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Birchs Creek is part of the broader Bullarook system, which contains two small storages — Newlyn Reservoir and Hepburn Lagoon — that provide water for irrigation and urban supply. The storages fill and spill during winter or spring in years with average or above-average rainfall. The VEWH holds water for the environment in Newlyn Reservoir, but there is no water held in Hepburn Lagoon.

Birchs Creek receives tributary inflows from Rocky Lead, Langdons, Lawrence and Tourello creeks. Groundwater provides reliable baseflows to the downstream reaches of Birchs Creek in most years.

The VEWH is allocated 100 ML in Newlyn Reservoir on 1 December each year, provided that seasonal determinations in the Bullarook system are at least 20 percent. Any unused allocation from 1 December can be carried over until 30 November of the following water year, but if Newlyn Reservoir spills from 1 July to 30 November, the volume held in carryover is lost. Any water remaining on 30 November is forfeited. When seasonal determinations are below 20 percent, the VEWH does not receive an allocation, and the system’s resources are shared equitably to protect critical human and environmental needs.

Traditional Owners
Storage manager
Environmental water holder

Environmental watering objectives in Birchs Creek

Increase the abundance and diversity of small- and medium-bodied native fish, including river blackfish, mountain galaxias, flat-headed gudgeon and Australian smelt
Platypus icon
Increase the platypus population and improve its resilience to future droughts and floods

Provide surplus juvenile platypus that can disperse to Creswick and Tullaroop creeks
Plant icon
Maintain the diversity and increase the abundance of in-stream aquatic plants

Maintain a diverse variety of fringing and streamside native vegetation communities
Insect icon
Increase the population of waterbugs and the diversity of functional groups to drive productive and dynamic food webs
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Maintain water quality to support aquatic life and ecological processes

Environmental values

Birchs Creek supports threatened aquatic plants, and its deep pools provide habitat for aquatic animals during dry periods. The creek contains native fish, including regionally significant populations of river blackfish and mountain galaxias, as well as flat-headed gudgeon and Australian smelt. Recent monitoring indicates that platypus are present throughout the entire creek.

Anecdotal reports suggest the removal of willows along the creek in 2018 has improved in-stream vegetation and habitat for populations of small-bodied fish.

Traditional Owner cultural values and uses

In planning for environmental flows in Birchs Creek, Dja Dja Wurrung Clans Aboriginal Corporation (trading as DJAARA) and North Central CMA have identified the creek as a potential site for future projects.

The Dhelkunya Dja (Healing Country) Country Plan 2014-2034 describes their aspirations around the management of rivers and waterways and articulates Djaara’s (Dja Dja Wurrung peoples’) support for the reinstatement of environmental flows as an overall objective for the management of water on Country.

The North Central CMA and DJAARA continue to work towards increased engagement on planning and delivery of environmental watering activities, including identifying opportunities for Dja Dja Wurrung to play a greater role in the management and administering of environmental water.

Social, recreational and economic values and uses

In planning the potential watering actions in Table 5.7.5, North Central CMA considered how environmental flows could support values and uses, including:

  • water-based recreation (such as fishing)
  • riverside recreation and amenity (such as cycling and walking [particularly in Newlyn, Smeaton and Clunes] and improved amenity at key community spaces like Anderson’s Mill)
  • improved water quality (such as for domestic and stock use).

Recent conditions

Rainfall in the Birchs Creek catchment during 2021-22 was above the long-term average. Water for the environment allocated in December 2020 was carried over into 2021-22, but it was lost due to spills from Newlyn Reservoir through winter and spring in 2021. These spills produced three distinct high flows in the winter/spring period, with the largest event peaking at 447 ML per day at Smeaton in early September 2021. Another spill in January provided a large summer fresh that reached 254 ML per day at Smeaton. Seasonal determinations against high-reliability water shares in the Bullarook system opened at 40 percent allocation on 1 July 2021 and reached 100 percent allocation by mid-July. The VEWH was allocated the full 100 ML volume on 1 December 2021.

The Bullarook system was managed in line with an average climate scenario throughout 2021-22. All planned watering actions for the year were met or exceeded through natural flows, including groundwater baseflows, spills from storage and consumptive releases. The allocation from December 2021 will be carried over to support watering actions in 2022-23.

A census of platypus and river blackfish in Birchs Creek was undertaken in 2021-22 using environmental DNA. The methods replicated a survey conducted in 2015-16, and the results indicate that platypus and river blackfish have increased their distribution and are now present at more sites throughout the system. Platypus also appear to have dispersed into Creswick Creek and Tullaroop Creek.

Scope of environmental watering

Table 5.7.5 describes the potential environmental watering actions in 2022-23, their expected watering effects (that is, the intended physical or biological effects of the watering action) and the longer-term environmental objectives they support. Each environmental objective relies on one or more potential environmental watering actions and their associated physical or biological effects.

Table 5.7.5 Potential environmental watering actions, expected watering effects and associated environmental objectives for Birchs Creek

Potential environmental watering

Expected watering effects

Environmental objectives

Birchs Creek (targeting reach 2)1

Winter/spring fresh (one to four freshes of 27-30 ML/day for three to five days during June to November)

  • Maintain and support the growth and germination of streamside vegetation by increasing soil moisture and depositing sediment on the bank and benches
  • Scour old biofilms and organic matter that has accumulated in the channel, and cycle nutrients throughout the creek
  • Improve water quality by freshening refuge pools and provide connectivity between pools for fish and platypus movement
Fish iconPlant iconWater drop iconPlatypus iconInsect icon

Summer/autumn fresh(es) (one to four freshes of 10-15 ML/ day for three days during December to May)

  • Increase the water depth to maintain and support seed germination and the growth of in-stream aquatic vegetation
  • Improve the condition of riffle/run habitats for waterbugs
  • Top up pools to refresh water quality (particularly oxygen levels) and enhance connectivity between pools for fish and platypus movement
Fish iconPlant iconWater drop iconPlatypus iconInsect icon

1 Environmental flows target outcomes in reach 3, but compliance can only be assessed in reach 2.

Scenario planning

Table 5.7.4 outlines potential environmental watering and expected water use under a range of planning scenarios.

The highest-priority action in the Boort wetlands in 2022-23 under all climate scenarios will be to continue the partial fill at Lake Boort that commenced in autumn 2022. That watering action aims to trigger the growth of aquatic vegetation, including many species that are culturally important to Traditional Owners. Additional top-ups may be required to ensure fringing river red gums are sufficiently inundated to improve their condition after being dry for more than five years.

Watering Little Lake Meran is a priority under dry to wet scenarios in 2022-23. Little Lake Meran was last watered in 2019-20, and it then underwent a drying phase. Watering Little Lake Meran in winter and spring 2022 will likely trigger the germination of aquatic plants and initiate a productivity boom of zooplankton and macroinvertebrates that will provide food for frogs and waterbirds. Subsequent top-ups may be required throughout the year to water fringing trees that have been dry for three years and support potential waterbird and frog breeding events. Watering Little Lake Meran is not a priority under a drought scenario, as the lake and its associated vegetation community can withstand up to two more years before their maximum recommended dry period is exceeded.

Lake Leaghur may be partially filled in spring/summer or autumn/winter under average or wet climate scenarios. In the past decade, Lake Leaghur has had its minimum recommended watering regime and is currently in a rehabilitation phase. Delivering water for the environment in 2022-23 will build on environmental outcomes from its partial fill in autumn 2021. An ecological assessment will be conducted in spring 2022 to determine if Lake Leaghur needs to be watered this year and the best time to deliver water. The assessment will consider the wetland’s condition, expected climatic conditions over summer/ autumn and potential delivery constraints, including concurrent deliveries to other Boort wetlands and the Loddon River.

Filling Lake Leaghur is a low priority under drought and dry scenarios because the watering event in 2021 has maintained the minimum required watering regime.

Lake Yando may flood naturally under a wet climate scenario or receive flood mitigation water. If either of these things occurs, water for the environment may be used to top up the water level and/or extend the inundation period, to support waterbird breeding and allow wetland vegetation to complete their life cycles through spring and summer.

Lake Meran will be allowed to draw down during 2022-23 to support dry-phase ecosystem processes in accordance with the recommended water regime in the Meran Lakes Complex Environmental Water Management Plan.

Priority carryover requirements for 2023-24 focus on completing any watering actions that commence in autumn/winter 2023. A carryover target of 500 ML has been set under scenarios where Lake Leaghur is likely to be watered. The final carryover requirements will be revised during the year once the likely status of planned watering actions becomes clear.

Planning scenario table

Table 5.7.4 Potential environmental watering for the Boort wetlands under a range of planning scenarios

Planning scenario

Drought

Dry

Average

Wet

Expected conditions

  • No natural   inflow to wetlands
  • Minimal   natural inflow to wetlands from local catchment run-off is possible
  • Moderate   inflow from local catchment run- off,   but little if any inflow from nearby creeks or flood runners
  • Extended durations of high flow and overbank   flow from creeks and flood runners, which fill most wetlands

Expected availability of water for the environment1

  • 18,002-23,745 ML
  • 21,568 ML
  • 21,568 ML
  • 21,568 ML

Potential environmental watering – tier 1 (high priorities)

Tier 1a (can be achieved with predicted supply)

  • Lake Boort   (partial fill in winter/ spring,   top-ups as required)
  • Lake Boort   (partial fill in winter/ spring,   top-ups as required)
  • Little   Lake Meran (fill in winter/ spring, top-ups as required)
  • Lake Boort   (partial fill in winter/ spring,   top-ups as required)
  • Lake   Leaghur (partial fill in spring/   summer or autumn/ winter)
  • Little   Lake Meran (fill in winter/ spring, top-ups as required)
  • Lake Boort   (partial fill in winter/ spring,   top-ups as required)
  • Lake   Leaghur (partial fill in spring/   summer or autumn/ winter)
  • Little   Lake Meran (fill in winter/ spring, top-ups as required)

Tier 1b (supply deficit)

  • N/A
  • N/A
  • N/A
  • N/A

Potential environmental watering – tier 2 (additional priorities)

  • N/A
  • Lake   Leaghur (partial fill in spring/   summer or autumn/ winter)
  • N/A
  • Lake Yando   (top up if triggered)

Possible volume of water for the

environment required to achieve objectives

  • 5,000 ML (tier 1a)
  • 6,400 ML (tier 1a)
  • 600 ML (tier 1b)
  • 7,000 ML (tier 1a)
  • 6,800 ML (tier 1a)
  • 600 ML (tier 2)

Priority carryover requirements for 2023-24

  • N/A
  • 500 ML2
  • 500 ML2
  • 500 ML2

1 Loddon system entitlements are shared between the Loddon River system and the Boort wetlands.
2 Priority carryover of 500 ML is required for delivery to Lake Leaghur if the partial fill is delivered in autumn/winter 2023.

Engagement

Table 2 shows the partners and stakeholder organisations with which North Central CMA engaged when preparing their seasonal watering proposals.

Seasonal watering proposals are informed by longer-term regional catchment strategies, regional waterway strategies, environmental flow studies, water management plans and other studies. These incorporate a range of environmental, cultural, social and economic perspectives and longerterm integrated catchment and waterway management objectives. For further details, refer to the North Central Regional Catchment Strategy and North Central  Waterway Strategy.

Table 2 Partners and stakeholders engaged in developing the Loddon system seasonal watering proposal

Partner and stakeholder engagement
  • Goulburn- Murray Water
  • Department of Environment, Land, Water and Planning (land manager)
  • Individual landholders
  • Central Highlands Water

Page last updated: 01/07/22