A New Approach to Determining Environmental Flow Requirements

Home , Millewa, Trigonella suavissima

MANAGEMENT doi: 10.1111/j.1442-8903.2011.00581.x REPORT A new approach to determining environmental ﬂow requirements: Sustaining the natural values of ﬂoodplains of the southern Murray-Darling Basin

By Paul Peake, James Fitzsimons, Doug Frood, Mel Mitchell, Naomi Withers, Matt White and Rick Webster

Paul Peake is Remnant Vegetation Investigation Summary Large overbank flood events play an important role in maintaining large- Team Leader at the Victorian Environmental Assess- scale ecological processes and connectivity along and across the floodplains and between ment Council (VEAC) (8 Nicholson Street, East Mel- the rivers and their floodplains in the southern Murray-Darling Basin. However, the regulation bourne VIC 3002, Australia; Tel: +61 3-9637-9896; of rivers means that extensive overbank flooding can only occur in the rare circumstance of Email: [email protected]). James Fitzsi- extreme flood events. Recent environmental water allocations have focussed on the largest mons was a Senior Project Officer at VEAC and is floodplain blocks (‘icon’ sites) and a small set of specific values (e.g. colonial nesting water- currently with The Nature Conservancy (Suite 3-04, birds), as well as on trialling fine-scale manipulation of infrastructure (e.g. pumping) to water 60 Leicester Street, Carlton VIC 3053, Australia) and relatively small areas. There has been no comprehensive systematic assessment of the entire the School of Life and Environmental Sciences, Dea- floodplain and its wider set of flood-dependent natural assets (such as ecosystems and spe- kin University (221 Burwood Highway, Burwood cies; herein referred to as ‘natural values’) to maximise the effectiveness of environmental VIC 3125, Australia; Email: james.fitzsimons@ water use and to catalogue values likely to be lost. This paper describes an assessment of deakin.edu.au). Doug Frood is a botanist with some 220 000 ha found to support flood-dependent natural values in Victoria. We mapped Pathways Bushland and Environment (PO Box 360, the geographic distribution and estimated components of the flooding requirements (natural Greensborough VIC 3088, Australia; Email: flooding frequency, and maximum period without flooding and minimum duration of each [email protected]). Mel Mitchell is a Senior flooding event before significant deterioration) for each natural value. Using an example of ProjectOfficeratVEAC(8NicholsonStreet,EastMel- one stretch of the River Murray, we show how the resultant spatial data can be used with bourne VIC 3002, Australia; Email: mel.mitchell@ floodplain inundation modelling to compare the outcomes of real or planned environmental dse.vic.gov.au). Naomi Withers was Senior GIS watering events; potentially providing tools for management agencies to conserve a wider Project Officer with VEAC and is now with the range of floodplain values than is currently the case. That is, water managers and the public Department of Sustainability and Environment (8 can see what ecosystems and threatened species are intended to be maintained by environ- Nicholson Street, East Melbourne VIC 3002, Australia; mental watering and what values are intended to be abandoned across the whole floodplain, Email: [email protected]). Matt White is rather than just seeing the small subset of values and ‘icon’ sites that are intended to be an ecologist with the Arthur Rylah Institute for Envi- maintained. Examples are provided to illustrate how information about the location, water ronmental Research, Department of Sustainability requirements and extent covered by potential floods for specific values can be used to build and Environment (123 Brown Street, Heidelberg VIC adaptive watering strategies for areas as large as the whole floodplain. 3084, Australia; Email: [email protected]). Rick Webster is a Director ⁄ Ecologist at Ecosurveys Key words: critical flood intervals, environmental flows, flood requirements, floodplains, threa- Pty Ltd (PO Box 13, Deniliquin NSW 2710, Australia; tened species. Email: [email protected]). This paper is a result of work commissioned by the Victorian Envi- ronmental Assessment Council to better identify the environmental watering needs of flood-dependent species and ecosystems in the southern Murray- Darling Basin.

Wales (VEAC 2008a; NRC 2009) are recent These flood events also maintain ecological Introduction attempts to redress this deterioration. connectivity along the length of the flood- he deteriorating state of the Murray- Pulsed flooding is the major factor influ- plains, across the floodplains and between TDarling Basin has been a cause of con- encing biota in river-floodplain systems the major rivers and their floodplains, siderable concern amongst ecologists, land (Ballinger & Mac Nally 2006). The flood- thereby playing a crucial role in the land- managers, politicians and the communities plains of northern Victoria support a scape ecology of the region (Ballinger & living in and relying on the basin. The unique biota in an otherwise semi-arid Mac Nally 2006). The floodplain forests guide to the Murray-Darling Basin Plan environment because of overbank riverine and woodlands not only provide important (e.g. MDBA 2010) and two significant flood events resulting from large rain habitat for a range of forest- and woodland- investigations into future land and water events in the somewhat distant Great adapted plants and animals, but also act as management in Victoria and New South Dividing Range to the south and east. a pathway extending the geographic range

ª 2011 Ecological Society of Australia ECOLOGICAL MANAGEMENT & RESTORATION VOL 12 NO 2 AUGUST 2011 1 MANAGEMENT REPORT of a number of species, particularly birds allocating scarce and expensive water and While vegetation types and threatened (e.g. Tzaros 2001). for determining priorities for infrastructure species are typically the foremost natural The rivers of northern Victoria, how- investment to natural assets. However, values targeted in analyses such as this, we ever, are now highly regulated, and much consideration of the water requirements of make a range of suggestions for future of their flows are diverted for irrigated agri- the full suite of floodplain ecosystems and work that would further improve the envi- culture. They are currently managed so taxa has been limited (Ballinger & Mac ronmental management of the floodplains, that extensive overbank flooding occurs Nally 2005). including the incorporation of additional only when water storages are full and spill- This situation is not unique to the Mur- natural values such as high species rich- ing at sufficient volumes for the rivers to ray-Darling Basin or Australia. Internation- ness, key non-threatened species and eco- break their banks (VEAC 2006). As a result ally, fish are typically used as an indicator logical connectivity. of this management regime, the frequency species for flood requirements (e.g. Richter of small and moderate floods has declined et al. 2006; Wang et al. 2009; Beilfuss & to around a third or less of the natural Brown 2010) as they can be relatively How the Analysis of Flooding frequency of flooding for most of the easily monitored. Indeed, Smakhtin (2008) Needs was Undertaken floodplain (e.g. DSE 2008a). Consequently, notes very few countries have set clear Assessment area there are now many indications of wide- procedures for environmental flow estima- spread substantial decline in the biodiver- tion and allocation. The assessment covered the Victorian sity of the floodplains including an In this paper, we interpret for managers floodplains of the Murray, Goulburn, increase in the number of dead and dying an approach to environmental watering Ovens and King Rivers downstream of River Red Gum (Eucalyptus camaldulen- that explicitly focuses on the flooding Lake Hume, Goulburn Weir, Porepunkah sis) and Black Box (E. largiflorens)trees requirements of species and ecosystems and Cheshunt respectively – an area of (MDBC 2003; Cunningham et al. 2007), across the landscape. This approach high- approximately 507 000 ha, collectively reduced River Red Gum growth rates lights, for the first time, those species and referred to here as the River Murray flood- (VEAC 2008a), and the development of ecosystems most in need of flooding and plain. The area is a subset of the Victorian acid sulfate soils (McCarthy et al. 2006). the locations where they occur. The Environmental Assessment Council’s River Despite a recent flood event, climate approach is management focused and can Red Gum Forests Investigation area (see change predictions translate to further easily incorporate new ecological and bio- Fitzsimons 2006; VEAC 2006) (Fig. 1). reductions in overbank flood frequency physical data. The process aims to move Determining the flooding (DSE 2008a) – and hence loss of biodiver- beyond the ‘icon sites’ approach to view requirements of natural sity into the future – if current river man- the River Murray floodplains as a dynamic values agement continues. Reduced precipitation interconnected system. This is based on an and increased evapo-transpiration resulting analysis undertaken as part of the Victorian Full details of how the flooding require- in reduced runoff are likely to greatly Environmental Assessment Council’s final ments for vegetation types and threatened reduce frequency and extent of floodplain recommendations for the floodplain forests flora and fauna were derived are provided inundation (e.g. DSE 2008a). and woodlands of northern Victoria (VEAC in Fitzsimons et al. (2011, contact the As a result, artificially generated and 2008a,b). During this analysis, we com- corresponding author for a copy) and are manipulated environmental watering has piled data on and mapped the flood summarised as follows. been increasingly relied upon to sustain requirements for all flood-dependent vege- Publicly accessible geospatial data main- floodplain forests and wetlands along the tation types, as a surrogate for ecosystems, tained by the Victorian Department of Murray Valley in recent years. However, and most flood-dependent threatened spe- Sustainability and Environment (DSE) (i.e. this watering has been limited to specific cies along the River Murray and its major relating to vegetation types and threatened places and values, such as parts of large for- tributaries in Victoria. (The full dataset is fauna and flora) were used as the basis of est ⁄ woodland blocks (i.e. ‘icon’ sites) and published in a separate paper, Fitzsimons this analysis. Ecological vegetation classes colonial nesting waterbirds (e.g. Cooling et al. 2011.) (EVCs) are the principal units for native et al. 2002; Leslie & Ward 2002; Stewart & Using a case study in the Robinvale area vegetation classification and mapping for Harper 2002), and the basis for the selec- of the River Murray, this paper provides an land-use planning and management in Vic- tion of watered sites and specific values example of how the dataset can be used to toria (Parkes et al. 2003). These are units ahead of others is often unclear. Environ- quantify the proportion of species habitats in a vegetation classification system that mental watering requires strategic plan- receiving water under different flooding are differentiated through a combination of ning to ensure the most effective use of regimes. The approach provides the basis floristic, life form and ecological character- water in sustaining biodiversity assets. A for a transparent, flexible and useable eco- istics, and through an inferred fidelity to prerequisite for such planning is a compre- logical dataset to inform decision-making, particular environmental attributes. hensive, systematic, spatially explicit and auditing and monitoring of environmental The major determinant of vegetation publicly transparent inventory of flood- management outcomes in the northern type in this region is riverine flooding; as dependent natural values as a basis for Victorian floodplains, and beyond. opposed to flooding or watering solely

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condition comparable to its reference state (DSE 2008b) was estimated based on the requirements of characteristic species and physical conditions at sites of occurrence. For ﬂora, point records for listed threa-

New south wales tened or rare species that occurred in the study area were extracted from the DSE’s

River Murray Flora Information System (FIS) (as at May 2007). Each taxon on this list was then South classed as flood-dependent or not by apply- Australia Victoria Kiewa River ing the same definition of ‘flood-depen- Goulburn Ovens River King dent’ that was used for the identification of River River flood-dependent EVCs to what was known of the taxon’s ecology and occurrence, Melbourne including a review of relevant literature and FIS data. As little specific information N on the flood requirements exists for most species, the flood requirements of the principal EVCs in which these species Present study area 04080 160 occurred was adopted as the flooding VEAC (2006) investigation area boundary km requirements for that taxon. The distribu- Area shown in Figures 2, 3 tion of each species was then mapped as the spatial extent of the coincident EVCs. Location of VEAC River Red Gum Forests Investigation area and floodplain values Figure 1. Records for threatened fauna (birds, mapped in this analysis. mammals, reptiles and amphibians) were extracted from DSE’s Victorian Fauna Data- from local rainfall. Within flood-prone chemistry. In the absence of long-term base and Birds Australia’s Atlas data (in areas, the major determinants of occur- historical information for the EVCs, the nat- May 2008), and flooding requirements rence for most EVCs are variations in flood ural flood frequency for each flood-depen- were determined through discussions with regime, particularly flood frequency and dent EVC was estimated based on what is experts (see ‘Acknowledgements’ below), duration. In the assessment, we built on known or surmised by our expert assessors and through reviewing relevant literature this spatial dataset by identifying the flood- of the flooding requirements and toler- (see Fitzsimons et al. 2011 for a list of pub- ing requirements for each flood-dependent ances of characteristic species and the lished sources used). The habitats of most EVC, based on the life-history traits, toler- physical (including hydrological) condi- fauna taxa were specified as one or more ances and competitive advantages of its tions at sites of occurrence, particularly in EVCs, which were then mapped as the dominant and characteristic plant taxa. comparison with these parameters for sites for each taxon within its known local This new information was appended to adjoining or similar EVCs. The critical inter- geographic distribution. The natural flood existing EVC polygons. As few of the plant val (the estimated maximum period that an frequency, critical interval and minimum species have been the subject of detailed EVC can persist without flooding and flood duration estimates for the EVC(s) autecological studies, estimates of flooding remain capable of returning to its refer- were then assigned to the sites. However, regime variables were based on a combina- ence or benchmark condition) was esti- for some taxa, notably colonially nesting tion of searches of the available literature mated on the basis of familiarity of the waterbirds, more specific information supplemented by the expert opinion of DF assessors with field indications of decline, derived from site visits was available and and MW who were closely involved in the combined with a knowledge of past flood used to map site locations and specify circumscription and mapping of EVCs in intervals. We did not use hydrological mod- watering requirements. 2006. elling to determine a volume for this pro- Geospatial data processing To identify flood requirements for EVCs cess as there was no hydrological model in the region, we first identified flood- for the entire floodplain at the time and A single digital geospatial layer was created dependent EVCs, i.e. those that were providing a volume was not the intent of incorporating all flood-dependent EVC (a) likely to significantly decline in condi- the approach. However, in this paper, we polygons from the DSE’s Corporate Geo- tion across the region in the absence of do provide an example of how hydrologic spatial Data Library. For threatened flora overbank flows from adjoining rivers or modelling could be used based on pre- and fauna, a separate digital geospatial (b) depended on geomorphological pro- existing CSIRO models (see below). layer was created for each taxon using cesses such as the deposition of silts, and Finally, the minimum flood duration new polygons where necessary but mostly the regulation of ground water depth and required to maintain each EVC in a using pre-existing polygons – usually EVC

ª 2011 Ecological Society of Australia ECOLOGICAL MANAGEMENT & RESTORATION VOL 12 NO 2 AUGUST 2011 3 MANAGEMENT REPORT polygons but sometimes others according every 4 years for Aquatic Herbland and a occurred and none in which sustained to details specific to particular taxa or sites further 20 EVCs, through to one flood flows of 81 or 159 GL per day occurred as described above. New polygons were event in 20–40 years for Riverine Cheno- (MDBA, unpublished data, 2011). While digitised from hand-drawn polygons on pod Woodland. Critical intervals to main- Figure 2 is a composite of all flood-depen- topographic maps or aerial photos. Natural tain healthy ecosystems ranged from one dent EVCs and threatened species, maps flood frequency, critical interval and mini- flood event every 2 years for around 30 can be readily produced for individual mum duration estimates were assigned to EVCs to one flood every 30–50 years for EVCs, species or combinations thereof. all polygons within a geographic informa- some EVCs dominated by Black Box. A The area of each flood-dependent EVC, tion system (ArcGIS). visual representation of the critical inter- threatened species habitat and the percent- vals for EVCs is presented in Map D of age of these areas inundated by the three Identifying flood-dependent VEAC (2008a). Minimum durations of different flood levels are outlined in values inundation ranged from <1 month to Table 2. For example, <5% of almost all val- A major aim of the analysis was to identify 6–36 months (Table 1). ues are inundated by a very small flood a broad range of natural values – such as In terms of threatened species, 124 rare whereas over three-quarters of Floodplain vegetation units, threatened flora and or threatened plant taxa were classified as Grassy Wetland EVC, half the Regent Par- fauna – that managers could take into at least partly flood-dependent of which 68 rot (Polytelis anthopeplus monarchoides) account when identifying conservation were sufficiently well known for their dis- breeding habitat and 100% of Silver Salt- management goals. To provide a visual rep- tributions to be mapped reliably (see Fitzsi- bush (Atriplex rhagodioides) habitat is resentation of the relative number of differ- mons et al. 2011 for the full list and inundated in a large flood. ent flood-dependent values at any one site, Table 1b as an example). Of the 62 threa- Identifying deficiencies in geospatial layers for EVCs and for each of tened vertebrate fauna taxa (excluding current management the threatened species were overlayed, a fish) found to be flood-dependent, 51 were composite layer generated and a new field sufficiently well known for their distribu- The large multifactorial dataset generated for the number of distinct features tions to be mapped reliably (see Table 1c by our original study and analysis can be attached to each resultant polygon. Over- as an example). A visual representation of readily used to provide insight into many laying the composite natural values layers the critical intervals for threatened species interesting questions. Perhaps the most with the CSIRO River Murray Floodplain is presented in Map E of VEAC (2008a). compelling of these would address the Inundation Model (RiM-FIM) (Overton comprehensiveness of the current ‘icon Mapped outputs – and an 2005) was undertaken in the Robinvale sites’ approach as illustrated by the follow- example of how they can be area of northwestern Victoria to show ing simple example. applied in management which values would or would not receive The eastern subspecies of the Regent planning water under differing flooding scenarios. Parrot occurs in the Murray Mallee of New Figure 2 and Table 2 provide examples of South Wales, Victoria and South Australia how the digital mapping generated in this and is listed as threatened nationally and in Outputs Relevant to project can be used to compare the extent each of these states. It feeds in mallee vege- Managers to which different modelled inundation tation but breeds in hollows in old flood- events assist or fail to assist in sustaining plain eucalypts – typically in loose colonies Data for EVCs and floodplain natural values for a particular in copses of tall, straight, leafy trees. In the threatened taxa area. Figure 2 shows the predicted extent absence of adequate flooding, these trees Some 224 247 ha of extant vegetation on of flooding for three different-sized floods would deteriorate in condition, die or not the River Murray floodplains in Victoria along a sample reach of the River Murray be recruited in the long term, all of which were determined to be at least partially floodplain east of Robinvale, resulting from would adversely affect the Regent Parrot flood-dependent including 162 266 ha on three different flow rates along the river population. Because there have been sys- public land. This vegetation comprised channel: 20, 81 and 159 GL per day, which tematic searches for breeding sites, it is 110 EVCs, confirming that a large area of correspond to very small, moderate and one of the few species for which specific significant ecological diversity is at risk large overbank floods, respectively. To give sites – the location of all known breeding from inadequate flooding (see Fitzsimons some context, prior to 1981 for example, sites in the study area – could be mapped, et al. 2011 for the full description of the sustained flows (more than five consecu- as opposed to using EVC maps to generate primary findings). tive days) of 20 GL per day occurred on habitat maps as documented above (Web- Examples of natural flood frequency, average in 8 of every 10 years. Sustained ster 2004). critical interval, minimum duration and flows of 81 and 159 GL per day occurred This process resulted in 26 breeding location information collected for a subset twice and once (respectively) in every 10 sites being mapped, with an estimated of the flood-dependent EVCs are provided years, on average. In the decade to the end minimum flood frequency of every 5– in Table 1a. Natural flooding frequencies of 2009, however, there were only 5 years 7 years. Significantly, ten of these sites are ranged from as many as 3–4 flood events in which sustained flows of 20 GL per day outside of The Living Murray’s ‘icon’ sites,

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Ta ble 1 . Examples of natural flood frequency, critical interval, minimum duration and location information collected for some (a) flood-dependent Ecological Vegetation Classes, (b) significant plant species and (c) significant fauna species (For full details of all mapped natural values, see Fitzsimons et al. 2011)

(a) Ecological vegetation class Natural flood frequency (years) Critical interval (years) Minimum duration (months) Alluvial Plains Semi-arid Grassland 1 in 2–15 25 1.5–6 Aquatic Herbland 3–4 in 4 2 6–12 Billabong Wetland Aggregate Variable 2 (variable) >6 Floodplain Riparian Woodland 3–5 in 10 7 <1 Grassy Riverine Forest 2–4 in 4 4 1–4 Red Gum Swamp 2–3 in 3 3 4–9 Riverine Chenopod Woodland 1 in 10–25 (1 in 20–40 Atriplex community) 30–50 <1–3 (b) Name and conservation Wetland ⁄ Importance Relevant Mapped Additional information status of plant species* floodplain of study area flood-dependent EVCs dependent† population Native Scurf-pea Cullen Y High Lake Bed Herbland · australasicum (e, L) 4 Hoary Scurf-pea Cullen Y High Lake Bed Herbland Drying phase of shallow lakes cinereum (e, L) 4 Small Scurf-pea Cullen Y High Sedgy Riverine Forest (upper edge), Upper edge of flooded zone, parvum (e, L) (in north) Riverine Swampy Woodland · flood-dispersed seed pods Annual Flat-sedge Cyperus Y High Drainage-line Aggregate, Riverine nervulosus (e, L) Swamp Forest, Riparian 4 Slender Love-grass Eragrostis Y High Drainage-line Aggregate exigua (e) 4 Jerry-jerry Ammannia Y High Drainage-line Aggregate, Lignum Annual of creeklines, multiflora (v) Shrubland, Lake Bed Herbland, lacustrine – following Alluvial Plains Semi-arid Grassland recession (c) Name and Location and flooding requirements conservation status of animal species Little Egret Egretta Sites mapped: Breeding sites: All DSE wetland polygons and other points with breeding records and a surrounding garzetta (endangered) 2 km buffer (for both) Non-breeding sites: 1. Lakes Ranfurley and Hawthorn: all areas of Lake Bed Herbland 2. Lakes Hattah, Little Hattah, Lockie, Yerang, Mournpall, Bulla and Arawak: all areas of Lake Bed Herbland 3. Ovens River c. 1.5 km E of Hume Highway (Wangaratta Bypass): all areas of Floodplain Riparian Woodland and Floodplain Wetland Aggregate within 1 km of record site 4. Ovens River c. 4 km E of Hume Highway (Wangaratta Bypass): all areas of Floodplain Riparian Woodland, Floodplain Wetland Aggregate and Water Body – natural or manmade within 1 km of record site 5. Ovens River SE of Whorouly: all areas of Swampy Woodland, Drainage-Line Aggregate, Floodplain Wetland Aggregate and Water Body – natural or manmade within 1 km of record site Minimum flood frequency: Breeding sites: 1 in 5 years; Non-breeding sites: as per EVCs; 1 in 2 years for Water Body Flood duration: Breeding sites: 5months; Non-breeding sites: as per EVCs, 6–12 months for Water Body Habitat ⁄ Location: All post-1960 breeding records in VFD and literature selected and mapped. Non-breeding records are sites with two or more post-1970 records Relative importance of study area: High – the study area nesting sites are the largest in Victoria (there are few in Victoria outside the study area) albeit not recent (2010 breeding in Barmah forest is not included in this analysis) and the species is endangered De Vis’ Banded Snake Sites mapped: Lake Bed Herbland, Floodway Pond Herbland, Shallow Freshwater Marsh, Intermittent Swampy Denisonia devisi Woodland at site records (vulnerable) Minimum flood frequency: as per EVCs. Flood duration: as per EVCs Habitat ⁄ Location: Site records from DSE (see also Clemann et al. 2007) and advice on EVCs from expert opinion. Watercourse ⁄ wetland-reliant as frogs are the main diet Relative importance of study area: Recently discovered in Victoria and entire known range in Victoria is in study area – so important. Nearest known site locality is some 500 km away at Broken Hill in NSW. Vulnerable on the DSE 2007 Advisory List and range restricted *Conservation status: e (endangered), v (vulnerable), L (listed under the Flora and Fauna Guarantee Act 1988). †Y – Taxa apparently requiring ⁄ responding to inundation. EVC: Ecological vegetation classes.

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watering strategies that maximise the effec-

Frequency of Extent of flooding tiveness of whatever watering is under- flooding required (with flows of 20, 81 or 159 GL/day) (years) taken in sustaining natural values. This is Very small flood Not flooded Flooded (20 gigalitres per day) enabled by providing digital mapping that 1 in 2–5 1 in 7 can be used to transparently predict the

1 in 15–30 extent to which any given inundation event assists in sustaining the natural values of the floodplain. By compiling the results of these analyses for many such Lake Powell events, it is possible to develop floodplain Lake Carpul watering strategies covering the entire River Murray floodplain for periods comparable to the largest estimated flood frequencies (i.e. 20–40 years). The predicted outcomes of the different strategies for Moderate flood floodplain natural values could then be (81 gigalitres per day) compared and the most favourable practi- cable strategy adopted for implementation. The essence of this comprehensive mapping approach enables the development of adaptive watering strategies that are readily communicated to the general public and facilitate transparent modifica- tion in response to new information or changes to key factors such as water availability. Importantly, it furthers the debate Large flood about how much water should be allo- (159 gigalitres per day) cated to the environment by documenting the ‘winners’ and ‘losers’ (of species and ecosystems) in any watering event or ser- ies of watering events. Such strategies would be developed by bringing together the most effective water regimes for each of the natural values targeted for protection along the entire length of the floodplain. Many of these regimes would be developed through their own adaptive process. For example, if a manage-

0 2.5 5 10 15 20 ment agency was interested in maintaining km River Red Gums in the Robinvale area Figure 2. Examples of coverage of flood-dependent natural values for various flood scenarios in (Fig. 2), they might interrogate our data set the Robinvale area. Note: The flooding extents shown in red are based on outputs from the CSIRO for Grassy Riverine Forest – the predomi- River Murray Floodplain Inundation Model (RiM-FIM) which is derived from satellite imagery of nant EVC supporting this species. This EVC actual floods. This figure provides an example of how the digital natural values mapping generated requires watering every 4 years to maintain in the present study can be applied. It is not intended that this figure represent actual outcomes of condition (its critical interval – Table 1) applying these amounts of environmental water. The maps apply to the Victorian side of the River and is predicted to be barely inundated in a Murray only. 20 GL ⁄ day flood (2% of extent), 27 and 35% inundated in 81 and 159 GL ⁄ day for which regular environmental watering deficiencies for many other taxa and eco- floods, respectively (Table 2). Based on this is planned. Other Regent Parrot breeding systems. information, the manager, with consider- areas interstate and along the Wimmera ation of other factors such as the approxi- River in Victoria are at least as unlikely to Discussion mate amount of environmental water receive adequate flooding as those covered available, might judge that flows of at least in our analysis. Further analysis of our The primary purpose of this analysis is to 81 GL ⁄ day be generated once every 4 years mapped dataset is likely to reveal similar facilitate the development of floodplain unless such flows occur naturally. This

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Ta ble 2 . Area and percentage of natural values in the Robinvale region inundated by the three ﬂood extents shown in Figure 2

Area of EVC Percent of mapped EVC or habitat or habitat (ha) covered by various ﬂood extents Very small Moderate Large Ecological Vegetation Class Floodplain Grassy Wetland 63 3 71 77 Floodway Pond Herbland 370 1 37 47 Grassy Riverine Forest 678 2 27 35 Grassy Riverine Forest ⁄ Floodway Pond Herbland Complex 567 2 22 28 Intermittent Swampy Woodland 1433 1 27 38 Lake Bed Herbland 130 0 0 0 Lignum Shrubland 3550 0 5 12 Lignum Swamp 562 0 2 7 Lignum Swampy Woodland 5488 0 5 11 Riverine Chenopod Woodland 5035 0 5 8 Riverine Grassy Woodland 980 0 4 9 Shallow Freshwater Marsh 394 0 42 51 Shrubby Riverine Woodland 1972 1 24 37 Spike-sedge Wetland 17 0 62 71 Sub-saline Depression Shrubland 82 0 0 0 Tall Marsh 42 0 9 21 Threatened Fauna Apostlebird Struthidea cinerea 6746 0 3 7 Blue-billed Duck Oxyura australis 434 0 0 0 Brown Quail Coturnix ypsilophora 35 0 0 0 Inland Carpet Python Morelia spilota metcalfei 16 452 0 12 19 Diamond Dove Geopelia cuneata 168 0 0 0 Diamond Firetail Stagonopleura guttata 121 0 2 6 Freckled Duck Stictonetta naevosa 2700 0 2 3 Grey-crowned Babbler Pomatostomus temporalis 215 0 0 0 Hardhead Aythya australis 592 0 0 0 Musk Duck Biziura lobata 592 0 0 0 Nankeen Night-Heron Nycticorax caledonicus 1690 0 4 6 White-bellied Sea-Eagle Haliaeetus leucogaster 550 0 0 0 Regent Parrot Polytelis anthopeplus monarchoides 321 1 29 49 Rare or Threatened Flora Annual Spinach Tetragonia moorei 89 0 2 3 Bluish Raspwort Haloragis glauca f. glauca 249 0 13 20 Common Joyweed Alternanthera nodiﬂora 259 0 0 0 Cotton Sneezeweed Centipeda cunninghamii 88 0 42 65 Desert Lantern Abutilon otocarpum 84 0 0 3 Desert Spinach Tetragonia eremaea s.s. 43 0 4 11 Dwarf Bitter-cress Rorippa eustylis 77 0 0 0 Goat Head Malacocera tricornis 559 0 2 4 Hoary Scurf-pea Cullen cinereum 81 0 10 15 Mealy Saltbush Atriplex pseudocampanulata 42 0 0 0 Native Couch Cynodon dactylon var. pulchellus 729 1 22 35 Native Peppercress Lepidium pseudohyssopifolium 518 1 9 13 Pale Plover-daisy Leiocarpa leptolepis 41 2 5 7 Pale Spike-sedge Eleocharis pallens 26 0 0 0 Purple Love-grass Eragrostis lacunaria 182 0 0 0 Reader’s Daisy Brachysome readeri 380 0 2 7 Riverina Bitter-cress Cardamine moirensis 132 1 25 39 Riverine Flax-lily Dianella porracea 69 0 0 0 Silver Saltbush Atriplex rhagodioides 23 8 79 100 Smooth Minuria Minuria integerrima 38 0 0 0 Spear-fruit Copperburr Sclerolaena patenticuspis 432 0 6 13 Spiny Lignum Muehlenbeckia horrida horrida 71 0 0 0 Spotted Emu-bush Eremophila maculata var. maculata 236 0 2 3 Spreading Emu-bush Eremophila divaricata divaricata 776 2 14 18 Squat Picris Picris squarrosa 509 2 33 55 Summer Fringe-sedge Fimbristylis squarrosa 381 0 1 5 Sweet Fenugreek Trigonella suavissima 86 0 0 0

ª 2011 Ecological Society of Australia ECOLOGICAL MANAGEMENT & RESTORATION VOL 12 NO 2 AUGUST 2011 7 MANAGEMENT REPORT

Ta ble 2 . (Continued)

Area of EVC Percent of mapped EVC or habitat covered by or habitat (ha) various flood extents Very small Moderate Large Tangled Copperburr Sclerolaena divaricata 127 0 5 14 Twinleaf Bedstraw Asperula gemella 1376 1 5 9 Warty Peppercress Lepidium papillosum 150 0 6 9 Ya kk a G ra ss Sporobolus caroli 189 0 1 4 Yarran Acacia melvillei 367 1 5 7 Flood extents based on the CSIRO River Murray Floodplain Inundation Model (RiM-FIM) for the following daily flow volumes: Very small (20 GL ⁄ day), Moderate (81 GL ⁄ day), Large (159 GL ⁄ day). EVC: Ecological vegetation classes. regime would then be integrated with overbank flows of various sizes), these potential result of sufficient water being numerous regimes for other values to come areas would be prime candidates for works made available for the environment, then it up with an overall strategy, which could such as levees, regulators or pumping to isimportantthatthe casefor such use clearly then be implemented and refined through meet their flooding requirements – particu- articulates its environmental benefits. analysis of actual flooding extents and larly given that they are terminal lakes that Our results greatly substantiate the case refinement of critical intervals for particular would not require large volumes of water for securing and using of water for the values. flowing down the river channel in order to environment, and in particular for flood- In some cases, the local regimes may meet flooding duration requirements. The plain watering, by showing that: end up being separate from any broader natural values of these lakes would then be 1 There are substantial numbers of eco- regime. For example, Lakes Powell and sustained through a small local pumping systems and threatened species that are Carpul near Robinvale in northwest regime specific to the lakes and not as part dependent on environmental watering. Victoria have high concentrations of natu- of broader regimes targeting many values ral values (Fig. 3) with critical intervals of in this part of the floodplain. 2 It is possible to compile, map and quan- 2–5 years, but are not predicted to be The allocation of water resources in the tify flooding requirements for a sub- inundated even in large floods (Fig. 2). Murray-Darling Basin to the environment on stantial proportion of flood-dependent That is, assuming this predicted lack of the one hand, and consumptive uses on the species and ecosystems. flooding in these areas was confirmed by other is one of Australia’s most important 3 It is possible (as a result of this map- site-specific investigation (such as actual environmental challenges. If significant ping) to investigate the benefits of and flooding extent in past and future social and regional economic costs are a optimality of environmental watering, to values at risk as a result of insuffi- Legend cient watering. Number of values present EVCs and threatened species By way of example, the data presented

1 9 – 10 from a part of the study area near Robin- 2 11 – 12 vale Victoria demonstrate the application 3 – 4 13 – 14 of our results. In combination with even 5 – 6 15 – 16 relatively cursory information about ﬂood- 17 – 24 7 plain watering and key values, it is possible 8 to identify values likely to be at greatest risk. For the nationally vulnerable eastern subspecies of the Regent Parrot, for example, a large majority of breeding sites are along the River Murray and highly depen-

Lake Powell dent on riverine flooding. Relatively few of these sites are within The Living Murray Lake Carpul icon sites that are currently considered the highest priority areas for environmental watering. In the context of river regulation, these breeding sites are unlikely to be 0 2.5 5 10 15 20 flooded regularly without intervention – km our results suggest only 49% of sites would Figure 3. Compilation of flood-dependent natural values on the Victorian side of the River Mur- be inundated by a large flood, which is ray in the Robinvale area.

8 ECOLOGICAL MANAGEMENT & RESTORATION VOL 12 NO 2 AUGUST 2011 ª 2011 Ecological Society of Australia MANAGEMENT REPORT predicted to occur once every several dec- biota, it is imperative to address the strategies should be taxonomically com- ades (DSE 2008a). These results clearly flag uncertainties in these initial estimates. prehensive and, in addition to the taxa the need for further investigation of the Environmental water planners could do presented in this paper and Fitzsimons watering of Regent Parrot breeding sites. this by testing our models against actual et al. (2011), include fish, invertebrates, There are many other such floodplain val- flood events, and a short-term priority non-vascular plants and regionally sig- ues that our results identify that would could be given to sensitivity analysis and nificant taxa. Similarly, the list of eco- otherwise likely go undetected. the initiation of research and monitoring logical characteristics used to identify to inform ongoing refinement of esti- natural values should be comprehensive Availability of the database mates and strategies in the longer term. and include important characteristics The geospatial dataset has been transferred such as: sites that are likely to assist the 2 Overbank flows and ecological connec- by the Victorian Environmental Assess- recovery of highly threatened taxa, sites tivity. The approach to floodplain water- ment Council to the Victorian Department of high species richness, colony sites ing taken here focuses on mapping of Sustainability and Environment follow- for non-threatened colonial breeding discrete natural assets with a view to ing the Victorian Environmental Assess- species, and corridors of habitat which meeting their watering requirements. To ment Council’s final recommendations for are important for the movement of also provide the environmental benefits the River Red Gum Forests Investigation in biota. This project and new information of extensive overbank floods and the 2008. As a result, it is now freely accessible on future flooding regimes (e.g. DSE resultant ecological connectivity (e.g. to land, water and threatened species man- 2008a) suggest that as insufficient Jenkins & Boulton 2003; Ballinger & Mac agers. In addition, the methodology and watering is a major threat to floodplain Nally 2005), further work would be nee- conceptual framework used in our analysis biodiversity, a review of the conserva- ded to quantify and incorporate these could be easily applied to other jurisdic- tion status of floodplain EVCs and taxa benefits into the formulation and evalua- tions with different vegetation mapping in Victoria is required. tion of floodplain watering – that is, a units and different species and in many quantification of the benefits of large- 6 Ongoing incorporation of floodplain cases, different flood requirements. scale inundation, additionaltothose from inundation modelling, hydrology, sa- Future work – development themaintenanceofsite-specific values. linisation and local climate. Improve- of strategies ments in inundation models and 3 Comparing different values and risks. information on the effects of groundwa- The future of water availability and alloca- In a water-constrained future, further ter, soil salinity and variations in local tion for the environment in the Murray- work is needed to develop a conceptual climate (including those resulting from Darling Basin is the subject of considerable framework within which to compare climate change) have the potential to recent financial investment and major insti- different sets of values and the risks to impact significantly on the formulation tutional change (e.g. Connell 2007). The them to optimise potential trade-offs and selection of watering strategies and framework of our analysis and the data it between values and to provide stake- should be pursued and incorporated generated provide essential information to holders with transparency and there- into those strategies as the improve- commence the process of formulating, fore confidence in the decision-making ments and new information becomes selecting and refining floodplain watering process. Such a framework would also available. strategies. However, substantial and endur- highlight key data gaps so that they can ing positive outcomes for biodiversity will be filled. Our analysis is the first to consider how require further work in a number of areas, flooding requirements for a broad range of 4 Additional flooding requirement vari- outlined below. The highest priority is to natural values can be incorporated into ables. For at least some EVCs and taxa, use the results of the analysis and inunda- environmental watering strategies. As a estimates of the following variables tion modelling to initiate the formulation, result of the paucity of existing empirical additional to those in this paper are comparison and implementation of flood- data and relative urgency associated with likely to be important in the develop- plain watering strategies. Development of better informing environmental watering ment of floodplain watering strategies: such strategies could be undertaken by policy and strategies, this analysis was pri- depth of inundation, season of inunda- environmental water planners and, in our marily based on expert opinion. However, tion, minimum and maximum flood view, would be enhanced by incorporation the framework readily allows for the incor- frequencies, and duration of periods of the following: poration of new data, particularly data without inundation. Minimum flood fre- gained from empirical field experiments on 1 Refining watering requirement esti- quency over a sustained period and flooding requirements of vegetation types mates and mapping. Given that the flood seasonality are likely to be a signif- and species. When provided to the agencies expert estimates of flooding require- icant factors for many EVCs and taxa responsible for environmental water alloca- ments in this paper would underpin (Robertson et al. 2001; Bren 2005). tion, such data would enable further expensive watering programs critical to 5 Comprehensive taxonomic and eco- improvement in the effectiveness of ongo- the persistence of much of the region’s logical coverage.Floodplainwatering ing environmental watering. Thus, our

ª 2011 Ecological Society of Australia ECOLOGICAL MANAGEMENT & RESTORATION VOL 12 NO 2 AUGUST 2011 9 MANAGEMENT REPORT approach is both flexible and adaptable, Leslie D. and Ward K. A. (2002) Murray River envi- which is important given the uncertainties References ronmental flows 2000–2001. Ecological Man- agement and Restoration 3, 221–223. for future flood events based on climate Aldous A., Fitzsimons J., Richter B. and Bach L. McCarthy B., Conallin A., D’Santos P.and Baldwin change predictions (Aldous et al. 2011). (2011) Droughts, floods and freshwater eco- D. (2006) Acidification, salinization and fish systems: evaluating climate change impacts kills at an inland wetland in south-eastern Aus- and developing adaptation strategies. Marine tralia following partial drying. Ecological Man- and Freshwater Research 62, 223–231. Conclusion agement and Restoration 7, 221–223. Ballinger A. and Mac Nally R. (2005) Flooding MDBA (2010) Guide to the Proposed Basin Plan, in Barmah-Millewa Forest: catastrophe or In conclusion, we contend that large areas Murray-Darling Basin Authority, Canberra. opportunity for non-aquatic fauna. Proceed- MDBC (2003) Preliminary Investigations Into of the Victorian, New South Wales and ings of the Royal Society of Victoria 117, Observed River Red Gum Decline Along the South Australian floodplain forests are 111–115. River Murray Below Euston. Technical Report Ballinger A. and Mac Nally R. (2006) The land- (despite a recent, rare flood event) highly 03 ⁄ 03. Murray-Darling Basin Commission, scape context of flooding in the Murray-Dar- Canberra. vulnerable to severe stress or mortality ling basin. Advances in Ecological Research NRC (2009) Riverina Bioregion Regional Forest owing to lack of sufficient flooding. 39, 85–105. Assessment: River Red Gums and Woodland Beilfuss R. and Brown C. (2010) Assessing the Despite significant investments in purchas- Forests Recommendations Report. Natural environmental flow requirements and trade- Resources Commission, Sydney. ing water and the delivery of that water in offs for the Lower Zambezi River and Delta, Overton I. C. (2005) Modelling floodplain inunda- the Murray-Darling Basin, there is little Mozambique. International Journal of River tion on a regulated river: integrating GIS, Basin Management 8, 127–138. understanding of which natural values are remote sensing and hydrological models. River Bren L. J. (2005) The changing hydrology of the Research and Applications 21, 991–1001. benefiting from this water and which are Barmah-Millewa Forests and its effects on Parkes D., Newell G. and Cheal D. (2003) Assess- not. Our preliminary work shows that an vegetation. Proceedings of the Royal Society ing the quality of native vegetation: the of Victoria 117, 61–76. efficient and effective watering regime to ‘habitat hectares’ approach. Ecological Man- Clemann N., Robertson P., Gibbons D. et al. agement and Restoration 4, S29–S38. sustain flood-dependent natural values is (2007) An addition to the snake fauna of Vic- Richter B. D., Warner A. T., Meyer J. L. and Lutz achievable. Identifying all flood-dependent toria: De Vis’ Banded Snake Denisonia devisi K. (2006) A collaborative and adaptive pro- (Serpentes: Elapidae) Waite and Longman. natural values and estimating their water cess for developing environmental flow recom- Victorian Naturalist 124, 33–38. mendations. River Research and Applications requirements should be a high priority Connell D. (2007) Water Politics in the Murray- 22, 297–318. across the entire Murray-Darling Basin. The Darling Basin. Federation Press, Sydney. Robertson A. I., Bacon P. and Heagney G. (2001) Cooling M. P., Lloyd L. N., Rudd D. J. and Hogan approach also has applicability for other The responses of floodplain primary produc- R. P. (2002) Environmental water require- tion to flood frequency and timing. Journal of river basins which rely on floodplain inun- ments and management options in Gunbower Applied Ecology 38, 126–136. dation to maintain natural values. Forest, Victoria. Australian Journal of Water Smakhtin V. (2008) Basin closure and environmen- Resources 5, 75–88. tal flow requirements. International Journal of Cunningham S. C., Mac Nally R., White M. et al. Water Resources Development 24, 227–233. (2007) Mapping the current condition of river Acknowledgements Stewart G. and Harper B. (2002) Barmah-Millewa red gum (Eucalyptus camaldulensis Dehnh.) forest environmental water allocation. Water stands along the Victorian Murray River flood- This project was overseen by Victorian Science and Technology 45(11), 217–223. plain. A report to the Northern Victorian Tzaros C. L. (2001) Importance of riparian vegeta- Environmental Assessment Council mem- Catchment Management Authorities and the tion to terrestrial avifauna along the Murray bers. Information and analysis on the fauna Department of Sustainability and Environ- River, south-eastern Australia. MSc thesis, ment. of the study area was provided by Peter Deakin University, Melbourne. DSE (2008a) Sustainable Water Strategy North- VEAC (2006) River Red Gum Forests Investigation Robertson, Martin O’Brien, Nick Clemann, ern Region Discussion Paper, Department of Discussion Paper. Victorian Environmental Peter Menkhorst, Chris Tzaros, Lindy Lums- Sustainability and Environment, Melbourne. Assessment Council, Melbourne. DSE (2008b) Ecological Vegetation Class (EVC) den, Mark Antos, Andrew Silcocks and Shar VEAC (2008a) River Red Gum Forests Investiga- Benchmarks for Each Bioregion. Department tion Final Report. Victorian Environmental Ramamurthy. Jane Roberts, Terry Hillman of Sustainability and Environment, Melbourne. Assessment Council, Melbourne. and Keith Ward assisted with information Available from: http://www.dse.vic.gov.au/ VEAC (2008b) Identifying flood-dependent natural dse/nrence.nsf/LinkView/43FE7DF24A1447 and analysis on the flora and EVCs. Don values on the Victorian floodplains of the River D9CA256EE6007EA8788062D358172E420C Murray and its tributaries. Version 1.0. Victo- Blackmore, Jane Doolan, Ray Evans, Gary 4A256DEA0012F71C (accessed 5 September rian Environmental Assessment Council, Mel- Jones and Julia Reed made valuable contri- 2008). bourne. Available from: http://www.veac.vic. Fitzsimons J. A. (2006) Public land use planning butions to the study more generally. The gov.au/reports/352-VEAC_Red_Gum_Flood- using bioregions and other attributes: deter- dependent_natural_values_Report_V1-0.pdf CSIRO RiM-FIM data was provided by Shar mining the study area of the VEAC River Red (accessed 13 September 2009). Ramamurthy (DSE). Jong Lee, Pradeep Gum Forests investigation. Proceedings of the Wang X., Zhang Y. and James C. (2009) Royal Society of Victoria 118, 75–85. Sharma and Tony McLeod at the Murray- Approaches to providing and managing envi- Fitzsimons J. A., Peake P., Frood D. et al. (2011) ronmental flows in China. International Journal Darling Basin Authority provided informa- Flooding requirements for biodiversity values of Water Resources Development 25, 283– tion on the frequency of daily river flows along the Victorian floodplain of the Murray 300. Valley. Victorian Naturalist 128, 48–85. near Robinvale. We thank Tein McDonald, Webster R. (2004) Surveys of potential Regent Jenkins K. M. and Boulton A. J. (2003) Connectiv- Parrot Polytelis anthopeplus monarchoides Barry Hart, Joan Phillips and two anony- ity in a dryland river: short-term aquatic micro- nesting habitat in Victoria between Piambie mous referees for helpful comments on invertebrate recruitment following floodplain State Forest and Lambert Island. Unpublished inundation. Ecology 84, 2708–2723. drafts of this paper. report to Mallee Catchment Management Authority, Mildura.

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