Oral Presentation 9th Australian Stream Management Conference 2018

When to break the habit: Adapting the FLOWS method for use in the highly modified Lower Broken Creek (#22)

Lisa Duncan 1 , Simon Treadwell 2 , Daniel Lovell 3
  1. Jacobs, Tatura
  2. Jacobs, Melbourne
  3. Goulburn Broken Catchment Management Authority, Shepparton

The Broken Creek in Northern Victoria extends from its confluence with the Broken River near Benalla to its mouth at the Murray River in Barmah Forest. The system was historically ephemeral and connected as a breakaway of the larger Broken River. Over 100 years of modification has seen the creek largely disconnected from the Broken River and changed into an irrigation and water supply network with 11 weirs constructed over the creek’s lower section. More than 100 kilometres of the creek are now a series of slow-flowing weir pools maintained at a near-constant level. The operation of the creek has reversed the natural flow regime so that it now flows at its highest in summer and lowest in winter. Although a highly modified environment, good native fish populations exist within the Broken Creek and weirs have fish passage. However, slow moving water, high nutrients, low dissolved oxygen and azolla outbreaks are all management challenges. The Goulburn Broken CMA developed interim environmental flow recommendations in 2008, mainly focussed around these key challenges. A full environmental flow study using the FLOWS methodology expanded on the interim flow recommendations and developed a full complement of environmental flow objectives and recommendations. A degree of flexibility is built in to the FLOWS method when determining environmental water requirements for Victoria’s waterways.  This flexibility proved invaluable during the Broken Creek study to address questions such as:

  • Which modelling method is used for static weir pools?
  • Can manipulate of weir pool levels to provide habitat variability?
  • How do we define and prepare ecological objectives and flow recommendations in such a modified system?

This project exemplifies the importance of adopting a flexible approach and explores the unique adaptations utilised employing the FLOWS method in highly modified creek environment.

  1. DEPI (2013) FLOWS - a method for determining environmental water requirements in Victoria, Edition 2. Report prepared by Sinclair Knight Merz, Peter Cottingham and Associates, DoDo Environmental and Griffith University for the Department of Environment and Primary Industries, Victoria
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