Appendix A

Lower Burdekin Badu Report

Townsville Enterprise Limited (TEL)

High-level review of potential lower Burdekin benefits and impacts associated with future water infrastructure development in the Burdekin catchment

3 July 2022

TEL – High-level review of lower Burdekin benefits and impacts associated with the future water infrastructure development in the Burdekin catchment –3 July 2022

Badu Advisory Pty Ltd

ABN 17613 863 602

Post: PO Box 2051

Keperra, QLD, 4054 AUSTRALIA

Email: info@baduadvisory.com

Web: www.baduadvisory.com

This report has been prepared in accordance with the scope of services described in the agreement between Badu Advisory and TEL (‘the client’). The report has been prepared solely for use by the client and Badu Advisory accepts no responsibility for its use by other parties. It is intended to provide high-level strategic advice regarding strategic water issues. Badu Advisory does not provide legal, engineering, financial services, or tax advice.

Copyright © Badu Advisory Pty Ltd

High-level review of lower Burdekin benefits and impacts associated with the future water infrastructure development in the Burdekin catchment –3 July 2022

Executive Summary

Badu Advisory was engaged by TEL to undertake a high-level review of lower Burdekin benefits and impacts, with a focus on the groundwater system, that might arise from future bulk water infrastructure development in the Burdekin catchment For the purposes of this review, the lower Burdekin is taken to be the area under irrigated agriculture area downstream of the Burdekin Falls Dam.

The following seven key considerations were identified and examined during this high-level review:

1. Implications for aquifer recharge including saltwater intrusion

2. Implications for water security and availability including for existing urban, industrial and irrigation water users as well as for future opportunities such as water for hydrogen

3. Implications for environmental flows

4. Implications for riverine and reef water quality including turbidity and sedimentation

5. Understanding the cumulative impacts of existing and proposed upstream water resource infrastructure and development

6. Shortcomings of the current siloed institutional, water allocation/management and regulatory arrangements and

7. Implications of climate change and variability including frequency/intensity of future riverine flow events (floods and droughts).

Table 1 is a summary of further studies and/or further investment, arising from this review, that might be pursued as part of the further assessment of future upstream bulk water infrastructure developments (such as the Hells Gate Dam Project). These are intended to complement (rather than duplicate) the range of programs already underway by research organisations in the lower Burdekin.

Key opportunities

1. Line Sunwater’s open-earth distribution channels in the BHWSS as a pathway for investing in infrastructure that would directly and immediately reduce the volume of water seeping into the groundwater system.

2. Commit to a research programme to enable the collaborative and coordinated management of coastal wetland ecosystems and their interconnections with the Great Barrier Reef and lower Burdekin Delta groundwater systems

3. Engage with stakeholders about the improved hydrologic performance that would be offered by extending the existing Burdekin Haughton Water Supply Scheme to incorporate a new upstream storage

4. investigate and assess, in consultation with the community, the pros and cons associated with the potential changes to the downstream flow regime particularly with respect to the impacts and benefits of reducing peak flood flows in the lower Burdekin. Other examples of environmental flow strategies that warrant future dialogue with stakeholders (as part of the upcoming water plan revision process) might include:

• extending low to medium environmental flow objectives beyond the trunk stream to better service important ecological assets located away from the main river and dependent on smaller off-river tributaries from the delta for their seasonal connection to coastal wetlands and

• including provisions that encourage greater use of groundwater at certain times when preservation of riverine and tributary flows is considered environmentally important.

4.1.1

4.1.2

4.3

High-level review of lower Burdekin benefits and impacts associated with the future water infrastructure development in the Burdekin catchment –3 July 2022

Key opportunities

5. Assess the potential benefits and costs of modifying the outlet works at Burdekin Falls Dam to enable active management and bypassing of occasional pulse-style environmental releases that are aligned with improving management of downstream sediment loads, aquifer recharge and sand dam performance, efficiency and lifespan and

6. Consider retrofitting a multi-level outlet work structure at Burdekin Falls Dam as a means of improving management of the water quality of dam releases for downstream environmental and water supply purposes.

7. Examine, in a whole of region context, the cumulative impacts of existing plus various combinations of new water infrastructure developments on riverine and coastal geomorphological considerations. This should include utilizing the hydrologic information available from the modelling studies that have been recently completed as part of Detailed Business Cases

8. Establish a renewed funding basis, focus and drive for all stakeholders – organisations and individuals – to reengage in the kind of joint visioning, collaborative thinking and learning, and community-driven action that previously espoused by Williams et al over a decade ago. This could also be supported by the engagement processes that will support DRDMW’s development and implementation of an updated water plan for the Burdekin.

9. Quantify the potential benefits that additional storage capacity might offer as a means of managing potential variations in climate that are more extreme than observed in the historical record (i.e. less frequent but more intense flood events interspersed with drought events of extended duration) and

10. Conceptualise the design and desired performance of existing and new bulk water infrastructure developments in terms of regional water grids that draw together multiple sources of water (including catchment surface water storages, groundwater and manufactured water etc.) and interconnectors (using bulk water pipelines) to provide overall reliability of a water supply portfolio that matches users’ needs.

4.4

4.5

4.6

4.7

High-level review of lower Burdekin benefits and impacts associated with the future water infrastructure development in the Burdekin catchment –3 July 2022

1 Introduction

Townsville Enterprise Limited (TEL) is an advocacy body that aims to attract major investment to the region encompassing Townsville, Magnetic Island, Palm Island, Burdekin Shire, Hinchinbrook Shire and Charters Towers (Townsville Enterprise Limited, 2022a) It is also the proponent of a business case for the proposed Hells Gates Dam development which would involve a major new dam at Hells Gates in the Upper Burdekin catchment with three downstream weirs and associated irrigation areas.

Badu Advisory was engaged by TEL to undertake a high-level review of lower Burdekin benefits and impacts, with a focus on the groundwater system, that might arise from future bulk water infrastructure development in the Burdekin catchment (‘future development’). For the purposes of this review, the lower Burdekin is taken to be the area under irrigated agriculture area downstream of the Burdekin Falls Dam.

The scope of this high-level review includes:

• examining the potential lower Burdekin aquifer impacts and opportunities associated with future development

• identifying high-level data and key facts to assist in consultation and engagement purposes with relevant stakeholders and

• considering published and anecdotal information including views voiced in meetings (held on 9-10 June 2022) with researchers and government agency representatives.

The purpose of this report is to present a summary of findings in relation to the above for TEL’s future consideration.

2 Methodology

The proposed approach to this high-level review was as follows:

• Review and reference existing literature and existing hydrological modelling1 to: o make a high-level assessment (in words only) of the potential impacts of future development on the lower Burdekin groundwater systems2 o describe potential water release management strategies for decreasing impacts on existing aquifers including, but not limited to, control of flows for optimising the effectiveness and lifespan of sand dams o list recommended studies / further assessments warranting further investigation and investment and

• Identify high-level data that may be used to: o consult verbally, and through graphical illustrations, with lower Burdekin stakeholders o to assist in explaining the potential impacts (and benefits) of future development with respect to (wrt):

High-level review of lower Burdekin benefits and impacts associated with the future water infrastructure development in the Burdekin catchment –3 July 2022

§ changes in water flows to the lower Burdekin wrt water security and aquifer concerns (e.g. through an explanation of water allocation in the Burdekin vs actual water usage)

§ rising water tables (and associated threats to agricultural production) in the lower Burdekin

§ the erosion of Cape Bowling Green due to sediment starvation3

§ increased turbidity (dirtiness) of the Burdekin River and

§ increased nutrient flows / containments to the Great Barrier Reef.

3 Overview of key considerations

The following key considerations were raised by and/or discussed with government agency representatives and researchers during this high-level review:

1. Implications for aquifer recharge including saltwater intrusion

2. Implications for water security and availability including for existing urban, industrial and irrigation water users as well as for future opportunities such as water for hydrogen

3. Implications for environmental flows

4. Implications for riverine and reef water quality including turbidity and sedimentation

5. Understanding the cumulative impacts of existing and proposed upstream water resource infrastructure and development

6. Shortcomings of the current siloed institutional, water allocation/management and regulatory arrangements and

7. Implications of climate change and variability including frequency/intensity of future riverine flow events (floods and droughts).

These are each examined in the following sections.

4 Analysis of implications and areas warranting further study

4.1 Aquifer recharge

The groundwaters of the lower Burdekin may generally be characterised in terms of two interlinked but distinct complex aquifer systems that are facing different water resource management challenges

The two systems and their respective challenges and opportunities are discussed in turn below.

4.1.1 Groundwater systems underlying the Burdekin River Irrigation Area

The first groundwater system effectively underlies the area of irrigated land that is supplied by the Burdekin Haughton Water Supply Scheme (BHWSS). The bulk and distribution water supply infrastructure within the scheme is owned and operated by Sunwater Limited4 . The BHWSS supplies surface water from water storages on the Burdekin River (e.g. Burdekin Falls Dam and Clare Weir) via open channel systems to an area of irrigated agriculture that extends from Dalbeg and Clare through to the Giru groundwater area (see Figure 1) This area is sometimes referred to as the Burdekin River Irrigation Area (BRIA) (Sunwater Limited, 2022)

3 Only included in scope to the extent of mentioning any prelim information gleaned from review of references.

4 Sunwater is a Queensland Government Owned Corporation

High-level review of lower Burdekin benefits and impacts associated with the future water infrastructure development in the Burdekin catchment –3 July 2022

In 2017, the Lower Burdekin Groundwater Strategy Project found that:

• the dramatic increase in surface water irrigation within the BRIA since the late 1980s had led to increased groundwater recharge and rising groundwater tables

• some parts of the BRIA had experienced a rise in groundwater levels of up to 10 m over the last couple of decades

• this had resulted in groundwater levels being less than 3m below the ground surface across approximately 15 per cent of the irrigated area within the project area, with some areas measuring the groundwater table at only 0.5 m below the surface

• such high water tables result in water logging of the soil profile and also mobilise salts from the underlying bedrock which can increase salinity levels, both of which can reduce the productivity of agricultural land and limit opportunities for future development and

• high groundwater levels can also lead to higher rates of property and catchment run-off flowing into downstream receiving environments (such as the Ramsar listed wetlands at Bowling Green Bay and the Great Barrier Reef lagoon), and nutrient and sediment loads in this run-off adversely affecting the quality of water entering these environments (State of Queensland, 2017)

Previous work by the Department of Natural Resources and Mines (DNRM) suggested that:

• rainfall deep drainage has increased (estimated from 1.5% to 20%) due to clearing and/or gypsum application and

• irrigation deep drainage is estimated to be approximately 23% of applied water (Queensland Government, 2017).

High-level review of lower Burdekin benefits and impacts associated with the future water infrastructure development in the Burdekin catchment –3 July 2022

The Queensland Competition Authority’s final report into Sunwater’s irrigation prices for the period 2020-24 provides a recent indication of the volume of surface water seeping from Sunwater channels into the groundwater system. It found that:

• the total volume of high and medium priority channel loss water allocations held by Sunwater in the BHWSS is 206,737 ML

• the estimated actual annual channel distribution losses ranged from 51,253 ML in 2018-19 up to 173,757 ML in 2013-14 and

• excessive growth of aquatic weed in 2013-14 (due to lower that usual levels of turbidity in surface water from the Burdekin River) caused the flow of water within the channel to slow down resulting in higher levels of distribution losses (Queensland Competition Authority, 2020)

This equates to an annual average of 100,548 ML/a as calculated over the seven period from 201213 to 2018-19. Such losses could be substantially reduced through the lining of the open-earth channels in the BHWSS

In June 2018, Sunwater also reported that a program was underway in the Burdekin region to improve the accuracy of meters that were incorrectly recording water use. Sunwater estimated that delivery losses and other water accounting-related water use aggregated to around 13% of total water supply (Munck, 2018)

In 2019-20, total nominal volume of high and medium priority water allocations in the BHWSS was 1,079,592 ML for which Sunwater’s reported total water deliveries (including distribution losses) was 663,465 ML5 (i.e. around 61% of water allocation nominal volume) 70,008 ML or about 10.5% of

High-level review of lower Burdekin benefits and impacts associated with the future water infrastructure development in the Burdekin catchment –3 July 2022 water delivered in that year was reportedly or channel distribution losses. Table 3 illustrates the breakdown of water allocation and usage volumes for that year (Sunwater Limited, 2021)

Table 3 - Water allocations and usage for the BHWSS

The above illustrates that there appears to be scope to:

• improve the metering and monitoring of water usage and channel losses within the BHWSS and

• reduce groundwater accessions through lining of BHWSS channel distribution systems.

DRDMW is currently developing a groundwater strategy to address the threat that rising groundwater levels and soil salinity pose to the economic productivity of the agriculture-rich Lower Burdekin region in North Queensland. DRDMW note that:

Sugar cane production in the Lower Burdekin groundwater strategy project area has an annual turnover estimated at between $160 to 180 million. The region has the highest sugar cane yield, in terms of tonnes per hectare productivity, of any region in Australia. Agriculture is the largest employer in the Burdekin local government area, employing over 1,500 people

Higher groundwater levels can waterlog the soil and increase salinity, reducing the productivity of agricultural land and limiting opportunities for further development. It can also result in additional run-off to sensitive downstream environments (e.g. the Ramsar-listed wetlands at Bowling Green Bay and the Great Barrier Reef) (Queensland Government, 2021b)

DRDMW released a Lower Burdekin Groundwater Strategy Project Discussion Paper which identified four categories of potential management actions that would either reduce groundwater recharge and/or extract groundwater from the aquifer:

• changes to more efficient onfarm irrigation practices and supporting programs – including promoting greater use of on-farm conjunctive use (mixing of saline groundwater and betterquality surface water)

• operational actions – including reducing channel seepage by lining open-earth channels with high-density polyethylene establishing scheme operated dewatering bores, upgrading Sunwater distribution infrastructure (such as replacement of inefficient channel regulation

High-level review of lower Burdekin benefits and impacts associated with the future water infrastructure development in the Burdekin catchment –3 July 2022 gates, greater use of balancing or offstream storages and better capture of system outflows from Clare main channel), dewatering aquifers disposing and saline water in evaporation ponds or waterways

• regulatory actions – including reviewing the Burdekin water plan and operations manual to include strategies to help reduce groundwater recharge, rising groundwater and salinity (such as placing restrictions on surface water use to prioritise groundwater use when groundwater tables reach critical levels, making changes to the licencing framework to encourage the use of groundwater instead of surface water and/or the supply of supplemented (blended) groundwater from dewatering bores to maintain water quality, developing environmental management rules to manage groundwater issues, or improving the security of groundwater entitlements to enable greater trading opportunities

• incentive measures – including revamping current pricing arrangements (e.g. by including the costs associated with the impact of surface water use on rising groundwater tables into surface water prices, or re-balancing the fixed–variable surface water price ratio with a smaller fixed charge and larger variable charge) that might encourage irrigators to use surface water more efficiently and to make greater use of groundwater, or utilizing marketbased instruments (e.g. such as establishing price signals that give landholders the choice and flexibility to decide whether to change their practices or incur higher costs) (State of Queensland, 2017)

Discussion with a BRIA irrigator in June 2022 indicated that Sunwater has previously restricted the volume of permanent water trades into the BRIA – ostensibly to avoid exacerbating groundwater and salinity issues in the area although existing channel delivery capacity constraints is also likely to be a key consideration in limiting the additional volume of surface water supplied to the area.

In June 2018, Sunwater presented a range of potential infrastructure solutions to supply water to identified future irrigation areas and also improve the water supply and energy use efficiency associated with the Burdekin- Haughton Water Supply Scheme (BHWSS) Whilst Sunwater’s report included examining the Haughton Channel Capacity Upgrade option, at that time the focus was primarily about allocating resources to projects that have higher commercial and/or economic merit although it acknowledged that many of the solutions considered had the potential to form part of the proposed lower Burdekin Groundwater Strategy to address the high groundwater levels present in the area (Munck, 2018).

Clearly the most effective overall approach for addressing the rise in groundwater levels and salinity in the BRIA appears likely to be a combination of the approaches as proposed by the Burdekin Groundwater Strategy Project. However, lining the open-earth distribution channels appears to offer a pathway for investing in infrastructure that would directly and immediately reduce the volume of water seeping into the groundwater system.

This presents an important opportunity for a new bulk water resource development (such as the Hells Gate Dam Project) that extends the reach of the existing BHWSS to well upstream of Burdekin Falls Dam Incorporating the cost of channel lining into the upfront capex of such a project would (a) arrest and potentially reverse the ongoing rises in groundwater and salinity levels within the BHWSS from channel losses and (b) enable up to 200 GL of channel loss water allocations to be freed up and repurposed to support productive use (e.g. irrigation and/or water for hydrogen) in areas that do not place any additional groundwater resource stress in BRIA (e.g. by opening up new irrigation areas upstream of the Burdekin Falls Dam)

4.1.2 Groundwater system underlying the area managed by Lower Burdekin Water

The second groundwater system effectively underlies an area of irrigated land that is supplied with water by Lower Burdekin Water (LBW) which was formerly made up of the North Burdekin Water

High-level review of lower Burdekin benefits and impacts associated with the future water infrastructure development in the Burdekin catchment –3 July 2022

Board (NBWB) and South Burdekin Water Board (SBWB) as shown in Figure 1 LBW is a locally managed organisation that manages the groundwater system in the lower Burdekin Delta including through its supplementation and replenishment (recharge) from surface water supplies sourced from the Burdekin River (Lower Burdekin Water, 2022)

LBW diverts water from the Burdekin River into modified natural and artificial recharge systems to replenish the large coastal, unconfined aquifer that beneath its area of authority. Water contained in this aquifer is pumped by irrigators, industry, the Burdekin Shire Council and residents. Customers also pump open water directly from LBW channels and lagoons. This reduces demand in the aquifer and assists in conserving and managing underground water levels as well as improving the quantity and quality of water available within the aquifer (Lower Burdekin Water, 2021)

NQ Dry Tropics consider that the main matters of concern – including the effects of seawater intrusion, a rising groundwater table, and increasing concentrations of salts – relate to the health of the Burdekin River Delta aquifer and coastal wetland ecosystems. They contend that contributing factors include the amount of water being released through watercourses and channels for irrigation access, deep drainage and channel leakage, and irrigation practices (NQ Dry Tropics, 2022a).

Natural recharge from rainfall is understood by LBW to be a key to the recovery of groundwater levels to healthy levels. Elevated water levels within the Burdekin River during flood events (such as that which occurred in 2021) is also believed by LBW to contribute to replenishment of the aquifer. However, LBW report that their ability to pump water from the Burdekin River can be negatively impacted during such events but may be offset by local rainfall (Lower Burdekin Water, 2021).

In 2020-21, the key challenges facing the LBW highlight the range of uncertainties or knowledge gaps that they currently face. These include:

• concerns about the impacts that proposed upstream dams might have on natural river flows, water allocation reliability and the environment in the lower Burdekin Delta area

• the need for groundwater research within the Burdekin Delta6 covering: o the influence of seawater intrusion of the Delta groundwater resource and the risk to this resource from sea-level rise ad changing rainfall patterns o predicting groundwater response to different irrigation surface water/groundwater conjunctive use scenarios o the influence of Burdekin River on groundwater recharge and the potential impacts of new or modified upstream dam proposals o the efficacy of LBW’s recharge pits, delivery channels and sand dams on groundwater recharge and extent of the benefited areas

• improving the technical design/management of, and clarity of the regulatory framework supporting, sand dams within the Burdekin River (Lower Burdekin Water, 2021)

The above suggests that there are a range of fundamental areas that warrant urgent and coordinated research to enable improved and more efficient management of the groundwater resources in the lower Burdekin Delta. Although LBW (as the authority responsible for managing access to the resource) is progressing such research, increased support for broader and longer-term study programme would appear to be warranted to enable the collaborative and coordinated management of coastal wetland ecosystems and their interconnections with the Great Barrier Reef and lower Burdekin Delta groundwater systems.

High-level review of lower Burdekin benefits and impacts associated with the future water infrastructure development in the Burdekin catchment –3 July 2022

Committing to such a research programme appears to be the key opportunity and potential inclusion for investment by a future upstream bulk water infrastructure development (such as the Hells Gate Dam Project)

4.2 Water security and availability

Water users have expressed concerns that future upstream bulk water infrastructure developments might result in changes in water flows to Burdekin Falls Dam and result in reduced water security and availability. As mentioned in section 4.1.2, this is also one of the specific issues identified by LBW In addition, discussion with mayors in June 2022 also confirmed that water security remains a priority for all local governments in the region. In addition, securing new sources of reliable water was identified as being important to support future hydrogen production in the region (Townsville Enterprise Limited, 2022b).

Hydrologic modelling was undertaken as part of the Hells Gates Dam Detailed Business Case to assess the impact of new development on the long-term hydrologic performance of existing high and medium priority supplemented water allocations in the BHWSS. This modelling found that the long-term hydrologic reliability of the existing supplemented water allocations held by urban, industrial and irrigation customers were similar or better than those of the water plan base case and exceeded the water allocation security objectives set out in the Burdekin water plan (Badu Advisory, Unpublished).

Using hydrologic modelling, sensitivity analysis was also undertaken to understand the relationship between the capacity of the proposed dam and the BHWSS’s hydrologic performance as well as resilience to climate change. These analyses suggested that a larger dam capacity (for a given volume of new water allocations) would materially increase the annual reliability of existing medium priority water allocations and of new medium priority water allocations supplied from Hells Gates Dam, as well as reduce the extent of impact of a drier climate on the reliability of medium priority water allocations (Badu Advisory, Unpublished).

The opportunity for a future upstream bulk water infrastructure development (such as the Hells Gate Dam Project) is to engage with stakeholders about the improved hydrologic performance that would be offered by extending the existing Burdekin Haughton Water Supply Scheme to incorporate the new upstream storage. As the Burdekin Shire Council Mayor observed to the media in March 2022:

The Burdekin Shire’s namesake is the delta on which our communities have grown. This River is an integral part of our community not only for its impressive size, but in the opportunities it provides to us. Our abundant water supply is fed by an underground aquifer, which each year is replenished in the wet season when the Burdekin Falls Dam spills and sends water downstream. I am aware that water security is important for all communities, however there needs to be more evidence that Burdekin Shire’s water security is not taken away from us for the development of new areas and benefit for others (Burdekin Shire Council, 2022)

Stakeholder engagement should also extend to examining the potential benefits of treating the new and existing water infrastructure as an integrated water supply scheme – this would enable new upstream storages, Burdekin Falls Dam and Clare Weir to be managed in such a way that optimizes the efficiency of water deliveries, water sharing and trading rules, water storage arrangements and environmental water releases (e.g. to mimic natural flow events as well as maintain fish passage flows) throughout the entire system (Badu Advisory, Unpublished)

High-level review of lower Burdekin benefits and impacts associated with the future water infrastructure development in the Burdekin catchment –3 July 2022

4.3 Environmental flows

Concerns have also been expressed by various stakeholders about the potential impacts of new upstream bulk water infrastructure developments on environmental flows in the lower Burdekin. Hydrologic modelling was undertaken as part of the Hells Gates Dam Detailed Business Case to assess the impact of new development on the flow regime in the lower Burdekin. The modelling found that at the mouth of the Burdekin River (water planning node 1) there was an improvement on the majority of the environmental flow objectives but an observable decrease in modelled flood flows (as indicated by the 5-year and 20-year high flow objectives).

There is no doubt that seasonal peak flood flow events are important for watering and connecting riverine and wetland habitats as well as contributing to riverine recharge of the lower Burdekin Delta groundwater system as mentioned in section 4.1.2. The environmental flow objectives within the water plan reflect the ecologically important components of the flow regime in hydrological statistical terms. Sheep Station Creek which is a floodplain distributary of the Burdekin River that historically only flowed seasonally during the wet season and transitioned to a chain of isolated lagoons in the dry season, is a case in point:

The main environmental management issues confronting the Sheep Station Creek system are associated with changed catchment hydrology, aquatic weed infestation, altered fire regimes, degradation of riparian zones, water quality impacts and barriers to fish passage connectivity. These issues have arisen since European settlement with the intensive development of the catchment’s land and water resources for irrigated agriculture and pastoral development. Hydrological change is arguably the primary driver of observed environmental impacts (Tait, 2021)

On the other hand, major peak flood events represent a serious threat to low-lying properties and communities within the lower Burdekin. Flood events generally follow heavy rainfall with most common floods occurring in February and March. Very large floods generally occur between January and April, and large events occurring from December to May. Local experience suggests that flooding at Giru is linked with flooding at Ayr and Home Hill: the Haughton and Lower Burdekin subcatchments merge in some events with floodwater spilling across the catchment delta. Home Hill is usually flooded first, followed by Ayr whereas Dalbeg and Millaroo are predominately above flood levels (Queensland Reconstruction Authority, 2022).

The lower Burdekin floodplain experienced large flood events in 1927, 1940, 1946, 1958, 1974, 1988 & 1991. The 1946 flood was the largest event for which recorded data is available with a peak discharge of 40,400 cubic metres/second recorded in March at the river gauge at Home Hill. This event was a similar height to the 1940 event but was more prolonged. During the event, the floodwaters broke the le bank of the Burdekin River at Gladys' Lagoon and joined up with floodwaters from the Haughton River, causing widespread flooding in very large areas in the north side of Home Hill (Queensland Reconstruction Authority, 2022)

Provision of additional upstream storage capacity coupled with multi-level dam outlet works that are capable of better managing the timing – and reducing the peak - of natural yet damaging peak flood flow events may present benefits of significant economic value and importance to downstream communities.

The opportunity for a future upstream bulk water infrastructure development (such as the Hells Gate Dam Project) will be to further investigate and assess, in consultation with the community, the pros and cons associated with the potential changes to the downstream flow regime particularly with respect to the impacts and benefits of reducing peak flood flows in the lower Burdekin.

Other examples of environmental flow strategies that warrant future dialogue with stakeholders (as part of the upcoming water plan revision process) might include:

• extending low to medium environmental flow objectives beyond the trunk stream to better service important ecological assets located away from the main river and dependent on

High-level review of lower Burdekin benefits and impacts associated with the future water infrastructure development in the Burdekin catchment –3 July 2022 smaller off-river tributaries from the delta for their seasonal connection to coastal wetlands and

• including provisions that encourage greater use of groundwater at certain times when preservation of riverine and tributary flows is considered environmentally important.

4.4 Water quality, turbidity and sedimentation

A key area of focus and investment for researchers and resource managers in the lower Burdekin continues to be in understanding and addressing the potential implications of existing and proposed water infrastructure developments on riverine, coastal wetland and reef water quality and condition including the effects of turbidity and sedimentation

However, as Burrows et al observe, aiming to restore natural function to wetlands in a highly and permanently modified environment may not be realistic:

Health and naturalness may be very different end-points for such wetlands, depending on the landscape context, creating the need for more holistic and expansive evaluations of end-point goals. Commonly, we find that the solutions proposed are often based on generic and simplistic views, including the reversal of the perceived root cause of the problem, though this is not always the best course of action. These simplistic views often result in unrealistic expectations and a failure to target the most effective outcomes and means of rehabilitation… [Three case studies in the lower Burdekin show that] end-point goals for wetland rehabilitation are quite different from restoration of their pre-European state… [and that] elevated turbidity and flow regimes, even though unnatural and often thought of in a negative context, are actually maintaining the health of key coastal wetlands by decreasing their vulnerability to other human pressures (Burrows, 1999)

In 2014, the Australian Institute of Science (AIMS) Fabricus et al found that the presence of fine sediment is one of the biggest pressures on the health of inshore reefs because it clouds the water and blocks sunlight from reaching photosynthetic algae in the coral. AIMS’ study also showed that large river flood events during the wet season washed sediment into the ocean which had a significant impact on water quality around the reef and could last several months (K.E. Fabricus, 2014). It was also reported that the fine sediment in the river was caused by land erosion but that: with better land management practices (which are currently going on in the catchment, we can probably reduce the amount of that erosion and reduce the amount of load the rivers are carrying into the reef (Whiting, 2014).

Clearly, AIMS’s work has confirmed that improved land management is a priority for targeted subcatchments within the Burdekin Basin. Fabricus et al observed that: a reduction in fine sediments and nutrient loads in the Burdekin River is likely to improve water clarity for six to eight months per year, potentially also providing cumulative benefits in consecutive years especially in the coastal band. The documented changes in water clarity are sufficiently large to affect coral reef and seagrass communities, hence reductions in river loads would likely lead to substantial ecosystem health benefits Specific sub-catchments that contribute most to the sediment and nutrient loads have been identified, and the relative roles of fertilizers, hill- slope, gully and streambank erosion to end-of-river loads have been quantified Land management efforts should therefore be prioritised to maximize the retention of nutrients, clays and fine silts in these sub-catchments, which would not only safe-guard the long-term productivity of farms, but also improve water clarity and ecosystem health in the central Great Barrier Reef, suggesting a win–win situation (K.E. Fabricus, 2014)

As part of a number of programs that contribute to the Reef 2050 Water Quality Improvement Plan a joint commitment of the Australian and Queensland governments that seeks to improve the quality of water flowing from the catchments adjacent to the Great Barrier Reef – AIMS are also continuing to work to monitor and further understand the impacts of water quality related pressures on tropical marine ecosystems (Australian Institute of Marine Science, 2022b). They report that they are: using field research, SeaSim experiments and modelling to understand the cumulative and interacting impacts of local pressures, and critical thresholds in the hope that the resilience of local marine ecosystems can be enhanced by reducing local pressures… [and have found that] corals in low nutrient waters have a greater temperature tolerance than those exposed to sediments, fertiliser-derived nitrogen and phosphorus, and pesticides (Australian Institute of Marine Science, 2022a).

High-level review of lower Burdekin benefits and impacts associated with the future water infrastructure development in the Burdekin catchment –3 July 2022

The Great Barrier Reef Marine Park Authority (GBRMPA) concur stating their position that:

Poor water quality is a major threat to the Great Barrier Reef, particularly inshore areas. Improving the quality of water entering the marine park is critical and urgent. GBRMPA supports actions that reduce loads from all landbased sources (GBRMPA, 2022)

NQ Dry Tropics are also engaged in a project to reduce the impacts of fine sediment from the Burdekin catchment through a range of practical initiatives focussed on stream bank repair, improving the health of key local waterways and wetlands, working with farmers to improve their farm management, and programs aimed at raising community awareness (NQ Dry Tropics, 2022b) The wide array of current research into these issues discussed above (and this is by no means a comprehensive summary of all the work that has been or is being done) clearly remains urgent and important to underpin the future health and sustainable management of the lower Burdekin including its coastal ecosystems and reef. Specific areas that warrant more detailed investigation as part of the further assessment of future upstream bulk water infrastructure developments (such as the Hells Gate Dam Project) include:

• assessing the potential benefits and costs of modifying the outlet works at Burdekin Falls Dam to enable active management and bypassing of occasional pulse-style environmental releases that are aligned with improving management of downstream sediment loads, aquifer recharge and sand dam performance, efficiency and lifespan and

• also considering retrofitting a multi-level outlet work structure at Burdekin Falls Dam as a means of improving management of the water quality of dam releases for downstream environmental and water supply purposes.

4.5 Cumulative impacts

Multiple stakeholders have expressed concern about the cumulative impacts of existing and proposed upstream water resource infrastructure and development.

Researchers from James Cook University are of the view that there have been insufficient studies into the long-term impacts on the lower Burdekin of existing dams let alone in relation to the suite of proposed upstream developments that currently under investigation. This view reflects the same theme of over twenty years ago when researchers flagged concerns about the effect of the then tenyear old Burdekin Falls Dam:

However, the coastal environments are of greater concern. The significant geomorphological features of the Burdekin delta, coastline and Cape Bowling Green, are supplied by sand from the Burdekin River. Reductions in delivery of sand, largely through reductions in the frequency of medium-large flow events may pose a serious threat to these coastal features. The impact of such a large dam on sediment transport processes and coastal environments is a critical point, as is its impact on coastal/marine fisheries (Burrows, 1999)

Davis et al pursued a similar argument in 2014:

Cumulative (and ongoing) changes to water regimes and the chemistry of both surface and subsurface waters now pose major threats to both the long-term viability of wetlands and large sections of the sugar industry itself. Substantial shifts in societal perceptions and expectations regarding the value of wetlands and water resources at national and global levels are reflected in the lower Burdekin region. The legacy of earlier perceptions and associated policy decision-making are, however, going to provide some of the most enduring management challenges for lower Burdekin coastal wetlands, and ultimately the viability of irrigation areas themselves (Davis et al., 2014).

Cooper et al also examined the effect of large storages on sediment loads in the lower Burdekin observing that:

When compared to similar large tropical to sub-tropical reservoirs, the Burdekin Falls Dam has a slightly longer reservoir useful life than dams in India and a much longer half-life than for both similar-sized and larger dams in China, Brazil, and Iran. Properties of the Burdekin Falls Dam that promote a longer useful life include a lower trap efficiency, relatively low annual sediment load delivered to the reservoir, limited sediment deposition behind the

High-level review of lower Burdekin benefits and impacts associated with the future water infrastructure development in the Burdekin catchment –3 July 2022 dam wall (and uniform distribution of deposited sediment), and the export of highly turbid annual floodwaters before settling and deposition of any remaining sediment within the reservoir (Cooper et al., 2018)

A 2019 Minister’s performance assessment report into the achievement of the Burdekin water plan’s outcomes identified a range of risks in relation to:

• Maintaining natural variability of flows to support habitats. Habitats are at risk from increased demand and potential new infrastructure, but these are risks that can be addressed under a plan review.

• Ecological connectivity. Impediments to a natural flow regime may have impacts on freshwater inputs to floodplain wetlands, estuaries and the Great Barrier Reef Lagoon. Further targeted science is required.

• Natural flows in the Barratta Creek systems. The plan aims to ensure there are no further impacts on natural flows in these areas. There is observed die-back of riparian vegetation and an overall freshening of the water in the associated estuaries. Regional ecosystem mapping identifies that the remnant riparian vegetation associated with the Barratta Creek system has the biodiversity status ‘of concern’. The science from the Lower Burdekin Groundwater Strategy will assist in informing understanding of this issue and ways to mitigate risks.

• Natural flows in the Haughton River systems. There is risk to the flow regime required to support fish passage to the mouth of the Haughton River. The science from the Lower Burdekin Groundwater Strategy will assist in informing understanding of this issue and ways to mitigate risks.

• The minimisation of adverse impacts to riverine morphology. A need has been identified to collect stream crosssection data for watercourses, waterholes, lakes and springs used for taking supplemented water in the BHWSS

• Lower Burdekin Groundwater Strategy a future plan review may need to accommodate the outcomes of the Lower Burdekin Groundwater Strategy currently in progress.

• Consistency with Reef 2050 Plan the Reef 2050 was released by the Australian and Queensland governments in July 2018 as an overarching framework for protecting and managing the Reef. The water plan must be consistent with the Reef 2050 (DNRME, 2019)

These have been flagged for review as part of the process of amending the Burdekin water plan prior to its expiry in September 2023 (DNRME, 2019)

Recently, modelling was undertaken as part of the Hells Gates Dam Detailed Business Case to assess the cumulative impacts of a range of combinations of upstream water infrastructure development proposals on the riverine hydrology of the lower Burdekin (Badu Advisory, Unpublished) Although this was useful in assessing the relative extent of hydrologic impacts on downstream environmental flows (as discussed in section 4.3), it was not designed to draw conclusions about the resulting implications for the long-term viability of coastal wetlands or the geomorphological stability of the coastline itself

The key area that warrants more detailed investigation as part of the further assessment of future upstream bulk water infrastructure developments (such as the Hells Gate Dam Project) is to examine, in a whole of region context, the cumulative impacts of existing plus various combinations of new water infrastructure developments on riverine and coastal geomorphological considerations This should include utilizing the hydrologic information available from the modelling studies that have been recently completed as part of Detailed Business Cases.

4.6 Institutional, water allocation/management and regulatory arrangements

Williams et al observed in 2009 that “the historical development of three relatively discrete irrigation communities with independent institutional arrangements coupled with an incomplete and fragmented understanding of the groundwater hydrology of the lower Burdekin region, has resulted in an array of institutional and management responsibility that to date has failed to serve the community and yield an integrated management of the surface and groundwater of the lower Burdekin”. They went on to observe that the “lack of strategic management is not due to an absence of hard work and commitment by any of the stakeholders [but] has been caused by stakeholders working on isolated projects with no overall integration coupled with a lack of institutional arrangements and responsibility which drive integrated management of the land and water resources within the lower Burdekin” (Williams et al., 2009).

High-level review of lower Burdekin benefits and impacts associated with the future water infrastructure development in the Burdekin catchment –3 July 2022

At the time, it was recognised by Williams et al that the relationship between the aquifers of the BRIA and the North and South Burdekin Water Board irrigation districts was not well-understood making it difficult to determine the impacts of changed groundwater management in the BRIA on the Water Board irrigation districts or to understand what actions will need to be undertaken in these irrigation districts Although the Lower Burdekin Water Futures (LBWF) group – involving state agencies, local government representatives, Sunwater, LBW (formerly through the NBWB and SBWB), irrigators, researchers and other stakeholders – subsequently emerged as a useful forum to foster discussions between the various players, it appears that the focus and energy of this group has receded in recent years.

Responsibility for the management of surface and groundwater resources in the lower Burdekin remains shared between multiple organisations (BOM, 2022). DRDMW develop and administer the water planning framework within the Burdekin Basin and are responsible for monitoring and enforcing compliance with that framework. They also manage unsupplemented water allocations along the river as well as the monitoring and licensing regime that applies to the groundwater system underlying the BRIA. Sunwater manage the supplemented water allocations. They also own and manage water bulk infrastructure within the Burdekin and Haughton Rivers as well as the channel and drainage system throughout the BRIA including the Giru benefitted groundwater area. LBW are very effective in managing all water distribution and replenishment infrastructure, as well as and water users’ access, within the footprint of the lower Burdekin Delta groundwater system in a coordinated way, although they clearly recognise their limitations in understanding of a range of key issues potentially impacting their future as described in section 4.1.2

Having

A Clear Focus Is A Necessary Ingredient For Any Organisation To Deliver Its Core Business

However, siloed drivers by themselves are not generally conducive to promoting a joint understanding or collaborative management of the various components of the surface and groundwater resources in the lower Burdekin. Organisational objectives and activities – whether they be in the areas of research, policy development or operations – are tend not to be driven by a sense of shared commitment to achieving integrated outcomes at a whole of landscape and community level An example of this relates to the lack of success this far in promoting the conjunctive use of surface and groundwater resources in the BRIA as mentioned in section 4.1.1

GBRMPA also support collaborative action observing that:

While there have been improvements in land management practices at the regional level, progress towards land and catchment management targets has been limited.21,22 Effective collaboration and cooperation between government, industry, regional bodies and farmers is essential to achieving these targets (GBRMPA, 2020)

There is therefore an urgency to rekindling a sense of joint understanding, purpose and commitment between organisations and stakeholders towards confirming the water resource related problems needing to be solved in the lower Burdekin and then working together in a coordinated and collaborative way to achieve tangible, measurable and timely improvements at a whole-of-region scale. There may also be value in considering giving accountability for overseeing such efforts to an independent institutional body subject to maintaining strong ties to local stakeholders (both individuals and organisations) As TropWater recently observed in relation to the ecology of the streams, rivers and floodplain wetlands of the Burdekin River system:

Effective management needs to integrate multiple uses via governance of activities and interactions of stakeholders, recognising basic hydrogeomorphic, water quality and ecological needs for adequate conservation (Pearson et al., 2022)

The opportunity for a new upstream bulk water resource development (such as the Hells Gate Dam Project) is to establish a renewed funding basis, focus and drive for all stakeholders – organisations and individuals – to reengage in the kind of joint visioning, collaborative thinking and learning, and community-driven action that previously espoused by Williams et al over a decade ago.

High-level review of lower Burdekin benefits and impacts associated with the future water infrastructure development in the Burdekin catchment –3 July 2022

This could also be supported by the engagement processes that will support DRDMW’s development and implementation of an updated water plan for the Burdekin (which is scheduled to expire in September 2023). As water plans are premised on defining and achieving outcomes at the basis scale, there would be significant synergies in aligning the water plan update process with the visioning, thinking, learning and actions contemplated for the lower Burdekin collaborative process as suggested above.

4.7 Climate change and variability

In 2019, the Minister’s performance assessment report into the Burdekin water plan identified climate change of an emerging issue:

Climate projections for 2030 predict an increase in evaporation in the plan area. This may increase water consumption and losses from storages, and may reduce the persistence of waterholes that are used for refugia by stream biota. A new hydrologic model is being developed that will assist in future assessments to build understanding of climate change risks (DNRME, 2019)

Climate change is key issues that will therefore be examined as part of the amendment or review of the water plan in close consultation with the catchment community prior to its expiry in 1 September 2023 (DNRME, 2019).

In the meantime, modelling was undertaken as part of the Hells Gates Dam Detailed Business Case to assess the implications of climate change and/or additional upstream storage size on various hydrologic performance measures. This sensitivity analysis was based on comparing historical climate data with the CSIRO-Mk3.6 GCM climate data which gives the median outcomes across the 11 tested GCMs. The modelling found that:

Assuming a drier climate than that experienced historically reduces headline environmental flow indicators and reduces the hydrologic performance of existing medium priority water allocations in the Burdekin Haughton Water Supply Scheme as well as of new medium priority water allocations supplied from Hells Gates Dam… [but] halving the full supply volume for Hells Gates Dam would increase the potential impact of a drier climate on the performance of medium priority water allocations The size of the dam was found not to change the extent of the impact of climate change on mean or median annual flows at the end of system (node 1) (Badu Advisory, Unpublished).

Testing the potential implications of climate change in this way suggests that additional water storage and outlet work capacity can assist in significantly improving water supply scheme resilience in a drier climate scenario

In reality, climate change is likely to manifest in terms of even more complex changes to seasonal and inter-annual patterns, as well as the frequency, duration and intensity of flood events and droughts Although such changes are more difficult to model, the Department of Environment and Science are progressing the development of more sophisticated techniques for assessing the potential effects of climate variability and change All water users – and the riverine environment –are likely to be sensitive to such changes including, for example, the reduced frequency but increased intensity of future riverine flood events, as well as the extended duration of extreme drought events.

There is a growing body of evidence that suggests that understanding the implications of natural climate variability may be of greater urgency and importance in Queensland river systems than climate change. As Kiem et al observe:

The instrumental record is short (~60-130 years) and fails to encompass enough climate variability to allow the calculation of robust statistics around the baseline risk of extreme events (i.e. multi-year droughts, decadal periods with clustering of major flood events). This climate variability is documented pre-1900 in paleoclimate records from sources such as corals, tree-rings, freshwater and marine sediments… A high resolution and highly correlated paleoclimate record from the Law Dome ice cores in Antarctica exists… [that] has identified eight mega-droughts (lasting from 5-39 years) during 1000-2009 AD. Most importantly, the paleoclimate information confirms that the post-1900 instrumental period (i.e. the period on which all water resources infrastructure, policy, operation rules and strategies is based) does not capture the full range of variability that has occurred.

High-level review of lower Burdekin benefits and impacts associated with the future water infrastructure development in the Burdekin catchment –3 July 2022

Recent work also shows that, out to 2050 at least, the impacts of natural variability dwarf even the worst-case climate change scenarios (i.e. obtained from Global Climate Models run under the highest emission scenarios) (Kiem et al., 2020)

The opportunities for a new upstream bulk water resource development (such as the Hells Gate Dam Project) are:

• to quantify the potential benefits that additional storage capacity might offer as a means of managing potential variations in climate that are more extreme than observed in the historical record (i.e. less frequent but more intense flood events interspersed with drought events of extended duration) and

• to conceptualise the design and desired performance of existing and new bulk water infrastructure developments in terms of regional water grids that draw together multiple sources of water (including catchment surface water storages, groundwater and manufactured water etc.) and inter-connectors (using bulk water pipelines) to provide overall reliability of a water supply portfolio that matches users’ needs.

High-level review of lower Burdekin benefits and impacts associated with the future water infrastructure development in the Burdekin catchment –3 July 2022

Appendix A – References

Australian Institute of Marine Science (2022a) Cumulative impacts and ecosystem resilience. <https://www.aims.gov.au/cumulative-impacts>.

Australian Institute of Marine Science (2022b) Monitoring water quality. Viewed 30 June 2022, <https://www.aims.gov.au/monitoring>.

Badu Advisory (Unpublished) Water Allocation Strategy for the Proposed Hells Gates Dam Project.

BOM (2022) Burdekin: Key findings for the water account period 1 July 2020–30 June 2021. Viewed 30 June 2022, <http://www.bom.gov.au/water/nwa/2021/burdekin/index.shtml>.

Burdekin Shire Council (2022) Water security for Burdekin questioned.

Burrows DW (1999) An Initial Environmental Assessment of Water Infrastructure Options in the Burdekin Catchment. Australian Centre for Tropical Freshwater Research - James Cook University. Available online:

<https://d3n8a8pro7vhmx.cloudfront.net/nqcc2/pages/1587/attachments/original/160645 8550/2.1.1_BURROWS_etal_1999_updated_%282%29.pdf?1606458550>.

Cooper M, Lewis SE, Stieglitz TC and Smithers SG (2018) Variability of the useful life of reservoirs in tropical locations: A case study from the Burdekin Falls Dam, Australia. International Journal of Sediment Research 33(2), 93-106. Doi: https://doi.org/10.1016/j.ijsrc.2017.11.002

Davis A, Lewis S, O'Brien D, Bainbridge Z, Bentley C and Mueller J (2014) Water Resource Development and High Value Coastal Wetlands on the Lower Burdekin Floodplain, Australia. Estuaries of Australia in 2050 and beyond, 223-245. Doi: 10.1007/978-94-007-7019-5_13.

DNRME (2019) Minister's performance assessment report (2019) : Water Plan (Burdekin Basin) 2007. Available online:

<https://qldgov.softlinkhosting.com.au/liberty/opac/search.do?mode=ADVANCED&corporat ion=DERM&limit=All&action=search&anonymous=true&queryTerm=wrpburdekin+wrpann&i ncludeNonPhysicalItems=true&resourceCollection=All&branch=All&operator=AND>.

GBRMPA (2020) Position Statement - Water quality. Available online:

<https://elibrary.gbrmpa.gov.au/jspui/retrieve/3a9336c3-b16d-457c-a815f06fda711c36/v0-Position-statement-water-quality.pdf>.

GBRMPA (2022) Land-based run-off. Viewed 30 June 2022, <https://www.gbrmpa.gov.au/ourwork/threats-to-the-reef/declining-water-quality>.

K.E. Fabricus ML, S. Weeks, J. Brodie (2014) The effects of river run-off on water clarity across the central Great Barrier Reef. Marine Pollution Bulletin 84(1-2).

Kiem A, Vance T, Tozer C, Roberts J, Pozza R, Vítkovský J, Smolders K and Curran M (2020) Learning from the past – Using palaeoclimate data to better understand and manage drought in South East Queensland (SEQ), Australia. Journal of Hydrology: Regional Studies 29, 100686. Doi: 10.1016/j.ejrh.2020.100686.

Lower Burdekin Water (2021) Annual Report 2020-21. Available online: <http://lowerburdekinwater.com.au/wp-content/uploads/2021/09/2020-21-LowerBurdekin-Water-Annual-Report-Letter-of-Compliance-and-Appendices.pdf>.

Lower Burdekin Water (2022) Welcome to Lower Burdekin Water. Viewed 20 June 2022, <http://lowerburdekinwater.com.au>.

Munck G (2018) Burdekin Channel capacity upgrade feasibility study - milestone 3 final report. Available online: <https://qldgov.softlinkhosting.com.au:443/liberty/OpacLogin?mode=BASIC&openDetail=tr ue&corporation=DERM&action=search&queryTerm=uuid%3D%220ec610bb0a0200f01fa004 1f00204a44%22&operator=OR&url=%2Fopac%2Fsearch.do>.

NQ Dry Tropics (2022a) Lower Burdekin Catchment Ground and Surface Water Interaction Issues. Viewed 20 June 2022, <https://nrm.nqdrytropics.com.au/water/lower-burdekin-subcatchment-ground-surface-water-interaction-issues/>.