Stream ecosystem health response to coal seam gas water release

Transcription

1 Healthy HeadWaters Coal Seam Gas Water Feasibility Study Stream ecosystem health response to coal seam gas water release Guideline for managing flow regimes Science Delivery Division Department of Science, Information Technology, Innovation and the Arts Prepared for the Department of Natural Resources and Mines

2 This document presents outcomes of Activity 4 (Stream ecosystem health response to coal seam gas water release) of the Healthy HeadWaters Coal Seam Gas Water Feasibility Study. The Healthy HeadWaters Coal Seam Gas Water Feasibility Study is analysing the opportunities for, and the risks and practicability of, using coal seam gas water to address water sustainability and adjustment issues in the Queensland section of the Murray-Darling Basin. The study is being funded with $5 million from the Commonwealth Government, with support from the Queensland Government, as part of the Healthy HeadWaters Program, which is Queensland s priority project funded through the Commonwealth Government s Water for the Future initiative. The study is being managed by the Queensland Department of Natural Resources and Mines (DNRM). This report was prepared by the Science Delivery Division, Department of Science, Information Technology, Innovation and the Arts (DSITIA) for the State of Queensland (DNRM). This report was originally developed by the Department of Environment and Resource Management in 2011 and has subsequently been reviewed and released as a final version by DSITIA in Disclaimers This document was prepared exclusively for the State of Queensland (Department of Natural Resources and Mines) and is not to be relied upon by any other person. DSITIA has made every effort to ensure that the information provided is accurate but errors and omissions can occur and circumstances can change from the time that the document was prepared. Therefore, except for any liability that cannot be excluded by law, DSITIA excludes any liability for loss or damage, direct or indirect, from any person relying (directly or indirectly) on opinions, forecasts, conclusions, recommendations or other information in this report or document. State of Queensland The State gives no warranty in relation to the contents of this report (including accuracy, reliability, completeness, currency or suitability) and accepts no liability (including without limitation, liability in negligence) for any loss, damage or costs (including consequential damage) relating to any use of the contents of this report. Citation McGregor G, Marshall J & Takahashi E Stream ecosystem health response to coal seam gas water release: Guidelines for managing flow regimes. Brisbane: Queensland Department of Natural Resources and Mines. Acknowledgements The authors would like to acknowledge the contributions of the Healthy HeadWaters Coal Seam Gas Water Feasibility Study team for their support, Queensland Hydrology (Water Planning Sciences) for their support in running the IQQM hydrological model scenarios, Bernie Cockayne for assistance with running the riffle analysis, and all reviewers of this report.

3 About this report This is one of a series of reports produced through Activity 4 (Stream Ecosystem Health Response to Coal Seam Gas Water Release) of the Healthy HeadWaters Coal Seam Gas Water Feasibility Study. This report reflects the state of knowledge and policy at that time it was written. A full list of reports from Activity 4 is provided below. Reports from Activity 4 of the Healthy HeadWaters Coal Seam Gas Water Feasibility Study McGregor G, Marshall J & Takahashi E Stream ecosystem health response to coal seam gas water release: Guidelines for managing flow regimes. Brisbane: Department of Science, Information Technology, Innovation and the Arts, Queensland Government. (This report) Rogers S, McGregor G, Takahashi E, Shaw M & McNeil V Stream ecosystem health response to coal seam gas water release: Salinity guidelines. Brisbane: Department of Science, Information Technology, Innovation and the Arts, Queensland Government. Shaw M Stream ecosystem health response to coal seam gas water release: Hazard characterisation. Brisbane: Department of Science, Information Technology, Innovation and the Arts, Queensland Government. Takahashi E, McGregor G & Rogers S Stream ecosystem health response to coal seam gas water release: Direct toxicity assessment. Brisbane: Department of Science, Information Technology, Innovation and the Arts, Queensland Government. Takahashi E, McGregor G & Rogers S Stream ecosystem health response to coal seam gas water release: Biological monitoring guidelines. Brisbane: Department of Science, Information Technology, Innovation and the Arts, Queensland Government. Takahashi E, Rogers S, McGregor G & Shaw M Stream ecosystem health response to coal seam gas water release: Decision support system. Brisbane: Department of Science, Information Technology, Innovation and the Arts, Queensland Government. The Healthy HeadWaters Coal Seam Gas Water Feasibility Study is analysing the opportunities for, and the risks and practicability of, using coal seam gas water to address water sustainability and adjustment issues in the Queensland section of the Murray Darling Basin. The study is being funded with $5 million from the Commonwealth Government and support from the Queensland Government as part of the Healthy HeadWaters Program, which is Queensland s priority project funded through the Commonwealth Government s Water for the Future initiative. i

4 Summary Many watercourses in the Queensland Murray Darling Basin (QMDB) exist as networks of ephemeral channels and waterholes that experience extended no-flow periods followed by episodic high magnitude flows and overbank flooding which are typically associated with summer sub-monsoonal rainfalls. Long-term, high volume continuous releases of coal seam gas (CSG) water to these watercourses have the potential to alter important natural hydrological cycles in aquatic ecosystems adapted to these conditions. Consequently, guidelines relating to hydrological modification (i.e. timing, magnitude, rate of rise and fall, etc.) of surface waters due to the discharge of CSG water are required to minimise the risk of potentially adverse environmental impacts in the QMDB. This document identifies some of the potential hazards and provides guidance on addressing the risks posed to flow dependent ecosystem components and processes from CSG water discharges to rivers and streams. The process uses an eco-hydraulic modelling approach, based on the principles of ecological risk assessment. Existing knowledge and available information on critical flow-dependent ecological assets are identified; and a process is described for assessing the risk to these ecological assets to provide guidance on the management of impacts from CSG water disposal on flow regimes. The following process is presented and discussed: 1. Identification of the hazards related to the disposal of CSG water. This requires an understanding of the hydrological characteristics of the receiving environment. 2. Selection of ecological assets which represent the ecological values of the system, to be used as indicators of hydrological alteration of the flow regime. Knowledge of biota relying on aspects of the flow regime needs to be considered when discharging large volumes of water. 3. Development of CSG water disposal hydrology scenarios using existing knowledge on discharge volume and timing. 4. Analysis of the potential risks associated with disposal of CSG water. 5. Characterisation of the risks and incorporation of these into a management framework. The seasonality and timing of flows must be explicitly considered. ii

5 Contents About this report... i Summary... ii Contents... iii List of figures... v List of tables... vi Definitions and abbreviations... vii 1 Background Introduction Guideline objectives Potential hazards associated with CSG water related flow modification Duration Timing Variability Predictability Magnitude Rate of rise and fall Hydrology of the QMDB CSG water discharge Ecological responses Existing knowledge and datasets relating to ecological responses to flow regime Guideline for assessing impacts on flow dependent ecological assets Ecological risk assessment framework Hydrological modelling Discussion Other ecological issues Recommendations References Appendix A Aggregated CSG industry scenarios Methods Ecological assets Electrical conductivity scenarios Results and discussion Flow regime iii

6 Ecological assets Electrical conductivity scenarios Hydrological alteration Appendix B Ecological assets with critical links to flow Macroinvertebrate families present in the QMDB and Fitzroy Basin iv

7 List of figures Figure 1. Components of the flow regime considered ecologically important (modified from Walker et al. 1995) Figure 2: Hydrological classifications of streams in the Queensland Murray-Darling Basin and the Surat and Bowen coal basins (after Kennard et al. 2008). Each point represents a gauging station with flows considered to have little or no hydrologic modifications due to human activities Figure 3: Conceptual model of ecological responses to flow modification (modified from Schofield & Ziegler 2010 in U.S. EPA 2011). Detailed sub-models for (1a) discharge pattern and (1b) structural habitat shown in figures 4 and Figure 4: Detailed sub-model of ecological responses to flow modification - (1a) discharge pattern (modified from Schofield & Ziegler 2010 in U.S. EPA 2011) Figure 5: Detailed sub-model of ecological responses to flow modification - (1b) structural habitat (modified from Schofield & Ziegler 2010 in U.S. EPA 2011) Figure 6: Ecological risk assessment and risk management framework for flow-dependent ecosystem components and processes Figure 7: Location of IQQM nodes used to model CSG water discharge scenarios. The Condamine- Balonne Basin is found within the Queensland Murray Darling Catchment (QMDC) Basin.. 29 Figure 8: Percentiles of the flow rate in Condamine-Balonne Basin at: a) node H, b) node I, and c) node J; and in Fitzroy Basin at: d) node 06 and e) node Figure 9: Box plots of two scenarios where varying ECs were investigated in the Fitzroy Basin at Taroom (node 06) and Utopia Downs (node 07). The box represents the 25th to 75th percentiles with the median in the middle of the box, and the error bars represent the minimum and the maximum EC Figure 10: Box plots of two scenarios where varying ECs were investigated at the Condamine-Balonne Basin nodes (H, J, I). The box represents the 25th to 75th percentiles with the median in the middle of the box, and the error bars represent the minimum and the maximum EC v

8 List of tables Table 1: Flow regime classes identified in the Queensland Murray-Darling Basin (Kennard et al. 2008).. 6 Table 2: Summary of common ecological responses to flow alteration (modified from Poff & Zimmerman 2010)... 9 Table 3: Features of intermittent and ephemeral streams (modified from Richardson & Danehy 2007).. 10 Table 4: Flow-dependent ecological risk assessment framework Table 5: Predicted volumes of CSG water discharge. Data provided for specific sites by CSG companies28 Table 6: Base flow and seasonal variation performance indicator values from Fitzroy Basin WRP (1999).29 Table 7: Percentage of flows exceeding environmental flow objectives in the Fitzroy Basin predicted using the IQQM for the pre-development case and for CSG water discharge Table 8: Impact of CSG water discharge scenario on performance indicators at three discharge points in the Condamine Balonne Basin, modelled using the IQQM Table 9: Results of riffle inundation model for two sites in the Dawson River using the ROP and the CSG scenarios Table 10: Percentage of days where EC <120 µs/cm and the longest low spell days where EC < 120 µs/cm. The model was run for 120 years with CSG discharge set to EC of 50 µs/cm, compared to the ROP case at specific nodes Table 11: Assets in Border Rivers Basin with critical links to flow identified through water resource planning (DERM 2009) Table 12: Assets in the Moonie Basin with critical links to flow identified through water resource planning (DERM 2009) Table 13: Preliminary draft list of assets in the Upper Condamine (Condamine and Balonne Basin) with critical links to flow identified through water resource planning (DERM 2009) Table 14: Preliminary draft list of assets in the Middle Condamine (Condamine and Balonne Basin) with critical links to flow identified through water resource planning (DERM 2009) Table 15. Assets in the Fitzroy Basin with critical links to flow identified through water resource plans (Cockayne 2007, DERM 2009) Table 16: Macroinvertebrate families reported in Queensland Murray-Darling Basin and Fitzroy sites through DERM monitoring vi

9 Definitions and abbreviations 1 in 2 year flood The daily flow that has a 50% probability of being reached at least once a year. 1 in 10 year flood The daily flow that has a 10% probability of being reached at least once a year. ANZECC/ARMCANZ Guidelines Aquatic ecosystem Aquifer Associated water Beneficial flooding flow Coal seam gas (CSG) CSG water DERM Ecological asset Ecological risk assessment (EcoRA) Electrical conductivity (EC) Ephemeral stream Environmental Authority (EA) Environmental Flow Objectives (EFOs) Australian and New Zealand Guidelines for Fresh and Marine Water Quality (2000)/Agriculture and Resource Management Council of Australia and New Zealand An ecosystem located in a body of water. Freshwater aquatic ecosystems include lakes, ponds, rivers, streams and wetlands. A geological formation containing or conducting ground water. Underground water taken or interfered with, if the taking or interference happens during the course of, or results from, the carrying out of another authorised activity under a petroleum authority, such as a petroleum well, and includes waters also known as produced formation water. The term includes all contaminants suspended or dissolved within the water (EPA, 2007). The median of the wet season 90-day flows for the years in the simulation period. Natural gas, consisting primarily of methane, which collects in underground coal seams by bonding to the surface of coal particles. The coal seams are generally filled with water, and it is the pressure of the water that keeps the gas as a thin film on the surface of the coal. Water that has been extracted from coal seams in order to release coal seam gas. Department of Environment and Resource Management A highly valued component of the environment. It can be defined as a species, biological function or place of value. The process of estimating the effects of human actions on a natural resource. The framework to assess the level of risk to the health of ecosystems by multiple stressors. These stressors can be physical, biological or chemical. Estimate of the amount of total dissolved salts (TDS), or the total amount of dissolved ions in the water. It is measured in micro Siemens per centimeter (µs/cm). A stream channel which carries water only during and immediately after periods of rainfall. An Environmental Authority (for Petroleum activities refer to section 309(a) of Environmental Protection Act 1994) is a permit to conduct relevant petroleum environmentally relevant activities. Flow criteria stipulated in Water Resource Plans (WRP) for the protection of the health of natural ecosystems. For example, the WRP could specify that the mean annual stream flow at a particular point must be maintained at or above 75% of the mean annual flow that would occur in the absence of all development. Guideline HEC-RAS Hydrology Integrated Quantity and Quality Mode (IQQM) Low flow Node A numerical concentration limit or descriptive statement recommended for the support and maintenance of a designated water use (ANZECC/ARMCANZ, 2000). Can be determined using either biological effects data for a contaminant (toxicity guidelines) or background water quality data for a local area of interest (referential guidelines). A computer program that models the hydraulics of water flow through natural rivers. The study of the movement, distribution, and quality of water for surface water or groundwater. A tool developed for planning and evaluating water resource management policies at the river basin scale. This model can be applied to regulated and unregulated streams, and is to be capable of addressing water quality and environmental issues, as well as water quantity issues. The total number of days in the simulation period in which the daily flow is not more than half the predevelopment median daily flow. A node is a place on a watercourse in a Water Resource Plan area for which environmental flow objectives are set for performance indicators. QMDB That portion of the Murray Darling Basin which occurs in Queensland. It incorporates the Border Rivers, Moonie, Balonne-Condamine, Warrego and Paroo catchments. QWQG Queensland Water Quality Guidelines (2009) Reverse osmosis (RO) A filtration method that pumps a solvent from a region of high solute concentration through a semi- vii

10 Resource operations plan (ROP) Riffle Schistosomiasis Streams Summer Summer flow Threshold of concern (ToC) Water Resource Plan (WRP) permeable membrane to a region of low solute concentration by applying a pressure in excess of the osmotic pressure. Finalised water resource plans are put into effect by resource operations plans. The resource operations plan is a statutory document, developed to align with any implementation schedule in the water resource plan. Sometimes a resource operations plan may be developed in parallel with a water resource plan. A short, relatively shallow and coarse-bedded length of stream over which the stream flows at higher velocity and higher turbulence than it normally does in comparison to a pool. Riffles are usually caused by an increase in a stream bed's slope or an obstruction in the water. Also known as bilharzia; is a parasitic disease caused by trematode flatworms of the genus Schistosoma. Larval forms of the parasites are released by freshwater snails. Otherwise known as riverine wetlands - wetlands and deepwater habitats within a channel. The channels are naturally or artificially created, periodically or continuously contain moving water, or form a connecting link between two bodies of standing water. (Queensland Wetlands Program, Period from 1 December in a year until the end of February in the following year. The average number of summer flow days in the simulation period, where summer flow day is a day in the summer in which the daily flow is more than the pre-development median daily flow. Hypothesis of the limits of acceptable change in the structure, composition and function of an ecosystem, following exposure to a known stressor (such as alteration to the flow regime). Represents scientifically described endpoints or ecosystem limits, derived using the full extent of current knowledge. Subordinate legislation under the Water Act 2000 which establishes a framework to share water between human consumptive needs and environmental values. Water resource plans are prepared for each major catchment area in the state. ( viii

11 1 Background Coal seam gas (CSG) is a natural gas, consisting primarily of methane, adsorbed onto coal. CSG is extracted by dewatering coal seams to reduce the pressure keeping the gas in place. This process results in significant quantities of associated water, which is typically saline, being brought to the surface. CSG production in Queensland is increasing rapidly, with further increases predicted as CSG producers seek new markets for their product by establishing a liquefied natural gas industry. The Queensland Government's CSG Water Management Policy states that the preferred options for managing CSG water are either injection into aquifers or beneficial use (DERM 2010a). There may be situations where both the demand for treated CSG water for beneficial uses and the potential for injection may fall short of extraction rates in some areas, resulting in surplus volumes requiring alternative management. Disposal into surface waters is not a preferred option under the CSG Water Management Policy. However, there may be some cases where this is the best viable alternative. In such cases a rigorous environmental assessment is required as part of a CSG Water Management Plan prior to any release of CSG water being authorised under an environmental authority (EA). The environmental authority will stipulate flow and water quality criteria that must be met to protect the defined ecosystem values and water quality objectives of the receiving environment, as well as stringent monitoring requirements. CSG resources in Queensland are located primarily in the Surat and Bowen basins; geological structures that underlie sections of the Queensland Murray-Darling Basin (QMDB). The QMDB, which is located in the southwest of the state, consists of the Border Rivers, Moonie, Balonne-Condamine, Warrego, and Paroo drainage basins. The majority of Queensland s CSG resources underlie the Balonne-Condamine drainage basin in the QMDB and the Fitzroy drainage basin, which is located to the north of the QMDB. Rivers in the QMDB support nationally significant wetlands that fall into the high ecological value (Level 1) classification of the Australian and New Zealand Guidelines for Fresh and Marine Water Quality (ANZECC/ARMCANZ 2000). Surface waters in the region are utilised for irrigation and human and livestock drinking water supplies. To ensure the quality of surface waters continues to meet these human and ecological needs, locally relevant guidelines are required to adequately assess any potential impacts associated with the discharge of raw CSG water or treated CSG water into surface streams. Many watercourses in the QMDB exist as networks of ephemeral channels and waterholes that experience extended no-flow periods followed by episodic flow pulses and overbank flooding which are typically associated with summer sub-monsoonal rainfalls. Changes to these hydrological characteristics through long-term high volume continuous releases of CSG water have the potential to alter important natural responses in aquatic ecosystems adapted to these conditions. Consequently, guidelines relating to hydrological modification (i.e. timing, magnitude, rate of rise and fall, etc.) of surface waters due to the discharge of CSG water are also required to minimise the risk of potentially adverse environmental impacts from GSG water releases in the QMDB. Under the Water for the Future Program, the Commonwealth Government has allocated $5 million towards a feasibility study to examine the use of CSG water in addressing water sustainability and adjustment issues in the QMDB. The Coal Seam Gas Water Feasibility Study will analyse the opportunities for, and the risks and practicability of, using CSG water to assist in achieving the long-term goals in the QMDB of: transitioning irrigation communities to lower long-term water availability securing the viability of ecological assets. Activity 4 of the Coal Seam Gas Water Feasibility Study relates to securing the viability of ecological assets by investigating stream ecosystem health responses to CSG water releases. This report examines potential ecosystem response to hydrological alteration and changes to electrical conductivity due to CSG water discharge in the QMDB. The report focuses on the possible ecosystem changes due to CSG input and provides guidance on assessing the influence of hydrological alteration on aquatic ecosystem components. 1

12 2 Introduction Ecosystems are directly influenced by the flow regime of watercourses. It drives key ecological processes, influences patterns of dispersal and connectivity, and modifies the physical habitat of rivers and streams (Bunn & Arthington 2002; Poff et al. 1997). Water management influences flow regime via extraction, flow supplementation, and alterations to the timing, magnitude, and duration of flow events. Furthermore, the presence of infrastructure, such as dams and weirs, establishes physical barriers to population movements, and alters water quality by means of water impoundment, and increased water residence time. The process of extracting coal seam gas (CSG) produces waste-water which poses a potential threat to local flow regimes via supplementation. The current Queensland CSG water production projections estimate large volumes of water may be produced and disposed in regions where rivers and streams are largely ephemeral. Growth of the Queensland CSG industry will result in increasing volumes of CSG water by-product until approximately 2018, when the industry predicts that production will stabilise, at an estimated annual production volume of 120 GL/year (Shaw 2010). Declining production and water by-product is predicted from 2027, depending on the performance of CSG reserves. This suggests that rivers and ecosystems in the region may need to adapt to a new CSG-influenced flow regime and a change back to pre-csg flow conditions within a relatively short time frame. Currently, limited information is available from the Queensland CSG industry regarding proposed discharge locations, volumes and duration. However, because rivers and streams that flow through these arid and semi-arid regions are characterised by highly variable and unpredictable flow regimes (Puckridge et al. 1998) additional water inputs from CSG releases are likely to lead to significant changes in hydrology. The operational policy regarding waste water discharge to Queensland waters (EPA 2008) identifies inputs of more than ten percent of natural minimum flow, as a threshold beyond which further assessment is required. Very low baseflow conditions in many of the CSG producing regions means that this threshold is likely to be exceeded, leading to a need for flow and ecosystem response modelling to understand the likely effects. Predicting potential ecological responses to an altered flow regime is complicated by various interactions between flow and the ecosystem components, and by the multiple spatio-temporal scales at which they occur. This complexity is heightened by the confounding effects of other non-flow related stressors present in the system (i.e. land use, toxicants, exotic species, pesticides, etc.). Consequently, generalised measures of ecological responses to managed flow regimes are rarely observed (Kennard et al. 2010; Poff & Zimmerman 2010). A practical approach to managing flow regimes for specific ecological outcomes requires identification and partitioning of the critical flow dependencies of ecosystem components and processes, and a consideration of their provision over time. Ecological assets are highly valued components of the ecosystem for which aspects of the flow regime are critical to support their long term viability. Ecological assets may be a species, group of species, an ecological function, an ecosystem, or place of natural value. Following a lifecycle or process logic, the approach explicitly identifies the critical flow-dependencies, e.g. (i) maintenance and persistence of the adults, and (ii) regeneration and recruitment via reproduction (Overton et al. 2009). For each stage, best current scientific understanding is used to describe the nature of the flow dependency by defining the flow related conditions needed to trigger the ecological response. This understanding is used to formulate eco-hydraulic rules which define an opportunity for the ecological response, based on components of the flow regime (i.e. timing, magnitude, frequency, rate of rise and fall, duration, quality, etc.). Lastly, these rules are applied to a flow time-series representing a management scenario, generating a time-series of opportunities for the ecological response under each management scenario. Quantifying what constitutes sufficient opportunities for an ecological response, in order to maintain the viability of an ecological asset, remains a significant knowledge gap (Overton et al. 2009). The application of coarse statistics for example, a percentage of the pre-development flow regime required for sufficient opportunities to be available is an oversimplification and can be misleading. It ignores the importance of time between opportunities (or spell duration) for maintaining ecological assets. Furthermore, the oversimplification is worsened if coarse hydrological metrics fail to capture the complex interactions between hydrology and ecology. Ideally, controlled observational or manipulation-based studies of flow-ecology interactions are needed to produce response functions that will inform definitions of sufficient opportunities. However, few of these studies have been successfully completed (Poff & Zimmerman 2010). Therefore, in the absence of widely applicable response functions, best available science can be used to derive step-functions. Termed Thresholds of Concern (ToC), they 2

13 define the frequency of opportunities required to protect asset viability (Rogers & Biggs 1999). ToC exceedance represent failure points for the ecological asset, and as such may represent their minimum flow requirements. Therefore, the probability of achieving a desired ecological outcome is directly related to meeting a ToC, over time. ToCs are hypotheses of the limits of acceptable change in the structure, composition and function of an ecosystem, following exposure to a known stressor in this case alteration to the flow regime. As such, they represent scientifically described endpoints or ecosystem limits, derived using the full extent of current knowledge. Where possible, ToCs are based on the biology of the asset. In the case of process or place-based ecological assets this is based on knowledge of how the critical process attributes interact with the flow regime. For species-based ecological assets, ToCs typically represent the known time biota will survive without experiencing a flow-based opportunity (for responses related to maintenance and persistence dependencies) or the reproductive lifetime of the biota (for responses related to regeneration and recruitment dependencies). Where limited knowledge of an ecological asset's life history prevents setting a ToC, the modelled frequency of opportunities provided by the predevelopment flow regime can be used. Due to the inherent variability in natural systems, pre-development flow regimes do not necessarily ensure the ToC of ecological assets is met at all times. Therefore, the risk ecological assets face from management scenarios must be compared with that of pre-development flow regimes. The acceptable risk to any given ecological asset is determined by the desired level of protection for that asset (ANZECC/ARMCANZ 2000). Ideally, this is achieved in an open and transparent process involving all key stakeholders. The process outlined above requires a sound conceptual understanding of the following: 1. flow-dependent ecological assts, representing the ecological values of the receiving environment 2. detailed biological and/or process knowledge, relating to ecological asset's critical flow dependencies. This report outlines a guideline for assessing risks to ecosystems from modified flow regimes. It follows an ecohydrologic modelling approach, used by DERM to assess the performance of Water Resource Plans (WRPs) in achieving their ecological outcomes (Cockayne et al. 2009). This approach has broad similarities to that applied to the Murray-Darling Basin, to inform the development of the basin plan (Overton et al. 2009). The approach focuses on ecological assets that (i) represent the ecological values of the system, (ii) are dependent on aspects of the flow regime; and (iii) are vulnerable to the types of flow alteration that could occur as a result of a particular development. 2.1 Guideline objectives This guideline summarises the knowledge of ecological asset responses to flow modification; and provides guidance on managing modified flow regimes to support the ecological values of the QMDB. Specifically the guideline aims to: 1. provide a conceptual understanding of the potential hazards posed to surface rivers and streams by the discharge of CSG water, and subsequent modification of the flow regime 2. identify existing knowledge and datasets concerning ecological responses to flow regimes in the QMDB 3. outline a process for assessing the risk to ecological assets to provide guidance on the management of CSG water disposals, in order to maintain flow dependent ecosystem components and processes. 3

14 3 Potential hazards associated with CSG water related flow modification Ephemeral rivers and streams are characterized by high flow variability, extended periods of zero surface flow, and the general absence of low flows; except during the recession periods immediately after moderate to large high flow events (Knighton & Nanson 1997). Much of the QMDB can be considered dryland, with its rivers and streams existing as networks of ephemeral channels, fluctuating between highly connected and highly disconnected habitats. Alteration to the flow regime can result in major impacts on the structure and function of these aquatic ecosystems, and their associated riparian corridors and floodplains. The six key components of the flow regime recognised as important for aquatic ecosystems include (Figure 1) (Boulton & Jenkins 1998; Bunn & Arthington 2002; Lloyd et al. 2003): duration timing variability predictability magnitude rate of rise and fall. Figure 1. Components of the flow regime considered ecologically important (modified from Walker et al. 1995) Duration Duration relates to the length of a specific flow event, for example a period of flood inundation, or a no-flow spell. Flow modification through water impoundment, extraction and flow supplementation can lead to the following: reduced frequency and duration of floods, resulting in less variable and more stable flows and altered patterns of connectivity increased duration of low or no flow periods. It has been shown that increased connectivity, resulting from high flow regulation and altered duration, can lead to loss of lake drying, reduced fish diversity and water bird breeding (Gawne & Scholz 2006). 4

15 3.1.2 Timing Timing of floods and flow events contributes to the seasonal variation of rivers and streams (Boulton & Lloyd 1992; Poff et al. 1997). Seasonal variation, which relates to the predictability of the flooding events, acts as a cue for the life history events of many organisms (Peckarsky et al. 2000). For example, the importance of first postwinter flows as a critical cue for flow-spawning fish species such as the golden perch and Hyrtl's catfish has been identified (DERM 2010b, 2010c). Therefore, predictable seasonal patterns are critical to their breeding success Variability Changes to flooding variability and periods between floods can alter the ephemeral or perennial nature of wetlands, and increase the return frequency of dry periods (Bunn & Arthington 2002). Consequently, this can affect the survival of the species relying on this hydrological cycle (Hillman & Quinn 2002). Loss of variability due to flow supplementation also has the potential to turn ephemeral rivers into perennial systems with concomitant changes to water quality, sediment production and ecological function (O'Keeffe & De Moor 1988) Predictability Predictability relates to the average variability of flow in each seasonal period (over years), and is a measure of the similarity of flow patterns from year to year. Constant discharge of water due to flow supplementation or waste water discharge can increase predictability by removing no or low-flow periods, whereas infrastructure can capture large flow events. This not only has a negative impact on certain species, but can also interfere with the seasonal pattern of those organisms relying on the natural flooding events. It is important to consider not only large flooding events, but also small scale alterations, as any spatial and temporal changes are likely to have a significant impact (Puckridge et al. 1998) Magnitude Changes to the magnitude of flow influence aquatic ecosystems directly, by altering habitat availability and connectivity (i.e. through interaction with water depth changes and flow velocity); and indirectly through the modification in stream geomorphology. Discharges of a given magnitude are responsible for the creation and modification of in-channel bars, influence sediment deposition and stream bed and bank scouring, and provide opportunity for lateral exchange of material and energy between channel and floodplain systems. Reduced small flow events can result in reductions in the frequency of filling or recharge of in-channel refugial pools. The same impact may apply if groundwater abstractions result in reduction to stream baseflow. The pools in ephemeral channels play an important ecological role. Changes to the quantity of water in pools may also be reflected by changes in the temperature and quality of the water (Hughes 2005), which reduce the capacity of these pools to function as refugia for biota Rate of rise and fall The rate of rise and fall relates to the increase and decrease of flow over time. These fluctuations in the flow regime serve important ecological and geomorphic functions in a river system. For example, rapid rates of flow reduction can result in fish stranding and bank slumping. The reproductive success of species can also be affected by the magnitude and rate of the rise and fall of the flow during breeding seasons. For example, high velocities can displace fish eggs, larvae and juveniles, and flood terrestrial nests of turtles and platypus burrows (Cockayne et al. 2009; DERM 2010b). 3.2 Hydrology of the QMDB The headwaters of the QMDB in the Great Dividing Range and the rivers that flow across the Queensland/New South Wales border form one of the largest catchments in the world. The rivers are flat and shallow over much of their courses, with extensive floodplains. Prolonged periods of low or no-flow are typical, as are unpredictable high-flow events that inundate the floodplains, ephemeral lakes and wetlands. Much of the QMDB can be considered arid or semi-arid, experiencing infrequent rainfall and high evaporation rates (Marshall et al. 2005). 5

16 General characteristics of hydrological conditions in the QMDB are as follows (Marshall et al. 2005): low base flow with 90% of flood flow from rainfall flow is seasonal, with wet season from January to May and dry season from June to December seasonal patterns have low repeatability between years so it can be wet when it is on average dry and dry when it is on average wet flow is intermittent with characteristic long periods without flow no-flow spells occur all year round including during the wet season. An Australia-wide classification of the hydrology of streams has been conducted to assist with prescribing management of environmental flows (Kennard et al. 2008). The classification system, based on 120 metrics describing ecologically relevant characteristics of the natural hydrologic regime, resulted in 12 distinct classes of flow regime. These varied according to the seasonal pattern of discharge, the degree of flow permanence, variations in flood magnitude, and other aspects of flow predictability and variability. Streams were only included in the analysis if they were considered to have experienced minimal anthropogenic disturbance, so these classification intend to represent the natural or reference condition for the catchment. The resulting classification for streams in the QMDB and Bowen and Surat geological basins are shown in Figure 2. Only one perennial stream was identified in the QMDB with the others being characterised by unpredictable and intermittent flows (Table 1). The classification of rivers by hydrology was based on the premise that rivers that share similar hydrological characteristics should also share similarities in assemblage composition, species traits and community functioning, and it should then follow that ecological responses to given anthropogenic change in flow regime should be similar in rivers of a similar initial natural flow regime (Kennard et al. 2008). Rivers within the one flow regime class should therefore represent an environmental flow management unit. Table 1: Flow regime classes identified in the Queensland Murray-Darling Basin (Kennard et al. 2008) Flow regime class Description 4. Unpredictable baseflow Perennial, less predictable flows than other perennial streams with discharge spread uniformly throughout the year (i.e. not seasonal). 7. Unpredictable intermittent Intermittent, rarely cease to flow. Intermediate baseflow and intermediate runoff magnitude. Variable flows with very low predictability. More uniform flows throughout the year than Class Unpredictable winter intermittent Intermittent, rarely cease to flow. Intermediate baseflow and intermediate runoff magnitude. Variable flows with very low predictability. Winter flows dominant. 9. Predictable winter highly intermittent Intermittent, regularly cease to flow. Usually zero flow days per year. Winter runoff flows dominant. 11. Unpredictable summer highly intermittent Intermittent, regularly cease to flow. Usually zero flow days per year. Minimum and maximum monthly flows showed low predictability and weak seasonality. 12. Variable summer extremely intermittent Intermittent, regularly cease to flow. More than 250 no flow days per year. Dominated by infrequent, large floods which could occur at any time of year. Geographic, climatic and some catchment topographic factors are generally strong discriminators of flow regime classes (Kennard et al. 2008). Based on this outcome, a classification of streams using geographic data is currently being conducted for all streams across Australia (not only for streams considered to be at or near reference condition). The 30 group classification is based on a set of 48 attributes describing the climate, water balance, topography, substrate and vegetation cover of the reach and its catchment (Stein et al. 2008). 6

17 Figure 2: Hydrological classifications of streams in the Queensland Murray-Darling Basin and the Surat and Bowen coal basins (after Kennard et al. 2008). Each point represents a gauging station with flows considered to have little or no hydrologic modifications due to human activities. 3.3 CSG water discharge The release of CSG water to rivers and streams has the potential to significantly alter the flow regime in the receiving environment with consequences for dependent ecosystems. Water release of this kind and at this scale is a novel issue related to flow alteration in the QMDB. Typical disturbances to flow regimes due to water resource development are associated with removing water from the system for irrigation or consumptive use (Hughes in press). In contrast, disposal of CSG water will add water into the system, therefore supplementing the flow regime. To determine the potential threats posed by the disposal of CSG water to surface streams, a preliminary study was conducted at several locations in the Condamine-Balonne and Fitzroy river basins using aggregated CSG industry disposal scenarios (Appendix A). These scenarios also incorporated estimates of potential alterations to electrical conductivity (EC), which is an additional potential threat to aquatic ecosystems. The study identified a significant reduction in no-flow days at all modelled sites as a result of continuous CSG water discharge. Notably, the hydrologic issues identified in the analysis included (i) loss of seasonality, (ii) loss of dry spells, (iii) increase in connectivity and (iv) increase in velocity. It also showed that discharging large volumes of low EC water for 7

18 prolonged periods of time resulted in a significant lowering of EC in the receiving environment; in some cases reducing the EC below a critical ecosystem response threshold of 120 µs/cm (Takahashi et al. 2011). 3.4 Ecological responses Designing a regulated or altered flow regime that preserves the ecological character of a river or stream, whilst enabling water disposals or abstractions, requires an understanding of how the ecosystem functions and is dependent on different components of the flow regime at different scales (Biggs et al. 2005; Biggs & Kilroy 2000). Our current empirical understanding of the critical water requirements of Queensland's aquatic ecosystems and their response to water management regimes ranges from rudimentary to non-existent, with few examples of general transferable quantitative relationships between flow alteration and ecological responses in the scientific literature (Poff & Zimmerman 2010). This is not surprising given that flow alteration generally co-occurs with other environmental stressors, therefore confounding relationships between measures of flow alteration and ecological responses (Konrad et al. 2008; Poff & Zimmerman 2010). Consequently, there is still much reliance on broad conceptual relationships and expert opinion. Current scientific understanding therefore remains the starting point of any assessment process, with the caveat that errors associated with subsequent estimates of risks are likely to be high. Ideally, by adopting an adaptive approach to managing ecosystem impacts, hypothesis driven monitoring and evaluation of water management strategies can be used to improve the empirical basis for understanding ecosystem responses. A summary of potential ecological responses to flow modification are shown in Table 2, and Figures 3 5. Discharges to intermittent and ephemeral systems require additional consideration due to a number of features which differentiate them from other rivers and streams (Table 3). In general, hydrological conditions affect the physical habitat for aquatic and riparian biota, the availability of refuges, the distribution of food resources, opportunities for movement and migration, and conditions suitable for reproduction and recruitment (Naiman et al. 2008). Based on the summary of key hydrological features of the QMDB as discussed above, the key ecological implications for flow-dependent ecosystem components and processes include (Marshall et al. 2005): many species have either flexible/opportunistic life histories or long life spans species may utilise annual cues for critical life history activities species utilise drought refugia (especially water holes) and/or have traits for surviving drought or rapidly recolonising afterwards. 8

19 Table 2: Summary of common ecological responses to flow alteration (modified from Poff & Zimmerman 2010) Flow component Organisms studied Primary flow alteration Magnitude Aquatic Stabilisation (loss of extreme high and/or low flows) Greater magnitude of extreme high and/or low flows Common ecological responses Loss of sensitive species, reduced diversity, altered assemblages and dominant taxa, reduced abundance, increase in nonnatives Life cycle disruption, reduced species richness, altered assemblages and relative abundance of taxa, loss of sensitive species Riparian Stabilisation (loss of peak flows) Altered recruitment, failure of seedling establishment, terrestrialisation of flora, increased success of non-natives, lower species richness, vegetation encroachment into channels, increased riparian cover Frequency Aquatic Decreased frequency of peak flows Aseasonal reproduction, reduced reproduction, decreased abundance or extirpation of native fishes, decreased richness of endemic and sensitive species, reduced habitat for young fishes Riparian Decreased frequency of peak flows Shift in community composition, reductions in species richness, increase in wood production Duration Aquatic Decreased duration of floodplain inundation Riparian Decreased duration of floodplain inundation Decreased abundance of young fish, changes in juvenile fish assemblage, loss of floodplain specialists in mollusc assemblage Reduced growth rate or mortality, altered assemblages, terrestrialisation or desertification of species composition, reduced area of riparian plant or forest cover Timing Aquatic Shifts in seasonality of peak flows Disruption of spawning cues, decreased reproduction and recruitment, change in assemblage structure Increased predictability Change in diversity and assemblage structure, disruption of spawning cues, decreased reproduction and recruitment Riparian Loss of seasonal flow peaks Reduced riparian plant recruitment, invasion of exotic riparian plant species, reduced plant growth and increased mortality, reduction in species richness and plant cover Rate of change Aquatic Reduced variability Increase in crayfish abundance, increase in schistosomiasis Riparian Increased variability Decreased germination survival and growth of plants, decreased abundance and change in species assemblage of waterbirds 9

20 Table 3: Features of intermittent and ephemeral streams (modified from Richardson & Danehy 2007). Feature Characteristic Ecological response Low hydraulic power Temporary storage of fine sediments depending on geomorphic setting Stable benthic habitats, greater proportion of biota intolerant of scouring Geomorphology Flow seasonality Disturbance regimes Recolonisation pathways Aquatic terrestrial linkages Aquatic vertebrates In areas of low relief, channels incised into colluvial deposits with various channel morphology In dryland zone: generally ephemeral flows unless supplemented by groundwater Vulnerable to low flows, droughts, landslides or debris flows. Vulnerable to local vegetation loss. From downstream, possible between catchments for winged biota High edge:area ratio Typically low in fish diversity due to shallow or intermittent flows, or because of downstream barriers Stable, but small habitat volume Drying of streams may have long-lasting effects on biota, however biota may be adapted to periodic drying and ephemeral water regimes Habitat loss and isolation, siltation, changes to soil hydrology and microbial processes. Long path length, possible barriers to dispersal Tightly integrated Food webs dominated by invertebrates 10