Native Vegetation
Over the past nine years, we’ve been monitoring and evaluating how water for the environment supports the Murray–Darling Basin’s unique, diverse, and iconic vegetation. Here, we share the key insights and lessons learned to inform future water management and ecological planning.
Image: Swamp buttercup (Rununculus inundatus), a species that usually requires flooding for more than 3 months per year, but can survive periods of damp and drying ground.
Flows for vegetation
Over the past nine years, Commonwealth water for the environment has played a vital role in maintaining healthy plant life across the floodplains and wetlands of the Murray–Darling Basin. Our research has identified five distinct groups of vegetation, each associated with different inundation regimes, three of which are largely the result of environmental watering. These wetter regimes have sustained a richer variety of vegetation, particularly submerged, amphibious, and damp-loving species that would struggle to persist under naturally drier conditions. Even in 2022–23, a year with high rainfall and unregulated flows, sites that received water for the environment continued to show more abundant submerged and amphibious plant life compared to drier areas. That year also highlighted the limits of some species’ tolerance to prolonged inundation, with the lowest number of plant species recorded in the nine-year program
Since monitoring began in 2014, 790 plant taxa have been recorded across various sites, including 520 native species. Notably, 79 species were only found in areas that received water for the environment, including several culturally significant plants used by First Nations people. Our overall monitoring to date shows that water for the environment is essential. It increases plant diversity, supports culturally and ecologically important species, and builds wetland and floodplain resilience, thereby reducing the risk of long-term ecological decline.
Note: The contents on this page includes summarised text from the following report: 2022-23 Basin-scale evaluation of Commonwealth environmental water – reports and supporting documents – DCCEEW. Page number references have been noted throughout the content below for anyone using the full report.
Our approach
To understand the impact of Commonwealth water for the environment on groundcover diversity in the Murray–Darling Basin, we used a counterfactual modelling approach. In simple terms, this meant comparing the plants that were observed at 73 floodplain and wetland sites over 9 years of monitoring, to the plants that were expected to be present at these sites without environmental water. This approach was basedon the relationship between inundation regimes (how often, how long, and how variably sites were flooded). This allowed us to compare vegetation outcomes with and without water for the environment, focusing on both species richness and the structure of plant communities. We paid particular attention to functional plant groups like submerged, amphibious, and damp-loving species, which are especially influenced by water availability.
The analysis brought together data from two major programs: the Long-Term Intervention Monitoring Project (2014–2019) and the Flow-MER Program (2019 to now). These programs track(ed) how vegetation responds across a range of water regimes, shaped by both natural flows and water delivered specifically for environmental purposes. While the study zeroed in on floodplain and wetland vegetation (rather than in-channel systems), it offers a meaningful picture of how environmental water supports the structural and functional diversity of plant communities across the Basin. We also made a point to highlight plants that are rare, threatened, or culturally significant, particularly those known to be used by First Nations peoples.
What have we learned?
In 2022-2023, we used the inundation history at each of the 73 floodplain and wetland sample points to identify 5 unique inundation groups using a statistical approach called clustering (see below). Inundation Groups 1 to 5 represent a gradient of flooding frequency and duration, from near-permanent inundation to infrequent wetting events. Over the 9 years of monitoring, these groups showed that hydrological regimes strongly influence vegetation structure and function.
This was the most frequently inundated group of sample points, with nearly permanent inundation since 2014 (82% of quarters), consisted of 10 sample points from the Murrumbidgee River System and 4 from the Lachlan River System (pg 16). Sample points in Group 1 were inundated on average for a little over 2 years, with an average maximum inundation event (longest flood) since 2014 of 4 years (pg 13).
Sample points from Inundation Group 2 were inundated in 50% of quarters for an average of 9 months and had an (average) maximum inundation duration (longest flood) of 2 years (pg 13).
Inundation Group 2 had an average dry phase of around 9 months, and anaverage maximum dry phase of a little over 1.5 years.
Inundation Group 2 consisted of 14 sample points all from the Gwydir River System (pg 16)
Group 3 were inundated slightly less frequently than Group 2 (42% of quarters) over the 9 year period, and had a lower average flood duration and (average) maximum flood duration (longest flood) (pg 14). Inundation Group 3 consisted of 6 sample points from the Gwydir River System (pg 16).
Inundation Group 4 was characterised by prolonged dry phases (average duration of dry phase of nearly21 months, and an average maximum dry phase of 3.5 years) and, once flooded, these sample pointsremained inundated for at least one year (pg 14). Inundation Group 4 consisted of 28 sample points of which 25 were from the Lachlan River System, one (Old Dramana Nursery-2) from Gwydir River System, and 2 from the Murrumbidgee River System (Avalon Swamp and McKenna’s Lagoon) (pg 16)
Inundation Group 5 had the driest inundation history of the inundation groups, only inundated in 20% of quarters over the 9-year period. The sample points in Inundation Group 5 were inundated infrequently (every 2 to 3 years) and remained inundated for 6 months on average. Inundation Group 5 consisted of 11 sample points (pg 14), of which 8 were from the Junction of the Warrego and Darling rivers, and 3 were from the Lachlan River System (pg 16)
As the cluster diagram and graphs show, different inundation regimes support distinct plant communities over time.
- Inundation Group 1 are the wettest areas and are dominated by aquatic and amphibious plants like spike rushes, red water fern, and water primrose. Few terrestrial or woody species are found here.
- Inundation Group 2 are areas that flood nearly every year, supporting species like water couch, narrow-leaved typha, and flat spike sedge—plants that thrive in regularly wet conditions.
- Inundation Group 3 is characterised by a mix of terrestrial and amphibious species, including black roly poly, mimosa bush and the flat spike sedge, reflecting moderately dry conditions and less frequent inundation.
- Inundation Groups 4 and 5 are characterised by drought-tolerant species, including the woody flood-dependent tangled lignum and a variety of terrestrial and short-lived species that respond to rainfall.
Importantly, 12 plant species traditionally used by First Nations people, including fibre and food plants, were found only in wetter groups (1–3). These species depend on regular flooding and would likely disappear without environmental water releases (pg 18).
The implications of these findings is that maintaining appropriate inundation regimes, by using environmental water, is critical to sustaining ecological diversity, culturally significant species, and the integrity of wetter wetland and floodplain habitats.
The counterfactual: without environmental water
The counterfactual modelling conducted as part of the evaluation demonstrates that, without Commonwealth environmental water, the vegetation condition and diversity across the Murray–Darling Basin would have been significantly degraded. Most monitored sample points (54 of 73) would have experienced a much drier inundation regime, most similar to Inundation Groups 4 and 5, that are characterised by infrequent or short-duration flooding. These groups support markedly less cover and diversity of water-dependent vegetation, such as submerged, amphibious, and damp-loving species.
In the absence of environmental water, nearly all sites currently in the wetter inundation Groups 1, 2, and 3 (which show greater biodiversity and unique functional assemblages) would have lost these features. Specifically, there would have been a near absence of submerged species and a substantial reduction in amphibious and damp-loving plants, which are unable to survive extended dry phases. For example, dry periods of 2 to 3.5 years—typical of Groups 4 and 5—exceed the tolerances of many key species like river ribbonweed (Vallisneria australis) and Cumbingi Typha spp., leading to their decline or local extinction. This shift would have led to:
- A homogenisation of vegetation communities, dominated by drought-tolerant terrestrial and woody flood-dependent species.
- A loss of unique vegetation structure and habitat complexity in both wetland and floodplain environments.
- A reduction in culturally significant plant species used by First Nations communities, many of which require regular or semi-regular inundation to persist.
In summary, without environmental water, the ecological integrity, functional diversity, and cultural value of the Basin’s floodplain and wetland vegetation communities would have been significantly diminished, with long-term implications for resilience and recovery potential (pg 21-22).
Functional group composition
Submerged
Species that either require permanent water in the root zone or those that live in the water column.
Amphibious
Species that either respond to, or tolerate, the presence of surface water. These species usually require flooding for more than 3 months per year, but can survive periods of damp and drying ground.
Damp
Species that germinate and establish on saturated or damp ground, but the adult plants don’t tolerate flooding. They grow on ground that has been flooded.
Woody Flood Dependent
Perennial trees or large shrubs that require flooding to complete part of their life cycle.
Terrestrial
Species with no flooding requirement.
Volume of Commonwealth water for the environment delivered to Murray-Darling Basin regions (2022-23)
In 2022–23, 68 out of 102 Commonwealth environmental watering actions were implemented for vegetation outcomes, delivering approximately 904 GL of water across 14 valleys in the Murray–Darling Basin. Despite being the third consecutive wet year, these watering actions played a key role in sustaining vegetation diversity and structure. Interestingly, the wet conditions led to the lowest number of taxa recorded since monitoring began, with the prolonged inundation exceeding the tolerance of many species. The greatest cover and proportion of native species were, however, observed in this period.
The delivery of water in 2022–23 continued to support distinct inundation regimes, particularly at sites in Inundation Groups 1–3, maintaining higher proportions of submerged and amphibious species. Even with widespread rainfall, it was evident that water for the environment helped maintain vegetation assemblages not supported by rainfall alone. Notably, 43 plant taxa used by First Nations people were recorded, 12 of which were found only at sites maintained under wetter regimes because of environmental watering. Click on different regions on the map to learn how the water was used, and the vegetation outcomes it was designed to achieve.
Volume of Commonwealth environmental water delivered: 48,279 ML
6 watering actions:
- Baseflows x 5
- Fresh x 1
Outcomes expected:
- Health of instream habitat
- Vegetation extent
- Vegetation condition
Volume of Commonwealth environmental water delivered: 1,072 ML
4 watering actions:
- Baseflows x 3
- Fresh x 1
Outcomes expected:
- Vegetation condition
- Seed germination
- Inundate habitat
Volume of Commonwealth environmental water delivered: 51,310 ML
1 watering actions:
- Fresh x 1
Outcomes expected:
- Vegetation condition
Volume of Commonwealth environmental water delivered: 113,253 ML
5 watering actions:
- Overbank/ Fresh x 5
Outcomes expected:
- Improve bird habitat
- Inundate habitat
Volume of Commonwealth environmental water delivered: 55,935 ML
19 watering actions:
- Baseflows x 12
- Wetland x 2
- Baseflow/ Fresh x 3
- Baseflow/ Fresh/ Overbank x 2
Outcomes expected:
- Vegetation condition
- Vegetation extent
- Health of instream habitat
- Restoration & recovery
Volume of Commonwealth environmental water delivered: 167,882 ML
3 watering actions:
- Baseflows x 2
- Fresh x 1
Outcomes expected:
- Health of instream habitat
- Recovery & restoration
Volume of Commonwealth environmental water delivered: 2,950 ML
1 watering actions:
- Wetland x 1
Outcomes expected:
- Vegetation extent
- Vegetation condition
Volume of Commonwealth environmental water delivered: 16,808 ML
3 watering actions:
- Wetland x 1
- Fresh x 2
Outcomes expected:
- Vegetation condition
- Vegetation extent
Volume of Commonwealth environmental water delivered: 3,356 ML
2 watering actions:
- Baseflows x 1
- Fresh x 1
Outcomes expected:
- Health of instream habitat
- Vegetation condition
- Vegetation extent
Volume of Commonwealth environmental water delivered: 148,432 ML
2 watering actions:
- Baseflows x 2
Outcomes expected:
- Vegetation extent
Volume of Commonwealth environmental water delivered: 162,292 ML
12 watering actions:
- Baseflows x 1
- Wetland x 8
- Baseflow/ Fresh x 1
Outcomes expected:
- Vegetation extent
- Vegetation condition
Volume of Commonwealth environmental water delivered: 10,244 ML
1 watering actions:
- Wetland x 1
Outcomes expected:
- Inundate habitat
Volume of Commonwealth environmental water delivered: 119,614 ML
6 watering actions:
- Wetland x 4
- Fresh x 2
Outcomes expected:
- Vegetation condition
- Vegetation extent
- Restoration & recovery
Volume of Commonwealth environmental water delivered: 5,823 ML
3 watering actions:
- Baseflows x 2
- Fresh x 1
Outcomes expected:
- Soil stabilisation
- Seed germination
- Regeneration
Watering Actions
Understanding vegetation outcomes
Water for the environment is used for a range of expected outcomes for vegetation. Learn more about these outcomes below, and use the dashboard above to see which vegetation outcomes were a focus for water use across the Murray-Darling Basin in 2022-23.
All page numbers relate to the Flow-MER Vegetation Basin Theme report, available at: 2022-23 Basin-scale evaluation of Commonwealth environmental water – reports and supporting documents – DCCEEW
Condition refers to the overall health or quality of vegetation. Although species richness declined due to persistent high water, native taxa proportion and cover remained stable over 9 years (~71–74% richness, ~79–96% cover). This suggests core ecological functions like productivity, habitat provision, and weed resistance are being maintained (p. 28).
Extent refers to the area occupied by vegetation. Over 9 years, the evaluation shows that without Commonwealth environmental water, key species assemblages would shrink significantly, leading to reduced vegetation richness, permanent shifts in community composition, and a substantial decline in the resilience of water-dependent plant communities (p. iv).
Natural regeneration is the natural regrowth of existing vegetation to replace plants which have died. We found that species that rely on periodic inundation for germination and growth, like nardoo, cumbingi, and spike rush, were more prevalent at sites with environmental water. This indicates regeneration and recruitment processes were supported at these locations (pg 37).
Germination is the process by which a plant grows from a seed into a seedling. Seeds tend to remain dormant until conditions are favourable for germination. Water for the environment has played a critial role in maintaining the soil seedbank and rhizomes so that these plant species could take advantage of wetter conditions (pg 29).
In-stream habitat describes aquatic vegetation, as well other components like wood and rock that maintain the health of a waterway. Noticeable differences were observed in 2022–23 vegetation assemblages at sites with wetter inundation regimes supported by environmental water, helping maintain key components of aquatic habitat (p. v).
Saline soils are those that contains enough soluble salt to adversely affect the growth of plants and prevent them from regenerating. In 2022–23 no vegetation monitoring was conducted in the Lower Murray River because of inaccessibility due to flooding – it is this Selected Area that is known to be more prone to salinity impacts (pg 26).
We examine how water for the environment can prevent the death and/or decreasing condition of vegetation.
The roots of vegetation maintain plant root mass, which helps to limit erosion, improve soil stability and contributes to soil fertility.
Our work identifies specific plant species that provide adequate cover and protection for bird nests and help provide a food source.
Restoration and recovery include improving the health of existing vegetation. Environmental water is preventing the loss of characteristic wetland and floodplain plants by maintaining wetter hydrological regimes which helps maintain biodiversity across the Basin (pg 6).
Resilience describes the ability for vegetation to recover after a decline. Without water for the environment, vegetation community richness would decline, increasing the risk of permanent shifts to altered assemblages and reducing the resilience of water-dependent plant communities (p. iv).
Inundate habitat is the delivery of water to inundate instream and/or riparian habitat. Commonwealth water for the environment has maintained distinct inundation regimes, delivering water to allow submerged and amphibious species to persist and thrive even after prolonged natural flooding. (pg. iv)
What does this mean for water managers?
The 2022–2023 Basin-scale vegetation evaluation provides clear evidence that environmental water continues to play a critical role in sustaining ecological function and biodiversity across the Murray–Darling Basin. Despite a third consecutive wet year, the evaluation highlights that managed water remains essential to maintain vegetation health, extent, and diversity—particularly in floodplain and wetland environments. The following messages summarise the most important insights from the evaluation to guide environmental water planning and management:
Environmental water is critical to maintaining diverse and functional vegetation
Without Commonwealth environmental water, most sites would have experienced much drier regimes, with significant losses of submerged, amphibious, and damp-loving species (pg 6)..
Distinct inundation regimes are essential to ecological outcomes
Vegetation responses and ecological outcomes differ among sites due to variation in watering regimes (Inundation Groups 1–5), each supporting different vegetation communities and maintaining diversity across wetland and floodplain habitats (pg. 13).
Environmental water delivers cultural and biodiversity benefits
In 2022–23, 43 Aboriginal-use plant species were recorded, including 12 only found at sites maintained by environmental water—demonstrating its role in supporting cultural values and biodiversity (pg 28).
Watering remains essential even in wet years
Despite natural flooding, distinct vegetation patterns persisted at sites that received environmental water, which buffered against over-inundation impacts and maintained functional vegetation (pp. v).
Monitoring and adaptive management should continue to evolve
There is a need to improve inundation modelling, refining vegetation sampling, and incorporating additional indicators to better evaluate environmental outcomes and guide water planning (pg 38).
Meeting Basin plan objectives
The Basin Plan sets out a framework to protect, restore and manage the water-dependent ecosystems of the Murray–Darling Basin. It outlines high-level environmental objectives in Section 8.04, supported by specific goals for the protection and restoration of ecosystems (Section 8.05) and their ecological functions (Section 8.06). These objectives guide the planning, delivery and evaluation of Commonwealth environmental water. The 2022–2023 vegetation evaluation demonstrates how environmental watering actions—both annual and cumulative over the past nine years—have made measurable contributions toward these objectives. The following points summarise how the use of Commonwealth environmental water has supported biodiversity, resilience, ecosystem processes, and cultural values across the Basin.
Protect and restore biodiversity, including plant species diversity.
From 2014 to 2023, Commonwealth environmental watering created and maintained distinct inundation regimes that supported diverse and functionally rich vegetation communities. Even after three wet years, greater diversity and cover of submerged, amphibious, and damp-loving species were consistently observed at sites supported by environmental water (p. 33).
Protect and restore diversity and ecological character of communities.
From 2014 to 2023, Commonwealth environmental watering created and maintained distinct inundation regimes that supported diverse and functionally rich vegetation communities. Even after three wet years, greater diversity and cover of submerged, amphibious, and damp-loving species were consistently observed at sites supported by environmental water (p. 33).
Ensure resilience to climate change and other risks.
The consistent delivery of environmental water has helped maintain seedbanks, vegetative propagules, and favourable hydrological conditions required for plant survival and recovery. This prevents irreversible transitions to dryland vegetation and supports long-term resilience of water-dependent ecosystems (pp. 33).
Protect and restore ecosystem functions that support water-dependent ecosystems.
Environmental watering enhanced regeneration, bank stability, and aquatic habitat quality, contributing to ecosystem function across riparian and wetland environments. (pg 33-34).
Basin Plan Objective: Recognise and integrate Indigenous cultural values in water management.
Of the 790 plant taxa recorded since 2014, 79 taxa (10%) only occurred at sites with wetter conditions maintained by environmental water, including 12 culturally significant species known to be used by Aboriginal people. This highlights the role of environmental water in supporting biodiversity with cultural value (pg 34).
Watering remains essential even in wet years
Even during the high rainfall years of 2021–22 and 2022–23, distinct vegetation patterns persisted at sites receiving environmental water, confirming that managed watering delivers additional ecological benefits beyond natural inundation (pg 6).
Recommended adaptive management actions:
Based on nine years of monitoring and evaluation, the 2022–2023 vegetation report outlines several key adaptive management actions to improve the effectiveness of environmental water delivery and monitoring, aligned with Basin Plan objectives.
Continue delivering water to maintain wetter inundation regimes
Maintain environmental watering to floodplain and wetland sites where it supports diverse and functionally important vegetation communities, particularly those with submerged, amphibious, and damp-loving species. These regimes are central to sustaining species richness and resilience across the Basin. (pg 36)
Support culturally significant vegetation through water planning
Engage Aboriginal communities to identify and prioritise culturally important plant species that can benefit from environmental water, and actively consider these in future watering plans. The evaluation found that 12 such species only occurred at sites maintained by environmental water. (pg 36)
Improve alignment between watering objectives and Basin Plan goals
Clarify and align the objectives of specific watering actions with those set out in the Basin Plan and the Basin-wide Environmental Watering Strategy. Objectives should be more consistent, quantifiable, and inclusive of ecological functions (e.g. habitat provision, regeneration). (pg 36–37)
Enhance inundation and counterfactual data quality
Improve the accuracy and resolution of inundation data (especially sub-annual data) and the modelling of counterfactual conditions. Better hydrological data will improve understanding of how vegetation responds to different watering regimes. (pg 37)
Develop hydrological metrics for riverine vegetation
Establish specific flow metrics to evaluate the effects of environmental water on riverine and in-channel vegetation, which are currently underrepresented in both monitoring and assessment frameworks. (pg 37)
Refine the Flow-MER vegetation monitoring design
Improve the representativeness and spatial distribution of monitoring sites across the Basin. Consider sampling effort in underrepresented ANAE types and include more vegetation indicators (e.g. condition, regeneration, cover) to better track ecological outcomes. (pg 37)
Group watering actions by objective to support evaluation
Consider grouping watering actions with similar objectives to evaluate them more effectively. This will help avoid conflicting assessments (e.g. actions aiming to both promote and suppress river red gum recruitment) and improve learning from monitoring data. (pg 36)
