Wetland ecosystems (palustrine) (pages 42-44)

There are 29 ANAE palustrine wetland types in the Basin, with 15 of the most common representing 99% of the total Basin wetland area. The managed floodplain contains 39% of Basin wetland area, comprised of the same 15 common types in similar proportions to the whole of the Basin. The palustrine wetlands on the managed floodplain, in scope for Commonwealth environmental water, are therefore qualitatively representative of palustrine wetlands in the Basin.

In the 9 years 2014–23, Commonwealth environmental water supported 125,743 ha of palustrine wetland of 21 different ANAE wetland types figure below.

Between 32,666 ha (2014–15) and 79,955 ha (2022–23) were watered in any one year (average 63,585 ha), with 15 wetland types (4,181 ha combined) receiving Commonwealth environmental water in every year. 8 wetland types did not receive any Commonwealth environmental water (values exclude the CLLMM). Including the CLLMM adds another 19,000 ha supported by Commonwealth environmental water (mostly fringing marshes and unvegetated depressions around lakes.

Temporary river red gum swamp was the wetland type with the largest area supported by Commonwealth environmental water over the 9 years (37,781 ha). Most of this area was inundated in seven of the nine years since 2014–15, corresponding to the years the Barmah–Millewa Forest received an allocation from the Commonwealth. Temporary river red gum swamp is an ecosystem type that is commonly supported by environmental water, due to its proximity and connectedness to lowland river channels. Fringing river red gums and swamps that are connected to waterways often receive water during channel freshes or weir pool raising actions, in addition to actions that specifically target overbank flooding. For example, weir pool raising at Locks 7–9 on the Murray River floods river red gum swamps and anabranches around Lindsay, Wallpolla and Mulcra islands.

Ecosystem types that did not receive Commonwealth water at all over nine years included 14,241 ha of saline systems (salt flats, saline wetlands and salt marsh) for which freshwater additions could be detrimental, and 187 ha of ecosystems that are consistently wet, and perhaps not in need of supplementary water (permanent springs, paperbark swamps, peat bogs and fen marshes).

The proportion of palustrine wetland types supported by Commonwealth environmental water was similar across all 9 years, with 3 notable exceptions:

• There was reduced watering of temporary river redgum swamp in 2014–15 and 2016–17, when Commonwealth environmental water was not used to inundate the river red gum dominated Barmah–Millewa Forest (The Living Murray Program delivered environmental water to Barmah–Millewa in these 2 years).
• Watering of temporary tall emergent marsh and freshwater meadow was lowest in 2019–20, when there were no significant overbank flows in the Gwydir Wetlands and Macquarie Marshes.
• There was no watering of permanent tall emergent marsh in 2016–17 due to widespread natural flooding. Note that 2022–23 was also a year with widespread natural flooding; however, in this year, tall marshes in the Macquarie Marshes and Gwydir Wetlands received Commonwealth environmental water to extend the flood duration, to support waterbird breeding.

Floodplain ecosystems (pages 44-46)

Approximately 28% of floodplains in the Basin align with the managed floodplain, and all 12 Basin floodplain ANAE types are represented there. The most common floodplain ecosystem types in the Basin (coolibah woodland and black box woodland floodplains) occur higher on the floodplain away from rivers, with only 24% of coolibah woodland floodplain and 17% of black box woodland floodplain located on the managed floodplain. In contrast, river red gum has a higher water requirement and is found lower on the valley floors closer to rivers, leading to a higher proportion of Basin river red gum (49%) being located on the managed floodplain. Despite these differences, the floodplain types located on the managed floodplain are representative of Basin floodplains.

Limited water volumes and policies to avoid inundating built assets or agricultural land often constrain Commonwealth environmental water to in-channel flows and watering of floodplain wetlands through regulators, and connecting channels rather than by overbank flooding. On average, from 2014–15 to 2020–21, only 3% of the managed floodplain received Commonwealth environmental water in any one year (area of all ANAE floodplain types). In 2021–2022 and 2022–23, Commonwealth environmental water was delivered to the Macquarie Marshes, Gwydir Wetlands, Narran Lakes and Lowbidgee to support the maintenance of water at waterbird breeding rookeries that formed in response to extensive natural flooding. As a result, the extent of floodplain supported by Commonwealth environmental actions in the most recent 2 years (2021–23) was higher than in any previous year (average 72,947 ha, 5% of the managed floodplain) (Figure below). Over the 9-year period of monitoring, 187,416 ha of floodplains (187,486 ha including the CLLMM), comprising 12% of the managed floodplain, was inundated by Commonwealth environmental water at least once.

River red gum forest riparian zone/floodplain was inundated by Commonwealth environmental water to the greatest extent, with 71,356 ha inundated over the 9 years at varying frequencies, representing 22% of this ecosystem type on the managed floodplain (Figure below). River red gum forest and woodland floodplain types comprised between 32% and 82% of the floodplain area inundated in any one year over the last 9 years. This reflects the proximity of river red gum ecosystems to river channels, and the high value of river red gum in priority assets (e.g. Barmah–Millewa Forest, the Lowbidgee floodplain and Macquarie Marshes).

The pattern of watering across years, seen in the Figure below, reveals some contrasts. The 2 years with the least floodplain inundation were 2016–17 and 2019–20: 2016–17 was a very wet year where watering of floodplains by Commonwealth environmental water was not seen as a priority; 2019–20 was the driest year on record and available Commonwealth environmental water was directed to supporting base flows, with only 2 of 155 planned watering actions targeting overbank flows. The 2021–23 period was also very wet, but unlike 2016–17, there was extensive use of Commonwealth environmental water to support completion of waterbird breeding in late summer, after winter rains reduced.

River ecosystems (pages 46-48)

The managed floodplain contains 11% of the total river length in the Basin. This includes 76% of the total length of permanent lowland rivers in the Basin, and 24% of the temporary lowland river length. On the managed floodplain, lowland rivers dominate representing 86% of the 53,542 km total river length that is estimated to be in scope for water management (47% temporary lowland rivers and 39% permanent lowland rivers). With such a high proportion of these river types present on the managed floodplain, it is likely these ecosystems are representative of the other lowland rivers in the Basins. The 6 transitional and upland stream ecosystem types on the managed floodplain (7,485 km, 14%) are generally high-energy outflow channels from storages, before they flow out into the flat lowlands of the central and western Basin.

Commonwealth environmental water primarily supports permanent and temporary lowland rivers, with 97% of flow delivery in any one year being in lowland reaches. At the Basin scale in 2014–23, the annual allocation to river flows was very consistent, with 14,102 km up to 22,211 km of waterways potentially benefiting from Commonwealth environmental water annually (Figure below).

Over the 9-year period, 27,715 km of river was supported by Commonwealth environmental water (52% of all the river length on the managed floodplain), with 35% (9,609 km) watered in every year along permanent lowland sections of the Barwon, Macquarie, Gwydir, Lachlan, Murrumbidgee, Edward/Kolety–Wakool, Murray, Ovens, Broken, Goulburn and Loddon rivers. Permanent reaches in the lowland sections of the Bokhara, Culgoa, Darling and Campaspe rivers, and the smaller upland, transitional Severn River, received Commonwealth environmental water in 8 of the 9 years. Some temporary rivers have also received water in 7–8 of the years: Gunbower Creek, Tuppal Creek, the Moonie River, and the lower end of the Warrego River.

The upland and transitional streams that received Commonwealth environmental water were mostly outflows from storages into the upper reaches of the King, Lachlan, Gwydir, Severn and Dumaresq rivers. However, there were some unregulated flows managed by water licence rules – in the Severn River above Glenlyon Dam (7 in 9 years) and in the upper Warrego River (5 in 9 years).

Barmah Forest (pages 55-57)

Barmah Forest Ramsar Site received Commonwealth environmental water in 7 of the 9 years 2014–23. During the 2 years that Commonwealth environmental water was not delivered, there were 2 natural floods in 2014–15, and ‘other’ environmental water (state and MDBA’s Living Murray Program) was used to inundate the site in 2016–17. The annual flooding is thought to mimic the natural regime for the site, as high winter–spring flows are constricted by the narrow channel of the Barmah choke, causing river water to back up and divert through channels in the floodplain. It is estimated that under pre-regulation scenarios, the site would have naturally flooded in 19 of the past 20 years. The extensive inundation in 2021–22 is the result of a large environmental water allocation of 414 GL (including 220 GL of Commonwealth environmental water) that was delivered to the site when it was already 45% inundated by naturally occurring high flows.

The Ecological character description (ECD) for the Barmah Forest Ramsar Site notes that, at the time of listing, the hydrological regime may have been insufficient to maintain the character of the site in the long term, emphasising that regular managed inundation by environmental water in dry periods is critical to maintaining and restoring the site.

Fivebough and Tuckerbil Swamps (pages 57-58)

Fivebough and Tuckerbil Swamps Ramsar Site received Commonwealth environmental water in 4 of the 9 years 2014–23. Fivebough Swamp is a permanent shallow wetland that was ‘topped up’ after 2 dry years in 2018–19 and 2020–21 using Commonwealth environmental water, to support its value as a significant waterbird drought refuge and waterbird feeding and breeding site. Tuckerbil Swamp is a brackish, seasonal shallow wetland maintained by Commonwealth environmental water more frequently (4 of the last 9 years) to support migratory waterbirds and threatened waterbird species, including brolga (Grus rubicunda), Australasian bittern (Botaurus poiciloptilus) and Australian painted snipe (Rostratula australis). The swamps were inundated by natural flooding in 2022–23.

Gunbower Forest (pages 58-59)

Commonwealth environmental water has been used in Gunbower Creek annually since 2015–16 to maintain native fish habitat and breeding. Gunbower Creek flows into the northern end of the Ramsar Site and regulators permit watering of adjacent wetlands. The Ramsar critical CPS include the ongoing presence of Murray cod (Maccullochella peelii peelii) and silver perch (Bidyanus bidyanus) in Gunbower Creek, and small-bodied fish in wetlands within the Ramsar Site, including Australian smelt (Retropinna semoni), carp gudgeons (Hypseleotris spp.), dwarf flat-headed gudgeon (Philypnodon macrostomus), flat-headed gudgeon (Philypnodon grandiceps), fly-specked hardyhead (Craterocephalus stercusmuscarum), and Murray-Darling rainbowfish (Melanotaenia fluviatilis). The Ramsar critical CPS for Gunbower Forest also include waterbird breeding and maintaining the extent and condition of river red gum floodplain, but these have not been objectives for Commonwealth environmental water during the monitoring period 2014–23.

Wetland inundation by environmental water has not been mapped at this site, but occurred in 2021–22 within some smaller wetlands connected to Gunbower Creek in the northern end of the site.

Gwydir Wetlands: Gingham and Lower Gwydir (Big Leather) Watercourses (pages 51-52)

The Gwydir Wetlands: Gingham and Lower Gwydir (Big Leather) Watercourses Ramsar Site received Commonwealth environmental water in 8 of the 9 years 2014–23. The exception in 2019–20 was when flows were constrained to the channel to protect river assets after 3 successive years of dry conditions. In early 2020, there was above average rainfall that provided a natural water source to revive the cooch grass meadows, and high flows have been maintained keeping the wetlands inundated from May 2021 – March 2023. In these wet years, Commonwealth environmental water was used to extend the duration of inundation over summer to keep water in waterbird nesting and foraging habitats until summer breeding was completed. The Ramsar Site consists of 4 isolated sub-units with Commonwealth environmental water primarily supporting Goddard’s Lease and Old Dromana, to support freshwater meadows dominated by water cooch and areas of tall marsh. The Gwydir River System Selected Area reports in detail on the outcomes from Commonwealth environmental water management at this site. This site does not have an ECD that defines the critical CPS.

Hattah–Kulkyne Lakes (pages 59-60)

In recent history, Hattah Lakes would connect to the Murray River via Chalka Creek when flows in the Murray River at Euston exceeded 36,700 ML/day. The ecological character of the site is now highly dependent on managed environmental water. Construction of a permanent pump station, regulators and environmental levees were completed as part of The Living Murray Program in 2014–15, when LTIM monitoring began. The pump infrastructure was used to deliver Commonwealth environmental water in 4 of the 9 years 2014–23. Watering ceased in 2019–20, to begin a planned ‘dry phase’. Recent reporting from The Living Murray Program indicates the lakes were dry in 2022–23. In the intervening years of 2016–17 and 2018–19, the floodplain was watered with contributions from The Living Murray. Mapping of other sources of environmental water in LTIM was not considered reliable or sufficiently comprehensive, and was discontinued in Flow-MER. Expanding the scope of this evaluation to include all water is recommended to provide a more accurate characterisation of the hydrological regime and, therefore, the contribution of Commonwealth environmental water as part of that regime. The lakes were partially filled in 2021 by Victorian environmental water aligned to high natural flows in the Murray River, and they drained back to the Murray over the summer. During winter and spring 2022, Victorian environmental water was delivered to the lakes, which were then flooded naturally by a flood event that was the largest since 1956 and estimated to have inundated 16,842 ha, compared to the 6,000 ha that can be inundated with environmental water alone.

Macquarie Marshes (pages 53-54)

Commonwealth environmental water contributed (along with jurisdictional water) to inundation of the Macquarie Marshes Ramsar Site, in 8 of the 9 years 2014–23. No inundation is shown for 2019–20. However, in this period approximately 4 GL of Commonwealth environmental water was accessed through supplementary licences on the Macquarie River, allowing some in-channel flows to replenish refuge pools and flow through to the marshes. Extensive inundation in 2022–23 was the result of watering actions following natural flooding events, to maintain waterbird breeding rookeries and provide waterbird foraging habitat.

Water management in the Macquarie Marshes is typically planned and executed for the larger extent of the marshes, and not just the 3 units that make up the Ramsar Site. Much of the southern marsh that is regularly inundated by Commonwealth environmental water is outside of the Ramsar Site boundary.

The Ramsar critical CPS for the site include indicators that are the focus of much of the jurisdictional monitoring, including the extent of tall marsh, lignum and river red gum, waterbird counts, and aggregate waterbird breeding.

Narran Lake Nature Reserve (Narran Lakes) (pages 52-53)

The Narran Lake Nature Reserve Ramsar Site received Commonwealth environmental water in 5 of the 9 years 2014–23. Substantial inundation of lignum floodplain in 2019–20 has been followed up with water allocations in 2020–23 to improve lignum health and build resilience in the system, to support waterbird breeding and recruitment. Significant natural flows in the 2021–22 and 2022–23 years have maintained inundation at the site. Supporting regular breeding of aggregate-nesting waterbirds (in no less than 1 in 9 years) is listed as a critical service that characterises this site. Waterbird breeding commenced at the site after natural flooding in 2021–22, and again in 2022–23.Commonwealth environmental water was used to maintain water at rookeries through to the end of summer to provide breeding habitat and foraging areas for juveniles.

NSW Central Murray Forests (Koondrook and Werai forests) (pages 61-62)

The NSW Central Murray Forests Ramsar Site received Commonwealth environmental water in 7 of the 9 years 2014–23. The site consists of 3 large river red gum forest groups: Millewa, Koondrook–Perricoota and Werai. The majority of environmental water is delivered via the Murray River, typically inundating approximately 4,000 ha or more of the Millewa section in conjunction with the Barmah Forest Ramsar Site on the opposite bank of the Murray River. In 2022–23, 214 GL (including 145 GL of Commonwealth environmental water) was delivered via the Murray when the site was already inundated by naturally occurring high flows resulting in 5,189 ha or 17% of the Millewa block being inundated. In 2016–17, the Barmah and Millewa sites were watered with 155 GL from The Living Murray Program to provide the annual inundation cycle for both the Barmah and Millewa forests combined.

Wholesale inundation of the Millewa group is likely to contribute to the maintenance of the ecological character of the site. The ECD for the site defines ecological character at large spatial scales, based on the current measured extent of marshes and river red gum forest in each of the forest blocks. For example, there should always be more than 20,000 ha of river red gum forest in the Millewa group, and loss of forest extent would represent a change in character. Hydrological requirements defining the character of the site are defined using recurrence intervals of floods in the Murray River. For example, maintaining channels and low-lying areas in the Millewa group requires a minimum of 5 high flows of more than 12,500 ML/day for 70-day durations downstream of Yarrawonga in any 10-year period.

Outside of the Barmah–Millewa, Commonwealth environmental water was only used at Pollock Swamp in the Koondrook group, a 700 ha nature reserve at the western end of the Ramsar Site (approximately 1% of the Ramsar Site area). A new program commenced annual pumping from the Murray in 2018–19, with 2–3.5 GL of Commonwealth environmental water released to restore approximately 100 ha of shallow wallaby grass and river red gum swamp. This project is likely to have successful outcomes, but, at this local scale, is a small contribution towards maintaining the ecological character of the Ramsar Site where critical CPS are defined at much larger scales. The remainder of the extensive Koondrook Forest Group (34,524 ha) and the Werai Forest Group (11,421 ha) have not received Commonwealth environmental water since monitoring began in 2014.

Riverland (pages 62-63)

The Riverland Ramsar Site received Commonwealth environmental water in all 9 years 2014–23, inundating the site to varying degrees. The site is a large floodplain of the Murray River that includes the Chowilla and Calperum wetlands, and has many interconnecting channels and anabranches. Water is managed strategically through regulators and pumping to protect waterbird habitat and water-dependent vegetation, including stands of black box higher on the floodplain. The ECD defines hydrological character by the water requirements of different wetland types, which align to the Basin ANAE mapping, to use in evaluating the contribution of environmental water to maintenance of the Ramsar Site ecological character. For example, the bar chart below shows that Commonwealth environmental water is supporting a high diversity of ecosystem types at the site and appears to be used to protect the more permanent habitats, with larger areas of inundation of permanent wetland, permanent lake, permanent saline wetland and the permanent lowland river (the Murray River).

The Coorong, and Lakes Alexandrina and Albert Wetland (pages 64-65)

The Coorong, and Lakes Alexandrina and Albert Wetland Ramsar Site received Commonwealth environmental water in all 9 years, either as allocations or end-of-system flows. Some attempts were made during LTIM to model changes in the large lake area in response to the relatively small quantities of environmental water received. However, the models were not sensitive enough to detect changes in inundation of wetland habitat that fringes the lakes. Flow-MER therefore uses the same inundated extent to represent the CLLMM in every year, and the composition of CLLMM ecosystem types supported by Commonwealth environmental water is mostly static, except for some small fringing areas that receive targeted allocations of water. For example, there was environmental watering of the Tolderol Game Reserve 2019–20 and 2020–21, and the Milang Snipe Sanctuary 2016–17 to 2021–22, to support migratory waders.