Tarago River

The Tarago River rises in the Tarago State Forest and flows into the Tarago Reservoir at Neerim. The reservoir harvests inflows from all upstream tributaries to supply towns on the Mornington Peninsula and around the Western Port area, and it is also used to manage flows for downstream irrigators. Below the reservoir, the river flows close to the town of Rokeby before meeting the Bunyip River at Longwarry North. From there, the Bunyip River flows through a modified, straightened channel — Bunyip Main Drain — that discharges into Western Port. The Bunyip Main Drain supplies many irrigators in the catchment.

Water available under the Tarago environmental entitlement is stored in and released from Tarago Reservoir. This water is primarily used to meet environmental objectives in reach 2, which is between the reservoir and the confluence of the Tarago and Bunyip rivers, as seen in the system map below. Water for the environment that is delivered to reach 2 also supports environmental flow recommendations in reach 6 (Bunyip Main Drain).

Year-round passing flows in the Bunyip and Tarago rivers are stipulated under both the environmental entitlement and Melbourne Water’s bulk entitlement. These passing flows are generally sufficient to meet the minimum lowflow requirements in summer/autumn, but are much less than the recommended minimum flows in winter/ spring; and do not provide any of the freshes or higher flows that are needed throughout the year to support environmental outcomes.

Water releases to meet irrigation demands create variable flow patterns in the Tarago and Bunyip rivers throughout the year. The magnitude and timing of these releases can influence environmental outcomes, and Melbourne Water continues to work with Southern Rural Water to optimise the shared value derived from irrigation releases.

System map

Tarago System — Grey river reaches have been included for context. The numbered reaches indicate where relevant environmental flow studies have been undertaken. Coloured reaches can receive environmental water.

Environmental watering objectives in the Tarago River

Increase populations of native fish including threatened species (such as the Australian grayling)

Maintain channel form and structure

Increase platypus populations

Increase native streamside and aquatic plant communities on the riverbank and in the channel

Increase the diversity and biomass of waterbugs, to support aquatic foodwebs

Environmental values

The Tarago system contains several significant and threatened native plant and animal species including Australian grayling, long pink-bells, tree geebung and swamp bush-pea. The upper catchment (reach 2) has healthy streamside vegetation and diverse in- stream habitat that supports platypus and native fish including river blackfish and mountain galaxias. The lower catchment (reach 6) has been highly modified, but it still contains patches of remnant vegetation and healthy populations of Australian grayling and platypus.

Recent conditions

The Tarago River catchment received below-average rainfall in winter 2019 but above-average rainfall in spring 2019 and summer 2020. Most of the rain fell downstream of the Tarago Reservoir, so although it provided natural flow in the river it did not translate to significant inflows into the storage.

Winter/spring high flows, winter/spring freshes, spring high flow and autumn high flow requirements and most of the recommended summer/autumn freshes were met from natural flows. Summer/autumn freshes were the highestpriority potential watering actions for all scenarios in 2019– 20; they play a critical role in providing habitat for native fish species (such as short-finned eels and common galaxias) and maintaining water quality throughout the system.

A volume of 1,000 ML of water for the environment will be carried over to help meet critical priorities in 2020–21.

Traditional Owner cultural values and uses

Melbourne Water has made initial contact with Boon Wurrung Foundation, Bunurong Land Council Aboriginal Corporation and Wurundjeri Woi Wurrung Cultural Heritage Aboriginal Corporation, to discuss environmental watering in the Tarago/Bunyip system.

Social, recreational and economic values and uses

If the timing or management of planned environmental flows may be modified to align with a community benefit, this is acknowledged in Table 1 with an icon.

Watering planned to support peaks in visitation (e.g. camping or other public activities on long weekends or school holidays)

Melbourne Water may time a summer fresh in the Tarago River to occur on the long weekends in January or March 2020, so visitors and long-term residents of the Glen Crombie Caravan Park alongside the river can enjoy the additional flows in the river.

Scope of environmental planning

Table 1 Potential environmental watering actions and objectives for the Tarago River

Potential environmental watering action	Functional watering objective	Environmental objective
Summer/autumn fresh (one to five freshes of 75 ML/day for two days during December to May)	Scour sediment from holes and around large woody debris to maintain habitat for native fish in low-flow periods Allow the localised movement of native fish Prevent terrestrial vegetation growth on sandbars Maintain water quality by aeration in times of low flow
Autumn high flow (one fresh with a peak of 100 ML/day for two days in a minimum seven-day duration during April to May)	Form and maintain scour holes around large wood Cue spawning for diadromous fish (e.g. Australian grayling) Allow the downstream movement of Australian grayling Assist the dispersal of juvenile platypus
Spring high flow (two to three high flows with a peak of 200–300 ML/day for two days in a seven-to-10 day duration during September to October)	Form and maintain scour holes around large wood Prevent the encroachment of terrestrial vegetation into the channel Cue the upstream migration of juvenile diadromous fish (such as Australian grayling) from the sea or estuary into the river Wet higher benches to maintain the fringing aquatic vegetation and ensure vertical zonation of the fringing vegetation Provide a cue for platypus to select nesting burrows above high water level
Winter/spring fresh (one to two freshes with a peak of 100–200 ML/day for two days during June to September)	Prevent sediment build-up and remove biofilm from large woody debris to maintain habitat for macroinvertebrates and fish including river blackfish Maintain access to habitats by ensuring sufficient depth through riffles to allow fish movement between pools and reaches Cue the downstream migration of species such as eel and tupong Wet the banks, wetting the lower benches to maintain the fringing aquatic vegetation
Winter/spring low flow (75 ML/day [or natural] during June to November)	Prevent the encroachment of terrestrial vegetation in the channel Wet the banks to promote streamside vegetation growth Maintain an adequate depth through riffles to allow access to habitats for fish and platypus Maintain water quality through increased low flows to flush the system and wet additional habitat for fish and macroinvertebrates Maintain foraging habitat for platypus

Engagement

Table 2 shows the partners and stakeholder organisations with which Melbourne Water engaged when preparing the Tarago system seasonal watering proposal.

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 Port Phillip and Western Port Regional Catchment Strategy and Melbourne Water's Healthy Waterways Strategy.

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

Partner and stakeholder engagement
Friends of Robin Hood Reserve Waterwatch co-ordinators Department of Environment, Land, Water and Planning \| Water and Catchments Melbourne Water Service Delivery Parks Victoria Southern Rural Water Baw Baw Shire Council Cardinia Shire Council Environment Protection Authority Port Phillip and Westernport Catchment Management Authority Individual landholders Glen Cromie Caravan Park Local Anglers VRFish Melbourne University – research collaborators Monash University Arthur Rylah Institute (Department of Environment, Land, Water and Planning Boon Wurrung Foundation Bunurong Land Council Aboriginal Corporation Wurundjeri Woi-Wurrung Cultural Heritage Aboriginal Corporation

Partner and stakeholder engagement

Friends of Robin Hood Reserve
Waterwatch co-ordinators
Department of Environment, Land, Water and Planning | Water and Catchments
Melbourne Water Service Delivery
Parks Victoria
Southern Rural Water
Baw Baw Shire Council
Cardinia Shire Council
Environment Protection Authority
Port Phillip and Westernport Catchment Management Authority
Individual landholders
Glen Cromie Caravan Park
Local Anglers
VRFish
Melbourne University – research collaborators
Monash University Arthur Rylah Institute (Department of Environment, Land, Water and Planning
Boon Wurrung Foundation
Bunurong Land Council Aboriginal Corporation
Wurundjeri Woi-Wurrung Cultural Heritage Aboriginal Corporation

Page last updated: 22/01/21