A review of Hydro Tasmania’s environmental flow release in Cataract Gorge is currently underway.
Background
Since the commissioning of Trevallyn Power Station in 1955, Hydro Tasmania has been providing an environmental release down the lower South Esk River through Cataract Gorge. The special water licence specified a flow of 0.43 cumecs. In 2003, Hydro Tasmania voluntarily increased the flow to 1.5 cumecs to provide suitable habitats for biota and to maintain recreational use of the site. We committed to review this release after a five-year period and this is well underway.
The review
The environmental flow review commenced in 2008-09. We sought stakeholder views and reviewed scientific information. Through a survey, stakeholders identified historical and new values and issues associated with the gorge. In September, stakeholders and Hydro Tasmania held a workshop and discussed the identified values and issues as well as potential flow options. Read the workshop report here.
The workshop considered the flow options that would meet most values to be:
- 2.5 or 3.0 cumecs for baseflows and
- 0.5 cumec between Deadmans Hollow and Duck Reach if a mini hydro is installed at Duck Reach Power Station.
Following the workshop, further scientific studies were conducted to determine which flow releases protect the identified values. The studies included flora and fauna surveys, and a fish passage assessment undertaken during different flow scenarios. See more about these reports.
Videos of trial flow releases of 0.5, 1.5, 2.5 and 3 cumecs were recorded at a number of locations through the gorge to provide a visual assessment of flows.
The studies and videos will assist to evaluate and determine the most appropriate environmental flow for Cataract Gorge that also satisfies the values identified by stakeholders.
Discussions are currently underway with the Tasmanian Department of Primary Industry, Parks, Wildlife and Environment (DPIPWE) regarding the results of the flora surveys.