A year in the Macquarie–Castlereagh catchment: 2019–20

This bar chart and table provide a summary of 4583 megalitres of water for the environment use in the Macquarie–Castlereagh catchment during the 2019–20 watering year. Volumes are indicative only. Watering event numbers in the bar chart and table relate to location numbers marked on the map.

Watering event number	Location	Outcomes	Start date	Finish date
		1			Mid-Macquarie River supplementary flow		01 Dec 2019	01 Dec 2019

Relocation program

A collaborative partnership between the Department of Planning, Industry and Environment – Environment Energy and Science and the Department of Primary Industry – Fisheries tracked the persistence of water in 153 refuge pools between Warren and downstream of Marebone Weir. With rapidly declining pool numbers and water quality, a native fish and turtle rescue and relocation program occurred between September and October 2019. This unprecedented intervention secured a genetic insurance population of Murray cod and golden perch in hatcheries, and translocated freshwater turtles upstream.

Fish kill events

When rains returned to the Macquarie catchment in February 2020, the heavily sediment-laden runoff from a catchment with very low groundcover created two significant fish kill events due to hypoxic conditions (no, or low, oxygen in the water). Fish deaths were reported in the river from Wellington to Dubbo and downstream of Warren. No mitigation interventions were possible and thousands of mature fish and freshwater shrimp perished.

Potential for drought recovery

Since February 2020, there has been widespread ongoing rainfall and growing capacity for drought recovery actions leading into the 2020–21 water year. Many lessons have been learnt, including:

• managing risk over time with carryover – a 3-year plan was ineffective when dam operations do not secure water for meeting orders beyond 22 months
• as predominantly general security entitlement, the utility of current water for the environment assets to offset the effects of significant drought (during that drought) is limited
• the risk of fish kills following significant drought is very high, even in catchments where they do not typically occur.

The aims of the Macquarie–Castlereagh Catchment Annual Environmental Watering Priorities 2019–20 were achieved through what was a very dry year thanks to relief provided from natural river flows in early 2020.

In September 2019, as part of the drought response, flows in the Macquarie River were stopped at Warren to secure water for critical human needs.

With no flow in the river, 158 refuge pools below Warren weir began drying down, reducing available habitat, interrupting movement of water-dependent species and threatening the survival of resident wildlife.

The Department of Planning, Industry and Environment – Environment, Energy and Science (DPIE – EES) Water for the Environment Team worked with Department of Primary Industries – Fisheries (DPI – Fisheries) staff to identify longer lasting alternative habitat.

Together with volunteers, DPI – Fisheries focused on native fish relocations, while DPIE – EES turned their attention to the turtles.

Turtle relocation

The Macquarie River is home to 3 species of turtle – broad-shelled, Macquarie River and snake-necked turtles. Over 3 days 63 turtles were relocated to more reliable waterholes further upstream.

Species relocated included:

• 15 snake-necked turtles
• 5 Macquarie river turtles
• 43 broad-shelled turtles.

Since February 2020, the catchment has received significant rainfall and flows were restored to the river below Warren. DPIE – EES, the Environmental Water Advisory Group and the Commonwealth Environmental Water Holder will work together to consider drought recovery in the river system over the next few years, which should benefit turtle species.