Big water under pressure: how climate change is reshaping the Murrumbidgee River - Lethal Heating Editor BDA

Key Points

The Murrumbidgee River is a heavily regulated Murray–Darling tributary under growing climate stress 1 Irrigation and regional economies depend on shrinking, highly contested flows 2 River health is declining, with reduced flows, habitat loss and frequent algal blooms 3 Climate change is projected to bring hotter conditions and more variable rainfall in the Murray–Murrumbidgee region 4 Environmental water targets in the upper Murrumbidgee are often not met because of limited allocations 5 Future water security will hinge on tougher allocation decisions, better governance and climate‑ready adaptation plans 6

The Murrumbidgee River is a lifeline for south‑eastern Australia, yet its future is being rewritten by a hotter, drier climate.

From its snow‑fed headwaters in the Australian Alps to its junction with the Murray River, this long, regulated system underpins city water supplies, high‑value irrigation, wetlands and First Nations cultures.

Over recent decades, climate change, river regulation and intensive extraction have combined to steadily erode flows, squeeze environmental water and increase pressure on river communities.

Scientists now warn that further warming will likely deepen these trends, sharpening trade‑offs between food production, town water security and the survival of already stressed ecosystems.¹⁴

In the Murrumbidgee this is not an abstract risk but a lived reality, visible in shrinking floods, rising salinity, recurring blue‑green algal blooms and wetlands that no longer fill as often or as long as they once did.¹

At the same time, the river remains central to a regional economy worth billions of dollars a year and to the identity of communities that have grown up along its banks.²

How governments, Basin authorities, Traditional Owners and local communities respond over the next decade will shape whether the Murrumbidgee can remain a working river that still supports healthy ecosystems in a rapidly changing climate.¹⁶

Big water: scale, seasons and regulation

Running for around 1,485 kilometres from the Snowy Mountains to the Murray, the Murrumbidgee drains a catchment of about 84,000 square kilometres and is one of the largest tributaries in the Murray–Darling Basin.⁷

The river’s name, from the Wiradjuri language, is often translated as “big water” or “overflowing”, reflecting the way it once spread across floodplains and wetlands during natural high flows.¹⁰

Today the system is classed as one of Australia’s most regulated rivers, with at least 26 major storage or diversion structures, including Tantangara, Burrinjuck and Blowering dams, weirs and extensive irrigation channels.¹

These storages smooth out natural flow peaks, capture snowmelt and rainfall, and divert large volumes for irrigation or into neighbouring basins through schemes such as the Snowy Hydro transfers.¹¹

In the upper Murrumbidgee, research shows that on average about 93 per cent of annual flow can be diverted at Tantangara Dam in some years, leaving only a small fraction to move downstream as planned environmental or base flows.¹¹

Further downstream, the river spreads into the mid‑Murrumbidgee and Lowbidgee floodplains, which once supported extensive red gum forests and wetlands but now receive far fewer and shorter floods because of both water extraction and a drying climate.¹⁶

This combination of infrastructure, inter‑basin transfers and climate‑driven drying underpins many of the river’s current challenges, from declining wetland health to heightened competition between users in dry years.²⁰

The Murrumbidgee valley is recognised by New South Wales authorities as one of the state’s most heavily regulated systems, which makes managing water for the environment particularly complex as conditions change.¹

River of food, culture and country

More than half a million people live in the wider Murrumbidgee catchment, including the regional cities of Canberra, Wagga Wagga and Griffith, along with dozens of irrigation towns and rural communities.⁷

The river crosses the Traditional lands of First Nations including the Ngambri, Ngunnawal, Wiradjuri and other groups, for whom its waters, fisheries and floodplains have long been central to culture, trade and story, as well as to spiritual responsibilities for Country.¹⁰

Economically, the Murrumbidgee Irrigation Area and surrounding districts form one of Australia’s most productive farming regions, with about 120,000 hectares irrigated annually across crops such as rice, cotton, nuts, grapes, citrus and vegetables.⁵

Studies estimate that the gross value of farm production in the irrigation area alone is in the order of hundreds of millions of dollars each year, with broader value chains for rice, horticulture and livestock lifting the regional economic contribution into the billions.²

At the same time, Canberra and other communities rely on the Murrumbidgee and its storages for drinking water, while tourism, recreation and cultural activities are tightly linked to the river’s flows and water quality.⁴

Environmental assets such as the mid‑Murrumbidgee and Lowbidgee wetlands are nationally significant habitats, supporting waterbird breeding and threatened species like the southern bell frog when they receive adequate flooding.¹³

These overlapping economic, cultural and ecological values mean that any decline in river health or reliability reverberates quickly through communities, industries and ecosystems.¹⁸

Analyses of water use in the catchment show that the value of irrigation water is high, underscoring how strongly regional livelihoods and export industries are exposed to changes in allocations and long‑term flow trends.⁸

Climate change: a drying, hotter future

Evidence is mounting that climate change is already reshaping the Murrumbidgee’s flow regime, with studies documenting significant declines in wet‑season river heights since the 1990s and increasingly frequent years of low inflow.¹³

An analysis published in 2021 linked these trends directly to reduced rainfall driven by global warming, warning that the catchment’s economic, social and ecological viability is at risk under ongoing drying.¹³

Regional climate projections for the Murray–Murrumbidgee show temperatures rising by around 0.7 degrees in the near term and close to 2 degrees by the latter half of the century, with more hot days and fewer cold nights.¹⁴

Rainfall is projected to become more variable, with likely decreases in spring, possible increases in some summer and autumn periods, and an overall higher risk of lower median inflows in key catchments such as the Murrumbidgee.¹⁶

National assessments of Australia’s changing climate also point to a trend towards more intense downpours when rain does fall, which can increase flood risks even as average conditions become drier and evaporative demand rises.¹⁷

For the river, this means longer dry spells, hotter summers that boost evaporation and water demand, and more erratic but sometimes heavier rainfall events that challenge existing dams, weirs and levees.²⁰

Scientists studying the Lowbidgee floodplain have concluded that both river regulation and climate change are now working together to reduce the frequency and extent of floods, undermining the ecological character of wetlands and forest systems.²⁰

New South Wales climate snapshots for the Murray–Murrumbidgee region emphasise that all key temperature measures are expected to rise and that climate change will intensify fire weather, heatwaves and water stress across the basin.¹⁴

Water allocation, quality and river health

Water in the Murrumbidgee is allocated through a complex mix of state water‑sharing plans, Murray–Darling Basin Plan settings and specific rules for urban supply, irrigation licences and environmental entitlements.¹⁵

In most years agriculture remains the largest consumptive user, ahead of town water, industry and stock, although many irrigators now hold a mix of high‑ and general‑security entitlements and participate in water trading to manage risk.⁸

The Basin Plan has seen substantial volumes of water recovered for the environment across the Murray–Darling, with more than 2,100 gigalitres of entitlements secured by 2020, including significant holdings in the Murrumbidgee to support regulated environmental flows and targeted floodplain watering.¹⁵

Despite this, recent research into the upper Murrumbidgee found that annual environmental release targets of 27 gigalitres were not met in two‑thirds of years from 2008 to 2022, largely because allocations to environmental accounts were constrained during dry conditions.¹¹

The same work highlighted that in some years up to 99 per cent of the upper river’s natural flow is diverted at Tantangara, contributing to poorer habitat, sediment build‑up, declining native fish populations and lower water quality downstream.¹¹

Further along the valley, Commonwealth environmental water has been used to deliver strategic pulses and base flows to support key wetlands, fish habitat and waterbird breeding, but managers report that meeting ecological objectives is increasingly difficult in a warming climate with tighter water constraints.¹⁸

Low flows, high temperatures and elevated nutrient loads have also contributed to recurring outbreaks of blue‑green algal blooms in lakes and river reaches linked to the Murrumbidgee system, with warnings issued for recreational and stock water use in areas such as Lake Wyangan and ACT lakes that drain to the river.³

Authorities note that the slow‑moving nature of regulated rivers, combined with drought and nutrient‑rich runoff, creates ideal conditions for algal blooms that reduce water quality, harm aquatic life and disrupt irrigation and tourism.⁶

The pattern of under‑delivery against environmental flow targets in the upper river has prompted calls for more enforceable rules, better outlet capacity at key dams and a re‑examination of how inter‑basin transfers interact with downstream ecological needs.¹²

Securing the Murrumbidgee in a hotter century

Climate change means the Murrumbidgee can no longer be managed on the assumption that past river behaviour will guide the future, forcing planners to confront more frequent water shortages and sharper trade‑offs between users.¹³

State adaptation programs already identify the Riverina‑Murray as highly exposed to climate impacts, pointing to the need for councils, governments and communities to factor lower inflows and more extreme events into infrastructure, land‑use and water‑security planning.¹⁶

Hydrological modelling suggests that without stronger action to reduce emissions globally and adapt locally, river flows to key floodplains could decline further, intensifying stress on wetlands, forests and the species that depend on them.²⁰

For irrigated agriculture, this will likely mean continuing pressure to upgrade on‑farm efficiency, shift to crops that can tolerate higher water prices and variable supply, and use water markets to move scarce water to higher‑value uses.⁸

Community‑led restoration projects along the Murrumbidgee, including habitat works, native revegetation and invasive species control, show how local groups can build ecological resilience even as large‑scale pressures mount.¹⁹

However, experts stress that such efforts must sit alongside reforms to river operations, environmental water delivery and land management, so that limited flows can be used more strategically to support both communities and ecosystems.

In the coming decades, the central task for policymakers will be to align water‑sharing rules, Basin Plan commitments and climate policy so that the river’s working role is preserved without sacrificing the environmental foundations that underpin long‑term regional prosperity.¹⁵

That will require clearer climate‑adjusted limits on extraction, stronger protection for environmental and cultural flows, and stable, long‑term investment in adaptation so that communities along the Murrumbidgee are not left to carry the risks of a hotter, drier basin alone.¹⁶

References

1. NSW Department of Climate Change, Energy, the Environment and Water – Murrumbidgee valley: Water for the environment
2. ACCC – Murrumbidgee Irrigation submission: Economic contribution of the Murrumbidgee Irrigation Area
3. Griffith City Council – Lake Wyangan water quality and algal blooms
4. Icon Water – Murrumbidgee River drinking water sources
5. Charles Sturt University – Irrigation in the Murrumbidgee Irrigation Area
6. ACT Government – Algal blooms in Canberra lakes and waterways
7. The Murrumbidgee – River region facts
8. Qureshi et al. – An empirical assessment of the value of irrigation water in the Murrumbidgee catchment
9. Encyclopaedia Britannica – Murrumbidgee River overview
10. McGuire et al. 2025 – Environmental flows in the upper Murrumbidgee River
11. NSW Water – Adequacy of environmental releases to the upper Murrumbidgee River
12. The Conversation – The Murrumbidgee River’s wet season height has dropped by 30% since the 1990s
13. NSW Government – Murray Murrumbidgee climate change snapshot
14. Wentworth Group of Concerned Scientists – Assessment of river flows in the Murray–Darling Basin
15. AdaptNSW – Climate change in the Riverina Murray
16. CSIRO/Bureau of Meteorology – Australia’s changing climate
17. Commonwealth Environmental Water Holder – Murrumbidgee 2019–20 monitoring and evaluation technical report
18. Murrumbidgee Landcare – Supporting the Murrumbidgee River: collaborative habitat restoration
19. Kreibich et al. 2024 – River regulation and climate change reduce river flows to the semi‑arid Lowbidgee floodplain

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