management guidelines.
The study confirmed that the natural hydrology of the rivers has changed substantially because of the historical level of water resource development in NSW. The modelling suggests that environmental flow rules, developed as part of water management plans, have not achieved the desired objective of partially reestablishing natural flows. Rather, they have produced an alternative flow regime that is as different to natural conditions as the river flows prior to the introduction of environmental flow rules (i.e. at 1993/94 levels of development).
Our current ability to predict responses of fish to environmental flow rules is limited, partly because the environmental flow rules appear to have created a new hydrological regime which does not mimic the natural regime, and partly because of the unavailability of data collected over suitable time frames. Further monitoring of fish communities is recommended, as is the possible use of contingency flow allocations to more directly test fish responses to changed environmental flows.