Environmental flows in the upper Murrumbidgee River: evaluating flow delivery and governance to inform future environmental flow agreements

Snowy Hydro Limited (SHL) is the Australian Government-owned company that operates the Snowy Hydro Scheme. The Snowy Water Licence (the Licence) was issued in 2002 by the NSW Government under the Snowy Hydro Corporatisation Act 1997 for a period of 75 years (New South Wales Government 2002). The Licence is the primary legal document defining how SHL is to account for and release water. Section 25 of the Act provides for mandatory, regular reviews of the Licence initially after 5 years and then every 10 years (New South Wales Government 1997).

The Water Act 2007 (the Act) provides the legislative framework for managing rivers in the Murray–Darling Basin. Section 8(2)(a) of the Act excludes structures that are part of the Snowy Hydro Scheme from being controlled under the Act, deferring to the Licence. Section 21(6–7) states that the Basin Plan, a regulated document issued under the Act, must not be inconsistent with the Licence. These sections effectively exclude the structures operated by Snowy Hydro from obligations under the Act. The SHL Statement of Expectations outlines the Shareholder Ministers’ expectations for energy production and distribution. It can be revised at any time at the discretion of the Shareholder Ministers (Commonwealth of Australia 2024b). It outlines priorities and influences operations by requiring particular transparency measures or prioritisation of particular policy objectives.

The Snowy Scientific Committee (SSC) was established in 2008 by the NSW Government to provide advice on environmental releases, which they did until 2012–13. The SSC was disbanded in 2014 following a review that recommended ‘a more contemporary framework that could better respond to community and government needs’ (New South Wales Department of Primary Industries 2024a). The Snowy Advisory Committee (SAC) was established in 2018 and includes broader representation. The Snowy Hydro Corporatisation Act 1997 sets out that the SAC must include at least two community representatives, at least one representative of environmental interest groups, at least one representative of Aboriginal interests; at least one representative of the NSW Government, and at least one representative of the Victorian Government (New South Wales Government 1997). The SAC is responsible for providing advice each year on the timing and annual pattern of releases.

The upper Murrumbidgee River is defined as the 320-km stretch of river from the headwaters in Kosciuszko National Park (where water is diverted by Tantangara Dam) to Burrinjuck Dam (see Fig. 1). On average, 93% of the annual flow of the upper Murrumbidgee River, and in some years 99% of flow, is diverted at Tantangara Dam and transferred to Lake Eucumbene in the adjoining Snowy River Basin (Pendlebury et al. 1997; Lintermans 2006; Upper Murrumbidgee Demonstration Reach Project 2022).

Fig. 1.

Map of the upper Murrumbidgee River. Source: New South Wales Office of Water (2011).

The SWIOID sets environmental release targets for the Snowy, Murrumbidgee, Goodradigbee and Geehi Rivers. It has not been reviewed since it was agreed in 2002. The SWIOID delivers water through the following three programs: the Snowy River Increased Flows (SRIF) program, which sets a target of 212 GL year⁻¹ for the Snowy River; the River Murray Increased Flows (RMIF) program, which sets a target of up to 70 GL year⁻¹; and the Snowy Montane Rivers Increased Flows (SMRIF) program, which sets a target of up to the equivalent of 150 GWh year⁻¹ of foregone energy for the Goodradigbee and Geehi Rivers, the Snowy River above Jindabyne Dam and the upper Murrumbidgee River at Tantangara Dam (Department of Climate Change Energy the Environment and Water 2024). Annexure Three of the SWIOID sets out formulas for converting gigawatt-hours of foregone electricity generation to gigalitres of water on the basis of the electricity generation potential of each site, with the combined total target of 150 GWh being equivalent to 118 GL of water (Commonwealth of Australia et al. 2002).

As set out in the Licence, the NSW Government sets the environmental release volumes annually, specifying the volume that SHL is to release each day. By setting daily targets, the NSW Government can require flow volumes and patterns that mimic natural seasonal flows such as high flow events that are important for scouring the river bed and washing sediments downstream. When there is sufficient water available, a flow-scaling approach is used to mimic natural seasonality. The allocations set by the NSW Government rarely reach the target volumes as they are restricted by water availability. The volume of water available for environmental releases each year is determined by inflows to the western catchment storages and water recovery in the western rivers, with less water being available when conditions are dry in these systems (New South Wales Department of Planning and Environment 2022; Department of Climate Change Energy the Environment and Water 2024). This is because water entitlements were purchased from these catchments to offset impacts on consumptive users of lower inter-basin water transfers when the Snowy Water Initiative was established in 2002. The SWIOID and the Licence set out that water available for SMRIF releases must be allocated at the same proportion as for SRIF releases. For example, if SRIF releases are at 40% of the target volume in a given year, SMRIF releases will also be available at 40% of the target volume.

The SWIOID defines a maximum target of 27 GL year⁻¹ for environmental releases from Tantangara Dam (New South Wales Department of Climate Change Energy the Environment and Water 2024). This target started at 5 GL in 2005, increased to 20 GL in 2006, then increased to 27 GL year⁻¹ in 2008 and has been in place since then (Commonwealth of Australia et al. 2002). The SWIOID states that 27 GLyear⁻¹ is 30% of long-term average annual natural flow (ANF) of the upper Murrumbidgee River, a statement then repeated in subsequent reports (Commonwealth of Australia et al. 2002; Snowy Scientific Committee 2010). This appears to be incorrect. A long-term average annual inflow to Tantangara Dam of 290 GL was applied in this research, on the basis of previous estimates used by the New South Wales Office of Water (2011) and supported by the flow gauge above Tantangara Dam (representing ~50% of the inflow to the dam) recording an average annual flow of 147.5 GL from 1978 to 2022 (Snowy Hydro Limited 2024b).

In addition to environmental releases, there is a requirement to release base passing flows, also referred to as riparian releases, to meet the needs of downstream water users. The Licence (Schedule Four, Section 12A.1) requires that each day SHL must release base passing flows from Tantangara Dam up to the lesser of 83 ML day⁻² or the inflow into Tantangara Reservoir to ‘as far as practicable maintain the flow of the Murrumbidgee River at Mittagang Crossing at 32 mL/day’ (New South Wales Department of Primary Industries 2024b, p. 81). The SWIOID specifies that SMRIF environmental releases are in addition to base passing flows (Commonwealth of Australia et al. 2002, Section 8.2 (5) and Annexure two Section 1.1). The SWIOID defines base passing flows for the upper Murrumbidgee River as ‘the long term average volume of 2 GL per water year from Tantangara Dam’ (Commonwealth of Australia et al. 2002, Section 1.1(6)).

The diversion of water at Tantangara Dam is leading to poor river health, including reduced habitat quality and availability, sediment build-up because of lack of flushing flows, declining native fish populations and poor water quality (Snowy Scientific Committee 2010; Upper Murrumbidgee Demonstration Reach Project 2022). These impacts have been observed over the past 30 years and are becoming more pronounced as the climate dries and the impacts of farming and settlements increase (Dyer et al. 2014; Office of the Commissioner for Sustainability and the Environment 2019). Prior to the completion of Tantangara Dam, the upper Murrumbidgee River featured high seasonal variability with high winter and spring flows driven by winter–spring rainfall and spring snow melt and usually low but consistent summer flows (Pendlebury et al. 1997). Constant flows without these peaks do not deliver the flushing flows that are needed to scour the riverbed of sediment and maintain healthy riffles (New South Wales Department of Primary Industries 2018).

There is little peer reviewed literature on the upper Murrumbidgee River, but its declining health is well documented in government and independent reports. The 2019 ACT State of the Environment Report includes a case study on the upper Murrumbidgee River that identifies sediment build-up and formation of sand slugs as significant ecological impacts of reduced flow and limited high-flow events (Office of the Commissioner for Sustainability and the Environment 2019). A report for the Upper Murrumbidgee Demonstration Reach Project (2022) found that this section of the river had been significantly affected by sand deposition, which had negatively affected fish habitat by smothering and created barriers to fish movement, with negative effects on ecosystem resilience. Tonkin et al. (2022) found that populations of the endangered Macquarie perch (Macquaria australasica) are declining because of the sedimentation of waterways, riparian degradation, interspecific competition, overfishing, and the modification of river flows and temperatures downstream of Tantangara Dam.

An expert panel established by the NSW Government in 1997 to evaluate environmental flow requirements for the upper Murrumbidgee River found significant negative effects on aquatic habitat, ecology and vegetation and that lack of flushing flows had contributed to sedimentation and accumulation of organic matter (Pendlebury et al. 1997). Observed impacts included reduced habitat variability, reduced refuge habitat such as deep pools, reduced diversity of macroinvertebrates, degraded fish habitat, and invasion of the streambed by exotic and native vegetation. The panel recommended that a minimum depth of flow of 0.4–0.5 m be maintained in the section of river below Tantangara Dam, seasonal flow targets be set to mimic natural flow, a spring high-flow event of 4–6 GL day⁻¹ be delivered with a duration of 6–7 days, and an ongoing monitoring program be implemented.

A report by the Snowy Scientific Committee (2010), an expert group established by the NSW Government to provide scientific advice on environmental releases, on the adequacy of environmental flows in the upper Murrumbidgee River found that environmental flows were not being delivered at target volumes. Environmental releases were lower than expected in all years and were delayed relative to the timing specified in Annexure Three of the SWIOID. The report identified that governance arrangements to protect environmental releases were poor and that the commitment to implement a flow response monitoring program had not been met because of insufficient funding being allocated by the NSW Government for the program.

Declining river health and low flows also affect the communities that live along the river. For example, in late 2019 the flow in the upper Murrumbidgee River downstream of Tantangara Dam fell below cease-to-pump thresholds, limiting access to water for agricultural purposes. The Murrumbidgee River stopped flowing at Tharwa in the Australian Capital Territory, where the community relies on pumping from the river to meet non-potable water needs. This event raised concerns about future events and the management of water abstraction upstream during low-flow events, which was considered to be a contributing factor (Murray–Darling Basin Authority 2020).

Issues of declining river health are not confined to the upper Murrumbidgee River, with impacts being observed in other montane rivers. Bender et al. (2022) examined environmental flows in the Snowy River from 2002 to 2019, finding that in no year had the target of 212 GL been met. Environment organisations continue to advocate for increased environmental flows for the Snowy River, stating that river health continues to decline because governance arrangements are failing to prioritise river health (Environment Victoria 2017; Snowy River Alliance 2017).

This research aims to provide an assessment of environmental flow delivery in the upper Murrumbidgee River, and to identify opportunities to improve governance and river health. The key research questions are as follows:

Environmental releases from Tantangara Dam were below the 27-GL target in 10 of the 15 years from 2008 to 2022 (67% of years) (refer the ‘Data sources’ section of the Supplementary material). The average annual environmental release during this period was 18.9 GL (70% of the target volume). The initial 5-GL environmental release target was met in 2005, but not in 2006 or 2007 (see Fig. 2).

Fig. 2.

Annual planned and actual environmental releases and base passing flows from Tantangara Dam and the environmental release target (refer to the ‘Data sources’ section of the Supplementary material). Note: the water year is from 1 May to 30 April, as used in water reporting, e.g. May 2011 to April 2012 is the 2011 water year.

SHL was generally within the compliance thresholds for delivering annual releases as set by the NSW Government (Snowy Hydro Limited 2011). This indicates that if the annual water allocation was higher, the NSW Government could set higher volumes and SHL would deliver them.

Base passing flows were typically released in dry periods and when environmental releases were below 10 GL year⁻¹ (Snowy Scientific Committee 2010; Snowy Hydro Limited 2011, 2022). Fig. 2 shows the relationship between high environmental releases and low or no base passing flows. In some years, no base passing flows were released, the highest annual volume from 2005 to 2022 was 11 GL in 2019 and the average annual volume was 2.5 GL.

On the basis of an estimated long-term average annual inflow to Tantangara Dam of 290 GL, 30% of ANF would be 97 GL year⁻¹ and the environmental release target of 27 GL is equivalent to ~9% of ANF (New South Wales Office of Water 2011). From 2005 to 2022, on average, 93% of the ANF was diverted, with an average of 6.1% of ANF (17.6 GL) being delivered as environmental releases and 0.9% (2.5 GL) as base passing flows (see Fig. 3). The diversion rate varied among years, ranging from 85 to 99% over this period.

Fig. 3.

Releases from Tantangara Dam as a percentage of annual natural flow (based on long-term average annual inflow to Tantangara Dam of 290 GL per year as per New South Wales Office of Water 2011). Sources for environmental release data are listed in the ‘Data sources’ section of the Supplementary material.

Seasonal variation of environmental releases is much reduced compared with seasonal and daily variability upstream of the dam. Data from flow gauge number 410535 on the Murrumbidgee River upstream of Tantangara Dam demonstrate the extent of high-flow events in the catchment between 2011 and 2023, with daily flows over 2 GL being a common occurrence, daily flows above 4 GL occurring several times and the highest recorded daily flow being almost 10 GL (see Fig. 4) (Snowy Hydro Limited 2023b). The upstream flows in Fig. 4 represent ~50% of the inflow into the Tantangara Dam, with the remaining flows being captured from tributaries that would have joined the Murrumbidgee River (Snowy Hydro Limited 2011, 2022). Assuming identical area–runoff relationships between the two tributary catchment areas, we could expect the high-flow events in Fig. 4 to represent ~50% of the daily flow volumes of pre-SHL high-flow events.

Fig. 4.

Daily mean flow upstream of Tantangara Dam (Snowy Hydro Limited 2024b) and environmental releases from Tantangara Dam (see Supplementary material for data sources) showing the reduced seasonal variation and reduced extent of high-flow events.

Fig. 5 shows the planned environmental releases for 2023–24 with winter and spring high-flow events. The volume of water available in 2023–24 was unusually high, 41.2 GL, because of high rainfall in previous years. When available water is reduced, the ability to deliver high-flow events will be diminished. The maximum daily release volume from Tantangara Dam since 2011 is 1.5 GL (Snowy Hydro Limited 2023b).

Fig. 5.

The 2023–24 planned daily environmental release volumes from Tantangara Dam (Snowy Hydro Limited 2023b).

The SWIOID is legally binding, but the environmental release target is a maximum volume and is therefore not enforceable. Setting a maximum target does not provide any assurance that flows will be delivered. The volume of water available for environmental releases to the upper Murrumbidgee River each year is usually below the target volume (see Fig. 2). This is because it is linked to water availability for environmental flows to the Snowy River, which is determined by inflows to the western catchment storages and water recovery in the western rivers (New South Wales Department of Planning and Environment 2022). When low water allocations are available in the western storages, less water is available for the Snowy River, and therefore to the Snowy montane rivers, including the upper Murrumbidgee River. If the full allocation of 212 GL is available for the Snowy River, the full 150 GWh of generation potential equivalence (118 GL) will be allocated to the Snowy montane rivers.

The link to western catchments is because water entitlements were purchased from these catchments to offset impacts on consumptive users of lower interbasin water transfers when the Snowy Water Initiative was established in 2002. Because water flowing down the Murrumbidgee River will eventually flow to the lower Murrumbidgee and Murray Rivers (with some losses), it seems unnecessary to restrict the environmental release volume for the upper Murrumbidgee on the basis of water availability for consumptive water users in western storages.

Further, the limited gauge coverage of the upper Murrumbidgee River and its tributaries means that base passing flow releases are being managed by SHL on the basis of modelling. This lacks precision, transparency and accountability.

Despite being legally binding, there has been no enforcement when parties fail to meet requirements in the SWIOID. Four requirements in the SWIOID do not appear to have been delivered. These are as the following: ensuring an outlet flow capacity of 2 GL day⁻¹; conducting an environmental monitoring program; preparing a riverine management strategy; and ensuring environmental releases are additional to BPF as per Clause 8.2(3) of the SWIOID (Commonwealth of Australia et al. 2002). Although the outlet can technically deliver up to 2.64 GL day⁻¹ when the dam is at full capacity, when operated at the usual low-water levels, the outlet allows for flows of up to 1.5 GL day⁻¹ and is not therefore meeting the functional requirement to deliver 2 GL day⁻¹ as set out in the SWIOID (Commonwealth of Australia et al. 2002, Annexure Two, Clause 4.2).

The SWIOID requires that ‘for each river…the parties must (1) determine a set of objectives…together with associated performance measures, and (2) prepare a riverine management strategy that includes provision for the management of habitat, native plant and animal species, introduced plant and animal species and river banks’ (Commonwealth of Australia et al. 2002, Annexure Two, Section 2.2). A riverine management strategy has not been developed for the upper Murrumbidgee River despite the SWIOID requiring this be in place by 2004. The 2022–23 Annual Plan for SMRIF releases sets the objective for the Murrumbidgee River as ‘to facilitate the rehabilitation and evolution of the Murrumbidgee River below Tantangara Dam into a smaller but healthy river’ (New South Wales Department of Planning and Environment 2022, p. 14). It does not set performance measures against which progress towards this objective will be assessed. A riverine management strategy would be a useful document for outlining objectives, setting performance measures to evaluate progress and providing clarity for the community and stakeholders. Ensuring environmental releases are additional to BPF would deliver improved environmental outcomes by reducing the risk of environmental releases being extracted downstream for consumptive use.

The SWIOID (Annexure Two, Section 12.2) and Licence (Schedule Three, Section 4.1) state that SHL may be notified by 13 February each year of the daily, monthly and annual volumes to be released in the year ahead (Commonwealth of Australia et al. 2002). This means that environmental flow volumes released normally lag natural variation in water availability by a year. If no values are notified, default monthly values apply. Setting release volumes 12 months in advance provides certainty for SHL, but does not enable adaptive management to optimise outcomes for the river. For example, it may be beneficial to coincide a release with a natural high-flow event to achieve higher peak flows, but the predetermined release schedule provides no opportunity to adjust flows in response to weather conditions.

The governance framework is complex and has limited transparency and accountability. There is some public reporting through the SHL Water Operations Plans; however, data are not easily accessible and some aspects, such as base passing flows, are not consistently included in public reporting. The complexity of management arrangements makes information difficult to interpret and limits opportunities for scientific and other public scrutiny.

There has been no review of the SWIOID since it was established in 2002, and little public reporting of progress against the objectives. The 10-year review of the Licence completed in 2018 provided an opportunity for community input (New South Wales Department of Primary Industries 2024b). Although being focused on the Licence, it provided an opportunity for broader commentary on the delivery of the SWIOID. Environmental organisations commented on the lack of transparency, the complexity of reporting that limits public understanding and scrutiny, the insufficient volumes of water released, and the low prioritisation of environmental objectives (Environment Victoria 2017; Snowy River Alliance 2017).

The Australian Capital Territory (ACT) relies on the Murrumbidgee River as a water source in times of drought, which can transfer of up to 100 mL day⁻¹ to Googong Dam and an offtake near the Cotter pump station (Icon Water 2024). The ACT Government has no role under current governance arrangements, which seems an oversight, given the implications for ACT water security.

It is not clear how inflows are estimated or what happens if more than the long-term average of 2 GL year⁻¹ of base passing flow is required. The lack of clarity could further erode environmental outcomes if SHL were to suggest that base passing flows exceeding 2 GL year⁻¹ should be ‘paid back’ from environmental releases in future years. As discussed, it appears that environmental releases are not additional to base passing flows in practice, which raises concern that environmental releases will be extracted downstream if not protected. Additionally, base passing flows are not always included in public reporting, which makes it difficult to understand the volume of water being released.

Although the broader representation of the SAC offers useful additional perspectives, it seems that, unlike the SSC, such a committee may not have the scientific expertise to provide in-depth analysis of implementation progress. In the absence of the SSC that previously performed that role, external scientific advice could be sought to ensure adequate oversight and rigour in evaluating performance.

The SSC published two reports in 2008 and 2010 assessing the adequacy of environmental releases in the Snowy and upper Murrumbidgee Rivers (Snowy Scientific Committee 2008, 2010). The reports found that environmental releases were not adequate to restore river health and identified governance flaws that were compromising delivery. The NSW Government published a response to both reports and made improvements in response to some recommendations. Although many of the recommendations were not agreed, and in many cases the issues identified remain unresolved, the reports highlighted the critical role of independent oversight.

The 1997 Expert Panel recommended an ‘ongoing [monitoring] program to assess the impacts of the environmental flow releases … and to assist in adaptive management of flow regimes’ (Pendlebury et al. 1997, p. 23). The SWIOID requires SHL to monitor and report the volumes of water released (Commonwealth of Australia et al. 2002, Annexure Two Section 7). It also states that the NSW Government ‘must measure the environmental benefits of the Snowy Montane Rivers Increased Flows on an ongoing basis’ (Commonwealth of Australia et al. 2002, Annexure Two, Section 9). There is no further detail in the SWIOID on how the monitoring should be undertaken.

The SSC concluded in 2010 that no flow response monitoring program was in place and that this requirement in the SWIOID had not been met (Snowy Scientific Committee 2010). The SSC observed that although there were monitoring programs covering water quality, macro-invertebrates and fish, which provided background on river condition, most of this monitoring was conducted at time-scales and with a sampling design that was not useful for flow response monitoring, and none of it was consistent with the objective of protecting endangered and threatened species. The SSC recommended the NSW Government ‘fund, commit to and implement a flow response monitoring program’ (Snowy Scientific Committee 2010, p. 30). The NSW Government response to this report stated that funds were not available to implement a comprehensive monitoring program and that additional funding had been sought to enable this (New South Wales Office of Water 2011). Many years after the SSC recommendation, there is no comprehensive flow response monitoring program in place for the upper Murrumbidgee River.

This raises the question as to why the NSW Government regulator has not implemented a cost recovery mechanism to ensure that a major industry that significantly damages a large river system pays for the requisite environmental management and monitoring. The National Water Initiative, the national plan for water reform, commits all states and territories to ‘implement water pricing and institutional arrangements which give effect to the principles of user-pays and achieve pricing transparency in respect of water storage and delivery in irrigation systems and cost recovery for water planning and management’ (Commonwealth of Australia et al. 2004, section 64(iv), p. 13). Under the Snowy Water Licence Clause 9.3)(2), SHL is exempted from paying ‘catchment management fees or other resource services fees or resource rent taxes, either with respect to the Snowy Water Catchment or New South Wales generally’ (New South Wales Department of Primary Industries 2024b, p. 24).

Environmental releases are not protected once released from Tantangara Dam, unless a temporary water pumping restriction is put in place. This means that the water can be extracted by downstream users, limiting the environmental benefits of the release. In 2016 (the most recently available public data), there was a total of 23.7 GL year⁻¹ of licenced entitlement for surface-water take across the upper Murrumbidgee catchment, excluding the ACT. Of this entitlement, 10.7 GL year⁻¹ was in the Murrumbidgee I and II catchment areas directly alongside the Murrumbidgee River between Tantangara Dam and the ACT border (New South Wales Department of Primary Industries 2016). This is a significant volume compared with the long-term average environmental release volume of 17.8 GL year⁻¹ and demonstrates the high likelihood of environmental releases being extracted downstream if they are not protected. Historically, temporary pumping restrictions were implemented to protect environmental releases in the upper Murrumbidgee River in 2023 and 2024 and are foreshadowed to remain in place until the water sharing plan is amended to provide protection in the long term (Department of Climate Change Energy the Environment and Water 2024). The restrictions mean that licence holders in the Murrumbidgee I and II catchment areas must not pump if flows are below the temporarily raised access thresholds published in the order for that day (New South Wales Department of Planning and Environment 2023).

As the SWIOID does not have review points and has not been updated since 2002, there has been no opportunity to revisit the allocated water volumes in the context of climate change. Relevant projections suggest a hotter climate with greater rainfall variability, less winter and spring rain and less runoff (Muhury et al. 2023; Commonwealth of Australia 2024a). The impacts of climate change will be compounded by a range of inflow interception activities that are poorly regulated and are expected to further diminish river flows (Pittock et al. 2023).

In this context, the volume of water allocated to environmental releases may need to increase if the health of the river system is to be maintained or improved. This is particularly relevant as the 27 GL year⁻¹ figure may have been selected on the understanding that this represents 30% of annual natural flow (ANF), which is not correct. The predicted decline in runoff would reduce water available for environmental releases, and competition for water, among electricity generation, consumptive use and environmental releases, would likely increase.

The assumption behind the limited volumes allocated for environmental flow releases is that SHL would lose income from water that bypassed its conventional ‘once-through’ hydropower generators. However, the construction of the Snowy 2.0 extension (which is due to be operating from 2028) adds 2.2 GW of pumped storage hydropower-generating capacity in addition to 1.8 GW at Tumut 3 power station (Snowy Hydro Limited 2024a). This means that of the 6.3 GW of hydropower-generating capacity of SHL, 4 GW (63%) will be directly from pumped storage generators that have the capacity to recirculate water almost indefinitely. For SHL this lowers the economic significance of each unit of environmental water released. Snowy 2.0 and mooted further extensions to the Snowy Hydro Scheme reinforce the need to review the SWIOID to reassess the balance that it codifies between electricity generation and river health.

The OECD Principles on Water Governance provide a framework to assess whether water governance arrangements are performing well and to help identify adjustments to governance. The Principles are based on the understanding that governance can be considered effective if it is helping ‘solve key water challenges … while fostering constructive state-society relations’ (Organisation for Economic Co-operation and Development 2018, p. 5). Water governance in the upper Murrumbidgee is evaluated against the following three main dimensions of the 12 principles: effectiveness; efficiency; and trust and engagement (see Table S2 in Supplementary material for further detail).

Effectiveness encompasses defining clear water policy goals and targets and implementing measures to meet objectives or targets. Governance in the upper Murrumbidgee River is performing poorly in this dimension because of management being removed from broader catchment management of the Murray–Darling Basin, failure to consider social and environmental values and lack of resourcing for the flow response monitoring program. Efficiency relates to maximising the benefits of water management and welfare at the least cost to society. Governance is performing poorly in this dimension because of data on river condition not being available to improve management, limited enforcement opportunities, and a low level of innovation. Trust and engagement relates to building public confidence and ensuring inclusiveness of stakeholders. Governance is performing poorly in this dimension because of data being unavailable or difficult to access and interpret, limited opportunities for stakeholder engagement, limited participation of Traditional Custodians in management, and detailed information on river condition being unavailable because of lack of monitoring.

Recommendations to enhance governance, deliver improved environmental outcomes and build public trust are as follows: