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The Wimmera River commences in the Pyrenees Range near Elmhurst and receives flows from several tributaries including the MacKenzie River and the Mount William, Burnt and Bungalally creeks. All of these can receive environmental water, as can the Wimmera River downstream of lower Mount William Creek. Just east of Mt Arapiles the Wimmera River swings to the north and continues through Dimboola and Jeparit to Lake Hindmarsh, one of Victoria's largest freshwater lakes. During exceptionally wet periods, Lake Hindmarsh overflows into Outlet Creek and on to Lake Albacutya, an internationally recognised Ramsar-listed wetland extending to the Wirrengren Plain in the southern Mallee.

Water in the Wimmera system is stored in three on-stream reservoirs — Lake Wartook on the MacKenzie River, Lake Lonsdale on Mount William Creek and Lake Bellfield on Fyans Creek — and in several off-stream storages: Taylors Lake, Lake Fyans and Toolondo Reservoir. The channel system enables water movement between storages and from the Glenelg to the Wimmera system. Inter-basin transfers of water can occur from Rocklands Reservoir (in the Glenelg system) via the Rocklands–Toolondo Channel and from Moora Moora Reservoir via the Moora Channel to the Wimmera system. Water from the system is also delivered to towns and several Wimmera–Mallee wetlands in the Loddon, Avoca and Mallee catchments.

Passing flows are provided to the Wimmera River and to Mount William and Fyans creeks. Where possible, environmental water releases will be combined with passing flows, unregulated flows and the delivery of consumptive water en route, to optimise environmental outcomes.

Priority reaches for environmental watering in the Wimmera system are the Wimmera River reach 4, MacKenzie River reaches 2 and 3, upper and lower Mount William Creek, upper and lower Burnt Creek and Bungalally Creek, due to the range of environmental values they support (see below).

Yarriambiack Creek, a distributary of the upper Wimmera River, has historically received some flows during high-flow events in the Wimmera River. However, the creek now receives more flows due to modifications to the offtake. This reduces the effectiveness of environmental water deliveries to the high-priority reaches of the Wimmera River. In line with past practice during dry years, flows entering the creek may be blocked to ensure watering objectives in the Wimmera River are not compromised.

Storage manager
Environmental water holder

System map

Wimmera System
Grey river reaches have been included for context. The numbered reaches indicate where relevant environmental flow studies have been undertaken. Coloured reaches represent potential watering sites.

Environmental watering objectives in the Wimmera system

Fish icon
Restore, protect and boost diverse populations of native fish including one of Victoria’s few self-sustaining populations of freshwater catfish
Insect icon
Support communities of waterbugs which provide energy, break down dead organic matter and support the river’s food chain
Plant icon
Improve the condition, abundance and diversity of aquatic, emergent and riparian vegetation
Platypus icon
Provide flows to support platypus, maximising habitat in which they can rest, breed, feed and allow dispersal to other areas
Water icon
Maintain water quality to provide suitable conditions for fish and other water-dependent plants and animals

Environmental values

The Wimmera River and its tributaries boast a wide range of environmental and social values. The Wimmera system is home to many significant plants and animals including one of Victoria's few self-sustaining populations of freshwater catfish. It also contains self-sustaining endemic fish species including the flat-headed gudgeon and Australian smelt.

The MacKenzie River contains the only stable population of platypus in the Wimmera and also supports good populations of native fish, waterbugs, threatened Glenelg spiny crayfish and turtles. Particularly in dry times, it provides diverse habitat and refuge for these populations.

Protecting and restoring riparian plants is an environmental water objective for the Burnt and Bungalally creeks. Upper Burnt Creek contains important native fish and a population of threatened western swamp crayfish. Burnt Creek in particular provides habitat corridors for both aquatic and terrestrial species. Mount William Creek is a priority reach to assist in maintaining the creek's important populations of river blackfish, southern pygmy perch and threatened western swamp crayfish, in both the upper and lower sections.

Social and economic values

The Wimmera system offers many popular recreational activities including walking, boating, rowing, waterskiing, fishing and camping. It's also important for Wimmera residents in what is a very dry landscape. There are several events held on the rivers including the annual Kanamaroo Festival, the Horsham Triathlon, the Dimboola Rowing Regatta and the Horsham, Jeparit and Dimboola fishing competitions on the Wimmera River. The rivers in the Wimmera continue to be important for Traditional Owners and their Nations in the region.

Conditions mid-2016

This year the Wimmera had the driest inflows on record, with environmental water releases making up the majority of flows for the lower Wimmera River as well as other waterways during drier months. Allocations to May 2016 were low (16 percent) and there were no passing flows (water released from reservoirs to operate river and distribution systems and maintain environmental values and other community benefits) in the Wimmera. As a result, actions in 2015–16 relied heavily on environmental water carried over from 2014–15. Given the low water availability, the focus in 2015–16 was on maintaining water quality as much as possible, to maximise the habitat available for plants and animals in the dry climate by maintaining drought refuges.

With the limited water available, watering in the Wimmera started in October 2015 and was restricted to two freshes (small pulses of water) for the Wimmera River, one top-up for Mokepilly pool on upper Mount William Creek and summer/autumn baseflows (low flows) for the MacKenzie River, with some through-flows to upper Burnt Creek. There was not enough environmental water in 2015–16 to deliver flows to reach 3 of the MacKenzie River, the lower Wimmera River downstream of Dimboola Weir, lower Burnt Creek, Bungalally Creek or lower Mount William Creek.

Despite the dry conditions, fish in the Wimmera River are withstanding the stresses of drought with a good diversity found this year and evidence of catfish recruitment (when animals survive to settlement or maturity) over a series of years. The western swamp crayfish in Mt William Creek at Mokepilly is a notable discovery as well as the southern pygmy perch recruitment there in 2015. Recent bird surveys have found a high diversity of birds along the lower Wimmera River indicating the importance of providing open water and habitat in the dry landscape.

While environmental flow targets were not achieved due to the limited water, the releases helped maintain water quality and habitat for aquatic animals. In March 2016, an adult male platypus and a juvenile female platypus were found in the MacKenzie River, indicating the continued growth of the platypus population in this river.

Scope of environmental watering

Table 1 Potential environmental watering actions and objectives for the Wimmera system

Potential environmental watering

Environmental objectives

Wimmera River (reach 4)

Summer/autumn baseflows (15 ML/day or natural in December–May)1

  • Maintain edge habitats in deeper pools and runs, and shallow water habitat availability for waterbugs and native fish from the local area
  • Maintain near-permanent inundated stream channel for riparian vegetation and to prevent excessive in-stream terrestrial species growth

Winter/spring baseflows (30 ML/day in June–November)

  • Provide flows variability to maintain diversity of habitats

Summer/autumn freshes (1–3 freshes of 70 ML/day for 2–7 days in December–May)

  • Provide variable flows during low-flow season for waterbugs, fish movement and to maintain water quality and diversity of habitat

Winter/spring freshes (1–5 freshes of 70 ML/day for 1–4 days in June–November)

  • Increase the baseflow water depth to provide stimulus for fish movement
  • Provide flow variability to maintain water quality and diversity of fish habitats

Moderate winter/spring freshes (1–3 freshes of 200 ML/day for 1–3 days in June–November2)

  • Wet lower benches, entraining organic debris and promoting diversity of habitat

Higher winter/spring freshes (1–2 freshes of up to 1,300 ML/day for 2–3 days in June–November)

  • Flush surface sediments from hard substrates to support waterbugs
  • Wet higher benches, entraining organic debris and promoting diversity of habitat

MacKenzie River (reach 2 and 3)

Year-round baseflows (of 2–27 ML/day or natural, year-round)1

  • Maintain edge habitats and deeper pools and runs for waterbugs
  • Maintain inundated stream channel to protect and restore riparian and floodplain vegetation communities (including the Wimmera bottlebrush) and support aquatic vegetation for fish habitat
  • Maintain sufficient area of pool habitat for intact fish communities and shallow water habitats for small-bodied fish
  • Facilitate annual dispersal of juvenile platypus into the Wimmera River

Summer/autumn freshes (3–4 freshes of 5–50 ML/day for 2–7 days each in December–May)

  • Provide variable flows during low-flow season for waterbugs, for fish movement and to maintain water quality and diversity of habitat

Winter/spring freshes (5 freshes of 35–55 ML/day for 2–7 days in June–November)

  • Stimulate fish movement and maintain water quality and habitat diversity

Higher winter/spring freshes (1–5 freshes of up to 130–190 ML/day for 1–4 days in June–November)

  • Stimulate fish movement and maintain water quality
  • Flush surface sediments from hard substrates to support waterbugs
  • Wet higher benches, entraining organic debris and promoting diversity of habitat

Burnt Creek

Year-round baseflows targeting upper Burnt Creek (1 ML/day or natural, year-round)1

  • Maintain edge habitats and deeper pools and runs for waterbugs
  • Maintain inundated stream channel to protect and mimic riparian and floodplain vegetation communities and prevent excessive streambed colonisation by terrestrial vegetation species
  • Maintain sufficient area of pool habitat for intact fish communities and shallow water habitats for small-bodied fish

Summer/autumn freshes targeting upper Burnt Creek (3 freshes of 30 ML/day for 2–7 days each in December–May)

  • Prevent decline in water quality by flushing pools during low flows

Winter/spring freshes targeting upper Burnt Creek (1–5 freshes of 55 ML/day for 3–7 days in June–November)

  • Provide variable flows for fish movement and diversity of habitat
  • Flush surface sediments from hard substrates for waterbugs

Higher winter/spring freshes targeting upper Burnt Creek (1–3 freshes of up to 160 ML/day for 1–3 days in June–November)

  • Disturb biofilms present on rocks or woody debris to support waterbugs

Year-round fresh targeting lower Burnt Creek (1 fresh of 45 ML/day or natural for 2 days at any time)

  • Inundate riparian vegetation to maintain condition and facilitate recruitment
  • Entrain organic debris in the channel to support waterbugs
  • Maintain structural integrity of channel

High-flow fresh targeting lower Burnt Creek (1 fresh of 90 ML/day for 1 day in August–November)

  • Inundate floodplain vegetation to maintain condition and facilitate recruitment
  • Entrain organic debris from the floodplain to support waterbugs
  • Maintain floodplain geomorphic features

Mount William Creek

Top-up of upper Mount William Creek pools

  • Maintain habitat for native fish and waterbugs

Year-round baseflows targeting lower Mount William Creek (5 ML/day or natural, year-round) 1

  • Maintain edge habitats and shallow water habitat for waterbugs and endemic fish
  • Maintain inundated stream channel to protect and restore riparian and floodplain vegetation communities and prevent excessive streambed colonisation by terrestrial vegetation species

Summer/autumn freshes targeting lower Mount William Creek (3 freshes of 20–30 ML/day for 2–7 days in December–May)

  • Prevent decline in water quality by flushing pools during low flows
  • Provide variable flows during low-flow season for waterbugs, for fish movement and to maintain water quality and diversity of habitat

Winter/spring freshes targeting lower Mount William Creek (1–5 freshes of up to 100 ML/day for 1–7 days in June–November)

  • Wet benches, entrain organic debris and promote habitat diversity
  • Flush surface sediments from hard substrates to support waterbugs

Higher winter/spring freshes targeting lower Mount William Creek (1–3 freshes of up to 500 ML/day for 1–3 days in June–November)

  • Wet highest benches, entrain organic debris and promote habitat diversity

Bungalally Creek

Year-round fresh (1 fresh of 60 ML/day for 2 days at any time)

  • Inundate riparian zone to maintain condition and facilitate recruitment for riparian vegetation communities
  • Maintain structural integrity of channel and prevent loss of channel capacity

1 Cease-to-flow events occur naturally in the Wimmera system and may be actively managed. In the most recent flow study, the recommendation is that cease-to-flow events should occur as infrequently as possible and not exceed the duration of events that might have occurred naturally, to reduce stress on environmental values. Cease-to-flow events should be followed with a fresh lasting at least seven days.

2 Dependent on catchment conditions, the timing of this fresh may vary to optimise environmental outcomes.

A study exploring the feasibility of creating a refuge pool in an anabranch of the Wimmera River near Jeparit Weir is now underway. Once the study is complete, the site may be considered as an additional potential environmental watering action.

Scenario planning

It is unlikely that there will be enough environmental water to deliver most potential environmental watering actions in 2016–17. Tier 1 watering actions represent those able to be delivered with the available water. Tier 2 watering actions include the water required to meet the remaining actions recommended by the scientific flow study under different climatic scenarios. While the actions are similar in each climatic scenario, the magnitude, duration and/or frequency differ between scenarios: therefore the volume required under each scenario also differs.

Due to the prolonged dry conditions in the region and associated low flows, water quality is likely to remain poor. This poses risks to aquatic species. Environmental water will help to minimise but not completely mitigate these risks. Under most scenarios, there will likely be periods of cease-to-flow. The priority is to protect water quality and refuge pools in rivers and creeks to ensure habitat is available for native fish and other animals (such as platypus) during the warmer months (when risks are highest). Winter watering will only be possible if there are significant inflows and allocations in the early part of the water year.

Dry conditions can limit the opportunity to deliver some environmental watering actions due to infrastructure constraints or water quality issues in the Wimmera. For example, opportunities to deliver environmental water to lower Mount William Creek are restricted under dry conditions because Lake Lonsdale is expected to remain empty, as was the case at the start of 2016–17. The Wimmera Catchment Management Authority and the Victorian Environmental Water Holder will work closely with GWMWater to maximise environmental outcomes within the constraints posed by dry conditions.

If wet conditions eventuate, the priority will be increasing the magnitude, frequency and duration of watering and provide flows in the winter/spring period. Natural river flows and passing flows are also likely to contribute to achieving these objectives. Reserving water to carry over into the 2017–18 water year will also be a priority if wetter conditions eventuate.

Table 2 Potential environmental watering for the Wimmera system under a range of scenarios

Planning scenario

Extreme drought

Drought

Dry

Average

Wet

Expected availability of environmental water entitlements 1

  • 6,334 ML carryover
  • 5,000 ML VEWH
  • 0 ML CEWH2
  • 11,334 ML total3
  • 6,334 ML carryover
  • 7,839 ML VEWH
  • 0 ML CEWH2
  • 14,173 ML total3
  • 6,334 ML carryover
  • 17,979 ML VEWH
  • 0 ML CEWH2
  • 24,313 ML total3
  • 6,334 ML carryover
  • 30,553 ML VEWH
  • 0 ML CEWH2
  • 36,887 ML total3
  • 6,334 ML carryover
  • 45,560 ML VEWH
  • 0 ML CEWH2
  • 51,894 ML total3

Expected river conditions

No passing or unregulated flows

No passing or unregulated flows

Restricted passing and no unregulated flows

Some passing and unregulated flows particularly in winter/spring

Some passing flows and unregulated flows

Potential environmental watering – tier 1 (highest priorities)4

MacKenzie River reaches 2 & 3

  •  Summer/autumn freshes
  • Winter/spring freshes
  • Summer/autumn freshes
  • Winter/spring freshes
  • Summer/autumn freshes and baseflows
  • Winter/spring freshes and baseflows
  • Summer/autumn freshes and baseflows
  • Winter/spring freshes and baseflows
  • Summer/autumn freshes and baseflows
  • Winter/spring freshes and baseflows

Wimmera River reach 4

  • Summer/autumn freshes
  • Winter/spring freshes
  • Summer/autumn freshes
  • Winter/spring freshes
  • Winter/spring freshes
  • Summer/autumn freshes and baseflows
  • Winter/spring freshes and baseflows
  • Winter/spring freshes and baseflows summer/autumn freshes and baseflows
  • Summer/autumn freshes and baseflows
  • Winter/spring freshes and baseflows

Upper Burnt Creek

  • Summer/autumn freshes
  • Winter/spring freshes
  • Summer/autumn freshes
  • Winter/spring freshes
  • Summer/autumn freshes and baseflows
  • Winter/spring freshes and baseflows
  • Summer/autumn freshes and baseflows
  • Winter/spring freshes and baseflows
Summer/autumn freshes and baseflows

Upper Mt William Creek

  • Pool top-ups
  • Pool top-ups
  • Pool top-ups
  • Pool top-ups



N/A

Lower Burnt Creek





  • Winter/spring freshes and baseflows

Bungalally Creek





  • Fresh any time of year

Potential environmental watering – tier 2 (additional priorities)

MacKenzie River reaches 2 & 3

  • Summer/autumn freshes and  baseflows
  • Winter/spring freshes and baseflows
  • Summer/autumn freshes and baseflows
  • Winter/spring freshes and baseflows
  • Summer/autumn freshes and baseflows
  • Winter/spring freshes and baseflows
  • Winter/spring freshes and baseflows

N/A

Wimmera River reach 4

  • Summer/autumn freshes and baseflows
  • Winter/spring freshes and baseflows
  • Winter/spring moderate freshes
  • Summer/autumn freshes and baseflows
  • Winter/spring freshes and baseflows
  • Winter/spring moderate freshes
  • Summer/autumn freshes and baseflows
  • Winter/spring freshes and baseflows
  • Winter/spring moderate freshes
  • Winter/spring higher freshes
  • Summer/autumn freshes and baseflows
  • Winter/spring freshes and baseflows
  • Winter/spring moderate freshes
  • Winter/spring higher freshes
  • Summer/autumn freshes and baseflows
  • Winter/spring freshes and baseflows
  • Winter/spring moderate freshes
  • Winter/spring higher freshes

Upper Burnt Creek

  • Summer/autumn freshes and baseflows
  • Winter/spring freshes and baseflows
  • Summer/autumn freshes and baseflows
  • Winter/spring freshes and baseflows
  • Summer/autumn freshes and baseflows
  • Winter/spring freshes and baseflows
  • Winter/spring higher freshes
  • Summer/autumn freshes and baseflows
  • Winter/spring freshes and baseflows
  • Winter/spring higher freshes
  • Summer/autumn freshes and baseflows
  • Winter/spring freshes and baseflows
  • Winter/spring higher freshes

Upper Mt William Creek

  • Pool top-ups
  • Pool top-ups
  • Pool top-ups
  • Pool top-ups
  • Pool top-ups

Lower Mount William Creek

  • Year-round baseflows
  • Summer/autumn freshes
  • Winter/spring freshes
  • Year-round baseflows
  • Summer/autumn freshes
  • Winter/spring freshes
  • Year-round baseflows
  • Summer/autumn freshes
  • Winter/spring freshes
  • Winter/spring higher freshes
  • Year-round baseflows
  • Summer/autumn freshes
  • Winter/spring freshes
  • Winter/spring higher freshes
  • Year-round baseflows
  • Summer/autumn freshes
  • Winter/spring freshes
  • Winter/spring higher freshes

Lower Burnt Creek




  • Fresh any time of year
  • Fresh any time of year
  • August–November high flow fresh

Bungalally Creek




  • Fresh any time of year
  • Fresh any time of year

Possible volume of environmental water required to achieve objectives5

  • 5,667 ML (tier 1)
  • 36,570 ML (tier 2)
  • 7,087 ML (tier 1)
  • 40,143 ML (tier 2)
  • 12,157 ML (tier 1)
  • 46,666 ML (tier 2)
  • 18,443 ML (tier 1)
  • 40,480 ML (tier 2)
  • 25,947 ML (tier 1)
  • 41,766 ML (tier 2)

1 Environmental water in the Wimmera–Glenelg system is shared between the Glenelg and Wimmera systems. The volumes specified show the likely availability across the shared systems and include 5,000 ML of allocation expected to be available through trade in 2016–17.

2Commonwealth environmental water is only available for use in the Wimmera system.

3 This volume is a forecast of the total water likely to be available under the VEWH entitlement in 2015–16, including carryover water and the forecast allocation for the complete water year. The forecast opening allocation for each climate scenario is 0 ML under all scenarios, meaning the only water available is likely to be carryover water of about 6,300 ML at the start of the water year.

4 As the entitlement is shared between the Wimmera and Glenelg catchments, planning for tier 1 for each CMA has included a simplifying assumption that half of the expected allocations will be available to each CMA. A prioritisation process will be undertaken in consultation with the Wimmera and Glenelg Hopkins CMAs to determine the potential watering actions that will be undertaken in each system in the 2016–17 year.

5 Environmental water requirements for tier 2 actions are additional to tier 1 requirements.

Risk management

In preparing its seasonal watering proposal, Wimmera Catchment Management Authority considered and assessed risks and identified mitigating strategies relating to implementing environmental watering. Risks and mitigating actions are continually reassessed by program partners throughout the water year.

Engagement

Waterway managers meet communities on environmental watering regionally, although other program partners also play a role.

In each region of Victoria, community engagement on environmental watering happens when environmental watering objectives and priorities are scoped (long term and annually), when delivering environmental water, and when reporting on environmental watering results.

In the Wimmera region communities are involved in decisions about the Wimmera and MacKenzie rivers, Mount William creek, Burnt creek, Bungallaly creek and some of the wetlands on the Wimmera-Mallee pipeline. This happens through direct engagement on an as needed, issues basis.

Who is engaged and how

Recreational users

Recreational user representatives are engaged by the Wimmera Catchment Management Authority through direct engagement on an issues basis. During drought periods in particular, the Catchment Management Authority holds meetings with recreational user groups. Recreational users are updated on planned environmental water deliveries. The Catchment Management Authority also regularly engages with recreational users through Facebook, web, SMS and media releases.

Environment groups

The main way that environmental groups are engaged on environmental watering is through opportunistic Catchment Management Authority attendance at Yarriambiack Creek Advisory Committee meetings. A Catchment Management Authority representative provides updates on environmental water scoping and delivery at these meetings. Meetings with other environmental groups are on an as needs basis.

An environmental advocate sits on the Catchment Management Authority rivers and streams advisory committee (which is engaged on natural resources management matters more broadly).

Landholders/farmers

Landholders are updated by the Catchment Management Authority on environmental water planning (scoping) and delivery. Landholders are notified by phone calls and emails and SMS during the delivery phase.

Landholders provide feedback on the outcomes of environmental watering such as photographs and observations of birds and frogs. The Catchment Management Authority attends relevant community events (including Wimmera Machinery Field Days) to raise awareness about the benefits of environmental watering.

Landholders sit on the Catchment Management Authority rivers and streams advisory committee (which is engaged on natural resources management matters more broadly).

Traditional Owners

The Barengi Gadjin Local Land Council has participated in the development of the Catchment Management Authority regional waterway strategy. These strategies identify the rivers and wetlands of the highest environmental, social, cultural and economic values in the Wimmera region.

The Catchment Management Authority and the Land Council meet on a regular basis to discuss natural resource management matters more broadly.

Councils

Horsham and Hindmarsh Councils are regularly engaged by the Catchment Management Authority. As these two Councils are the managers of weirs from which environmental water is managed, the Catchment Management Authority discusses planned environmental watering with them to assist weir management (specifically to assist aims of reducing water losses and achieving 'shared benefits' such as timing environmental watering around community events). Northern Grampians Council and Yarriambiack Council are also engaged on environmental watering on an as-needs basis.

General public

The Catchment Management Authority engages with the general public on environmental watering via SMS, their website, Facebook, and media releases.

The Catchment Management Authority conducted a community survey on waterway values and observations related to environmental watering.