Seasonal rivers - the conundrum of determining environmental water requirements and environmental triggers (#54)
Douglas Green
1
,
Kumar Savadamuthu
1
- Department of Environment, Water and Natural Resources, Adeliade, SA, Australia
- Quantification of the water regime needs of water-dependent ecosystems is a fundamental need for water planners. Until recently, environmental water requirement (EWR) assessment methods for South Australian seasonal rivers used a simple pass/fail approach a complex series of flow metrics. This approach could be considered blunt as a single threshold value for each metric was produced for any given time window. It also meant that trigger values were broad, complex and difficult to assess and interpret.
- In order to address this, we developed a new method of assessing EWRs for the Barossa Valley in South Australia using moving averages of six critical ecologically-relevant flow metrics. Triggers were then established by comparing EWR values to recent critically dry periods where ecological condition was deemed to be outside the desired condition.
- By incorporating a moving average method we are able to capture the variable nature of seasonal rivers into a logical and assessable series of metrics that allow for, and are not perturbed by, annual variability. By comparing the results experienced during previous stable periods with more recent extreme dry periods, thresholds are able to be identified based on observed changes in environmental condition. This lifting of the assessment to a multiple year scale takes the focus off individual years allowing a refocus on short term trends.
- Consequently, this method allows for a robust and defendable way of quantifying the trigger values for seasonal rivers that passes both scientific scrutiny and, in some ways more importantly, the ‘pub test’.
Download Full Paper