Loddon River system (including Tullaroop, Serpentine and Pyramid creeks)

The Loddon River flows from the Great Dividing Range in the south to the Murray River in the north (Figure 5.7.1). The middle section of the Loddon River is characterised by many distributary streams and anabranches that carry water away from the river onto the floodplain. Pyramid Creek joins the lower Loddon River at Kerang, at which point the Loddon becomes part of the Murray River floodplain.

The two main storages on the Loddon River are Cairn Curran Reservoir and Tullaroop Reservoir. Laanecoorie Reservoir is a smaller storage used to regulate water released from the larger upstream storages. Flow in the Loddon River downstream of Laanecoorie Reservoir is regulated by the operation of the Bridgewater, Serpentine, Loddon and Kerang weirs.

Water for the environment can be delivered to the Loddon River from Cairn Curran or Tullaroop reservoirs or from the Goulburn system via the Waranga Western Channel, which intersects with the Loddon River at Loddon Weir. Water is provided to Pyramid Creek through releases from Kow (Ghow) Swamp, which receives water diverted from the Murray River at Torrumbarry Weir. Water is diverted from the Loddon River to the Loddon Valley Irrigation Area to supply agriculture and to Serpentine Creek to support environmental values and supply agriculture.

The highly regulated nature of the Loddon system provides challenges and opportunities for the effective management of water for the environment. The ability to manipulate the timing of releases at multiple locations can help achieve environmental outcomes at discrete locations. However, coordinating environmental and consumptive flows is difficult through the irrigation season, especially when irrigation demand is high or the flow in the river is highly variable. These issues can constrain the timing and delivery of water for the environment or lead to a flow that exceeds the recommended flow rates above Loddon Weir. The structures used for managing irrigation water also form barriers in the waterway that restrict native fish movement throughout the river and make it difficult to meet ecological objectives.

Proportion of water entitlements in the Loddon system held by private users, water corporations and environmental water holders on 30 June 2020

System map

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 Loddon River

Increase populations of small and large-bodied native fish

Provide habitat for fish to feed and breed and opportunities for movement between habitats

Enhance the channel form and features, including deep pools and benches

Maintain the condition of suitable substrate to maintain ecosystem processes

Engage flood runners, distributary channels, anabranches and backwaters

Increase the population and recruitment of resident platypus

Maintain a stable rakali (water rat) population in the long term

Maintain productive and dynamic food webs

Maintain the diversity and abundance of biofilms

Maintain the condition of streamside and floodplain vegetation

Maintain and increase the extent of in-stream vegetation

Maintain the diversity and abundance of waterbugs and waterbug functional feeding groups

Maintain water quality to support aquatic animals and minimise the occurrence of blackwater events

Environmental values

The Loddon River system supports platypus, rakali (water rats) and several species of native fish (such as Murray cod, golden perch, silver perch, river blackfish and Murray-Darling rainbowfish). Streamside vegetation varies in condition depending on the recent water regime, the extent of clearing and historic and current land management practices. The areas that remain relatively intact support a variety of woodland birds and other native animals. Important plant species across the system include cane grass, tangled lignum, black box and river red gum.

Although fish populations in the Loddon system are affected by the many barriers caused by weirs and reservoirs, a large range of species are still found through the catchment. Native fish are most abundant and diverse in the upper catchment. River blackfish are found in Serpentine Creek, and rare Murray-Darling rainbowfish are found in the middle and lower sections of the Loddon River.

The highest-priority reach for water for the environment is from Loddon Weir to Kerang Weir. The reach does not carry irrigation water, and it relies heavily on environmental flows to maintain its environmental condition. Environmental flows to this reach aim to maintain water quality, increase the abundance and diversity of native fish and improve the condition of streamside vegetation. Environmental flows are delivered to the upper Loddon River and Serpentine Creek to maintain or increase populations of river blackfish and platypus.

Pyramid Creek and the lower Loddon River support large-bodied fish (such as golden perch, Murray cod and silver perch) and are important corridors for fish migration between the Loddon and Murray systems. Engineering works to provide fish passage at the Chute, Box Creek regulator, Kerang Weir, Fish Point Weir and Little Murray Weir on the Little Murray River in recent years have been important in reopening these migration routes. The Arthur Rylah Institute has monitored fish movement and populations in Pyramid Creek and the lower Loddon River since 2017. The monitoring indicates that the combined flows in the lower Loddon River and Pyramid Creek are stimulating native fish movement through the fishways.

Traditional Owner cultural values and uses

The Dja Dja Wurrung Clans Aboriginal Corporation (trading as Djaara) are recognised as the Traditional Owners in the upper part of the Loddon catchment. The Barapa Barapa and Wamba Wemba people are recognised as Traditional Owners in the lower part of the catchment. There are artefacts of cultural practices throughout the Loddon and Pyramid system and its floodplain.

In planning for environmental flows in the Loddon River system, Djaara, Barapa Barapa, Wamba Wemba and North Central CMA have considered how environmental flows in the Loddon system can be managed to support their respective values, priorities and uses.

In the upper part of the catchment, the Djaara Kapa Gatjin (water advisory) Group and the North Central CMA work together to identify opportunities and sites where water for the environment can support Djaara’s aspirations for the Loddon River. A key aspiration is for Djaara to be more involved in the management and administering of environmental water, with the aim of future ownership and management of environmental water.

In August 2022, Dja Dja Wurrung Traditional Owners joined North Central CMA staff for a field visit to three sites along the Loddon River. Key points of discussion included the need to maintain a low river level for cultural burning and to support the growth of weaving plants, the need for restoration projects on creeks that flow into the Loddon, the need to inform Traditional Owners about inter-valley transfer trades and when water is leaving one Country and flowing into another, and the need for more water quality and ecological monitoring (including eDNA sampling and yabby surveys).

Dja Dja Wurrung Traditional Owners plan to undertake more field visits to conduct Cultural Values Assessments in the Loddon catchment. Djaara plans to develop a live and comprehensive report based on the assessments that will inform Loddon water management in the future, including seasonal watering proposals.

In early 2023, Barapa Barapa and Wamba Wemba Traditional Owners joined North Central CMA staff on Country to reflect on environmental water management in the Loddon River system in 2022-23 and to discuss aspirations for 2023-24.

Longstanding concerns were raised about constraints and limitations to delivering environmental water and, in the future, cultural water in the Loddon River system. Related to this, Barapa Barapa and Wamba Wemba Traditional Owners raised that private land tenure often creates impediments to floodplain watering and Traditional Owner restoration efforts on Country.

Building on 2021 discussions about the importance of water for the environment supporting native fish populations in summer, Barapa Barapa and Wamba Wemba Traditional Owners said they would like to be involved in projects and monitoring to investigate fish migration out of the lower Loddon River in response to poor water quality.

The impacts of a carp boom after the 2022 flooding in the Loddon River were also discussed. It was agreed that flow and habitat management (rather than manual control efforts) were more likely to reduce carp numbers in the long term in the Loddon River.

Barapa Barapa and Wamba Wemba Traditional Owners noted that the Loddon west arm at Canary Island contains significant cultural heritage, and they would like to see environmental flows continue to target this reach.

Barapa Barapa custodians have communicated their cultural objectives for the Loddon River and other waterways in the Barapa Barapa Healthy Country Plan 2018-2021. Objectives that relate to the Loddon River system include:

that all wetlands surrounding the Murray River, Gunbower Forest, Loddon River and associated lakes will have good plant life and healthy native fish (cod and yellow belly), mussels and turtle populations by 2033
by 2033, the Murray, Gunbower and Loddon rivers and associated lakes will have enough water, their water quality is improving, and the water will be clear for most of the year in good years
Barapa people are actively involved in water management
there are fewer fish and plant deaths from toxic blackwater events.

Social, recreational and economic values and uses

In planning the potential environmental watering actions in Table 5.7.1, the North Central CMA considered how environmental flows could support values and uses, including:

water-based recreation (such as fishing, powered and non-powered boating, water skiing and water sports)
riverside recreation and amenity (such as birdwatching, bushwalking, camping and cycling)
community events and tourism (such as water skiing competitions at Bridgewater and associated visitation)
socioeconomic benefits (such as diverters for domestic and stock uses, local and regional economic benefits from increased visitation and ecosystem services, including carbon storage, groundwater recharge and nutrient recycling).

If the timing or management of planned environmental flows may be modified to align with a community benefit, this is acknowledged in Table 5.7.1 with the following icon.

Watering planned to support water sports activities (e.g. water skiing)

If possible, North Central CMA will work with Goulburn-Murray Water to manage the delivery of low flow rates and the timing of freshes over summer/autumn to support optimum conditions for annual water skiing competitions at Bridgewater weir pool, where possible.

Scope of environmental watering

Table 5.7.1 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 objective(s) they support. Each environmental objective relies on one or more potential environmental watering actions and their associated physical or biological effects.

Table 5.7.1 Potential environmental watering actions, expected watering effects and associated environmental objectives for the Loddon River system

Potential environmental watering action	Expected watering effects	Environmental objective
Loddon River (targeting reach 4)
Winter/spring low flow (50-100 ML/day during June to November)¹	At 50 ML/day, a low flow will provide a minimum level of continuous flow through the reach and maintain water quality and adequate depth in pools to provide habitat for aquatic plants, waterbugs, fish and rakali (water rats) At 100 ML/day: increase the water depth for fish, platypus and rakali (water rat) dispersal (especially for male juvenile platypus) to colonise new breeding territory in winter and provide foraging habitat prevent silt and fine sediment from settling on submerged wood and other hard surfaces inundate a variety of habitats to increase the growth of biofilms and support waterbug productivity inundate native fringing bank vegetation to support seed germination and growth and prevent the encroachment of exotic terrestrial plants in the river channel
Winter/spring low flow trial (100-200 ML/day for one to 30 days during June to November, if triggered by an unregulated flow event)	Increased longitudinal connectivity by drowning out fish barriers to allow fish to access new habitats Inform future works to modify or remove fish barriers
Winter/spring high flow (one high flow of 400- 450 ML/day for 10 days during August to November)	Provide sufficient velocity to scour accumulated sediment from pools and scour biofilms, promoting the growth of new biofilms and increasing waterbug productivity Flush accumulated organic matter from the bank and benches to increase productivity and reduce the risk of a hypoxic blackwater event in summer Wet the banks to promote the recruitment and growth of streamside and emergent vegetation Stimulate native fish movement and breeding
Summer/autumn low flow (50 ML/day during December to May)²	Maintain an adequate depth in pools for aquatic plants and to provide habitat for waterbugs, fish and rakali (water rats) Provide a continuous flow through all reaches Maintain water quality throughout most of the reach, except the Loddon River west branch, during warm weather Wet the banks and shallow riffles to support the growth of in-stream and fringing non-woody vegetation
Summer/autumn low-flow trial (50-100 ML/day for six weeks during December to May)	Maintain water quality and mitigate against a hypoxic blackwater event in the Loddon River west branch Prevent the emigration of native fish species due to poor water quality
Summer/autumn freshes (three freshes of 100 ML/ day for three days during December to May)	Increase the water level to promote seed germination and the growth of fringing emergent macrophytes Increase connectivity between deep pools to promote the local movement of fish and prompt the dispersal of juvenile platypus in autumn Generate sufficient force to flush fine sediment and old biofilms from submerged wood and other hard surfaces, promoting the growth of new biofilms and increasing waterbug productivity Freshen water quality and reoxygenate pools
Autumn high flow (one high flow of 400 ML/day for six days³ during March to May)	Trigger and facilitate the upstream movement of golden perch, silver perch and Murray cod older than one year Facilitate the dispersal of juvenile platypus Generate sufficient force to flush fine sediment and old biofilms from submerged wood and other hard surfaces, promoting the growth of new biofilms and increasing waterbug productivity
Year-round fresh (trigger- based, 100-200 ML/day as required) Triggers: dissolved oxygen level is below 5 mg/L low or cease-to-flow river conditions high water temperatures	Destratify pools and improve water quality (increase oxygen levels) along the river in reach 4, ensuring there is adequate oxygen to support aquatic animals (such as native fish and platypus)
Pyramid Creek and Loddon River (targeting reach 5)
Year-round low flow (90-300 ML/day at Box Creek regulator)	At 90 ML/day, the low flow will maintain connectivity between pools, maintain water quality at a level that can support fish and macroinvertebrates and provide habitat for aquatic animals At 200 ML/day: increase longitudinal connectivity to allow native fish and platypus to access new habitats improve water quality by reducing salinity levels increase the wetted area to maintain and promote the growth of fringing emergent (non-woody) vegetation along the lower banks of the channel At 300 ML/day: facilitate greater movement for large-bodied native fish increase hydrodynamic diversity and improve the quality of flowing habitats
Winter/spring high flow (one high flow of 650 ML/ day at Kerang Weir for 10 days during August to November)⁴	Trigger the migration, spawning and recruitment of native fish species, including Murray cod Maintain connectivity between habitats and improve water quality Provide sufficient energy to flush accumulated sediment from pools and substrates
Autumn high flow (one high flow of 650 ML/day at Kerang Weir for 10 days³ during March to April)⁴	Trigger and facilitate the upstream movement of golden perch, silver perch and Murray cod older than one year Maintain connectivity between habitats and improve water quality Facilitate platypus dispersal Provide sufficient energy to flush accumulated sediment from pools and substrates
Serpentine Creek (targeting reach 1)⁵
Winter/spring low flow (10-30 ML/day⁶ during June to November)	At 10 ML/day, the low flow will maintain connectivity between pools to allow the dispersal of small to medium-bodied native fish provide a sufficient flow to maintain water quality by oxygenating pools maintain foraging habitat for platypus maintain the wetted area to support in-stream aquatic vegetation (such as water ribbons, eel weed and milfoil) At 20-30 ML/day: maintain habitat for larger native fish and facilitate movement for aquatic animals wet exposed roots, woody debris, emergent vegetation and leaf packs to provide habitat for aquatic animals inundates low benches, banks and some secondary channels, supporting increased macroinvertebrate productivity and native fish breeding, including river blackfish breeding provide flow variability to maintain the diversity of the fringing vegetation
Winter/spring fresh (one fresh of 40-120 ML/ day⁶ for two days during August to November)	Provide connectivity for fish and waterbugs to access different habitat areas, supporting a diversity of functional feeding groups Transport organic matter that has accumulated in the channel to facilitate its breakdown and incorporation into the foodweb, with a low risk of hypoxic blackwater Wet the banks to promote the recruitment and growth of streamside and emergent vegetation At 120 ML/day: maintain the channel form and scour pools encourage female platypus to select nesting burrows higher up the bank to reduce the risk of a greater flow later in the year flooding burrows with juveniles in them flush accumulated leaf litter from the banks and low benches to reduce the risk of blackwater events during summer
Summer/autumn low flow (10-20 ML/day⁶ during December to May)	At 10 ML/day: the low flow will provide connectivity between pools to allow the dispersal of small to medium-bodied native fish provide a sufficient flow to maintain water quality by oxygenating pools maintain foraging habitat for platypus maintain the wetted area to support in-stream aquatic vegetation (such as water ribbons, eel weed and milfoil) At 20 ML/day: maintain habitat for larger native fish and facilitate movement of aquatic fauna wet exposed roots, leaf packs and woody debris to provide habitat for aquatic animals
Summer/autumn freshes (three freshes of 40 ML/ day⁶ for two days during December to May)	Maintain the channel form by inundating benches Generate sufficient force to flush fine sediment and old biofilms from submerged wood and other hard surfaces, promoting the growth of new biofilms, increasing waterbug productivity and replenishing the food supply for aquatic animals Increase connectivity between pools to promote the local movement of fish and prompt the dispersal of juvenile platypus in autumn Provide flow variability to maintain the diversity of fringing vegetation (such as emergent macrophytes) Freshen the water to improve its quality by diluting salt, reoxygenating the water and flushing poor-quality water in pools, transporting accumulated nutrients and carbon downstream

¹ Winter/spring low flow of 50 ML per day is below the passing flow magnitude and will result in the VEWH banking passing flows savings for use in other potential watering actions.
² Under all scenarios, a 100 ML/day summer low flow rate may be trialled in January and February to mitigate hypoxic blackwater and prevent the emigration of native fish species.
³ The high flow of this event is planned to be delivered for six days, but there is an extended, 14-day ramp-down period.
⁴ Winter/spring and autumn freshes are planned to occur at the same time in the Loddon River and Pyramid Creek, with the peak timed to meet at Kerang Weir. 650 ML/day is the total combined target at Kerang Weir.
⁵ The flow in Serpentine Creek may be allowed to either return to the Loddon River or continue down Pennyroyal and Bannacher creeks or Nine Mile creeks with the agreement of landholders.
⁶ The flow delivered from Serpentine Weir may be restricted to manage end-of-system out falls to avoid third-party impacts until an alternate solution is determined.

Page last updated: 01/12/22