Oral Presentation Australian Freshwater Sciences Society Conference 2018

Learning from Commonwealth environmental flows in the lower Lachlan:  when no two years are the same. (#42)

Fiona Dyer 1 , Ben Broadhurst 1 , Ross Thompson 1 , Alica Tschierschke 1 , Joanne Lenehan 2 , Jason Thiem 3 , Sharon Bowen 4 , Patrick Driver 5 , Ebony Mullin 6 , Damian McRae 6
  1. Institute for Applied Ecology, Faculty of Science and Technology, University of Canberra, ACT, Australia
  2. Regional Operations and Heritage Group, Office of Environment and Heritage, Cowra, NSW, Australia
  3. DPI Fisheries, Department of Industry, Department of Primary Industries, Narrandera, NSW, Australia
  4. University of Technology, Sydney, NSW, Australia
  5. Water Branch, NSW Department of Industry, Orange, NSW, Australia
  6. Commonwealth Environmental Water Office, Department of the Environment and Energy, Canberra, ACT, Australia

The lower Lachlan river system is one of seven selected areas monitored as part of the Commonwealth Government’s Long Term Intervention Monitoring (LTIM) program. The hydrology of the lower Lachlan is highly variable and unpredictable. In the four years of monitoring the lower Lachlan has experienced vastly different climate, river flow conditions and environmental water deliveries. In the first year of monitoring (2014-15) conditions were dry and a small watering action was delivered to achieve modest environmental outcomes. In 2015-16, greater availability of water enabled the delivery of three watering actions designed to achieve a broad suite of environmental outcomes. These were accompanied by translucent flows (planned environmental water) which provided water into a number of dry or drying wetlands. In 2016-17, widespread flooding across the Lachlan river system meant environmental water use was limited and focused on the protection of vulnerable populations, including supporting bird breeding. In the fourth year (2017-18) Commonwealth environmental water was used to support the recovery of native fish populations which had been adversely affected by blackwater associated with the 2016-18 flooding. The observed responses to natural flood events and translucent flows were far greater than those achieved with purchased environmental water. Environmental watering in the Lachlan has been successful in achieving modest site-based outcomes that differ on a yearly basis which clearly reflects the relative volumes of water used and a targeted delivery approach. In systems such as the lower Lachlan river system that experience highly variable flows, understanding the ecological significance of small and moderate sized flow events remains a challenge. Addressing this will help better optimize the use of environmental water for ecological outcomes.