MURRAY-DARLING BASIN COMMISSION 0 100 200 300 400 500 600 700 Narran Ecosystem Project

The response of a terminal wetland system to variable wetting and drying. Final report to the Murray-Darling Basin Commission MURRAY-DARLING BASIN COMMISSION 0 100 200 300 400 500 600 700 Narran Ecosystem Project

The response of a terminal wetland system to variable wetting and drying. Final report to the Murray-Darling Basin Commission

Project Leader Professor Martin Thoms Science Team Dr Samantha Capon, Dr Cassandra James, Dr Mark Padgham, Dr Scott Rayburg

September 2007 Published by the Murray-Darling Basin Commission Postal address: GPO Box 409, Canberra ACT 2601 Office location: 51 Allara Street, Canberra City Australian Capital Territory

Telephone: (02) 6279 0100, international + 61 2 6279 0100 Facsimile: (02) 6248 8053, international + 61 2 6248 8053 Email: [email protected] Internet: http://www.mdbc.gov.au

For further information contact the Murray-Darling Basin Commission office on (02) 6279 0100

This report may be cited as: The Narran Ecosystem Project: the response of a terminal wetland system to variable wetting and drying. Final report to the Murray-Darling Basin Commission.

MDBC Publication No. 40/08

ISBN 978 1 921257 80 3

© Murray-Darling Basin Commission /eWater CRC 2008

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Contents

1. Executive Summary...... 1 6.3 Ecological Responses...... 44

6.3.1 Aquatic ecology...... 44 2. Preamble...... 5 6.3.2 Vegetation...... 48 3. Overview of Study Area...... 7 6.3.3 Waterbirds...... 57

4. Overview of Project...... 9 6.3.3.1 Waterbird breeding in the Narran Ecosystem...... 57 5. Key Activities...... 12 6.3.3.2 Landscape scale influences 5.1 Overview...... 12 on waterbirds in the Narran Ecosystem...... 58 5.2 Physical template...... 12

6.4 Conceptual Model...... 61 5.2.1 Regional context...... 12

6.4.1 Physiacl factors...... 63 5.2.2 Topography...... 13

6.4.2 Hydrological factors...... 64 5.2.3 Soils...... 13

6.4.3 Ecological factors...... 65 5.2.4 Channel network...... 13 6.4.4 Interactions among physical, 5.2.5 Environmental history...... 15 hydrological and ecological factors...... 67 5.3 Hydrological drivers...... 16 6.5 Knowledge Exchange...... 68 5.3.1 Climate...... 16 6.5.1 Community and Industry 5.3.2 Hydrology...... 16 fact sheets...... 68

5.4 Ecological responses...... 18 6.5.2 Oral History...... 68

5.4.1 Aquatic ecology...... 18 6.5.3 Newsletters...... 69

5.4.2 Vegetation...... 20 6.5.4 Scientific papers...... 69

5.4.3 Waterbirds...... 23 6.5.5 Community presentations...... 70

5.5 Knowledge Exchange...... 23 6.5.6 Industry presentations...... 71 6.5.7 Scientific presentations and 6. Key Findings...... 24 conferences...... 71 6.1 Physical template...... 24 6.5.8 Media...... 73 6.1.1 Regional context...... 24

Appendix 1: Groundcover species list...... 75 6.1.2 Topography...... 25

6.1.3 Soils...... 26 Appendix 2: Tree species list...... 77

6.1.4 Channel network...... 27 Appendix 3: Methodology and Management

6.1.5 Environmental history...... 27 Implications...... 78

6.2 Hydrological drivers...... 30 References...... 106 6.2.1 Climate...... 30

6.2.2 Hydrology...... 30

6.2.3 Hydraulic and hydrologic models...... 38

iii

1. Executive Summary

1. Executive summary

Background to manage these types of systems have not been based on sound scientific data and information Large floodplain ecosystems are a feature of to date. Questions remain concerning how much Australia’s dryland rivers. They are associated water these ecosystem require in order to maintain with numerous wetlands, lakes and small creeks and conserve their ecological integrity. The Lower that dissect the extensive floodplain surfaces. The Balonne region has been subjected to large water Narran Ecosystem, located in northwest New South resource developments. Most water resource Wales, is a key refugia for many aquatic and water- development in the Condamine-Balonne Catchment dependent terrestrial plants and animals in an has occurred since the advent of irrigated agriculture otherwise dry landscape. In June 1999, the Narran in the 1960s. There are three main irrigation Lakes Nature Reserve, which occupies the northern developments within the Condamine-Balonne section of the Narran Ecosystem was inscribed on catchment; the St George Irrigation Area located on the List of Wetlands of International Importance the Lower Balonne Floodplain is the largest. There under the Convention on Wetlands of International are also four significant public water storages in Importance (Ramsar). It is also an integral part the catchment, which service irrigation, agricultural of three international migratory bird agreements: and domestic supply. These being Leslie Dam the Chinese Australian Migratory Bird Agreement (106 250 Ml); Chinchilla Weir (9800 Ml); Beardmore (CAMBA), the Japanese Australian Migratory Bird Dam (81 800 Ml) and Jack Taylor Weir (10 100 Ml). Agreement (JAMBA) and the Republic of Korea- There are also numerous private off-stream water Australia Migatory Bird Agreement (ROKAMBA). storages on the Lower Balonne Floodplain that have The ecological integrity of floodplain ecosystems, like an estimated combined storage volume in excess of Narran, is maintained by hydrological connections 500 000 Ml (Thoms, 2003). between the floodplain and its associated wetlands, lakes and the adjacent river channel. This report provides the results of a four-year interdisciplinary scientific study of the Narran The Narran Ecosystem is part of the Lower Balonne Ecosystem. The overall aim of the study was floodplain region within the Condamine Balonne to investigate the ecosystem response of this catchment. It is a region of diverse physical floodplain wetland complex to flow variations. This habitats and wetland types, and of high biodiversity. scientific study was funded by the Murray Darling Downstream of St George, the Condamine-Balonne Basin Commission. While focused on the Narran River divides into five main channels; the Culgoa Ecosystem, it was established to also increase our and Narran Rivers are the main channels, conveying understanding of terminal floodplain-wetlands in 35% and 28% respectively, of the long-term mean the dryland region of Australia and more importantly annual flow at St George. Unlike the other river to allow the prediction of the response of these systems of this region the Narran River does not types of systems to disturbances – both natural flow into the Barwon Darling system but flows and those induced by continued water resource into a terminal floodplain–wetland complex – the and floodplain development. While this integrated Narran Ecosystem. Water, sediments and associated project recognised the importance of the Narran nutrients supplied to the Narran Ecosystem Ecosystem itself, it was also important that this originate from the catchments of the Condamine and ecosystem be viewed as part of a network of Maranoa Rivers, which drain the Eastern Australian floodplains and wetlands within the Murray-Darling Highlands. Although these inputs are highly variable Basin. Therefore, three scales of investigation were over time, they produce a complex mosaic of patches employed with ecological questions framed at the of varying physical and ecological character within local, catchment and broader landscape scale. The the Narran Ecosystem. fundamental aims of this project concerned linking No detailed environmental studies of the Narran ecological (both physical and biological) responses Ecosystem have previously been undertaken. of selected components of the Narran Ecosystem to Indeed, studies of the structure and function of variability in flow regime. Specifically, it aimed to: large floodplain wetland ecosystems are limited, • Determine the physical and biological especially those subjected to naturally high responses of the Narran Ecosystem to variability in terms of water supply. Answers of how variations in the flow regime.

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• Predict the responses of selected components The Narran Ecosystem has been functioning as of the Narran Ecosystem to alterations in a wetland ecosystem for at least 46 000 to 70 000 flow regime under different water resource years. It is an old aquatic feature of the Australian development and long-term climate change landscape. Indeed, water and sediments have been scenarios. These predictive models would flowing into the Narran floodplain region for even emphasise the links between flow regime and longer. Dating of sediments from cores extracted biota through habitat availability and changes from various locations in the northern lakes provide in ecological processes such as primary an age of 440 000 years. productivity. Flows into the Narran Ecosystem were available • Evaluate the ecological significance of the Narran for the Wilby Wilby gauging station (the nearest Ecosystem in the regional context of wetlands upstream station to the Narran Ecosystem) from within the northern Murray Darling Basin. the 1960s. This allowed an assessment of the actual • Develop a conceptual model that links physical hydrology of inflows to the Narran Ecosystem. Flows and biological responses of the Narran into the Narran Ecosystem occurred in nearly 90% Ecosystem to past and future changes in water of all years on record. Medium to large floods have resource development, land-usage and climate. also been relatively common historically with more than 66% of all years recording 50 000 Ml or more In order to address these specific aims, the project of discharge at the Wilby Wilby gauge. However, was organised to investigate and report information flows at Wilby Wilby show a systematic decline in in four key areas: the occurrence of medium-sized floods since 1992 • Characterising the physical template of the and an overall decrease in discharge volumes when Narran Ecosystem and surrounding regions, compared to the earlier part of the record. This has resulted in an increase in the recurrence intervals • Analysing the principal drivers of change in the for all flood magnitudes (floods are more rare Narran Ecosystem and surrounding regions, irrespective of size) since 1992. • Interpreting the change in the template as a result of these drivers in the Narran Ecosystem The high variability of inflows to the Narran and the surrounding regions, and, Ecosystem results in a high degree of spatial and temporal variability in terms of the inundation of • Investigating the ecosystem responses to any the floodplains, lakes and channel network in the changes in the original template of the Narran Narran Ecosystem. However, the lakes have been Ecosystem and surrounding regions. partially inundated in 27 out of the last 32 years.

Key findings A coupled hydraulic–hydrologic model was developed for the Narran Ecosystem. This model The Narran Ecosystem is comprised of several predicts the spatial patterns of wetting and drying physical units: across the Narran Ecosystem and can be used to • the main Narran River channel assess the impact of different hydrological scenarios such as climate, water resource development and • an extensive secondary river channel network land-use change on the timing, magnitude and • four lakes, the Narran Lake in the south, Clear duration of inundation. This model has an accuracy Lake, Back Lake and Long Arm in the north and of nearly 90% when correlated between actual and predicted flow levels. • a series of floodplains. The model predicts that significant inundations The four lakes have a combined surface area of of each lake (taken to be 50% full or more) are 131.1 km2, with the Narran Lake being the largest common with Narran Lake being at least 50% full (122.9 km2), followed by Clear Lake (5.4 km2), Long more than 40% of the time and the Northern Lake Arm (1.5 km2) and Back Lake (1.3 km2). The river being at least 50% full more than 30% of the time channel network contains over 8000 individual under a natural-flow scenario –— one that has no channel sections of 44 distinct channel types with water resource development and influenced by a combined length of 804.5 km. As a collective the same climatic regime. A comparison of other they offer a high degree of physical diversity to the scenarios suggests the impact of land use and water floodplain–wetland complex. As a collective the resource development far outweighs any potential floodplains of the study area have a surface area of climate change impacts on the frequency, timing and 135.7 km2. These four physical units are intimately duration of inundation in the Narran Ecosystem. linked especially during periods of inundation thus forming the physical template of this ecosystem.

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Under current water development levels the longest High mortality (38–54% dead) is evident amongst all dry periods (times without significant inundation) commonly occurring tree species with seedlings and increase from about 1–2 years to nearly 20 years. saplings of Eucalyptus camaldulensis, E. coolabah and mature Acacia stenophylla exhibiting particularly Vegetation in the Narran Ecosystem is spatially and high levels of mortality and stress. temporally heterogeneous and distinctive in terms of its floristic composition in comparison to that During a flow event in 2004 a relatively small area of supported by surrounding upland ecosystems. the Narran Ecosystem was inundated. During this event 31 955 fish were collected from eight families There are large, diverse soil seed banks present including 11 species. This included eight native throughout the Narran Ecosystem and these species and three exotic species. This suggests comprise more than 70 groundcover species there is rapid colonisation of the Narran Ecosystem including at least 23 monocot and 54 dicot species. upon receiving a filling event. Analysis of the fish The abundance and diversity of propagules which population during this inundation event also notes may germinate are greatest in soil seed banks of that spawning did occur in the lakes. Thus the intermediately flooded habitats such as the large duration of the event is important. areas of lignum floodplain. A diverse and abundant zooplankton fauna was Groundcover vegetation development from soil observed in the 2004 flood event. Micro-invertebrate seed banks depends primarily on recent flooding assemblages varied over time as the system dried characteristics. High floristic diversity and out as well as between habitat types. A high number productivity occurs in response to intermediate of taxa (24) were recorded solely in floodplain durations of submergence followed by long periods habitats. of floodwater drawdown. The Narran Ecosystem is a significant refugia for Exotic groundcover species are present in the birds. At least 65 species of waterbirds have been vegetation of the Narran Ecosystem and in soil seed recorded in the complex of which five are listed as banks, especially those of more frequently flooded threatened within NSW, with an additional nine being habitats. Establishment of exotic species from noted of conservation concern in western soil seed banks, however, may be limited by long New South Wales, these being the Australian durations of submergence and slow drawdown of Pelican, Little Egret, Glossy Ibis, Pacific Heron, floodwaters. Intermediate Egret, Straw-necked Ibis, Pied Cormorant, Great Cormorant and Royal Spoonbill. In The character of lignum (Muehlenbeckia florulenta) addition, over 1.1 million waterbirds were recorded shrubland varies throughout the Narran Ecosystem at Narran in 1984. By comparison, data from the in relation to long-term flood history. Frequently Eastern Australian Water Bird Survey (1983 to flooded areas are dominated by few but large the present) recorded in excess of seven million individual clumps while infrequently flooded areas waterbirds associated with the various wetlands support many small lignum clumps. Lignum is in the survey area. Thus, the Narran Ecosystem is absent from the most frequently flooded habitats, important at the landscape scale for water birds. e.g. the centre of Clear and Narran Lakes. There is a high degree of association between water Recent flood history exerts a strong influence on the in Narran and waterbird breeding at this site. 17 condition of lignum shrubland. waterbird breeding events have occurred in 34 years The establishment of lignum seedlings is favoured by in the Narran Ecosystem. For successful waterbird waterlogged and damp conditions and is likely to be breeding both the lakes and the floodplain must inhibited by long periods of submergence. be inundated. Floodplain inundation is essential as this functions as a feeding area whilst water in the Mature-tree communities vary considerably in their lakes is required to initiate breeding. Both functions composition and structure throughout the Narran (feeding and breeding) must be satisfied for Ecosystem and are dominated by four species; successful breeding in the Narran Ecosystem. Eucalyptus camaldulensis, E. coolabah, Acacia stenophylla and Eremophila bignoniiflora. Little At the landscape scale waterbirds have declined in recent recruitment was observed for these species abundance along eastern Australia by around 85% within the surveyed tree communities. since 1983, but numbers vary enormously from year to year. Climatic variation is the major determinant of inter-annual variations in waterbird abundance

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across eastern Australia. The climatic systems of greatest influence are coherent rainfall systems that traverse distances of 700–1000 km over periods of 13–21 days. Bird numbers, and the structure of these coherent rainfall systems, are very significantly related to the Madden–Julian Oscillation (a global, equatorial climatic cycle). Climatic influences explain 70% of the inter-annual variation in avian abundance, but only 12% of the overall decline.

The remaining portion of this decline in waterbird numbers is very strongly related to declines in flow volumes within the MDB. Declines have been far more pronounced within the Murray-Darling Basin than surrounding regions. Flow volumes within the MDB are also related to the same climatic systems, but their declines are similarly independent of climate. Declines in flow volumes that have occurred independent of climatic influences have the largest influence on avian declines.

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2. Preamble

Floodplain ecosystems wetlands greater than 5 ha in size within the Murray Darling Basin (Blackley et al., 1996). In excess of Large floodplain ecosystems are a characteristic 3400 wetlands have been identified, the majority feature of Australian inland river systems (Pickup, of which are freshwater wetlands associated with 1986; Thoms, 1995). Many are associated with floodplain areas (53%). This floodplain ecosystem extensive wetlands and terminal lakes. The is sustained by water, sediments and nutrients ecological integrity of these floodplains, wetlands from the upstream Condamine-Balonne catchment and terminal lake ecosystems is maintained – which comprises 14% of the Murray Darling Basin. by hydrological connections between them and Hydrological variability is a feature of this system and the adjacent river channels. The abundance of is influenced by climatic conditions such as El Nino– floodplain wetlands in Australia is not well known, Southern Oscillation (ENSO) events, because flows in but Blackley et al. (1996) lists 900 in a directory of the Condamine-Balonne correlate significantly with important Australian wetlands. Of these, 263 are the Southern Oscillation Index (SOI). The long-term associated with the rivers of Australia’s inland river hydrograph of the Condamine-Balonne is highly systems. In another inventory, Kingsford et al. (1999) variable, with a large proportion of average flows identified over 28 000 floodplain wetlands across the occurring in very wet years. Indeed, the coefficient Murray-Darling Basin, covering about six million of variation (CV) for flows in the Condamine-Balonne hectares. However, a glance at any water resource or ranges from 1.35 to 2.78, which is comparable to topographical map of Australia would suggest these other dryland systems worldwide. numbers to be an underestimate. Floodplains are a vital part of any riverine ecosystem because their The Narran Ecosystem is a significant floodplain biota rely on floodplains for refuge, breeding and wetland in the Lower Balonne region. It has been replenishment of food resources. identified as one of nine significant refugia for biological diversity in semi-arid and arid New Floodplain wetlands are areas of high biodiversity South Wales (Kingsford, 1999). Its significance (Williams, 1988; Kingsford and Porter, 1999) and was recognised in 1999 when a section of the have been referred to as ‘oases’ in an otherwise dry northern lakes was listed as a Ramsar Wetland of landscape (Morton et al., 1995). At many different International Importance in June 1999, 11 years scales, floodplain wetlands are key refugia for after being gazetted as a Nature Reserve by the both terrestrial and aquatic biota in Australia’s dry NSW National Parks and Wildlife Service. The interior. They have a crucial role as feeding, breeding Narran Lakes Nature Reserve is also listed on the and resting sites for migratory birds as well as for Register of National Estate as a natural heritage fish and other animals. The role as biodiversity site. This listing of the Narran Lakes Nature Reserve hotspots is maintained despite their highly variable as a Ramsar site was in recognition of it being and unpredictable hydrology and thus wetting an excellent example of a relatively undisturbed and drying regimes. They have been referred to terminal lake system for NSW. It is a significant site as ‘boom–bust’ systems, with high productivity for waterbirds, both nationally and internationally; occurring in periods inundation (booms) and very and because it provides habitat for some species little in periods of dry. Indeed, floodplain ecosystems that are recognised as being of conservation are dynamic mosaics where water plays an concern, either regionally, at the State level or important role in connecting the various patches that nationally. Together these attributes reflect the occur within them (Thoms, 2003). Flooding facilitates underlying ‘ecological character’ (incorporating the exchanges of water, sediments, nutrients and biota physical, chemical and biological attributes of an between river channels and floodplain patches and ecosystem and including the ideals of health and these transfers are considered to be essential for the integrity) of the site, which the Ramsar Convention functioning and integrity of these systems (Amoros obliges Australia to protect. Similarly, national and Bornette, 2002). legislation (Environment Protection and Biodiversity Conservation Act, 1999) is committed to protection of such sites from threats. In addition, the site The Narran Ecosystem offers important habitat for several species listed The Lower Balonne floodplain wetland complex under Australia’s bilateral agreements with the which straddles the Queensland–New South Wales Governments of China (CAMBA), Japan (JAMBA) and border between St George (Qld) and Walgett (NSW) Republic of Korea (ROKAMBA) for the conservation is a region that supports the largest number of of migratory birds.

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Threats to the Narran Ecosystem Whilst recognised as being environmentally and economically valuable, wetlands are also a threatened resource due to past and current land and water management practices. The character of many Australian inland river systems has been altered since European settlement (Thoms et al., 1999, 2000; Ogden, 2000) because of large-scale floodplain development and the loss of connectivity due to flow regulation and the construction of levees. The grazing industry has had a long association with floodplain wetland systems (Heathcote, 1988). However, since the 1980s these systems have become the focus for major water resource developments. These activities have the potential to severely degrade these ecosystems.

The ‘flow regime’ of the Narran Ecosystem is important and central to maintaining its ‘ecological character’ (Thoms et al., 2001) i.e. the combination of physical, chemical and biological components of the system. Floods in the Narran River in particular are important for the filling of the Narran Ecosystem and the success of waterbird breeding colonies is highly dependent on water levels. Water resource development on the nearby Macquarie River system has decreased the frequency and abundance of breeding of colonial waterbirds in the Macquarie Marshes (Kingsford and Johnson, 1998). Further, waterbird breeding in terms of reproductive success and clutch size appears to be directly related to flooding. The wetlands of the Narran Ecosystem need to reach at least 86% capacity in order to trigger breeding (Qld DNRM, 2000). Since the late 1980s, flows in the Condamine Balonne River upstream of the Narran Ecosystem have been modified by large-scale water resource development. Median annual flows at St George have been reduced by 30% and there have been major reductions in the magnitude and frequency of important flood events.

Furthermore, recent studies on the Lower Balonne floodplain demonstrate that rates of sediment delivery to this area have increased by an order of magnitude as a result of upstream land use changes since European settlement (Thoms et al., 2007). Combined, these developments have the potential to significantly influence the ecological character of the Narran Ecosystem.

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3. Overview of study area

The Narran Ecosystem is a terminal floodplain at St George, in the lower catchment, ranging complex of the Narran River; a major distributary between 23 960 Ml and 7 385 000 Ml (1975–2000) channel located in the lowland section of the with an annual median of 728 175 Ml. Flood events Condamine Balonne Catchment (Fig. 3.1). Like many generally occur between November and April; hence Australian inland rivers the Condamine-Balonne the annual flow pattern is summer-dominated. is an allogenic river originating in a well-watered Downstream of St George, the Condamine-Balonne area but flowing for most of its length across a dry River divides into five separate channels (Fig. landscape (Thoms and Sheldon, 2000). According to 3.1). The Culgoa and Narran Rivers are the main the Köppen Climate Classification scheme the lower channels, conveying 35% and 28% respectively, of sections of the catchment and the Narran region in the long-term mean annual flow at StGeorge. The particular, are classified as hot with minimal rainfall. Ballandool River, Bokhara River and Briarie Creek Maximum summer temperatures often exceed 50°C only flow during higher discharge periods. All five while winter minimums are around 20°C. The long- rivers have low channel gradients (0.0002 to 0.0003), term median annual rainfall (n = 73 years) decreases are tortuous in planform (sinuosities exceed 2.2, cf. from east (1105 mm at Toowoomba) to west (517 mm Schumm, 1977) and transport predominantly fine at St George) across the Condamine Balonne sediments. Bankfull cross-sectional areas of most of catchment. Most rainfall occurs in the summer the channels (the Briarie is the exception) decrease months (November–April) and is associated with with distance downstream, so there are regular tropical monsoonal activity. Overall, rainfall is highly overbank flows. variable both within and between years but there is The hydrology of the five main channels in the Lower a pronounced wet/dry periodicity, a common feature Balonne differs substantially. A large proportion of of dryland regions in Australia (Gentilli, 1986). Mean average flows occur in very wet years. Variability in annual evaporation ranges from 230 mm in the flow is also high: coefficients of variation (CVs) for headwaters to over 2000 mm in the lower catchment. annual flows range from 1.03 to 2.00, and median Thus large portions of the lower floodplain region annual flows are less than 30% of mean annual of the Condamine Balonne catchment have a large flow. Flows (both annual volumes and flood peaks) negative water balance. Flows in the Condmaine- generally decrease downstream towards the end Balonne are also highly variable, with annual flows

Figure 3.1: Location of Narran Lakes within the Murray-Darling Basin.

Narran River Long Arm

Back Lake

Condamine-Balonne Catchment

Clear Lake Narran Lakes Narran Lake

Floodplain

Murray-Darling Basin N

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of the system because of transmission losses Land use in the surrounding region is predominantly and a lack of tributary contributions, which are a sheep grazing and mineral exploration. Further characteristic feature of Australian inland river upstream, in the Lower Balonne, land use is systems (Thoms and Sheldon, 2000). There have increasingly dominated by intensive irrigation been changes in the hydrological regime of the which has been associated with substantial water Lower Balonne over the last 100 years, with the resource developments in recent years, influencing period prior to the 1900s and since the mid-1940s the catchment’s hydrology on a number of scales being wetter, on average. This has been associated (Thoms, 2003). Consequently, altered hydrology with greater runoff and flood activity than for the is currently perceived as a major threat to the period 1900 to 1945 (Riley, 1988). These changes ecological integrity of the Narran Lakes Ramsar site reflect the shift in the geographical pattern of (Thoms and Parsons, 2003). correlation between precipitation and the SOI for the years before the 1950s compared with the years since the 1950s (Simpson et al., 1993).

The local catchment area of the Narran Ecosystem is relatively small (~ 46 km2). Consequently, the lakes do not fill as a result of local precipitation. Rather, floods in the Narran River, which are generated in the upper catchment areas of the Condamine and Maranoa (Fig. 3.1), are responsible for lake-filling events. No flows occur approximately 60% of the time in the Narran River immediately upstream of the Narran Ecosystem. Mean annual flow in the Narran River is about 141 000 Ml with a standard deviation of greater than 150 000 Ml and a maximum recorded annual flow of 567 100 Ml. The high inter-annual variability of flows in the Narran River insures that the Narran Ecosystem has a complex flood history with periodic wet/dry cycles (Thoms, 2003).

The Narran Ecosystem is comprised of four distinct morphological features; a complex network of river channels, floodplain lakes, ephemeral wetlands and an extensive floodplain surface. There are four main lakes or water bodies; Clear Lake, Back Lake and Long Arm (the northern Lakes) and Narran Lake, and a large floodplain area (Fig. 3.1). These have been the focus of previous work in the region and for current management. Filling of the various waterbodies occurs sequentially with Clear Lake filling first, then Back Lake, Long Arm, and if the event is sufficiently large, Narran Lake. Over the last 33 years Clear Lake and Narran Lake have filled with water from the Narran River 23 and 16 times respectively, while the intervening floodplains have only been inundated on six occasions.

A significant portion (5531 ha) of the northern section of the Narran Ecosystem was designated as a Ramsar site in June 1999. This lake–wetland system is characterised by large areas of the flood- tolerant shrub Muehlenbeckia florulenta (tangled lignum) that provides an important breeding habitat for waterbirds, most notably Threskiornis spinicollis (Straw-necked ibis).

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4. Overview of project

The Narran Lakes Ecosystem Project inland river systems (Thoms and Sheldon, 2000). However, there are limited data on the role of flow Floodplain ecosystems, like the Narran Ecosystem, in maintaining habitat connections for many of are important ecotones that regulate interactions Australia’s inland river systems, like the Narran. across a broader riverine landscape. They respond to disturbance (both natural and human induced) over At the local scale the project was to determine a range of scales – from organism-level responses, • the habitat requirements of key biotic through population and community changes and components of the ecosystem (plants, fish, finally ecosystem-level changes. The nature of waterbirds), these changes depends on the organism or group of organisms or ecosystem component in question. • the distribution of habitats for the key biota under Additionally, there will be a lag time before an different flow states, and ecosystem response can be detected in floodplain • the importance of bottom-up control of water bodies and the extent of this lag time will ecosystem processes, especially productivity. again depend on the component in question. For Catchment scale. The Narran Ecosystem is an many of the more familiar organisms (large fish, ephemeral, terminal system in the lower reaches riparian trees), there would be a considerable lag of the Condamine Balonne River, in the northwest time, with the effects of changing water regimes section of the Barwon Darling system. The ecology of possibly taking decades to be detected. Studies of this ecosystem is influenced by the supply of water, similar systems (e.g. Kingsford, 2000) have tended sediments, nutrients and carbon from upstream to ignore their multi-scaled functioning and the and through the exchanges between the river and requirement for an interdisciplinary and integrated adjacent riverine landscape as well as colonisation approach to study these ecosystems. of organisms. These ecological components will The Narran Ecosystem Project was established to also depend upon the stage of wetting and drying investigate the responses of this key ecosystem to in the system. However, changes in flows in the variations in the flow regime. Based upon a series Narran River and across the floodplain will have of initial conceptual models of the key ecological consequences for the ecology of the lakes. Impacts functioning of the Narran Ecosystem, it takes that may arise as a result of catchment modifications an interdisciplinary approach to the study of this may include the reduction in the abundance of floodplain ecosystem (for further methodologies see zooplankton colonising the lakes after drying events appendix 2). because of decreases in floodplain interactions. Fish communities in the river and hence fish This integrated project recognises the importance of communities colonising the lakes after drying the Narran floodplain, lakes and the river network, events may also change as a result of increases which make up the Narran Lakes ecosystem. It in base flows. There are no data to investigate, also notes the importance of viewing the Narran or begin to model, the response of the Narran Lakes ecosystem as part of a mosaic of floodplain Ecosystem to changing water resource development ecosystems within the Murray-Darling Basin and or land use modifications. beyond. Therefore, three scales of investigation are used. This project aimed, through the development of a hydrological������������������������������������������������ model, to predict habitat availability Local scale. The ecological character of the under different flow scenarios for the Narran Narran Ecosystem itself and its role as providing Ecosystem. It also aims to determine the significance significant refugia for a range of organisms is largely of patterns of wetting and drying of the lakes and determined by the flow regime in the Narran River. how these patterns are modified by changing flow This river is being subjected to changing hydrological regimes in the Narran River. Therefore data from regimes because of upstream developments. this project has enabled the development of a model However, the ecological effects of changed flow that can be used to predict the influence of water regimes can only be investigated, at least in the resource development and changing catchment short term, by understanding the links between conditions on the ecology of the Narran Ecosystem. hydrology and habitat availability for key biota. These flow-habitat connections are being recognised Landscape scale. Wetland systems, of varying as an increasingly important component in the degrees of water permanency, are a feature of sustainability of the ecological character of our inland Australia (Williams, 1998). Hence, the Narran

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Ecosystem must be put into this larger landscape The approach taken context. It has been suggested (e.g. Kingsford et al., 1999; Thoms et al., 2001) that the Narran Ecosystem The focus of Narran Ecosystem Project was has a unique collection of habitats that are important interdisciplinary in nature, in that it required the for migratory birds in that they provide a key collaboration of different scientific disciplines. refugium when other wetlands are not providing For this study, the disciplines of ecology, appropriate habitat. However, this has not been geomorphology and hydrology were brought quantitatively assessed. Data collected from the together to address the research aims of the project. Eastern Australian Water Bird Survey has enabled Previous works in the lower Balonne floodplain the construction of a landscape model of the use and that on the Narran Lakes all acknowledge the of wetlands in the region and therefore assess the complexity of the physical environmental and its importance of the Narran Ecosystem for both local ecology. The ecosystem structure and behaviour and migratory birds. of the Narran Ecosystem reflect many internal and external influences – geomorphological, Research aims hydrological and ecological – that interact closely. While the importance of this interaction has been This project is built on a conceptual framework that recognised, issues of how to study complex and was formulated from a detailed review of the relevant variable ecosystems, like Narran, are not prescribed scientific literature on the structure and functioning in any text book or manual. In addition, there are few of floodplain ecosystems in dryland regions. large interdisciplinary studies of such ecosystems. This review was supplemented with a review of Successful interdisciplinary studies require that the information, mostly management orientated, on the separate disciplines gain a common understanding Narran Ecosystem. The initial conceptual framework of the nature of the problem at hand, and identify was that flood pulses and dry phases are particularly the scales of relevant subsystem components, important for the ecology of the Narran River system the underlying processes or phenomena, and the and its associated floodplains, wetlands and lakes. important variables involved. Therefore, the fundamental aims of this project focus on the linkage of ecosystem (both physical and Conceptual frameworks are useful tools for ordering biological) responses of selected components of the phenomena and material, thereby revealing patterns Narran Ecosystem to variations in flow. and processes. Recent interdisciplinary ecosystems studies (Dollar et al., 2007; Hughes et al., 2007; Specifically, the project aimed to: Parsons and Thoms, 2007) all recommend the • Determine the physical and biological responses establishment of a conceptual framework upon of the���������������������������������������������� Narran Ecosystem to variations in the flow which to base research activities. A conceptual regime. framework can help different disciplines work together in an integrated way by ordering • Predict the responses of selected components phenomena and materials, thereby revealing of the Narran Ecosystem to alterations in patterns (Rapport, 1985). flow regime under different water resource development and long-term climate change The basis for the Narran science framework scenarios. These predictive models would recognises the key aspects of the driver, template, emphasise the links between flow regime and altered state and the ecosystem response (Fig. 4.1). biota through habitat availability and changes Drivers create, maintain or transform structural in ecological processes such as primary and functional features of an ecosystem. Drivers productivity. include biotic activities and abiotic disturbances such • Evaluate the ecological significance of the Narran as floods. The template is the entity the driver(s) Ecosystem in the regional context of wetlands act(s) upon. Templates are bounded spatially by within the northern Murray Darling Basin. the research question and they can be both abiotic and biotic. The physical surface of a floodplain or • Develop a conceptual model that links physical lake bed is an abiotic template while vegetation is and biological responses of the Narran an example of a biotic template. The interaction Ecosystem to past and future changes in water between a driver and the template produces an resource development, land-usage and climate. altered state or template. The inundation of a floodplain surface (template) by floodwaters (a driver) produces a wetted floodplain landscape which represents an altered template or state.

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The ecosystem responds to the formation of this organised systems like floodplain ecosystems. altered state. The relative importance of downward constraint and upward integration is different at each level Frameworks, like the Narran Ecosystem Project of organisation. The higher levels are controlled framework, have been used to demonstrate, among predominantly by downward influence, while features other things, modes of change in heterogeneity at lower levels are more manifestations of upward (Pickett et al., 2003), but such models are not influence. At all levels, the altered state depends on generally spatially explicit. For our framework we the context provided from above and the integration use a multi-level framework to allow integration of processes from below – the same basic drivers between processes operating at different scales could produce different forms within different (Fig. 4.1). This structure accommodates feedback constraining contexts. Interpreting the relationship responses, allowing biotic consequences to between downward constraint and upward contribute to the altered state. It also allows for integration of explanation is critical in interpreting consideration of downward constraint by higher complex ecosystems like floodplain wetlands. levels and upward integration of processes from lower levels – an important factor in hierarchically

Figure 4.1: The conceptual framework for the study of the Narran Ecosystem.

Ecosystem Driver Scale one response

Abiotic

Template Altered template Biotic

Ecosystem Driver response Scale two Abiotic

Template Altered template Biotic

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5. Key activities

5.1 Overview 5.2 Physical template The Narran Ecosystem Project comprised four major 5.2.1 Regional context arenas of research activity: PT1 1. Physical template Activity description: 2. Hydrological drivers • Mapping of key wetlands along the Narran River 3. Ecological responses using satellite imagery and radiometric data.

4. Knowledge exchange. Aims:

This chapter outlines the key activities conducted in • To determine the local extent of the Narran each of these components including research aims, Ecosystem using radiometric characteristics. and methods produced as a result. A summary of the • To compare the Narran Ecosystem with known key activities is provided in Table 5.1 and Fig. 5.1. wetlands in the region in terms of wetland area, volume and radiometric characteristics.

Table 5.1: Summary of key activities

Activity Activity description Activity Activity description code code 1. Physical template 3. Ecological responses (continued) PT1 Mapping of key wetlands along the Narran River ER3 Zooplankton egg bank mesocosm using satellite imagery and radiometric data experiment PT2 Collection and analysis of LiDAR data ER4 Aquatic macroinvertebrate field sampling PT3 Soil mapping of the Narran lakes Ecosystem ER5 Fish sampling PT4 Digitisation and change analysis of the Narran ER6 Vegetation survey Lakes Ecosystem channel network PT5 Sediment coring of the Narran Lakes Ecosystem ER7 Lignum survey 2. Hydrological drivers ER8 Lignum establishment experiment HD1 Collection and analysis of climate data For the ER9 Tree patch survey Narran Lakes Ecosystem and region HD2 Collection and analysis of surface water flow data ER10 Soil seed bank mesocosm 1 experiment for the Narran River HD3 Mapping of wetted extents for historical floods ER11 Soil seed bank mesocosm 2 experiment in the Narran Lakes Ecosystem from Landsat imagery HD4 Patch analysis of wet and dry patches In the ER12 Waterbird breeding in the Narran Lakes Narran Lakes Ecosystem Ecosystem. HD5 Hydraulic and hydrologic modelling of the ER13 Landscape scale influences on Narran Lajes Ecosystem waterbirds in the Narran Lakes 3. Ecological responses 4. Knowledge exchange ER1 Water quality sampling KE1 Publications ER2 Zooplankton field sampling KE2 Presentations KE3 Field days

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Figure 5.1: Location of research activities within the Narran Ecosystem.

Mesocosm 1 Infiltration Soil cores Surface soils Aquatic sampling Productivity Shrub facilitation Tagged lignum Tree survey Vegetation survey

Elevation (m) High: 124

Low: 118

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Methods: • To map soil characteristics across the Narran • Large format Landsat images for 1990 and 2000 Ecosystem. were acquired and used to delimit all of the 12 Methods: known wetlands along the Narran River. • 163 surface soil samples were collected • Surface areas and estimated volumes were throughout Narran Ecosystem including: computed for each of these 12 wetlands. – 130 samples from a regular 1800 m square • An independent verification of wetland extent was grid. determined using three radioactive elements: thorium, uranium and potassium. – an additional 33 soil samples from vegetation survey sites. • Potassium concentrations highlight lake and floodplain regions and high potassium – Each soil sample comprised five sub-samples concentrations show areas that are filled by collected from the corners and centre of a Narran River flows. 10 m quadrat. – 22 soil properties were measured (see below). 5.2.2 Topography grain size distribution pH soil colour liquid limit PT2 organic matter content plastic limit Activity description: aluminium manganese • Collection and analysis of LiDAR data. barium nitrogen calcium phosphorous Aims: cobalt sodium • To obtain an accurate digital elevation model of copper potassium the Narran Ecosystem. iron strontium • To describe the topography of the Narran lead titanium Ecosystem. magnesium zinc • To determine heights of dominant structural – Interpolation of soil properties was conducted vegetation across the Narran Ecosystem. using geostatistical approaches in order to Methods: map the soil characteristics for the entire Narran Ecosystem. • LiDAR was flown in October 2004. • LiDAR data was calibrated using more than 5.2.4 Channel network 20 000 ground control points with positional and vertical accuracies of less than 1 cm. PT4 • Areas of the Narran Ecosystem that were wet Activity description: during the LiDAR survey (i.e. several deep • Digitisation and change analysis of the Narran waterholes) were surveyed using differential GPS Ecosystem channel network. with positional and vertical accuracies of less than 1 cm. Aims: • Hypsometric curves were produced from the • To describe the distribution and character of the LiDAR data to determine the surface area and Narran Ecosystem channel network. volume of each of the principal lakes within the • To determine the stability of the channel network Narran Ecosystem. Surface areas and volumes through time. were computed at 10 cm elevation intervals. Methods: 5.2.3 Soils • The channel network for the Narran Ecosystem PT3 was digitised from three sets of 1 : 50 000 scale aerial photographs: 2003, 1992 and 1969. Activity description: • The area covered by river channels during each • Soil mapping of the Narran Ecosystem. time was determined: 1969, 1992 and 2003. Aims: • Changes in the channel network through time • To determine the physical and chemical were assessed by comparing the extent of the properties of soils within the Narran Ecosystem. channel network at each time.

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• The character of the river channel network at conditions are exceeded. The character of these each time was determined by classifying the links alluvial stores is dependent upon the nature of the and nodes comprising the network. This was depositing environment, the type of sediments and accomplished through the development of a new processes that govern their delivery to a site. technique specifically designed to characterise • 31 sediment cores up to a depth of 25 m were anastomosing river channel networks (Fig. 5.2). extracted using a piston-driven coring rig from the Narran Ecosystem. 5.2.5 Environmental history • The stratigraphy of each core was described PT5 using modified lithofacies classifications of Lewin (1996) and Miall (1985). Sediments were Activity description: classified as mud, muddy sand >( 50% mud), • Sediment coring of the Narran Ecosystem. sandy mud (< 50% mud) and sand. Specific inclusions such as lenses, gravel and carbonate Aims: nodules, organic matter, mottling, banding and • To investigate the long-term environmental basal contact, were also recorded. In addition, history of the Narran Ecosystem. sediment colour was determined on dry samples • To determine how long the Narran Ecosystem using the Munsell Soil Colour Chart. has existed in the landscape. • Sediment sub-samples were taken from each stratigraphic unit for textural and geochemical Methods: analysis. A total of 28 textural and geochemical This section of the project is based upon the premise variables were measured from each sub-sample. that sediments in a depositional sequence are • These data were subjected to a range of standard indicative of the environment in which they were laid sedimentological and multivariate statistical down. Floodplain–wetland complexes, like Narran, analyses. For the multivariate analyses, the that are located at the termini of river systems are Gower distance measure was used in the three-dimensional sinks into which eroded and calculation of the association matrix. A one-way sorted sediments accumulate. Unlike other river analysis of similarity (ANOSIM) was conducted floodplains, they are not temporary storage areas of on this association matrix to test similarity alluvium because they do not experience significant between a priori determined groups (geomorphic episodic working and/or removal of sediment units and stratigraphic sequences), then the during extreme events, or when certain threshold data were ordinated using Semi-Strong-Hybrid- Multidimensional-Scaling and expressed graphically. A Principal Axis Correlation (PCC) Figure 5.2: A method for the classification of was also conducted to identify relationships channels in distributary networks. Each two letter between sediment variables and their position in code represents a link identifier with thefrom node multivariate space. A Monte Carlo permutation first and theto node second. For example, FJ = From test (Belbin, 1993) was also performed to test the fork to Join. significance of the correlation values. Variables with R2 greater than 0.8 were considered to have a strong association with sediment character and those with R2 between 0.5 and 0.79 were considered to have a moderate association with sediment character. • A selection of the sediments from the cores extracted from the Northern lakes were used for dating via Optical Stimulated Luminescence. Optical dating can be used to estimate the time elapsed since buried sediment grains were last exposed to sunlight (Aitken, 1998). This method of sediment dating makes use of the fact that daylight releases charge from light-sensitive electron traps in crystal lattice defects in minerals such as quartz and feldspar. The release of trapped charge by light resets the optically stimulated luminescence (OSL)

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signal; this process is commonly referred to as Aims: bleaching. When grains of quartz are buried and • To quantify the temporal and spatial aspects of hidden from light, they begin to accumulate a historically recorded surface water flows in the trapped-charge population due to the effects Narran River. of ionising radiation, such as that arising from radionuclides naturally present in the deposit. Methods: This trapped-charge population increases with • Flow data for the period from 1964–2004 were burial time in a measurable and predictable way. obtained for the three principal gauges along the As a result, the time elapsed since sediment Narran River: grains were buried can be determined by – Dirranbandi (1964–2004), measuring the OSL signal (burial dose) from a sample of sediment and estimating the ionising – New Angledool (1929–2004), radiation to which it has been exposed since – Wilby Wilby (1964–2004) . burial (the dose rate) such that: • Daily flows for the New Angledool gauge were Burial time = Burial dose/Dose rate. plotted and investigated with respect to the magnitude and frequency of floods over the 5.3 Hydrological drivers period of record. This gauge has a significantly longer record than the other gauges along the 5.3.1 Climate Narran River and so extends our understanding of longer-term variations in flow. HD1 • Flows at Wilby Wilby (the closest long-term Activity description: gauge to the Narran system) were examined • Collection and analysis of climate data for the with respect to the magnitude and frequency Narran Ecosystem and region. of flooding and changes in the flow regime through time. Aims: • To determine the current climatic condition that HD3 prevails over the Narran Ecosystem and region. Activity description: • To determine if climate change has occurred over • Mapping of wetted extents for historical floods in the last 50–100 years over the Narran region. the Narran Ecosystem from Landsat imagery.

Methods: Aims: • Data were obtained from regional climate • To determine the frequency of wetting across the stations surrounding the Narran Ecosystem Narran Ecosystem. including: • To determine drying times for the two principal – Walgett lakes within the Narran Ecosystem. – Lightning Ridge • To ascertain the amount of time various parts – Brewarrina. of the Narran Ecosystem have been wet since the 1970s. • Mean annual precipitation for the region was compared to the southern oscillation index to Methods: explore large-scale influences on local rainfall. • 32 Landsat images from the period 1974 to 2004 • Trends in precipitation and the occurrence of were selected in order that the largest wetted persistent wet/dry periods in the region were extent in a given year was represented. examined by looking at long-term patterns in the • Wetted extents were delineated from each deviation of the rainfall from the mean rainfall for Landsat image. the period of record (1898–2004). • Wetted extents were then overlaid to create a map 5.3.2 Hydrology illustrating the number of times various parts of the Narran Ecosystem were inundated by the HD2 largest flood in a given year during this period. Activity description: • Mapped wetted extents from 1981 to 2004 (a period over which every flood event was • Collection and analysis of surface water flow data measured) were also combined to create a map for the Narran River. illustrating the number of times various parts of

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the Narran Ecosystem were uniquely inundated. topographic map. A minimum of 20 ground This measure incorporates both the frequency control points (GCPs) were collected for each of wetting and the rapidity of drying in that a new scene and all RMS errors were kept below one value is recorded only after a site has dried and pixel (30 m). A Band 5 (1.55–1.75 μm) density then been re-wetted. slice was performed on all images as this near • Drying times for the two principal lakes within infrared (NIR) band shows very high absorption the Narran Ecosystem were determined by taking of radiant flux for water and significant reflection the maximum lake depth and removing water for vegetation and bare soils. This analysis from the����������������������������������� lakes according to the mean annual delineates a sharp boundary between land and evaporation for inundations occurring during water. In some cases, where the above method different seasons. produced unsatisfactory results, an unsupervised ISODATA classification (maximum number of • The percentage time that various parts of classes: 235; iterations: 24) was performed and the Narran Ecosystem have been inundated classes were grouped into water and dry classes. during the recorded period were determined by combining the satellite-derived inundation • The resultant rasters were converted to vector frequencies with calculated drying times. format for ‘cleaning’ and editing (i.e. connection of channels where expert knowledge suggested HD4 connection would exist, removal of water tanks, clouds, errors and inundated areas unrelated Activity description: to the Narran River inflow). Vectors were then • Patch analysis of wet and dry patches in the converted to signed 32-bit integer grids for use in Narran Ecosystem. the spatial pattern analysis program FRAGSTATS Version 3.3 McGarigal and Marks 1995. Aims: • A series of spatial metrics were obtained and • To determine the inundation character of the analysed with FRAGSTATS using the 8-cell Narran Ecosystem. rule such that diagonally touching pixels were • To examine patch heterogeneity (and potentially considered as one patch. Metrics analysed biodiversity) during the expansion and include number of patches, area, shape index contraction of floodwaters across the Narran and a proximity index. A full explanation of each Ecosystem. metric is given in McGarigal and Marks, 1995.

Methods: • Four measures of diversity were calculated to provide a reflection of the overall distribution of • A series of near cloud-free Landsat Thematic the different inundated patch character (area, Mapper (TM5) scenes were obtained. These shape and proximity). The measures calculated covered each major flood event in the ecosystem were Margalef Richness Index (DMg), Shannon since the mid 1970s and then a series covering Eveness Index (DSe¬), Shannon Weiner Diversity two flooding and drawdown sequences that took Index (DSw), and the Simpson Diversity Index place from December 1995 to February 1997 and (DSi) (Zar, 1984). Combined, these indices provide from February to December 2004. a measure of abundance and components • For the later series total discharges the two of diversity of individual inundated patches flood events were 496 000 Ml and 26 000 Ml for calculated from each image. the 1995–1997 and 2004 floods respectively • The character of floodplain inundation during immediately upstream of the study area. These the two flood events was examined via a range floods have a 20 and 50 per cent probability of of multivariate statistical analyses. Initially, occurrence, respectively, in any one year based a similarity matrix of Gower’s similarity on a Log Pearson annual series. Antecedent coefficients was calculated using the area of conditions for each flood were relatively dry and inundation, number of patches and the four consisted of a few pools of stagnant water in the diversity measures for each flood image and channel entering the wetlands equating to areas this similarity matrix was used to test between of ~31 ha and ~25 ha respectively. flood differences using the analysis of similarity • All images were geometrically corrected to (ANOSIM) routine in the PRIMER computer Geodetic Datum of Australia 1994 (GDA94), package (Clarke and Warwick, 1994). Semi- Universal Transverse Mercator (UTM) zone Strong–Hybrid Multidimensional Scaling (MDS; 55S by cubic polynomial rectification. Image- Belbin, 1993) was used to represent the similarity to-image rectification was used with the base matrix graphically. A stress level of less than 0.2 satellite image being rectified to a 250 K digital indicated that the ordination solution was not

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random (Clarke and Warwick, 1994). In order • A predictive (daily) hydrologic model was to reduce the possible influence of flood size developed that incorporates spatial patterns this statistical routine was undertaken with of wetting and drying in the Narran Lakes and without the total surface area inundated ecosystem and which can be used to assess and patch number as variables. Relationships the impact of different climate and land-use between the different inundated-patch variables scenarios on the timing, magnitude and duration and the position of each image in multi- of inundation in the Narran Ecosystem dimensional space were determined using • The hydrologic model for the Narran Ecosystem Principal Axis Correlation (PCC; Belbin, 1993) includes information on the inflow discharge (and and only those variables with an R2 greater than the flows down specific pathways as determined 0.8 were considered. from the hydraulic model), precipitation, soil losses and storage and evaporation. HD5 • The hydrologic model was calibrated and Activity description: validated using more than 65 satellite images • Hydraulic and hydrologic modelling of the including the ‘before and after’ of every flood Narran Ecosystem. event in the Narran Ecosystem since 1981 as well as several long drying sequences. Aims: • The strength of the model was ultimately • To understand the movement of water through assessed by comparing the actual to the the Narran Ecosystem. predicted inundated surface areas of the • To model patterns of inundation and drawdown in Northern and Narran Lakes for all of these the Narran Lakes ecosystem. 65+ images. • To predict the effects of development and/or • Once a high level of agreement between actual climate change on the timing, magnitude and predicted inundated surface areas was and duration of inundation within the Narran attained the model was used to reproduce the Ecosystem. pattern of inundation and drawdown that would have occurred within the Narran Ecosystem Methods: given the known flow inputs from the Wilby • A hydraulic model (built in Mike21) was created Wilby gauge. to facilitate the understanding of how water • moves through the Narran Lakes ecosystem These data were then used to create inundation and to provide a set of control points for use in curves for the Northern and Narran Lakes. building a predictive hydrologic (water balance) • Finally, the hydrologic model was used to model for the Narran Ecosystem. assess the impact on the timing, frequency and • The LiDAR topographic data were used as the duration of inundation of a series of climate and bathymetric input into the hydraulic model. development scenarios. These scenarios were derived from IQQM data at the Wilby Wilby gauge. • Three model runs were conducted, the first for calibration, the second for validation and the third for data collection. 5.4 Ecological responses • Calibration and validation were accomplished by 5.4.1 Aquatic ecology comparing the temporal pattern of inundation during the calibration and validation runs to the ER1 actual pattern of inundation as determined from Activity description: satellite imagery of the floods. • Water quality sampling. • The hydraulic model outputs included: a general map of the dominant, secondary and tertiary flow Aims: pathways within the Narran Ecosystem; and a • To describe spatial and temporal patterns set of data along these important flow pathways in water quality parameters of the Narran that would allow us to determine what fraction Ecosystem during a wetting and drying event. of the input discharge would travel down any given pathway at any given time (this represents Methods: the volume of water that is delivered to various • Sampling was conducted at five sites including parts of the landscape under different inflow Narran River, Clear Lake Centre, Clear Lake scenarios). shore, Back Lake and Long Arm.

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• Sampling occurred on six occasions: 15/2/2004, • Microcrustacean and rotifer fractions were 4/3/2004, 16/4/2004, 4/6/2004, 15/7/2004 and identified (generally to species or genus level) 27/10/2004 as the system gradually dried. and counted using standard methods. (N.B. Some sites were not available for the • Analysis was conducted using univariate analysis full sampling period as they dried out faster of assemblage metrics (richness and abundance than others.) of broad taxonomic groups) and ordination of • At each site, physico-chemical measurements assemblage data. The procedure MVDISP was were made using a field Horiba U-10 multiprobe. used to compare the dispersal between sample All measurements were made approximately times and sites and the BIOENV procedure was 10 cm below the water surface either from a used to evaluate the relationship between the boat where possible or by wading into the water. species distance matrix and physico-chemical • A 1 L unfiltered water sample was collected from parameters. each location on each sampling date and frozen ER3 for later analysis of major nutrients. • A second water sample was filtered the same Activity description: day (usually 500 ml sample) and the filter papers • Zooplankton egg bank mesocosm experiment frozen for later analysis of chlorophyll. Aims: • Water quality parameters measured are • To examine spatial and temporal patterns in detailed below: zooplankton emergence from egg banks of the Water quality parameters: Narran Ecosystem. conductivity pH Methods: turbidity oxygen • Sediment sampling was conducted at seven temperature total phosphorus sites: Narran River, Narran River Bank, Clear total nitrogen sodium Lake Centre, Clear Lake shore, Back Lake, magnesium potassium Lignum floodplain and Chenopod Floodplain. chlorophyll • Three random sediment samples were taken from each site and placed in a plastic tray ER2 (dimensions of 16.3 × 11 cm) to a depth of 2.5 cm. Activity description: • Samples were flooded individually in 4 l plastic containers to a depth of 10 cm and placed outside • Zooplankton field sampling. under clear plastic sheeting to prevent air-borne Aims: contamination. • To examine spatial and temporal patterns in • Water samples were then taken from containers zooplankton taxon richness, abundance and every three days starting within 12 hours of initial composition during a wetting and drying event inundation. After 30 days the sampling interval in the Narran Ecosystem. was increased to seven and 14 days until day 89. On each sampling occasion all the water in each Methods: container was carefully siphoned through a 35- • Sampling was conducted at five sites including µm mesh and replaced in the container. Samples Narran River, Clear Lake Centre, Clear Lake were preserved immediately in 90% ethanol. shore, Back Lake and Long Arm. • The microcrustacean fraction was identified • Sampling occurred on six occasions: 15/2/2004, (generally to species or genus level) and counted 4/3/2004, 16/4/2004, 4/6/2004, 15/7/2004 and using standard methods. 27/10/2004 as the system gradually dried. (N.B. Some sites are not available for the full sampling ER4 period as they dried out faster than others.) Activity description: • A 10 l water sample was collected using a one • Aquatic macroinvertebrate field sampling metre integrated sampler along a 50 m transect and poured through a 53-µm mesh net. Samples Aims: were preserved immediately in 90% ethanol. • To describe the composition and structure of Three replicate samples at each site were taken aquatic macroinvertebrate assemblages in the on each sampling occasion to produce a total of Narran Ecosystem. 72 samples.

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• To examine spatial and temporal patterns in entrance of off-take channel, Clear Lake at the aquatic macroinvertebrate species composition midden, Back Lake and Long Arm). and abundance during a wetting and drying event • Sampling occurred up to four times February in the Narran Ecosystem. 2004, April 2004, July 2004, and November 2004 Methods: depending on the presence of water at sites. • Sampling was conducted at seven sites including • Fish were sampled using large fyke nets and three river sites: Narran River at the weir, Narran large and small seine nets. Three fyke nets were River at the off-take channel to Clear Lake and set at each site. Three replicate hauls of the Narran River at the delta of Narran Lake, and small and large seine net were also made four lake sites: Clear Lake at entrance of off-take at each site. channel, Clear Lake near the midden, Back Lake and Long Arm. 5.4.2 Vegetation • Sampling occurred on three occasions: February ER6 2004, April 2004 and July 2004. • Three habitats were sampled within river sites Activity description: including (i) edge with no cover, (ii) edge with • Vegetation survey. cover (coarse woody debris, large woody debris, Aims: root mass) and (iii) edge with lignum. • To describe spatial and temporal patterns in • Three habitats were sampled within lake sites vegetation composition and structure in the including (i) shore with no cover, (ii) shore with Narran Ecosystem. lignum and (iii) open water (depth > 30 cm). • To determine environmental factors influencing • Three replicate samples from each habitat were spatial and temporal patterns in vegetation taken at each site on each sampling occasion. composition and structure in the Narran Back Lake and Long Arm sites could not be Ecosystem. sampled in July 2004 as they dried out earlier. A total of 171 samples were collected. Methods: • Macroinvertebrates were collected by sweeping a • A total of 33 sites were surveyed comprising: standard triangular 250 µm mesh dip net along a – 15 sites in each of two regions (northern basin, 1 m transect for 30 seconds. southern basin) • Samples were sieved, transferred to storage jars, – in each region, three replicate sites in each preserved in 70% ethanol and transported to of five flood frequency classes (frequent, the laboratory where macroinvertebrates were moderate, infrequent, rare and terrestrial) sorted, enumerated and identified to family level. – additional three sites located in bird colony, ER5 Back Lake. Activity description: • Sites selected based on flood frequency classes determined using prior inundation mapping as • Fish sampling. this represented the best available information Aims: prior to the more detailed analyses conducted as part of the current project. • To describe the species composition, abundance and size structure of fish assemblages in the • Sites were surveyed in November 2004 following Narran Ecosystem. the recession of floodwaters and again in May 2005 following 6 months of drying. • To examine spatial and temporal patterns in assemblage composition and structure during • During surveys, the following variables were a wetting and drying event in the Narran recorded within each site (50 m × 50 m quadrat): Ecosystem. – tree counts Methods: – % cover of lignum • Sampling was conducted at six sites selected to – % cover of groundcover species (within cover the main aquatic patches at the ecosystem 10 random 1 m2 quadrats) scale. These included two river sites (Narran – soil samples collected for analysis. River at the weir and Narran River at the off- take channel) and four lake sites (Clear Lake at

20 0 100 200 300 400 500 600 700 5. Key Activities

ER7 • 25 buckets (five per watering treatment) were randomised in a glasshouse. Eight pots (four clay Activity description: and four sand/clay mix) each containing a single • Lignum survey. lignum seedling were placed in each bucket. Aims: • On each of four harvest times (1, 2, 4 and 6 • To describe spatial patterns in the character months), one seedling growing in each sediment and condition of lignum shrubland within the type in each bucket was destructively harvested Narran Ecosystem. (total = 50 harvested per time interval) and the following variables recorded: • To determine environmental factors influencing – total biomass and biomass of roots, shoots the character and condition of lignum shrubland. and leaves separately Methods: – length of shoot and root • A total of 75 5 m × 5 m quadrats were surveyed – leaf area with five quadrats in each of 15 sites haphazardly – leaf and shoot number. distributed throughout study area in places where lignum cover was greater than 10% . • Analysis conducted as a split plot design using a partially nested ANOVA model with treatment, • The survey was conducted in May 2006. Within sediment type and time as fixed variables and each 5 m × 5 m quadrat, the following variables bucket as random. Where sediment effects were were measured: weak, sediment types were pooled. – % cover of lignum – number of lignum clumps (density) ER9 – morphology (clump height, clump perimeter) Activity description: – reproductive status (flowering, sex) • Tree patch survey. – condition (presence of leaves, % greenness, Aims: evidence of grazing) • To describe spatial patterns in the distribution, – soil moisture and soil samples collected for character and condition of mature tree analysis. communities in the Narran Ecosystem.

ER8 • To determine environmental factors influencing the character and condition of mature tree Activity description: communities in the Narran Ecosystem. • Lignum establishment experiment. Methods: Aims: • A total of 15 mature-tree patches were identified • To investigate growth responses of lignum within the study area based on vegetation height, seedlings to flooding, waterlogging and water density and area criteria (determined using stress. LiDAR and Landsat imagery). Tree patches were identified by selecting those which had a > 50% • To determine effects of sediment type (i.e. clay tree coverage and which were greater than and sand) on growth of lignum seedlings. 50 000 m2. Methods: • Within each patch, four randomly located • A glasshouse experiment was conducted in the replicate 25 m × 25 m sites were surveyed first 6 months of 2005 in which lignum seedlings between November 2005 and May 2006. were grown under one of five water treatments: • The following variables were measured with – Deeply submerged (DF) respect to every tree within each 25 m x 25 m quadrat: – Shallowly submerged (SF) – species – Waterlogged soil (WL) – position – Damp soil (DP) – morphology (height, dbh) – Dry soil (DRY) – developmental stage • Two sediment types (100% clay and a 50 : 50 mix of clay and river sand) were crossed with water – reproductive status (i.e. presence of fruit) treatment in a factorial design. Clay sediment – condition (index from 0–5 where 0 represents was collected from the Narran Ecosystem. dead trees and 5 represents healthy trees)

21 0 100 200 300 400 500 600 700 Murray-Darling Basin Commission Narran Ecosystem Project

• Environmental variables recorded for each site: ER11 – elevation (from LiDAR) Activity description: – soil characteristics (soil sample collected) • Soil seed bank Mesocosm 2 experiment. – soil moisture Aims: – canopy cover • To determine the effects of flood pulse – litter cover. characteristics (e.g. duration, timing, frequency and rate of drawdown) on the productivity and ER10 diversity of plant communities establishing from the soil seed bank. Activity description: • Soil seed bank Mesocosm 1 experiment. • To determine effects of long-term flood history on plant community responses from the soil seed Aims: bank to annual flood pulse scenarios. • To determine the composition and structure of Methods: soil seed banks in the Narran Ecosystem. • A large mesocosm experiment was run from • To describe spatial patterns in the distribution January to December 2005 using soil samples of the soil seed bank in relation to broad collected from vegetation survey sites during hydrogeomorphic habitats. November 2004 (excluding bird colony and Methods: terrestrial sites). • Soil sampling was conducted within seven • Soil samples from each site were distributed predefined hydrogeomorphic habitats: Clear amongst 13 pots and subjected to annual flood Lake centre (CLC), Clear Lake shore (CLS), Back pulse scenarios as follows: Lake (BL), Lignum floodplain (LFP), Chenopod – 6SF: 6 month summer flood with fast floodplain (CFP), the Narran River channel (NRI) drawdown and the Narran River bank (NRB). – 6SS: 6 months summer flood with slow • Three sites were selected randomly within drawdown each habitat and within each site three – 3SF: 3 month summer flood with fast replicate soil samples were taken producing drawdown a total of 63 samples. – 3SS: 3 month summer flood with slow • A seedling emergence experiment was drawdown conducted at Goondiwindi in which sediment samples were subjected to two treatments: – 6W: 6 month winter flood (drawdown not waterlogging and submergence. The relevant as still submerged at 12 month experiment was run for 5 months from harvest time) March to September 2004 to encompass – 3WF: 3 month winter flood with fast drawdown a broad range of temperatures. – 3 WS: 3 month winter flood with slow • Species were counted and identified as they drawdown germinated and removed prior to further – 12: 12 month flood contributions to the soil seed bank. Species identifications were verified with the NSW – 3S3W: 3 month summer flood with fast Herbarium drawdown and 3 month winter flood with fast drawdown (N.B.������������������������������ Of the 13 pots from each • At the final harvest, species that were not vegetation survey site, nine pots with all of sufficiently developed for identification were the above treatments were harvested after transplanted and grown in pots until positive 12 months. An additional four pots were identifications could be made. harvested after 6 months with treatments • Controls containing vermiculite only were also comprising (1) 6 months submerged, monitored to check for wind dispersed seed (2) 3 month summer flood with fast drawdown, contamination. None was observed. (3) 3 month winter flood with slow drawdown • Analysis conducted as a partially nested ANOVA and (4) rainfall only.) design with habitat and treatment treated as • Weekly rainfall was delivered by hose across all fixed variables and site within habitat as random. pots as per Walgett rainfall station data obtained from the Bureau of Meteorology.

22 0 100 200 300 400 500 600 700 5. Key Activities

• At 6 and 12 months, all plants in relevant pots analyses to separate the effects of inter-annual were harvested, counted, identified and their climatic variation from those of the extraction reproductive status noted. and regulation of water for human purposes. • Total biomass, above-ground biomass and below-ground biomass (i.e. dry weights) were 5.5 Knowledge exchange then obtained for each species for each pot. KE1 5.4.3 Waterbirds Activity description: ER12 • Publication of findings from the Narran Ecosystem Project. Activity description: • Waterbird breeding in the Narran Ecosystem. Aims: • To publish the findings of the Narran Ecosystem Aims: Project in a range of community, management • To determine the history of waterbird breeding and scientific fora. in the Narran Ecosystem. Methods: • To associate waterbird breeding with the • Publication of manuscripts in refereed scientific hydrology of the Narran Ecosystem. journals Methods: • Publication of an oral history of the Narran region • Records of colonial waterbird breeding events • Publication of fact sheets detailing main findings at Narran were collated from journal articles, of the Narran Ecosystem Project. government reports, and anecdotal evidence. • These data were compared to hydrological KE2 conditions at the time of breeding events. Activity description: ER13 • Presentation of the approach and main findings of the Narran Ecosystem Project. Activity description: • Landscape scale influences on waterbirds in the Aims: Narran Ecosystem. • To present the approach taken and main findings of the Narran Ecosystem Project in a variety of Aims: community, management and scientific fora. • To understand the important landscape-scale influences and constraints upon the ability of Methods: waterbirds to successfully utilise the larger • Presentation of the Narran Ecosystem Project at landscape region of the Narran Ecosystem to a range of community meetings complete a cycle of breeding, dispersal, and • Presentation of the Narran Ecosystem Project to return to the larger landscape. the various management jurisdictions Methods: • Presentation of the Narran Ecosystem Project at • Semi-continental scale analyses were conducted national and international scientific conferences. on climatic and hydrological influences on patterns of migration and abundance within the KE3 area covered by the Eastern Australian Aerial Activity description: Waterbird Survey. • Community field days at the Narran Ecosystem. • Techniques were developed to establish and confirm connections from global-scale climatic Aims: patterns, to semi-continental scale climatic • To promote interaction between the Narran manifestations, to more localised hydrological science team and the local and regional response, and avian abundance. By doing community. so, to develop a comprehensively detailed understanding of the major causes of inter- Methods: annual variations in the abundance of migratory • Field day for community participation in the waterbirds within the larger landscape. This Narran Ecosystem Project. may then be combined with detailed hydrological

23 0 100 200 300 400 500 600 700 Murray-Darling Basin Commission Narran Ecosystem Project

Figure 6.1. Satellite image showing the locations of 6. Key findings the 12 principal wetlands (outlined in yellow) and the four stream gauging sites (orange dots) along the Narran River. 6.1 Physical template 6.1.1 Regional context

• Twelve lakes and wetlands were identified along Dirranbandi the Narran River; the largest of which is the Narran Ecosystem at the terminus of the Narran River (Fig. 6.1). The physical character of each Bokhara of these floodplain features is provided in Table 6.1. These floodplain lakes and wetlands were New Angledool identified using geophysical data. Angledool • The normalised Potassium (K) ratio: K/(K + Th + U); where Th is Thorium and U is Uranium, also depicts those floodplain lakes and wetlands that were predominantly filled by stream flow Bohdi Coocoran Wilby Wilby (shown as red in Fig. 6.2) and those that are filled by rainfall (shown as light blue in Fig. 6.2). Morendah East Mullane and Wilkie are two large floodplain Marella wetlands in the Narran region that are shown to Lianillo Narran Park fill primarily from rainfall rather than flows from Rotten the Narran River. Northern • The use of the normalised K ratio also appears Wilkie Narran to clearly depict the floodplain area of the East Mullane Narran Ecosystem; a task that is often difficult in very flat terrain.

Table 6.1: The sizes of the principle lakes and wetlands along the Narran River.

Wetland Surface area (km2) Storage volume (ML) Narran Lake 122.9 122 876 Northern Lake 19.5 9 372 Clear Lake 5.4 4 476 Back Lake 1.3 861 Long Arm 1.5 0.6 Intervening storages 11.3 4 035 Narran floodplains 135.7 13 730 All Narran 278.1 145 210 Bokhara 11.6 1 152 Angledool 15.9 15 885 Bohda 110.4 110.54 Coocoran 39.1 39.07 Morendah 193.0 193.00 Morella 16.6 16 580 Lianillo 15.4 15 366 Rotten 34.5 34 516 East Muflane 41.6 41 569 Willkie 11.6 11 644

Note: assumes 1 m depth for all non-Narran wetlands

24 0 100 200 300 400 500 600 700 6. Key Findings

6.1.2 Topography • There are two principal lakes within the Narran Ecosystem: Narran Lake and the Northern Lakes • A detailed digital elevation of the Narran have their own unique isometric relationship Ecosystem highlights its complex topography – (water depth vs surface areas). This is because (Fig. 6.3). The study area is characterised by of a number of different sub-storages within the several lakes, wetlands, floodplains and a diverse different lake systems being activated at different channel network. inundation levels (Fig. 6.5). • In general the topography of the Narran Ecosystem is very flat but the two lake systems (Narran and the northern lakes of Clear, Back Figure 6.4: A close-up of the LiDAR topography Lake and Long Arm) are clearly defined within data. Note that the lakes show up clearly as broad the landscape (Fig. 6.4). flat areas within the landscape.

122

121 Figure 6.2: Geophysical map of the 12 principal 120 wetlands along the Narran River overlaid on the 119 118 regional topography. 5000 10000 15000 From

To

Angledool

135 Coocoran 130 From Morendah Marella To 125

120 Northern Rotten 2500 5000 7500 10000 12500

Narran Figure 6.5: Hypsometric curves for the Northern East (a) and Narran (b) Lakes. Mullane Barwon floodplain (a)

250002500 3000

200002000 2500 surface area 2000 Figure 6.3: The LiDAR derived data for the Narran 15000 Ecosystem: (a) the topography of the Narran 1500 10000 volume

Ecosystem; and (b) vegetation heights. (ML) Volume 1000 Surface area (ha) 5000 500

0 0 119.6 119.8 120.0 120.2 120.4 120.6 120.8 121.0 121.2 121.4 121.6 Elevation (m)

(b)

180000 14000 160000 surface area 12000 140000 10000 120000 100000 8000 80000 6000 Volume (ML) Volume 60000 volume 4000 Surface area (ha) 40000 20000 2000 0 0 117.8 118.0 118.2 118.4 118.6 118.8 119.0 119.2 119.4 119.6 119.8 120.0 Elevation (m)

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6.1.3 Soils and the boundary Red Soils to provide a more robust way to analyse the soil data. • The soils of the Narran Ecosystem are very fine in texture, with over 65% of the material being • Multivariate statistical approaches show that the comprised of silts and clays, on average. Soils of Red Soils are significantly different to the Lake the Narran Ecosystem can therefore be classified and Floodplain soils within the Narran Ecosystem as being clayley mud soils according to the (Fig. 6.11) and several of the Lake and Floodplain standard soil nomenclature. regions are different in soil character to one another (Table 6.2). • There are several distinct patterns in both the physical and chemical character of the soils Figure 6.7: Kriged soil surfaces showing soil within the Narran Ecosystem. The lakes and properties which have higher concentrations or floodplains show relatively high concentrations levels in the red soil regions surrounding the lakes of some chemical elements (Fig. 6.6) and these and wetlands. soils are predominantly fluvial in origin. In contrast, other soil properties have higher levels in areas around the boundary of the Narran Ecosystem (Fig. 6.7). For these soil properties, local geology or rainfall may be the dominant control on their character. • Sodium displays a west to east pattern in concentration which is consistent with the dominant wind direction (Fig. 6.8). Therefore wind action has an important influence on the Titanium (%) character of some of the soils in the Narran Sand (%) Ecosystem. 03.60–14.35 0.40–0.48 14.35–20.75 0.48–0.50 • Several other soil properties show no obvious 20.75–26.30 0.50–0.51 pattern. For these, it is difficult to determine the 26.30–32.75 0.51–0.52 factors controlling their distribution (Fig. 6.9). 32.75–40.00 0.52–0.54 40.00–48.35 0.54–0.56 • In combination with the topographic information 48.35–56.35 0.56–0.57 presented earlier, the Narran Ecosystem can 56.35–63.35 0.57–0.59 be broken up into a series of geomorphic sub- 63.35–69.50 0.59–0.61 69.50–82.00 0.61–0.67 regions (Fig. 6.10) including Lakes, Floodplains

Figure 6.8: Kriged soil surfaces showing soil Figure 6.6: Kriged soil surfaces showing soil properties which show higher concentration in properties which have higher concentrations or a west to east pattern reflective of the dominant levels in lakes and wetlands. wind direction.

Clay (%) Aluminium (%) Calcium (%) Sodium (%) 01.50–12.25 2.50–4.65 0.09–0.31 0.08–0.16 12.25–18.90 4.65–5.10 0.31–0.51 0.16–0.20 18.90–26.60 5.10–5.50 0.51–0.66 0.20–0.23 26.60–34.60 5.50–5.95 0.66–0.80 0.23–0.26 34.60–42.00 5.95–6.35 0.80–0.96 0.26–0.31 42.00–48.65 6.35–6.75 0.96–1.11 0.31–0.38 48.65–55.65 6.75–7.25 1.11–1.27 0.38–0.48 55.65–63.70 7.25–7.75 1.27–1.45 0.48–0.62 63.70–74.40 7.75–8.40 1.45–1.70 0.62–0.83 74.40–87.10 8.40–9.70 1.70–2.48 0.83–1.32

26 0 100 200 300 400 500 600 700 6. Key Findings

Figure 6.9: Kriged soil surfaces showing soil Figure 6.11: Multi-dimensional scaling plot showing properties which show no distinguishable pattern the soil character for each of the eight geomorphic in concentration or level. regions in multidimensional space.

Northern Lake 1.5 Ne floodplain Narran Lake

1.0

0.5 Cw floodplain Ce floodplain 0 –1.5 –1.0 –0.5 0.5 1.0 1.5

Silt (%) Lead (ppm) Manganese (ppm) S floodplain –0.5

07.25–16.50 05.6–9.3 0203.6–373.8 Nw floodplain 16.50–20.75 09.3–10.2 0373.8–433.0 –1.0 20.75–23.85 10.2–10.9 0433.0–507.0 23.85–27.25 10.9–11.5 0507.0–588.4 Red soil –1.5 27.25–31.15 11.5–12.1 0588.4–677.1 31.15–34.50 12.1–12.7 0677.1–788.1 34.50–37.90 12.7–13.4 0788.1–943.5 6.1.4. Channel network 37.90–41.50 13.4–14.3 0943.5–1158.0 41.50–48.00 14.3–15.9 1158.0–1461.4 • The river channel network of the Narran 48.00–79.30 15.9–20.0 1461.4–2097.6 Ecosystem is very complex and comprises more than 8000 channels spanning 44 link types, as shown in the 2003 aerial photographs (Fig.6.12), (Rayburg and Thoms, in press). Figure 6.10: The eight geomorphic units used to analyse the soils in the Narran Ecosystem showing • Overall, the channel network maintained its the locations of 163 soil sample points. extent between 1969 and 1992 but contracted over the period between 1992 and 2003 (Fig. 6.13).

North-eastern • In addition to this contraction, the channel floodplain Northern Lakes network has also shown a loss of complexity with four fewer link types in 2003 than were present in North-western 1969 (Fig. 6.14). floodplain • A more detailed comparison between 1969 and 2003 shows that the channel network is very Central-western dynamic with less than 20% of the network floodplain unchanged over this period (Fig. 6.15).

Central-eastern 6.1.5 Environmental history floodplain • Contemporary flows in the Narran River are very Narran Lake low energy, transporting mostly fine silts and clays. Consequently, the surface material in the study area is of similar origin and character. The Red soil dominance of clay-size sediment differentiates the surface sediment layers from those found at depth in each of the four cores investigated (Fig. 6.16). Given the close proximity of the cores and their similarity in geological setting (i.e. down thrust basin), it should come as no Southern surprise that the cores exhibit a great deal of floodplain overlap in sediment characteristics. In fact, there are no statistically significant differences in the sediment properties of the cores when taken as a whole. However, the stratigraphy of the individual cores suggests there to be a great deal of spatial and temporal variability in the sedimentation

27 0 100 200 300 400 500 600 700 Murray-Darling Basin Commission Narran Ecosystem Project

of the Narran Ecosystem. This is reflected in deposition patterns; and the lower phase is the clear differences between sediments within characterised by regular episodic fining upwards individual cores and stratigraphic sequences sequences. The lowest portion of the Clear Lake between cores. core exhibits four cyclic periods of deposition, • The Narran Ecosystem has been in the landscape suggesting a periodic change in the hydraulic functioning as a terminal floodplain ecosystem environment from high energy (sand deposition) for at least 46,000 and 70,000 years. to low energy (deposition of fines). The chaotic nature of the sediments mid-core illustrates • The infilling of sediment to Clear Lake has a much more irregular and unsettled period occurred in three distinct phases (figure 6.16): of sediment supply to Clear Lake. Finally, in surface sediments are unique in character and the uppermost section of the core, a shift to a are dominated by fine clay-size sediments; dominance of fine sediments likely reflects a shift the middle phase exhibits irregular sediment towards conditions similar to those seen today

Table 6.2: Similarity between geomorphic regions (ANOSIM results) Groups Northern Narren Lake Lake Red soil S Fp NE Fp NW Fp CE Fp CW Fp Northern Lake Narran Lake 0.337 Red soil 0.877 0.834 S Fp 0.446 0.009 0.76 NE Fp 0.147 0.613 0.839 0.608 NW Fp 0.213 0.5 0.696 0.427 0.18 CE Fp 0.183 0.068 0.672 0222 0.264 0.085 CW Fp 0.182 0.114 0.68 0.162 0.326 0.097 0.062

Global R = 0.688 Significance level of sample statistic: 100% Number of permuted statistics greater than or equal to global R: 999 >0.75 well separated S Fp = southern floodplain, NE Fp = north east floodplain 0.50 some overlap but clearly different NW Fp = north west floodplain, CE Fp = central east <0.25 not separable floodplain, and CW Fp = central west floodplain

Figure 6.12: The 2003 channel network including Figure 6.13: The channel networks for 1969, 1992 the Northern Lakes. and 2003 including the network extents.

1969 1992

2003

Network area (km2) 1969 9.50 1992 9.80 2003 7.70

Rate of change (km2/y) 1969 1992 –0.01 2003 –0.81

28 0 100 200 300 400 500 600 700 6. Key Findings

Figure 6.14: The channel network link composition for 1969, 1992 and 2003. 5000 2003 4500 1992 1969 4000 3500 3000 # 2500 2000 1500 1000 500 0 FF FJ FT FO JF JJ JT JO EF EJ ET EO TT TJ TF LF LJ LT SF SJ Link type

with low energy flows bringing in fine silts and Figure 6.15: Changes in the channel network clays during regular flooding. In contrast, the between 1969 and 2003. floodplain core shows well-bleached sand-sized sediments at depth, which likely result from Network area (km2) aeolian processes. The surface sequence, on the 1969 6.64 other hand, is upward fining suggesting vertical 2003 4.84 Both 2.86 accretion of sediment resulting from overbank flows from the Narran River. The character of % of Total the surface sequence is similar to that of other 46.32 floodplain sediments in the lower Balonne 33.76 19.92 complex (Thoms et al., 2006). 2 • The infilling of Back Lake and Long Arm has Rate of change (km /y) –0.19 differed to that of Clear Lake and the flood –0.14 plain. Regular upward fining sequences suggest that the supply of sediment has been episodic through time. This could be the result of two factors: the migration of the river channel away from the lakes resulting in a decrease in energy, or alternatively, a change in sediment supply up river possibly resulting from climatic fluctuations. Mottling of sediments within all of Neither the lake profiles suggests that post-deposition- 1969 al processes resulting from groundwater 2003 interactions have also influenced the character 1969 and 2003 of the sediments. It is hypothesised that the observed gravel and carbonate nodules are the result of this groundwater interaction. a series of different environment process • Sedimentation within the Narran Ecosystem trajectories, converged to form a contemporary highlights distinct interactions between fluvial, floodplain surface and three floodplain lakes. In aeolian and hydrological processes – both addition, numerical analyses further highlight surface and groundwater. These processes have the similarities of sediment proprieties in the been responsible for a convergence of physical uppermost sediment sequences. form in the Narran Ecosystem, where different processes and causes produce similar effects • Four geomorphic units – three lakes and a – often referred to as equifinality. Each of the floodplain – have undergone convergent evolution four geomorphic units studied have, through from vastly different initial states (figure 6.16).

29 0 100 200 300 400 500 600 700 Murray-Darling Basin Commission Narran Ecosystem Project

Figure 6.16: The stratigraphy of sediment cores extracted from the northern section of the Narran Ecosystem. Clear Lake Back Lake Long Arm Floodplain

‘a’ ‘b’ ‘c’ ‘a’ ‘b’ ‘c’ ‘a’ ‘b’ ‘c’ ‘a’ ‘b’ ‘c’ 0 2 4 6 8 10 Depth in Profile (m) 12 Mud Muddy Sand Carbonate Mottling Lense 14 Sandy Mud Sand Nodules Laminating Layer

‘a’ ‘b’ ‘c’ ‘a’ ‘b’ ‘c’ ‘a’ ‘b’ ‘c’ ‘a’ ‘b’ ‘c’ 0 2 4 6 8 10 Depth in Profile (m) 12 14 78 k a 330 k a 440 k a 40 k a 4.2 k a 15 ka 25 ka

Surface Cyclic Bulk Back Water Billabong Dune

Further, the path each unit has undergone to • The rainfall for the gauges surrounding the arrive at its present state (fluvial depositional Narran Ecosystem have a close correlation with environments) has been markedly different and the Southern Oscillation Index (Fig. 6.19). This highly variable through time. Thus, there has been results in considerable periodicity in wet and dry a complex response to environmental change in cycles within the Narran Ecosystem. the Narran Ecosystem. The interaction of �������fluvial • This periodicity is well captured by looking at the (surface and sub-surface) and aeolian processes deviations from mean rainfall over the Narran has combined to form this rich sedimentology. Ecosystem since 1886 (Fig. 6.20). Most wet/dry The use of standard sedimentological and cycles persist for only three years or less. numerical techniques has facilitated the interpretation of the sedimentology of each of the 6.2.2 Hydrology cores illustrating the value of this approach in the reconstruction of the environmental history. Flow history • The flows in the three principal gauges along 6.2 Hydrological drivers the Narran River have a very close correlation with the highest flows upstream and lower 6.2.1 Climate flows downstream (Fig. 6.21). This indicates • There is a close association between the that, in most cases, flows are generated in the precipitation for all of the rain gauges headwaters, transported downstream, and the surrounding the Narran Ecosystem (Fig. 6.17) Narran River is generally a losing stream. • There is no apparent pattern of either increasing • The New Angledool gauge has a very long flow or decreasing rainfall with time for any of the record and provides a window into historical flow three principal rainfall stations surrounding the patterns in the Narran River (Fig. 6.22). Narran Ecosystem (Fig. 6.17). • The flood history in the New Angledool gauge • The overall climate pattern for the Narran yields some interesting information (Table 6.3). Ecosystem reflects that of the region, with hot One such finding is that the most recent period summers and cool winters. The highest rainfall (2000–2006) is the longest historical period typically occurs in the summer while the lowest without a significant flood (one that falls within rainfall occurs during winter (Fig. 6.18). the upper half of the rank table).

30 0 100 200 300 400 500 600 700 6. Key Findings

Figure 6.17: Rainfall patterns for the three principal climate stations surrounding the Narran Ecosystem.

1200 Lightning Ridge New Angledool 1000 Walgett

800

600

Precipitation (mm) 400

200

0 1881 1885 1889 1893 1897 1901 1905 1909 1913 1917 1921 1925 1929 1933 1937 1941 1945 1949 1953 1957 1961 1965 1969 1973 1981 1985 1989 1993 1997 2001 1977 Year

Figure 6.18: Monthly mean temperature and Figure 6.20: Deviations from mean annual rainfall rainfall data for the Walgett, NSW climate station. for the climate stations surrounding the Narran Ecosystem. (a) 1886–1942; (b) 1943–2004. 60 70 (a) 50 60 40 50 30 40 20 40 10 30 0

30 Rainfall (mm) –10

Temperature (°C) Temperature 20 –20 20 Precipitation (mm) –30 10 Minimum T 1886 1942 Maximum T 10 (b) 50 Total P 0 0 40 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 30 Month 20 Figure 6.19: Comparison of the median rainfall of 10 climate stations surrounding the Narran system to 0 the Southern Oscillation Index. Rainfall (mm) –10 –20 –30 50 1943 2004 40 Median SOI Year 30 20 10 600 000 Ml would need to flow down the Narran 0 River in the next 2.5 years.

Rainfall (mm) –10 • A closer look at the flood history of the Narran –20 River shows that flows occur in nearly 90% of –30 all years on record (Table 6.5). Medium to large –40 floods have also been quite common historically 1886 2004 with more than 2/3 of all years recording 50000 Year Ml or more of discharge. • The flows per decade are an indicator of how wet • The flows in the Wilby Wilby gauge (closest to the or dry particular periods have been in the past Narran system) show a systematic removal of (Table 6.4). Prior to now, the driest period was the medium sized floods since 1992 (Fig. 6.23) and an 1930s. However, for the current decade to avoid overall decrease in discharge when compared to becoming the new driest period on record, nearly the earlier part of the record

31 0 100 200 300 400 500 600 700 Murray-Darling Basin Commission Narran Ecosystem Project

Table 6.3: Ranked annual flows for theN ew Angledool gauge. Year Discharge Rank Year Discharge Rank 1956 1 146 798 1 1969 86 054 39 1983 768 146 2 1953 83 714 40 1950 576 390 3 1929 80 532 41 1976 541 286 4 1940 79 946 42 1971 497 788 5 1965 76 119 43 1954 437 072 6 1967 75 078 44 1988 433 919 7 1995 70 437 45 1984 387 742 8 1946 68 114 46 1996 387 463 9 1957 65 984 47 1974 342 322 10 1958 58 402 48 1959 337 673 11 1973 58 183 49 1962 300 798 12 1966 54 459 50 1990 298 698 13 1968 52 135 51 1941 288 982 14 2004 48 006 52 1989 257 434 15 2000 44 782 53 1947 255 851 16 1938 36 369 54 1998 236 393 17 1964 33 576 55 1963 220 844 18 1993 26 371 56 1972 212 335 19 1991 18 529 57 1982 170 507 20 1979 17 231 58 1981 157 102 21 1949 13 871 59 1999 147 555 22 1952 13 736 60 1977 143 463 23 1985 9 148 61 1931 133 865 24 1987 7 382 62 1997 133 455 25 1992 7 104 63 1937 132 805 26 1932 4 803 64 1994 128 254 27 1980 4 182 65 1933 122 617 28 2002 3 698 66 1955 122 230 29 2003 3 454 67 1978 117 114 30 1986 55 68 1948 114 468 31 1930 0 69 1975 114 057 32 1934 0 70 1961 113 160 33 1936 0 71 1939 106 033 34 1944 0 72 1943 99 916 35 1945 0 73 1970 99 773 36 1951 0 74 1935 93 209 37 1960 0 75 1942 91 796 38 2001 0 76

Table 6.4: Decadal flows for the Table 6.5: Number of years with threshold flow levels and the likelihood New Angledool gauge. of occurrence for these flow levels at theN ew Angledool gauge. Decade Total Flow (ML) Years % Chance 1930 629 701 Total 76 1940 1 012 949 No flow 8 10.5 1950 2 841 997 1–50 000 17 22.4 1960 1 012 224 50 000–100 000 17 22.4 1970 2 143 551 100 000–200 000 15 19.7 1980 2 195 617 200 000–500 000 15 19.7 1990 1 454 258 500 000–750 000 2 2.6 2000 55 158 750 000–1 000 000 1 1.3 >1 000 000 1 1.3

32 0 100 200 300 400 500 600 700 6. Key Findings

• A more detailed comparison of pre- and post 1992 • Water is much more persistent in the larger flows shows that the recurrence intervals for floods Narran Lake, however, resulting in a much lower of all magnitudes has increased (meaning floods score (than the Northern Lake) for the number have become more rare) since 1992 (Table 6.6). of times uniquely inundated (Fig. 6.25 (b)). In floodplain areas, the number of times uniquely Lake hydrology inundated equates to the total number of years • There is a high degree of spatial variability in the inundated which highlights the rapid drying times frequency and duration of inundation in the Narran in floodplain areas. Ecosystem (Fig. 6.24). • In Narran Lakes, the average time to dry, in the • The Northern and Narran Lakes are inundated in absence of top up events, is about 15 months most years (27 out of 32 years) while floodplains although this depends on the season in which areas are inundated with much less regularity inundation occurs (Fig. 6.26) (Fig. 6.25 (a)).

Figure 6.21: Comparisons between annual flow levels at the three principal gauges on theN arran River.

140000 Wilby Wilby New Angledool Dirrinbandi 120000

100000

80000

60000 Total flow (ML) Total

40000

20000

0 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 Year Figure 6.22: Daily flows at theN ew Angledool gauge. 20000

18000

16000

14000

12000

10000

Discharge (ML) 8000

6000

4000

2000

0 1/10/1929 1/10/1931 1/10/1933 1/10/1935 1/10/1937 1/10/1939 1/10/1941 1/10/1943 1/10/1945 1/10/1947 1/10/1949 1/10/1951 1/10/1953 1/10/1955 1/10/1957 1/10/1959 1/10/1961 1/10/1963 1/10/1965 1/10/1967 1/10/1969 1/10/1971 1/10/1973 1/10/1975 1/10/1977 1/10/1979 1/10/1981 1/10/1983 1/10/1985 1/10/1987 1/10/1989 1/10/1991 1/10/1993 1/10/1995 1/10/1997 1/10/1999 1/10/2001 1/10/2003 Date

33 0 100 200 300 400 500 600 700 Murray-Darling Basin Commission Narran Ecosystem Project

Table 6.6: Changes in the number of floods and flood recurrence intervals pre- and post- large-scale development upstream of the Narran system.

Number of floods Recurrence interval Size of Flood 1969–1991 1992–2003 1969–1991 1992–2003 Larger than 50 000 ML 17 7 1.30y 1.85y Larger than 100 000 ML 14 5 1.50y 2.63y Larger than 200 000 ML 8 2 2.78y 6.67y Larger than 300 000 ML 7 1 3.13y 12.50y Larger than 400 000 ML 4 0 5.56y <25.00y Larger than 500 000 ML 1 0 20.00y <100.00y

Figure 6.23: Daily flows and critical flood magnitudes at theW ilby Wilby gauge.

9000 10000–50000 50000–100000 Over 100000 8000 7000 6000 5000 4000

Discharge (ML) 3000 2000 1000 0 1/10/1969 1/10/1970 1/10/1971 1/10/1972 1/10/1973 1/10/1974 1/10/1975 1/10/1976 1/10/1977 1/10/1978 1/10/1979 1/10/1980 1/10/1981 1/10/1982 1/10/1983 1/10/1984 1/10/1985 1/10/1986 1/10/1987 1/10/1988 1/10/1989 1/10/1990 1/10/1991 1/10/1992 1/10/1993 1/10/1994 1/10/1995 1/10/1996 1/10/1997 1/10/1998 1/10/1999 1/10/2000 1/10/2001 1/10/2002 1/10/2003 1/10/2004 Date

Figure 6.24: The number of satellite images on which water occurred in a particular location. Note: this data set includes 72 images which means that no water was present in a total of 11 images.

0 1 2 3 4 5 6--8 9--11 12--15 16--20 21--25 26--30 31--35 36--50 51--61

34 0 100 200 300 400 500 600 700 6. Key Findings

Figure 6.25: Flood frequency for the Narran Ecosystem as determined by satellite imagery. (a) Records a value of one for every year that a location within the Narran Ecosystem was wet by the largest recorded flood during that year; (b) records a value of one for every instance in which a location within theN arran Ecosystem was wetted after having been previously dry.

(a) (b)

Number of times uniquely inundated (1981–2004) 0 1 2 3 4 Number of times wet 5 by the largest flood 6 extent in any given 7 year (1972–2004) 8 0 9 1–2 10 3–4 11 5–6 12 7–9 13 10–12 14 15 13–15 16 16–18 17 19–22 18 23–27 19

Figure 6.26 Average time to dry for Narran Lake given mean evaporation rates and different inundation times.

119.8 Jan Apr 119.6 Jul Oct 119.4 Lake dry

119.2

119.0

118.8

118.6

118.4 Water surface elevation (m) Water 118.2

118.0

117.8 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Months since full

35 0 100 200 300 400 500 600 700 Murray-Darling Basin Commission Narran Ecosystem Project

• In the Northern Lake, the average time to dry of size in discriminating between the two floods. is about 10 months (Fig. 6.27), although the The results of the PCC analysis indicate that only shallower parts of this lake may dry much three inundated-patch variables, the Margalef more quickly (e.g., Long Arm dries in about Richness for size (R2 = 0.811), shape (R2 = 2 months while Back Lake dries in about 0.841 ) and proximity (R2 = 0.823), were strongly 3 months on average). associated (R2> 0.8) with the two flood events. • Summary data of the distribution of inundated- Floodplain hydrology (wet patch character) patch character in terms of the size, shape • The area of inundated flood plain in the various and proximity between inundated-patches are 2 satellite images ranged from 0.49 m (December presented as box and whisker plots (Fig. 6.29). 2 2004) to 117.78 km (August 1996). There were Median inundated-patch size did not vary significant changes in the number of inundated greatly between individual images for both patches from image to image and between the two floods and an anticlockwise hysteresis Figure 6.28 Number of patches and inundated pattern was observed during both floods (Fig. surface areas (log10 ha) for the 1995–1997 and 2004 6.28) – the number of inundated-patches being flood sequences. The solid line is the line of best fit higher during drawdown than inundation. and the dashed lines trace the flood sequences for Overall, only nine inundated-patches were both flood events. recorded in the December 2004 image, whilst a maximum 165 inundated patches were recorded 180 in the August 1996 images. A strong positive 1995–1997 160 2004 power relationship (y = 0.8301 × 0.4943, r2 = 140 0.6265, P <0.001) between floodplain-inundated y = 0.8301x0.4943 area and the number of inundated-patches was 120 R2 = 0.6265 observed when data for the two flood events 100 were combined (Fig. 6.28). The results of the ANOSIM indicate a significant difference between 80

the two flood events in terms of the character of Patch number 60 floodplain inundation (Global R = 0.823, 40 P <0.001). However, when total inundated area and patch number were removed as variables, 20 there was no significant difference between the 0 two floods (ANOSIM: Global R = 0.245, 10 100 1000 10 000 100 000 P <0.001), thereby minimising the importance Log10 surface area inundated

Figure 6.27: Average time to dry for the Northern Lake given mean evaporation rates and different inundation times.

121.4 Jan Apr 121.2 Jul Oct Lake dry 121.0

120.8

120.6

120.4

Water surface elevation (m) Water 120.2

120.0

119.8 1 2 3 4 5 6 7 8 9 10 11 12 Months since full

36 0 100 200 300 400 500 600 700 6. Key Findings

flood sequences (Fig. 6.29(a)), although there fragmentation prior to a sharp increase at the is an increase in the median size of inundated- end of each flood. patches towards the end of each flood sequence, • Strong positive power relationships were presumably as a result of smaller patches drying observed between the surface area inundated out leaving larger water bodies remaining. A and Margalef Richness indices for inundated- similar pattern was recorded for the Shape index patch size (y = 0.2139 x 0.4002, r2 = 0.4636, (a size standardised shape regularity index) (Fig. P <0.007 ), shape (y = 0.211 x 0.4712, r2 = 0.6095, 6.29(b)) with median patch shape ranging from P <0.001) and proximity (y = 0.1315 x 0.2783 , 1.14 to 7.92 for the two flood events. However, r2 = 0.4601, P <0.003) (Fig. 6.29) when data for median patch shape generally ranged between both flood events are combined. However, these 1.14 and 1.97 for the two flood events, although relationships were more complex during the the last two images of the 2004 event are an individual floods. Clear clockwise and anti- exception with median inundated-patch values clockwise hysteresis relationships were observed increasing to 7.92. Median proximity values between surface area inundated and the (Fig. 6.29(c)) fluctuated from less than 0.01 to various richness indices during individual flood over 5000 but there was a general decrease events, the only exception was the relationship throughout the two flood events suggesting

Figure 6.29: Box and whisker plots for log10-transformed shape metrics for (a) patch sizes; (b) patch shapes; and (c) patch proximity for the 1995–1997 and 2004 Narran Lakes flood sequences.

(a) (b) 100000 20

ha) 10000 10 1000 ha) 10 10 100 8 6 10 5 4 1 3 0.1

SHAPE Index (log 2 0.01 Inundated surface area (log 0.001 1 3 Feb 04 3 Feb 04 7 Aug 96 7 Aug 96 7 12 Jul 04 12 Jul 04 23 Apr 04 23 Apr 04 23 16 Oct 04 16 Oct 04 10 Jun 04 10 Jun 04 16 Mar 96 16 Mar 96 15 Feb 97 19 Feb 04 15 Feb 97 19 Feb 04 17 Nov 04 19 Dec 04 17 Nov 04 19 Dec 04 27 Dec 95 27 Dec 95 14 Sep 04 14 Sep 04 19 May 96 19 May 96 Image dates for flood sequence Image dates for flood sequence

(c)

100000

10000

ha) 1000 10 100

10

1

0.1 Proximity index (log 0.01

0.001 3 Feb 04 7 Aug 96 7 12 Jul 04 23 Apr 04 23 16 Oct 04 10 Jun 04 16 Mar 96 15 Feb 97 19 Feb 04 27 Dec 95 17 Nov 04 19 Dec 04 14 Sep 04 19 May 96 Image dates for flood sequence

37 0 100 200 300 400 500 600 700 Murray-Darling Basin Commission Narran Ecosystem Project

between surface area inundated and proximity each patch characteristic. Thus, the expansion��������� for the 2004 flood. For patch area and shape, and contraction phases of an inundation event anticlockwise hysteresis was observed indicating are important drivers of floodplain inundated- a greater diversity of inundated-patch sizes and patch diversity. shapes during the contraction of floodwaters in comparison to the expansion of floodwaters 6.2.3 Hydraulic and hydrologic models across the Narran Ecosystem floodplain. However, patch proximity for the 1995–1997 flood • The Narran Ecosystem has a complex net of displayed a clockwise hysteresis indicating that primary, secondary and tertiary flow pathways the richness of proximities between patches is (Fig. 6.31(a)). greater on the expansion of floodwaters across • These flow pathways represent the critical water the floodplain. delivery routes to the two principal lakes within • The expansion and contraction of floodwaters the Narran Ecosystem and so are important across the Narran Ecosystem floodplain surface locations for the collection of detailed hydraulic produced a dynamic mosaic of inundated- information (Fig. 6.31(b)). patches. There was a complex response from • Focusing in on one flow pathway, the main off- the size of the inundated floodplain area, the take to Clear Lake, illustrates the method used to number of inundated-patches (Fig. 6.27) and the take the hydraulic model output and use it as an richness of their sizes, shapes and proximities input into the hydrologic model (Fig.6.32). Using to each other, during the two floods (Fig. 6.30). this method, it is possible to obtain quite accurate Flood size and the number of inundated-patches measurements of the amount of water that will appear to be the most important discriminators flow down any particular flow pathway under of inundated-patch character as indicated by different input flow conditions. the multivariate analyses. Once these variables • The water balance model has an excellent are removed from the statistical analyses, no correlation between the actual and predicted statistical difference between the two floods, inundated surface areas for both the Northern in terms of the diversity of inundated-patch and Narran Lakes (Fig. 6.33) with r2 values in character, was observed. Overall, there was excess of 0.87 for both lakes. a high degree of overlap in the richness of inundated-patch character between the two • The success of the model in accurately floods, although maximum diversities for size predicting the surface area of both lakes is and shape richness were recorded in August further illustrated by looking at an image by 1996, and for proximity in March 1996 (Fig. 6.30). image plot of actual vs. predicted inundated The complex response to the expansion and area (Fig. 6.34). In nearly all of these images, contraction of floodwaters is further illustrated the actual and predicted areas are quite close by pronounced hysteresis in the relationship and the long-term average is such that the between surface area inundated and patch model neither consistently over or under richness for size, shape and proximity. In predicts the surface area. addition, this pattern was not the same for

Figure 6.30: Relationships for Margalef richness indices and inundated surface area for the 1995–1997 and 2004 flood sequences: (a) richness of patch sizes; (b) richness of patch shape; (c) patch proximity. The solid lines are the line of best fit and the dashed lines trace the flood sequences for both flood events.

1995–1997 2004 (a) (b) (c) 35 20 y = 0.2139x0.4002 y = 0.211x0.4712 4.0 y = 0.211x0.2783 18 2 2 2 R = 0.4636 30 R = 0.6095 3.5 R = 0.4601 16 14 25 3.0 12 20 2.5 10 2.0 15 8 1.5 6 10 1.0

Patch size richness 4 Patch shape richness 5 0.5 2 Patch proximity richness 0 0.0 01 10 100 1000 10000 100000 1 10 100 1000 10000 100000 1 10 100 1000 10000 100000

Log10 surface area inundated (ha) Log10 surface area inundated (ha) Log10 surface area inundated (ha)

38 0 100 200 300 400 500 600 700 6. Key Findings

Figure 6.31: Hydraulic model outputs: (a) flow pathways in theN arran Ecosystem; (b) locations where stage-discharge data were extracted from the hydraulic model.

(a) (b) Dominant flow pathway Secondary flow pathway Tertiary flow pathway Hydraulic control point

Elevation (m) 124.0

119.0

N

0 1.5 3 5 9 12 km

• Plots of the surface area for the Northern and • The calibration and validation periods for the Narran Lakes over the period of flow gauging hydraulic and hydrologic models are presented data at Wilby Wilby (1964 to 2004) shows that in (Fig. 6.37). This highlights the quality control Narran Lake has been wet for a significant of both models and is part of the reason we have percentage of time over this period and it been able to achieve such good model outcomes. receives many top up events that keep it wet for • A comparison of a series of climate and many years at a time. Meanwhile, the Northern development scenarios shows that, for the most Lakes tended to wet and dry quite regularly over part, the impact of land use and water resource this period and in some cases may experience development far outweighs any potential climate four or more wet/dry cycles within the span of change impacts on the frequency, timing and one inundation event (Fig. 6.35). duration of inundation in the Narran Ecosystem • Inundation duration curves for the two lakes (Fig. 6.38). show that Narran has been wet approximately • Indeed, comparing the natural and current 75% of the time since 1964 while the Northern development scenarios reveals the profound Lakes have been wet nearly 60% of the time impact development has had on the inundation (Fig. 6.36). Significant inundations in each lake of the Narran Ecosystem, where the amount of (taken to be 50% full or more) are also very time the Narran Lake and the Northern lakes common in both lakes with Narran Lake being at are dry has increased dramatically, with the least 50% full more than 40% of the time and the longest dry periods (times without extended Northern Lakes being at least 50% more inundation) increasing from about 1–2 years to than 30% of the time. nearly 20 years (Fig. 6.39).

39 0 100 200 300 400 500 600 700 Murray-Darling Basin Commission Narran Ecosystem Project

Figure 6.32: Hydraulic model outputs at locations where stage-discharge data were extracted: (a) plot of flow down the main off-take to Clear Lake and the input flows into theN arran River; (b) comparison of the discharge inflow discharge against the discharge into the main clear lake off-take channel illustrating the cutoff point at which no additional flow moves towards Clear Lake down this pathway irrespective of increases in inflow discharge; (c) regression showing the predictive relationship between inflow discharge and discharge into Clear Lake via the main off-take channel.

(a) 80.0 Inflow Line 1 70.0 )

–1 60.0 s 3 50.0 40.0 30.0

Discharge (m 20.0 10.0 0.0 1/09/83 8/02/84 8/04/84 7/06/84 11/10/83 20/11/83 23/07/83 12/08/83 21/09/83 31/10/83 10/12/83 30/12/83 19/01/84 28/02/84 19/03/84 28/04/84 18/05/84 27/06/84 17/07/84 Date

(b) 8.0

) 7.0 –1 s 3 6.0

5.0

4.0

3.0

2.0 Line 1 discharge (m 1.0

0.0 0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 Inflow discharge (m3 s–1)

(c) 7.0 y = 0.5844x r 2 = 0.8438

) 6.0 –1 s 3 5.0

4.0

3.0

2.0

1.0 Line 1 discharge (m 0.0

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.08.0 9.0 10.0 Inflow discharge (m3 s–1)

40 0 100 200 300 400 500 600 700 6. Key Findings

Figure 6.33: Hydrologic (water balance) model calibration results: (a) predicted against actual inundated surface area for the Northern Lake; (b) predicted against actual inundated surface area for Narran Lake.

(a) (b) 12000 3000 y = 1.0168x y = 0.941x r 2 = 0.8732 r 2 = 0.8841 2500 10000

2000 8000

1500 6000

1000 4000

500 2000 Predicted surface area (ha) Predicted surface area (ha) 0 0 0 500 1000 1500 2000 2500 3000 0 2000 4000 6000 8000 10000 12000 Actual surface area (ha) Actual surface area (ha)

Figure 6.34: Hydrologic (water balance) model calibration results: (a) image by image comparison of the actual and predicted inundated surface area of the Northern Lake; (b) image by image comparison of the actual and predicted inundated surface area of Narran Lake.

(a) (b) 3500 Actual Predicted 12000 Actual Predicted 3000 10000 2500 8000 2000 6000 1500 4000 Surface area (ha) Surface area (ha) 1000

500 2000

0 0 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 Year Year

Figure 6.35: Predicted inundation pattern in the Northern and Narran Lakes over the period of gauging record at the Wilby Wilby gauge.

12000 Narran Lake Northern Lake

10000

8000

6000

4000 Surface area (ha)

2000

0 9/12/2004 10/12/2001 10/12/2003 19/12/1964 19/12/1965 19/12/1966 19/12/1967 18/12/1968 18/12/1969 18/12/1970 18/12/1971 17/12/1972 17/12/1973 17/12/1974 17/12/1975 16/12/1976 16/12/1977 16/12/1978 16/12/1979 15/12/1980 15/12/1981 15/12/1982 15/12/1983 14/12/1984 14/12/1985 14/12/1986 14/12/1987 13/12/1988 13/12/1989 13/12/1990 13/12/1991 12/12/1992 12/12/1993 12/12/1994 12/12/1995 11/12/1996 11/12/1997 11/12/1998 11/12/1999 10/12/2000 10/12/2002 Date

41 0 100 200 300 400 500 600 700 Murray-Darling Basin Commission Narran Ecosystem Project

Figure 6.36: Inundation duration curves for the Northern and Narran Lakes as determined by the hydrologic model.

12000 Narran Lake 10000 Northern Lakes

8000

6000 50% full

4000

2000 50% full Surface area innundated (ha)

0 0 10 20 30 40 50 60 70 80 Percentage occurrence

Figure 6.37: Calibration and validation discharge periods for the hydraulic and hydrologic models of the Narran Ecosystem.

Hydrologic model Hydrologic model calibration period validation period 10000 Basis for simulated 9000 hydraulic model run Hydraulic model validation event 8000 Hydraulic model calibration event 7000

6000

5000

4000 Discharge (ML) 3000

2000

1000

0 1998 2000 2002 2004 1964 1966 1968 1970 1972 1974 1976 1978 1980 1982 1984 1994 1986 1988 1990 1992 1994

Year

42 0 100 200 300 400 500 600 700 6. Key Findings

Figure 6.38: Model predictions of the inundated surface area of the Narran Ecosystem given: no water resources development and no climate change (0); no water resource development but a 50% likelihood climate change scenario (50); no water resource development and a 5% likelihood climate change scenario (95); no climate change but current levels of water resource development (current).

12000 0 50 95 10000 Current

8000

6000

Surface area (ha) 4000

2000

0 1/01/65 1/01/70 1/01/75 1/01/80 1/01/85 1/01/90 1/01/95 1/01/00 1/01/05 1/01/10 1/01/15 1/01/20 1/01/25 1/01/30 1/01/35 Date

Fig. 6.39: Model predictions of the inundated surface area in the Narran Ecosystem under natural conditions and current water resource development.

12000 Natural Current

10000

8000

6000

Surface area (ha) 4000

2000

0 1/01/65 1/01/70 1/01/75 1/01/80 1/01/85 1/01/90 1/01/95 1/01/00 1/01/05 1/01/10 1/01/15 1/01/20 1/01/25 1/01/30 1/01/35 Date

43 0 100 200 300 400 500 600 700 Murray-Darling Basin Commission Narran Ecosystem Project

6.3 Ecological responses • Turbidity measurements showed a distinct pattern of increasing variability over time 6.3.1 Aquatic ecology (Fig. 6.40). Lowest turbidity measurements were recorded at the Long Arm and Back Lake sites Water quality (15 and 16 NTU respectively). Both the Narran • The measured physico-chemical variables varied River and Clear Lake locations had the highest both spatially and temporally during the field turbidities overall. sampling period (Fig. 6.40). • Oxygen and pH increased between February and • Conductivity values remained below 0.50 mS March sampling events (Fig. 6.40). Long Arm cm–1 across all sampling sites between February values were typically higher than those recorded and July 2004. At the final October sampling date, at other sites. however, Clear Lake values were almost three • Nutrient concentrations were generally high times higher than previous readings (1.36 mS and in excess of 0.1 mg L–1 and 0.5 mg L–1 for –1 cm ) (Fig. 6.40). phosphorus and nitrogen respectively (Table 6.7). • Predictable seasonal variations in temperature • Chlorophyll a measurements ranged between were observed with lowest water temperatures 0.7 and 10.0 mg L–1. Highest values were recorded in July and highest temperatures in recorded in Long Arm during March and April. February (Fig. 6.40).

Figure 6.40: Physico-chemical characteristics of sampled floodplain locations (BLC: Back Lake centre; CLC: Clear Lake centre; CLS: Clear Lake shore; LA: Long Arm; NR: Narran River).

(a) (b) 1.5 24.0 ) –1 1.0 16.0

0.5 8.0 Oxygen (mg L Conductivity (mS)

0.0 0.0 (c) (d) 1200.0 33.0

800.0 22.0

400.0 11.0 Turbidity (NTU) Temperature (°C)

0.0 0.0

(e) 9.3 BLC CLC 8.2 CLS

pH LA 7.1 NR

6.0

Mar May Jul Sep Nov Sampling Date

44 0 100 200 300 400 500 600 700 6. Key Findings

Table 6.7: Water chemistry of the five sampled habitats (TP = total nitrogen,N FR = non filterable residue). Chemical parameter Site TP TN NFR Na Mg K Ca (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) Back Lake Min 0.4 1.15 165.7 88 30 87 106 Max 1.08 2.07 415.5 308 140 110 352 Clear Lake Min 0.35 0.67 280 76 22 49 80 Max 2.03 5.09 673.7 1598 219 173 465 Clear Lake shore Min 0.41 0.97 261 115 42 71 142 Max 0.56 1.18 712 148 57 71 179 Long Arm Min 0.24 1.73 60.7 175 54 85 137 Max 0.92 3.28 530 340 129 141 387 Narran River Min 0.14 0.55 134.7 71 31 43 75 Max 0.27 1.05 885.5 124 50 67 128

Zooplankton most abundant component of the zooplankton fauna (approximately 80%) followed by • 52 microinvertebrate genera were recorded cladocerans (6.7%) (Fig. 6.43). from field samples. Twenty-four of these were recorded exclusively from floodplain samples and • Analysis of abundance data indicated overall were absent from river samples. In contrast, only a strong interactive effect between habitat two genera were found uniquely in river samples. and time. Variance in cladoceran abundances, however, was explained predominantly by site • Total densities of zooplankton in field samples (Anova, F = 28.31, p <0.001). Long Arm had varied from <30 animals L–1 to over 3500 animals 3,40 significantly higher abundances of cladocerans L–1 with highest densities (>3000 animals L–1) than the other sampled habitats (Tukey, recorded in the Narran River and Clear Lake sites p = 0.001). (Fig. 6.41). • Ordination of species abundance data revealed • Relative abundances of broad taxonomic groups that sites typically showed the greatest varied considerably both across time and dissimilarity during the July sampling (Fig. 6.43). between sites (Fig. 6.42). Rotifers comprised the

Figure 6.41: Zooplankton densities at sampled locations from February 2004 to October 2004. Note missing samples occur where locations dried out earlier.

(a) Moina sp. (b) Macrothrix sp.

CLC CLC LA LA BLC

200 200

150 150

100 100 Total number of cladoceran sp. 50 50

0 0 0 20 40 60 80 100 0 20 40 60 80 100

Number of days since flooding

45 0 100 200 300 400 500 600 700 Murray-Darling Basin Commission Narran Ecosystem Project

Figure 6.42: Relative abundances of broad zooplankton taxonomic group.

NR CL 4000 CLS )

–1 BL LA

3000

2000

1000 Total zooplankton density (animals L Total

0 Feb Mar Apr Jun Jul Oct Sampling date

This was supported by the analysis of dispersion • Only one genera (Neothrix) recorded from the (MVDISP) which revealed that highest dispersion mesocosm experiment was not recorded from between sites occurred in the June and July the field samples. samplings (1.508 and 1.708 respectively). • The BIOENV procedure indicated that the rank similarity of sites based on zooplankton Figure 6.43: Dominant cladoceran genera emerging assemblages were best explained by a from flooded soil samples (a)Moina sp. and (b) combination of the variables turbidity, Macrothrix sp. Only habitats with emergence are conductivity, depth and temperature shown. Habitat codes are: CLC = Clear Lake Centre, (correlation = 0.408). The only variable measured BLC = Back Lake Centre, LA = Long Arm. that did not explain zooplankton assemblage structure was pH. • Numbers of zooplankton emerging from egg BL_5 banks in the mesocosm experiment were BL_4CLC_5 generally very low and depauparate in taxon richness (eight genera). Zooplankton emerged from only a third of the containers (seven). CLC_6 NRW_1BL_1 BL_2CLC_2CLC_4CLC_3 CLS_2 NRW_6 • No zooplankton emergence was recorded from LA_2 CLS_1 Narran River or the Narran River bank samples BL_3 LA_1 LA_3 and only one animal emerged from the Chenopod Axis 2 NRW_5 floodplain sediments. NRW_2CLC_1NRW_4NRW_3 • The most abundant microcrustacean fauna were Moina sp. and Macrothrix sp. which accounted LA_5 for more than 96% of all emergent animals. The two dominant cladocerans genera exhibit distinct LA_4 patterns in emergence (Fig. 6.44) with Moina sp. reaching a maximum abundance after 20 days

inundation and Macrothrix sp. after 60 days. Axis 1

46 0 100 200 300 400 500 600 700 6. Key Findings

Figure 6.44: nMDS ordination plots based on zooplankton abundances in five habitats on six sampling occasions. Stress = 0.15 in two dimensions. Habitat codes are: CLC = Clear Lake Centre, CLS = Clear Lake Shore, BLC = Back Lake Centre, LA = Long Arm, NR = Narran River. Numbers indicate sampling date: 1 = 15/02/2004, 2 = 3/03/2004, 3 = 16/04/2004, 5 = 4/06/2004, 5 = 15/07/2004 and 6 = 27/10/2004.

Clear Lake Clear Lake Shore 100

50

Dry 0 Back Lake Long Arm 100

50

Dry Dry 0 Narran River 100 Cladocerans Cyclopoids Zooplankton group relative abundances Ostracods 50 Calanoids Nauplii Rotifer 0 Feb Mar Apr Jun Jul Oct Sampling Month

Fish Figure 6.45: Total fish abundance (CPUE) at study sites between February and November 2004. NW: • A total of eleven fish species in eight families Narran weir, NO: Narran off-take, CE: Clear Lake were recorded including eight native species entrance, CC: Clear Lake centre, BL: Back Lake, (bony bream, western carp gudgeon, golden and LA: Long Arm. perch, spangle perch, silver perch, Murray cod,

Hyrtl’s tandan, Australian smelt) and 3 exotics 4000 Feb Apr Jul Nov (carp, mosquitofish and goldfish). • Fish assemblage was dominated by three species 3000 (spangle perch, Leiopotherapon unicolour; bony bream, Nematalosa erebi; and exotic carp, 2000 Cyprinus carpio).These three species collectively CPUE contributed 99% of total catch per unit effort 1000 (number). • Considerable variation in total fish abundance 0 was observed among sites and sampling times NW NO CE CC BL LA (Fig. 6.45). More fish were caught in April than Site any other sampling time. • Ordination and ANOSIM also showed large • Native species found in the Narran Ecosystem differences in composition between sampling during the 2004 flood included spangled perch, times. Spatial differences, however, were less bony bream, Australian smelt, Hyrtl’s tandan, clear (Fig. 6.46). yellowbelly, Murray cod, silver perch and western carp gudgeon. • Length frequency data for three most abundant species indicates some periods of recruitment • Exotic species found included carp, goldfish and the Narran Ecosystem. mosquito fish.

47 0 100 200 300 400 500 600 700 Murray-Darling Basin Commission Narran Ecosystem Project

6.3.2 Vegetation Figure 6.47: Mean total cover (± S.E.) of groundcover vegetation for sites within each Extant groundcover vegetation original region and flood frequency class in (a) • In the field, groundcover vegetation was most November 2004 and (b) May 2005.

diverse and productive following the recession of North floodwaters in late 2005. (a) November 2004 Bird Colony

2 South

• Total cover of groundcover vegetation m 2000 was greatest in sites subjected to short to 1500 intermediate periods of submergence followed by long periods of soil waterlogging (e.g. bird 1000 Total Cover Total colony sites, moderately and infrequently flooded sites in the northern region and frequently 500 flooded sites in the southern region) (Fig. 6.47(a)). 0 Relatively low total cover, comparable to that in Frequent Moderate Infrequent Rare Terrestrial non-flooded wetland and terrestrial sites, was Flood Frequency Zone observed in sites subjected to long period of deep (b) May 2005

submergence (e.g. Clear Lake sites) (Fig. 6.47(a)). 2

m 2000 • A marked reduction in total cover and the disappearance of spatial patterns along the flood 1500 frequency gradient occurred following 6 months 1000

of drying (Fig. 6.47(b)). Cover Total

• Species richness of groundcover plants 500 was greatest in sites subjected to short to 0 intermediate periods of submergence followed by Frequent Moderate Infrequent Rare Terrestrial long periods of soil waterlogging (e.g. bird colony Flood Frequency Zone sites, moderately and infrequently flooded sites in the northern region and frequently flooded sites in the southern region). (Fig. 6.48(a)). Figure 6.48: Mean species richness (± S.E.) of • Relatively low species richness, comparable to groundcover vegetation for sites within each that in non-flooded wetland and terrestrial sites, original region and flood frequency class in (a) was observed in sites subjected to long period November 2004 and (b) May 2005. of deep submergence (e.g. Clear Lake sites). November 2004 (Fig. 6.48(a)). (a) North 30 Bird Colony South Figure 6.46: Spatial and temporal variations in 25 CPUE based on transformed data log10 (CPUE+1) 20 at the study sites during the course of study 15 February (F), April (A), July (J), and November (N). Abbreviations as in Fig. 6.44. 10 Species richness 5 0 Stress: 0.06 Frequent Moderate Infrequent Rare Terrestrial C Flood Frequency Zone N C L W (b) B A May 2005 L 30 C 25 E N 20 O N W 15 B C C L 10 N E C O N Species richness 5 N WN F O W A 0 Frequent Moderate Infrequent Rare Terrestrial J N Flood Frequency Zone O N

48 0 100 200 300 400 500 600 700 6. Key Findings

• A marked reduction in species richness and the Soil seed bank composition and structure disappearance of spatial patterns along the flood • The germinable soil seed bank of the Narran frequency gradient occurred following 6 months Ecosystem study area, is large and diverse. A total of drying. (Fig. 6.48(b)). of 77 taxa were positively identified to species, • Composition of groundcover communities was comprising 23 monocot and 54 dicot species. found to be very distinctive between wetland and • Sediment samples subjected to waterlogged neighbouring terrestrial sites, even with respect conditions had significantly greater species to rarely inundated wetland areas (Fig. 6.47). richness (ANOVA, F1,14 = 522.85, P <0.0001) and

• Recent flood history has an overriding influence seedling abundances (ANOVA, F1,14 = 394.18, on the composition and structure of groundcover P <0.0001) than those subject to submergence communities (Fig. 6.48). in the first mesocosm experiment (Fig. 6.50(a) and (b)). Figure 6.49: nMDS ordination of sites by • Amongst the hydrogeomorphic habitats groundcover species cover (stress = 1.78). BC = bird examined in the first mesocosm experiment, colony sites, NT = northern terrestrial sites, species richness was lowest in Clear Lake centre ND = northern wetland sites not inundated in 2004, and the Narran River channel and highest in NW = northern wetland sites inundated in 2004, the lignum and chenopod floodplain samples ST = southern terrestrial sites, SD = southern (Fig. 6.50(a)). Seedling abundances were wetland sites not inundated in 2004, SW = southern highest in Back Lake, Clear Lake shore and the wetland sites inundated in 2004. N.B. All data log lignum floodplain habitats. These habitats are (x + 1) transformed. likely to receive durations of flooding that are intermediate between the Clear Lake centre BC and river channel samples, and the chenopod NT ND floodplain habitat (Fig. 6.50(b)). NW ST • The composition of the germinable soil SD SW seed bank differed significantly between hydrogeomorphic habitats. Three distinct groupings were identified from multivariate analysis (Fig. 6.51). Two groups identified correspond to the chenopod floodplain and the Narran River bank. These were distinguished from the other habitats sampled as they occupy their own distinct regions in the ordination space. The other sampled habitats were relatively

Figure 6.50: Seedling abundances (a) and species richness (b) of plants germinating from waterlogged and submerged sediments. Habitat codes are described above. Values are means ± S.E.

(a) (b) Waterlogged Waterlogged 120 Submerged 15 Submerged

80 10 Species richness

Seedling abundance 40 5

0 0 NRI CLC BLC CLS LFP NRB CFP NRI CLC BLC CLS LFP NRB CFP Habitats Habitats

49 0 100 200 300 400 500 600 700 Murray-Darling Basin Commission Narran Ecosystem Project

Figure 6.51: nMDS ordination plots based on Figure 6.52: Box plot of Bray–Curtis dissimilarity species abundances in waterlogged treatment scores for pairwise comparisons of replicates showing (a) habitats and (b) species vectors. Axes nested within sites. Habitat codes are described 1 and 3 are shown as these explained the greatest above. variation in the composition data.

90

60

30 Bray–Curtis dissimilarity score

Axis 3 0 NRI CLC CLS BL LFP NRB CFP Back Lake Habitat Chenopod floodplain Clear Lake centre Clear Lake shore • The long-term flood frequency of soil samples Lignum floodplain Narran River Bank also had a significant (p< 0.001) effect on Narran River channel the species richness of plant communities harvested from experimental pots after 12 Axis 1 months with lower values occurring in pots from the frequently flooded class. Annual flood treatment also influenced species richness with similar to each other. The greatest overlap significantly (p< 0.05) fewer species occurring in occurred between the two most frequently pots that were submerged at the time of harvest flooded habitats, Clear Lake centre and the (i.e. 6W and 12) (Fig. 6.54). Narran River channel. • Amongst the major plant groups present, • Spatial variability of the germinable soil seed the total biomass of annual forbs was not bank also differed between hydrogeomorphic significantly influenced by annual flood pulse habitats. Viable propagules of more than 75 taxa treatment but did differ between flood frequency are present in the soil seed bank including close classes with significantly (p <0.01) lower values to 25 monocot species and over 50 dicot species occurring in frequent and moderate samples as well as charophytes (Fig. 6.52). (Fig. 6.55). Effects of flood pulse characteristics on • Conversely, flood frequency class had no vegetation development from the soil seed bank significant effect on the biomass of perennial forbs but annual flood pulse treatment did • In the second mesocosm experiment, both the (p <0.05) with significantly higher values long-term flood history of soil samples and flood occurring in pots subjected to 12 months of pulse characteristics influenced the composition submergence (Fig. 6.56). and structure of plant communities that established from soil seed banks. • Amongst the annual and perennial grass/rush/ sedge plant groups, no significant effect of flood • The long-term flood frequency of soil samples pulse treatment on biomass was detected but in significantly (p< 0.001) influenced the total both groups biomass was significantly (p <0.01 biomass harvested from experimental pots after and p <0.0001 respectively) higher in pots from 12 months with greater biomass occurring in the rarely flooded zone (Figs 6.57 and 6.58). pots from infrequently and rarely flooded flood frequency classes. There was no significant • The biomass of exotic species was significantly effect of annual flood treatment on total biomass higher in pots from the frequently flooded class although greater biomasses tended to occur in but exotics tended not to emerge (or were pots that were submerged throughout the latter significantly less abundant) in pots subjected to 6 months of the experiment (i.e. 6W and 12) long durations of inundation and/or slow rates of (Fig. 6.53). drawdown (i.e. 6SS, 3SS, 6W, 3WS and 12, Fig. 6.59).

50 0 100 200 300 400 500 600 700 6. Key Findings

Figure 6.53: Effects of annual flood pulse treatment x( axis) and flood frequency class (see legend) on total biomass of plant communities developing in experimental pots after 12 months. N.B. Mean values shown ± S.E.

30 Frequent 25 Moderate Infrequent Rare 20

15

Total biomass (g) 10

5

0 6SF 6SS 3SF 3SS 6W 3WF 3WS 12 3S3W Flood treatment

Figure 6.54: Effects of annual flood pulse treatment x( axis) and flood frequency class (see legend) on total biomass of plant communities developing in experimental pots after 12 months. N.B. Mean values shown ± S.E.

10 Frequent 9 Moderate 8 Infrequent 7 Rare 6 5 4

Species richness 3 2 1 0 6SF 6SS 3SF 3SS 6W 3WF 3WS 12 3S3W Flood treatment

Figure 6.55 : Effects of annual flood pulse treatment (x axis) and flood frequency class (see legend) on total biomass of annual forbs developing in experimental pots after 12 months. N.B. Mean values shown ± S.E.

8 Frequent 7 Moderate Infrequent 6 Rare

5

4

3 Total biomass (g) 2

1

0 6SF 6SS 3SF 3SS 6W 3WF 3WS 12 3S3W Flood treatment

51 0 100 200 300 400 500 600 700 Murray-Darling Basin Commission Narran Ecosystem Project

Figure 6.56 Effects of annual flood pulse treatment (x axis) and flood frequency class (see legend) on total biomass of perennial forbs developing in experimental pots after 12 months. N.B. Mean values shown ± S.E.

7 Frequent 6 Moderate Infrequent 5 Rare

4

3

Total biomass (g) 2

1

0 6SF 6SS 3SF 3SS 6W 3WF 3WS 12 3S3W Flood treatment

Figure 6.57 Effects of annual flood pulse treatment (x axis) and flood frequency class (see legend) on total biomass of annual grasses, rushes and sedges developing in experimental pots after 12 months. N.B. Mean values shown ± S.E.

25 Frequent Moderate 20 Infrequent Rare

15

10 Total biomass (g)

5

0 6SF 6SS 3SF 3SS 6W 3WF 3WS 12 3S3W Flood treatment

Figure 6.58 Effects of annual flood pulse treatment (x axis) and flood frequency class (see legend) on total biomass of perennial grasses, rushes and sedges developing in experimental pots after 12 months. N.B. Mean values shown ± S.E. 14 Frequent 12 Moderate Infrequent 10 Rare

8

6

Total biomass (g) 4

2

0 6SF 6SS 3SF 3SS 6W 3WF 3WS 12 3S3W Flood treatment

52 0 100 200 300 400 500 600 700 6. Key Findings

Figure 6.59: Effects of annual flood pulse treatment (x axis) and flood frequency class (see legend) on total biomass of exotic species developing in experimental pots after 12 months. N.B. Mean values shown ± S.E.

4 Frequent Moderate Infrequent Rare

2 Total biomass (g)

0 6SF 6SS 3SF 3SS 6W 3WF 3WS 12 3S3W Flood treatment

Lignum Figure 6.60: Mean % cover of lignum shrubland at sites in relation to flood frequency.N .B. The flood • The character of lignum shrubland in the Narran frequency index used here is based on analyses of Ecosystem study area varies spatially in relation to Landsat imagery and indicates number of years long-term flood history. Frequently flooded areas, a site was inundated by the largest annual flood such as the bird colony, tend to be dominated extent from 1972–2004. by fewer but larger lignum clumps while less frequently flooded areas support shrubland 100 comprising many small lignum clumps. – Total cover of lignum was higher in frequently 75 flooded sites (Fig. 6.60) and lignum density (i.e. number of clumps per unit area, Fig. 6.61) 50 higher in less frequently flooded sites. Mean % cover 25 – Individual lignum clumps were larger, in terms of both height (Fig. 6.62) and perimeter 0 (Fig. 6.63), in frequently flooded sites. 3 7 11 15 19 23 27 • The condition of lignum shrubland varied Flood frequency considerably throughout the Narran Ecosystem study area at the time of survey. Although Figure 6.61: Mean number of lignum clumps per recent rainfall clearly promotes a growth site in relation to flood frequency.N .B. The flood response, recent flood history appears to have frequency index used here is based on analyses of an overriding influence on lignum condition Landsat imagery and indicates number of years (in terms of % greenness): a site was inundated by the largest annual flood – % greenness of lignum was significantly extent from 1972–2004. higher in sites inundated during the 2004 50 flood event (Fig. 6.64). – No clear relationship was evident between % 40 greenness of lignum and soil moisture levels 30 (proxy for recent rainfall receipt) (Fig. 6.65). 20

Lignum seedling establishment # Lignum clumps 10

• In the lignum establishment experiment, water 0 treatment had a significant effect upon 11 out of the 3 7 11 15 19 23 27 12 lignum seedling variables measured. Significant Flood frequency effects of time were also detected for all variables.

53 0 100 200 300 400 500 600 700 Murray-Darling Basin Commission Narran Ecosystem Project

• Seedlings grown under the non-flooded • Proportionally, plants subjected to the non- conditions (waterlogged, damp and dry flooding treatments and in particular the damp treatments), responded with higher biomasses treatment, allocated����������������������������������� greater biomass to leaves (Fig. 6.66), increased leaf numbers, larger total at the expense of root biomass compared with leaf surface areas and larger surface area per leaf those under the flooded treatments (Fig. 6.68). compared with seedlings subjected to the flooding The proportion of shoot biomass, however, did treatments. No differences in leaf specific area not show a significant difference across the (leaf area/leaf weight) were detected. water treatments. • Independent sediment effects were only detected Trees for one variable, root relative increase in length, although some significant interactions between • Fourteen species of trees were present within sediment and time were detected for the biomass the surveyed tree patches. Of these four species variables (e.g. by the final 6 month harvest plants (Acacia stenophylla, Eucalyptus coolabah, grown in 100% clay had higher total biomasses E. camaldulensis and Eremophila bignoniiflora) than those grown in the sand mix). accounting for greater than 90% of more than 4000 trees surveyed (Fig. 6.69). • Lignum seedlings exposed to flooding did not respond with increased shoot length and no • A. stenophylla occurred in > 70% of surveyed significant differences between the shallow and sites and was the most widely distributed tree deep submergence treatments were detected. followed by Eucalyptus coolabah (coolibah), Relative length increases were generally highest Eremophila bignoniiflora (cooba) and E. in the non-flooding treatments (Fig. 6.67). camaldulensis (river red gum) (Fig. 6.70).

Figure 6.62: Mean height of lignum clumps per Figure 6.64: Relationship between soil moisture site in relation to flood frequency.N .B. The flood and the mean % greenness of lignum clumps at frequency index used here is based on analyses of sites in May 2006. Landsat imagery and indicates number of years 75.0 a site was inundated by the largest annual flood extent from 1972–2004. 50.0 3.0

25.0 % Greenness

2.0 0.0 Height (m) 0 4 8 Number of months wet in 2004 event 1.0 3 7 11 15 19 23 27 Flood frequency

Figure 6.63: Mean perimeter of lignum clumps per Figure 6.65: Relationship between the duration of site in relation to flood frequency.N .B. The flood inundation of sites in the 2004 event and the mean frequency index used here is based on analyses of % greenness of lignum clumps in May 2006. Landsat imagery and indicates number of years a site was inundated by the largest annual flood 75.0 extent from 1972–2004. 50.0 2500

2000 25.0 % Greenness 1500

1000 0.0

Perimeter (mm) 0 5 10 15 500 Soil Moisture 0 3 7 11 15 19 23 27 Flood frequency

54 0 100 200 300 400 500 600 700 6. Key Findings

Figure 6.66: Above ground and root biomass of lignum seedlings across the five watering treatments. Different letters indicate significant differences (Tukey, p = 0.05) in total biomass between treatments at each harvest time. (No significant differences were found between treatments at months 1 and 2.)N ote different scaling of y axis.

Above ground Month 1 Above ground Month 2 0.4 biomass 0.4 biomass

0.2 0.2

0 0

Root biomass Root biomass –0.2 –0.2 DF SF WL DP DRY DF SF WL DP DRY

Above ground Month 4 Above ground Month 6 Dry weight (g) 1.2 b 0.4 biomass biomass bc b bc 0.6 0.2 ac bc ac a a a 0 0

Root biomass Root biomass –0.2 –0.6 DF SF WL DP DRY DF SF WL DP DRY Treatment

Figure 6.67: Relative shoot length increase of lignum seedlings across the five watering treatments. Different letters indicate significant differences (Tukey, p = 0.05) between treatments at each harvest time. (No significant differences were found between treatments at month 1).

Month 1 Month 2 100 100 a a ab b ab a a a b b 80 80 60 60 40 40 20 20 a a a a a a a a b b 0 0 DF SF WL DP DRY DF SF WL DP DRY Month 4 Month 6 100 100 a ab bc cd aa ab abb

Proportion of biomass 80 80 60 60 40 40 20 20 a ac ac bc a ab ab ab b 0 b 0 DF SF WL DP DRY DF SF WL DP DRY Leaf Shoot Root Treatment

55 0 100 200 300 400 500 600 700 Murray-Darling Basin Commission Narran Ecosystem Project

• High mortality of trees was observed amongst states. A higher proportion of mature and pole all common species. 54% of all river red gums, individuals remain healthy but there are still 45% of all river coobas and 38% of all coolibahs significant numbers of dead and stressed trees in surveyed were classed as dead, i.e. no leaves these groups (Fig. 6.72). present (Fig. 6.71). • Similar population structure and trends in • Amongst river red gums, little evidence of recent condition were observed amongst coolibahs recruitment was observed and there was a high although a smaller proportion of mature, percentage of dead (i.e. no leaves) and stressed pole and sapling individual species were dead plants in the seedling and sapling developmental (Fig. 6.73).

Figure 6.68: Proportions of total dry weight of lignum seedlings under the five watering treatments allocated to roots, shoots and leaves. Different letters indicate significant differences (Tukey, p = 0.05) between treatments at each harvest time. No significant differences in shoot allocation were detected. 0.025 0.025 Month 1 Month 2

) 0.02 0.02 –1 b 0.015 0.015 bc day

–1 abc 0.01 0.01 ac 0.005 0.005 a

0 0 DF SF WL DP DRY DF SF WL DP DRY 0.025 0.025 Month 4 Month 6 0.02 0.02 0.015 c 0.015 0.01 bc bc b ab 0.01 ab Relative shoot length increase (cm 0.005 ab a a a 0 0.005 –0.005 0 DF SF WL DP DRY DF SF WL DP DRY Treatment

Figure 6.69: Abundance of species in Narran Figure 6.70: Distribution of most common tree tree patches. species amongst surveyed sites.

1800 80.00

1600 70.00 1400 60.00 1200 50.00 1000 40.00 800

% Sites present 30.00 600 20.00

Number of trees 400 200 10.00 0 0.00 sp. E. coolabah Hakea G. parviflora E. coolabah E. populnea A. stenophylla G. parviflora E. bignoniiflora Other Myoporaceae E. largiflorens Other Acacias A. stenophylla E. bignoniiflora E, camaldulensis E. camaldulensis

56 0 100 200 300 400 500 600 700 6. Key Findings

• Similarly, little successful recent recruitment • Waterbird breeding is very strongly related was recorded for river coobas. In this species, to water in the Narran Ecosystem (Fig. 6.75) however, the highest levels of mortality occurred – analysis of flood hydrographs show that amongst mature individuals (50% of surveyed flood events that resulted in breeding events trees) as opposed to juveniles (43%) or seedlings were typically characterised by an initial flow (32%) (Fig. 6.74). followed by a secondary flow. These second flows following initial flooding events may play a critical 6.3.3 Waterbirds role in extending the duration of flooding and maintaining depths of water at colonial sites. It 6.3.3.1 Waterbird breeding in the Narran has been observed that a rapid decrease in water Ecosystem levels can result in desertion of nests by Straw- • 65 species of waterbirds have been recorded in necked Ibis and Glossy Ibis. Narran Lake and 46 in the Northern Lakes. • The shape of the hydrograph is important – two • Five of these species of waterbirds are listed flood events in 1973, both dual peaked, but were under the NSW Threatened Species Act (1995), small events (< 2000 Ml maximum flow at Wilby at least eight species are of conservation concern Wilby) and no breeding event was recorded. in western NSW and eight wader species are • Flows will be required to fill the Northern Lakes listed under international agreements for and inundate the floodplain. One acts to provide a migratory waders. breeding habitat whilst the other (the floodplain • The Narran Ecosystem is a significant breeding inundation) activates the feeding habitat. Flows site with the largest ibis breeding event in in January/February 2004 (42 416 Ml Wilby Wilby) Australia being recorded in the lakes in 1983. whilst sufficient to fill the Northern Lakes did not The Narran Ecosystem is one of the 12 most initiate breeding because there was no floodplain significant ibis breeding sites in Australia. wetting. An aerial survey on the 9/10 February

Figure 6.71: Tree mortality amongst three most Figure 6.73: Abundance and condition of surveyed common species surveyed. coolibahs in different developmental stages.

2000 800 Healthy Alive 720 Stressed Dead 1500 640 Dead 560 1000 480

Number of trees 400 500 320

Number of trees 240 0 E. camaldulensis E. coolabah A. stenophylla 160 80 0 Mature Pole Sapling Seedling

Figure 6.72: Abundance and condition of surveyed Figure 6.74: Abundance and condition of surveyed river red gums in different developmental stages. river coobas in different developmental stages.

280 Healthy 1200 Healthy Stressed Stressed 240 1080 Dead Dead 200 960 160 840 120 720

Number of trees 80 600 40 480 0 Mature Pole Sapling Seedling Number of trees 360 240 Developmental stage 120 0 Mature Juvenille Seedling

57 0 100 200 300 400 500 600 700 Murray-Darling Basin Commission Narran Ecosystem Project

Figure 6.75 The flow requirements for colonial waterbird breeding in theN arran system.

1400000 Wilby Wilby New Angledool Dirrinbandi Breeding events

1200000

1000000

800000 Breeding threshold = 100,000 ML

Total flow (ML) 600000

400000

200000 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1965 1966 1967 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

Year

2004 did not observe any large numbers of Global climate colonial waterbirds or breeding. Further ground • Waterbird abundance is very strongly related based observations throughout the duration of to the activity of a global climatic cycle known inundation did not find any breeding occurring. as the Madden–Julian Oscillation (MJO) (Fig. • Events that filled the Northern Lakes and 6.77), as quantified by the Real-time Multivariate inundated the floodplain were associated with index of the MJO (the RMM), while exhibiting successful breeding events. no relationship whatsoever with the El Niño Southern Oscillation (ENSO). The MJO is 6.3.3.2 Landscape scale influences on waterbirds understood as a global, equatorial standing in the Narran Ecosystem wave of pressure variability. This wave slowly • Waterbirds have declined precipitously rotates around the equator, enhancing tropical throughout eastern Australia since the start of convection, as well as spawning large-scale the survey in 1983 (Fig. 6.76). Although occasional convective systems that propagate into extra- sightings have been reported from the Narran tropical regions, such as that of Narran. The MJO region within the past few years, compared is known to be particularly important within the with numbers a few decades ago, waterbirds Australian tropics. have effectively disappeared entirely from the region. The causes of these declines must be Regional climate understood in order to prevent further decline • Detailed analyses of the coherence of large-scale towards otherwise imminent extinction of many rain-bearing meteorological systems propagating species. Inter-annual variations in abundance, south-west from the tropical monsoon over however, approach around 60% of the range northern Australia were conducted. This of the overall decline. Any explanations of this coherence measures the extent to which large- decline, and actions to arrest further declines, scale systems maintain the same statistical can only be effective after first understanding structure, or identity, as they propagate across possible causes for such enormous variability. the landscape. Coherence analyses conducted The findings of this section address this latter throughout the entire eastern Australian issue, primarily through explaining the climatic mainland (i.e. all states and Territories except mediation of waterbird abundance throughout Western Australia and Tasmania) were very eastern Australia. strongly related both to the RMM and to inter-

58 0 100 200 300 400 500 600 700 6. Key Findings

annual variations in avian abundance within Hydrology and climate the bird survey region. Explicit descriptions • The primary requirement of migratory waterbirds of such connections have not previously been in inland Australia is for water. The observed demonstrated, even though these coherent relationship with the MJO undoubtedly reflects systems are precisely the kind hypothesised to be a climatic determinant of the amount of water related to the MJO. available within the habitats of waterbirds • The strong inter-relationships between the RMM, (rivers, lakes, and floodplains). These climatic coherence, and bird numbers, provide very firm connections with avian abundance should thus be evidence that the MJO plays a critical role in reflected in similar connections with hydrologic the migration of waterbirds into and throughout measures of available water. The only measure eastern Australia, and that it does so through available with sufficient geographic extent and influencing the coherence of large-scale rain- spatial density was flow volumes through river bearing systems. gauges. Data were collated from a total of 456 stations (96 from Queensland, 317 from New South Wales, and 43 from Victoria, Fig. 6.78). Figure 6.76: Numbers of birds counted each year Aggregate flow volumes were obtained on a in the Eastern Australian Aerial Waterbird Survey daily basis, then converted to mean annual have declined precipitously since 1983. The linear values starting and finishing in mid-October, regression shown corresponds to a decrease of to synchronise with the bird survey. These flow 85% over the years of the survey. Note, however, volumes are similarly strongly related to the that the logarithmic scale implies that this is an RMM, as well as to the local coherence patterns exponential decrease. Spatial coverage of the (Fig. 6.79). The climatic mediation of avian survey is estimated at 10%, thus total population abundance demonstrated in the above section estimates are ten times greater than these figures. is thus likely to be directly equivalent to climatic mediation of the spatially and temporally dynamic availability of water within the broader landscape. 6.0 Birds migrate either with or to these large-scale coherent convective systems, in effect reading (and perhaps flying with or following) large-scale 5.5 synoptic patterns to predict those places likely to have large amounts of water at a given time. (number of birds)

10 5.0 log Figure 6.78: Location of the 456 stations within the MDB used to estimate total daily flow volumes. 1985 1990 1995 2000 2005 Year

Figure 6.77: Bird numbers (shown here after removal of the linear decline of Fig. 6.71) are very strongly related to the RMM (R = –0.7140, p = 0.0002).

–1.0 5.6

–1.2 5.4

–RMM 5.2 –1.4

5.0 Bird counts –1.6 RMM

4.8 log bird numbers (de-trended) 1980 1990 2000 Year

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Hydrology and avian abundance the Condamine-Culgoa systems are even more severe that this larger-scale pattern, having • Having demonstrated climatic associations between avian abundance and hydrology, declined at a somewhat greater rate, resulting this can then be used to provide a residual in the local disappearance of all waterbirds (as dependence of birds upon water not related to measured by counts from the aerial bird survey) natural climatic variability. Doing so produces since the year 2000. a stark relationship (Fig. 6.80), revealing highly • Our technique also requires that, to demonstrate synchronous declines in both volumes of water causality, cumulative lags along all paths and avian abundance. While the decline in water through such a causal web sum (within error volume may not be entirely unrelated to climatic limits) to the same value. Fig. 6.81 reveals that variation, it is at least unrelated to any climatic this is indeed the case for climatic mediation variation that may be considered important from both of flow volumes and avian abundance. the perspective of waterbirds. In other words, The greatest portion of the resultant lags of although other aspects of climate may have around 500 days is that between the MJO and played a role in naturally reducing flow volumes, the observed local manifestations of coherence, and thus have partly contributed to the decline being 465 days, or 466 days between the MJO of Fig. 6.80, the climatic determinants of avian and flow volumes. Very little is understood abundance (Sections (i) and (ii), above) explain about the manifestations or effects of the MJO a major portion of all inter-annual variation in across tropical Australia, let alone into extra- bird numbers, and thus any extraneous climatic tropical regions. This connection with flow, after influence on flow volumes must, from the a lag of around 15 months, provides tantalising perspective of the birds, be considered minor. suggestions for the predictability of flow volumes The decline in flow volumes seen in Fig. 6.80 within the MDB, and the kinds of meteorological is a result of influences not associated with systems that most influence basin-wide flows. climate changes. The most likely explination is • Most of the techniques used in developing this the extraction and regulation of water for human causal web – from the local climatic analyses of activities, including the effects of dams. coherence patterns, to the parameter estimation • Declines in volumes of water flowing through techniques used for lags mediating connections all rivers within the Murray-Darling Basin have between processes – were developed specifically caused the major portion of declines in avian for the Narran Project. The resultant web of abundance, to the point where less than 30 000 causal connection is thus more detailed, and birds have been sighted within the basin over statistically robust, than any previous large-scale the past few years, from previous counts of ecological studies. around half a million per year. Declines within

Figure 6.79: Annual flow volumes, averaged Oct– Figure 6.80: After accounting for climatic Sept, are very strongly related to the coherence dependence of both bird numbers and flow analyses described above (R = 0.5873, p = 0.0002), volumes, time series of both throughout the as well as to the RMM (now shown, R = –0.4746, years of the bird survey reveal a very pronounced p = 0.019). synchrony of decline (R = 0.5234, p = 0.013).

Flow Coherence

6.0 5.5 6.0 5.9

5.0 5.8 5.8 (number of birds)

10 5.7 (flow volume in ML/day) (flow volume in ML/day)

log Birds

10 4.5 10 Flow 5.6 log

5.6 log

1970 1980 1990 2000 1985 1995 Year Year

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Figure 6.81 Causal web relating the MJO, via the index of the RMM, to the coherence of large-scale convective systems across eastern Australia, to volumes of flow within the Murray-Darling Basin, and to the abundance of migratory waterbirds. All connections are considered to be directly causal, and aggregate lags along the four possible paths sum to within aggregate error bounds.

r = –0.61 (p = 0.002)

r = –0.44 r = 0.70 (p = 0.021) (p = 0.0002) RMM Coherence Birds

r = 0.59 (p = 0.0002) r = 0.52 (p = 0.013) r = 0.48 Flow (p = 0.020)

Direction 465 ± 66 465 ± 66 25 ± 62 466 ± 61 75 ± 29 13 ± 108 13 ± 108 Final lag (days) 478 ± 162 540 ± 95 503 ± 236 479 ± 169

6.4 Conceptual model this wetland complex for the recruitment of ibises, along with other species of waterbirds, within Conceptual models are normally designed for a the greater landscape. Reflecting this singular particular context and the concepts need to be importance, the focus of the present conceptual directed towards an aim to have meaning. In this model is on requirements for a successful cycle of section, a conceptual model of the functioning of breeding, dispersal, and return to the site – referred the Narran Ecosystem is described. The focus has to here as a cycle of recruitment. The primary been chosen as the most spatially and temporally question addressed through this conceptual model integrative component of the Narran Ecosystem, is, How does the Narran Ecosystem facilitate that being the requirements of migratory waterbirds successful recruitment of ibises? However, the to successfully utilise the lakes to complete a cycle model has also been developed to address a more of breeding, dispersal, and return to the site. The specific issue, that of the design of a monitoring system of four major lakes interspersed with an program to establish the importance for recruitment extensive network of hydraulic channels supports of ibises of (changes within) the Narran Ecosystem. very large numbers of breeding waterbirds, and The term monitoring is used here in a very general hosted the country’s largest recorded ibis breeding sense, for, although it will require much on-going, event in 1983. The lakes are one of the 12 most active monitoring, it will also require access to, significant ibis breeding sites in Australia, and and collation of, a wealth of pre-existing data, as were listed in 1999 as a Wetland of International described below. These questions necessitate a Importance under the Ramsar Convention on wide range of scales, particularly because the Wetlands. All three species of ibis that inhabit interaction with, and utilisation of, a landscape by Australia utilise the wetlands – the very common and migratory birds is fundamentally different to that abundant Australian white ibis (Threkiornis molucca); of flightless animals. The vastly greater distances the straw-necked ibis (Threskiornis spinicollis); and able to be traversed by birds than by land-bound the glossy ibis (Plegadis falcinellus). Although many animals (or, equivalent, the vastly lower energetic other waterbirds of regional and national significance costs in covering similar distances) demand that breed within the wetlands, the conceptual model the model encompass the broadest scales over presented here focuses on the three ibis species, which they might travel. The spatial scale here must which intermix at the breeding site. encompass a large part of the eastern half of the The recognition of Narran Lakes within the Ramsar Australian continent. In contrast to this broadest Convention expresses the singular importance of scale, the ecological needs of waterbirds may be

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generally similar to those of other flightless animals species of ibises may themselves be influenced by across some narrower temporal or spatial range, their own, much smaller scale, food species. Without e.g. through utilisation of shared food resources explicitly quantifying lower limits in time or space, that respond almost exclusively to very localised their notional existence will be taken as granted determinants. throughout to include only direct influences, while excluding (relatively indirect) influences of those To incorporate this enormous range of scales, influences, etc. the conceptual model has been developed within an explicitly hierarchical framework. Relative In contrast, the upper limits of constraint upon the advantages of this hierarchical approach, compared focal level may be clearly quantified. In spatial terms, with a more traditional concept-mapping approach, ibises within eastern Australia are generally thought are discussed following descriptions of the model to migrate within the eastern Australian landmass itself. The focal level encompasses the ranges of (with perhaps some movement within nearby time and space required or utilised by ibises during northern islands), and so the upper level excludes a successful cycle of recruitment. The higher level the greater continental and Asian areas, and is here that acts to constrain processes at this focal level taken as ~5000 km. An upper temporal limit will be encompasses the entire spatial scale of eastern in the order of a few thousand years, within which Australia within which ibis migration occurs, and time span all current migratory patterns and habits the temporal scale over which the general ecology will have been established. For convenience, this will of ibises has evolved. The lower level describing be taken as 1000 years. These scales of hierarchy are influences on focal level concerns all processes shown in Table 6.8. that are spatially heterogeneous within the Narran Although the conceptual model is designed to Ecosystem, over all time scales less than a single examine the recruitment of ibises, and will thus recruitment cycle. This lower level encapsulates have a primarily ecological focus, the existence and the kinds of influences that might be considered functioning of large, episodic wetland complexes like within a typical ecological field study or experimental Narran Ecosystem is influenced and constrained by procedure, including variation in all resources both hydrological and physical factors. The model directly utilised during breeding. will consider these three factors – ecological, These spatial and temporal ranges may be hydrological, and physical, at all three scales. Each quantified, although the values derived here will act factor will be given separate consideration initially, primarily as guides in conceiving of relationships with possible relationships between the three within and between the levels of this hierarchy. considered later. This itself will be approached from The shortest temporal scale is that of an entire a hierarchical perspective, via the general notion recruitment cycle, i.e. 2 years, while the longest of the precedence of physical factors constraining encompasses the combined, ���������������������life span of a single hydrological factors, which in turn constrain parent and offspring, and is here taken as 50 years. ecological factors – although many exceptions to The Narran Ecosystem covers a relatively narrow this are noted. The considerations below follow the longitudinal range of around 10 km while extending same order. In all three cases, important aspects of for slightly less than 100 km latitudinally. However, those factors will be established at the focal level during a successful cycle of recruitment, all birds first, followed by the lower level of influences and disperse from the Ecosystem, and return during the upper level of constraints. This identification of next wetting event for subsequent breeding. The important factors is equivalent to the identification upper spatial limit must encompass range of this of factors exhibiting or reflecting high degrees of dispersal and return, and is therefore taken as ~1000 km. (Note that different species of ibis have different migratory patterns, particularly in that the glossy ibis predominantly inhabits the northern parts of the Table 6.8 Temporal and spatial scales that define continent, and thus migrates southward towards the the three levels of the hierarchical model. Ecosystem, while the other two species are more widespread, and may migrate from a much greater Hierarchical Physical scale Temporal scale range of directions.) level (km) (y) L + 1 1000–5000 km 50–1000 For the present purposes, quantitative limits on the lower hierarchical level can simply be defined L 10– 000 2–50 by these upper limits, as < 10 km and < 2 years, L – 1 <10 <2 although there may be some lower limit below which influences become negligible. For example, the food L = Level of organisation or scale

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heterogeneity within those scales. While much is Apart from these morphological characteristics, a known or suspected regarding the ecology of ibises, host of������������������������������������������� soil-geochemical processes may determine undoubtedly much more remains unknown. The aspects of the Narran Ecosystem that influence following descriptions of influences and constraints ibis recruitment. By far the greater portion of such incidentally represent a general summary of influences however will be indirect, for example, knowledge, and lack thereof, of ibises in Australia, through influencing availability and distributions particularly with regard to breeding. All factors of species required or desired for food and shelter. described below, and their hierarchical relationships, As described above, these influences of influences are summarised within Table 6.9. are explicitly excluded from this model. Perhaps the only geochemical processes directly influencing 6.4.1. Physical factors ibis recruitment are those determining such things as acidity and salinity, within both soil and water. Focal level However, these are expected to be of far less importance than the above morphological aspects. Heterogeneity in physical factors at the focal spatial scale is predominantly morphological. The primary Lower level of influences aspect of morphology is the actual structure that defines the lakes, but the heterogeneity within With morphology being identified as the most that structure is likely to be important, given the important physical attribute at this level, all diverse ecological requirements of ibises (cf. below). processes influencing morphology over shorter Core samples reveal the three main lakes to have times and smaller scales are encapsulated formed once only, and to have remained as episodic under general notions of erosion and deposition. lakes until the present. In contrast, the network These are particularly important influences on of channels connecting the lakes and otherwise the morphological characteristics of the channel occupying the remainder of the wetland area is network, while probably less important on the highly dynamic, and has changed substantially lakes themselves (over these shorter scales). over the past thirty years. The rates of change Their importance is further enhanced through the in morphology that accompany both the change contribution of farming practices in the upstream in channel morphology, and the apparent lack catchment basin to the transport of sedimentary of change in main lake morphology, will also be material into the ecosystem. The last decade or presumed to be important factors. two have seen rapid and extensive development of

Table 6.9: Factors identified as important within the three categories at the three scales quantified in Table 6.8.

Hierarchical Level Physical factors Hydrological factors Ecological factors L+ 1 • Topography – both Asynchronous behaviour: • P/A* of food species distribution and • Temporal scale • P/A of appropriate structures for diversity • Spatial scale breeding, including comparison of • Geology Relative uniqueness lignum with other species • Weather and climate • P/A of predators • Evolutionary ecology of ibises L Morphology: Central tendencies and • Population dynamics of food species • Structure distributions • Population dynamics of lignum and • Heterogeneity of multiple events: other structures • Rate of Change • Period • Population dynamics of predators (Soil geochemistry?) • Duration • Population dynamics of ibises, • Magnitude including intra- and inter-specific • Timing competition L – 1 Processes of deposition Attributes of single events: • Local abundance of food species and erosion • Duration • Life history response of lignum • Magnitude • Season • Distribution • Antecedent conditions

* P/A = Presence/Asence.

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large areas of the upstream land, much of which as the period of repetition, the timing of events has been converted to large-scale cotton farms, and (i.e. the seasonality), and the average duration and so changes in (rates of) erosion and deposition are magnitude. Success in ibis recruitment may depend expected to be particularly significant for the near upon some central tendency in any or all of these future of the Narran Ecosystem. parameters, or it may depend upon the ways these attributes are distributed – and perhaps in ways not Because geochemical processes are considered captured in simple measures of variance. These a distant second to the morphological at the focal hydrological factors will be much more likely to level, lower-level influences upon them are not change over shorter time scales than most of the considered here. physical factors described above, and so, for the Upper level of influences purposes of a monitoring programme, will need to be monitored at a correspondingly finer resolution. The primary upper-level constraint upon morphology is topography. Again, reflecting the importance Lower level of influences of both overall state and internal heterogeneity, The major hydrological properties that vary over both the distribution and diversity of topography temporal scales of less than two years, and physical are included. At the same level, the geology of the scales of less than the entire extent of the Narran Australian landmass will also be related to, and Ecosystem, are those reflecting the characteristics reflect, these aspects, as well as the less-important of individual wetting events. These include several geochemical aspects. readily identifiable properties similar to those at An entirely separate aspect that is included here the focal level, namely the season of occurrence as a physical factor concerns prevailing weather of a single event, and its duration, magnitude, and climate regimen. The Narran Ecosystem is and distribution within the local area. A separate situated at the approximate southern limit of the influence at this scale concerns the conditions monsoonal wind and rain belt that prevails across antecedent to a wetting event. For example, non- northern Australia during the flooding season filling rain events may (partially) pre-determine (around December–March). At the same time of any of the above properties prior to a subsequent year, large high-pressure systems generally lie over filling event. In terms of a monitoring programme, the southern expanse of the landmass, bringing there is an unavoidable degree of overlap between steady easterly winds onto much of the eastern these factors and those at the focal level, although coast. These easterly winds extend several hundred this may or may not reflect overlap in ecological kilometres inland, and thus the Narran Ecosystem functioning. The distribution, magnitude, and season lies within a zone of convergence between these will aggregate to form the values at the focal level, onshore easterlies, and the monsoonal north- yet successful breeding within a single event may westerly winds. Birds migrating from anywhere east, reflect nothing other than one particular magnitude, north, or north-west of the Narran Ecosystem will duration, distribution, or combination thereof, and be highly likely to be able to ride very favourable thus not be relatable in any way to central tendencies winds to the Ecosystem, and these physical factors or distributions of these parameters. Nevertheless, certainly need to be considered as a constraint upon these aspects of single events are placed at the the overall utility of Narran for ibis recruitment. In lower level here because the focus is on recruitment, this case, weather and climate are a constraint to which has been defined as more than a single migrating waterbirds especially over longer fight breeding event, and thus the focal level must distances. For example, birds migrating from the concern aggregates of these finer-scale properties north are highly likely to be able to follow rain- – even if the only desirable aggregation for birds is bearing weather patterns southwards, monitoring approximate repetition of very particular conditions flooding patterns as they travel towards the Narran unrelated to any central tendencies or distributions. Ecosystem. Interupted weather patterns resulted in One of the tasks of a monitoring programme failure to cover long distances. will be to determine the general or particular hydrological properties, at the respective focal and 6.4.2 Hydrological factors lower levels, most strongly related to successful recruitment. This is perhaps the only point within Focal level the conceptual model where there is uncertainty in The temporal scale of the focal level, being the appropriateness of the focal scale. In spite of 2–50 years, is longer than the duration of any this, the initial definition of the model in Table 6.8 typical wetting event, and thus encompasses the reflects an assumption that aggregate hydrological hydrological attributes of multiple events. Several properties are likely to be of greater importance than important attributes may be readily identified, such particular properties of individual events.

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Upper level of influences over which counts are averaged, although these data were collected at a relatively coarse scale (minimal At the upper spatial scale, a particularly important resolutions of hundreds of kilometres), and so are question is, To what extent are the properties of unsuitable for examining the possibilities of finer- Narran general within the landscape, so that its scaled anti-correlations of a similar nature. utility may be revealed through landscape-scale considerations? The obvious question is, To what extent is the Narran Ecosystem representative 6.4.3 Ecological factors of specific properties unable to be (accurately or readily) considered at the landscape scale? If the Focal level Narran Ecosystem is entirely and distinctively The temporal scale of the focal level, between 2 and unique, this places an absolute constraint upon their 50 years, explicitly reflects the decision to focus importance for ibis recruitment, in that they must ecological questions upon the population dynamics consequently be seen as absolutely irreplaceable. of ibises. The upper limit lies at or beyond two These two questions are certainly applicable to all average ibis lifespans (17 years), and thus this focal three categories of factors considered here, although level should encompass all major frequencies of they are perhaps more pertinent with regard to variation within a population. In other words, any hydrological and ecological characteristics than single population will be entirely replaced within to physical characteristics. In fact, the physical this time range, and thus any changes in factors characteristics described above are highly unlikely directly influencing recruitment will be captured to reflect properties unique to the Narran Ecosystem in population changes observed within this same at the upper level of spatial influence. Certainly, range. Within the physical scale of the Narran some of the ecological characteristics of the Narran Ecosystem, population dynamics include such things Ecosystem described below may be unique within as intra- and inter-specific competition for food, the larger landscape scale, yet many of them may nesting, and other resources. Ibises are always likely not be. Within the present domain, the question observed to return to exactly the same nesting area, of hydrological uniqueness remains particularly near the northern tip of Clear Lake. At this site, all important, and demanding of consideration within a nesting occurs on top of lignum clumps; all feeding monitoring programme. occurs on dry land slightly outside the border of the Lakes Ecosystem; and roosting occurs both A separate issue from that of relative uniqueness day and night in nearby trees (which are almost arises from the finding that wetlands within the exclusively Eucalyptus species), both alive and greater eastern Australian landmass may exhibit dead. Those things necessary for ibis recruitment, asynchrony in filling over distinct temporal and and thus important to include within a monitoring spatial scales. (Note that the present authors can programme, include all of the above. find no convenient alternative than the strictly meaningless reference to spatial asynchrony, Again, the time scale of the focal level is such that whose meaning we trust is still abundantly clear.) all major frequencies of variation in population Where one wetland is dry at one time, another dynamics of all competitors, food species, and adjacent wetland may be more likely to be wet. The nesting structures, will be captured. The full meaning of adjacent can only be gauged through spectrum of population variation in species of spatially explicit analyses of wetland inundation roosting trees is likely not to be captured, because patterns. Temporal asynchrony may occur entirely these are generally long-lived eucalypts, but as their independently of spatial asynchrony, in that a role is almost certainly expressed in a single aspect particular wetland that is full one particular year (or of mere presence, this is unlikely to greatly reduce other appropriate time period) may be less likely to the accuracy of the model. be full the following year (or time period). And there may of course be some kind of interaction between Given the large range of the continent inhabited by spatial and temporal asynchrony. These notions of ibises, they obviously do not depend upon specific the importance of asynchrony are in fact reflected food species. Nevertheless, their requirements in patterns of waterbird abundance across eastern for food may be rather particular, and information Australia, through a very significant anti-correlation will be needed on the distribution of potential in a roughly north-south direction: in any one year, food species������������������������������������������� within the large landscape, as well a higher abundance of birds (relative to the total as variations in life history response over these number seen for that year) in either the north or scales. It seems possible that the nesting site at south is likely to reflect a lower abundance in the Narran offers an optimal combination of extensive, contrasting section (i.e. south or north). The strength concentrated breeding sites, proximity to water and of anti-correlation increases with������������������� ������������������the spatial extent roosting sites, and proximity to adjacent drylands

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for feeding. Thus, the spatial configuration of and as these clumps provide the exclusive nesting these aspects will need to be examined, along substrate for ibises, the importance of this pattern of with estimates of the same for as many wetland growth and dormancy for the construction and utility complexes within the larger landscape. of ibis nests needs to be understood.

One factor likely to further influence ibis recruitment Very little is known about selection of food species at the focal level is the presence, abundance, and by ibises, other than that they preferentially forage in behaviour of predators. Successful breeding of an area immediately adjacent to, but slightly outside ibises requires water levels directly below the of, the actual wetland area of the Narran Ecosystem. lignum clumps to exceed a certain minimal level The sheer mass of food necessary to support a large throughout the entire breeding cycle. This effectively colony of breeding ibises is unlikely to be met by negates any impact of terrestrial predators, such species perpetually present in the adjacent drylands, as the feral pigs common throughout the area. and it seems highly likely that the ibises feed on The major predators are almost certainly airborne terrestrial species exhibiting a strong response to raptors, for which all of the above comments wetting events. Identification of food species will be regarding time scales of population dynamics necessary, as well as some understanding of their apply. However, mere measures of presence and life history response to wetting events. abundance of raptor species are likely sufficient to Although there may be significant heterogeneity capture the importance of airborne predators for in the behaviour of raptors within these scales, for ibis recruitment. Potential predators of secondary example, through raptors preferentially nesting in importance include snakes, but whether snakes even the same structures that the ibises use for roosting, consume the eggs of ibises within the Ecosystem this variation is unlikely to add a great deal above remains unknown, let alone within the scope of and beyond the mere presence described above. any practical monitoring programme. Incidental or anecdotal observations of such behaviour may the Upper level of influences best one could hope for in addressing this issue. Ecological questions at the upper spatial and Some of the most important ecological factors temporal levels primarily concern evolutionary determining the success of ibis recruitment lie processes leading to the presence of all of the above outside the above considerations, namely those factors within the eastern Australian landscape. determining and describing all dynamics of ibis Specifically, this includes understanding of the populations at all other places away from the evolutionary ecology of ibises, of their predators, Narran Ecosystem. Explicit collection of data on ibis their food species, and those species required populations across the entirety of eastern Australia for breeding. These questions, however, must be is obviously an impractically enormous task, and situated within the scale of the larger landscape, furthermore one with an inherently large degree of requiring very broad-scaled comparisons of the redundancy. Much data already exists on waterbirds presences (or absences) of all of these factors, throughout Australia, and incorporating this major as well as interactions among these factors. As aspect of population dynamics may be as simple mentioned above, ibises are certainly capable of as the logistical task of negotiating access to pre- breeding with the (semi-)permanent waterbodies existing data in an attempt to build as comprehensive nearer to the coast where they spend the remainder a model as possible of population dynamics within of their times. The distant Narran Ecosystem lies the greater landscape. far inland, and their use demands long migratory journeys for most birds. The high expenditures of Lower Level of Influences energy during migration must reflect a relative For the factors described above, perhaps the only unsuitability of their non-breeding habitat for ones that may exhibit significant heterogeneity breeding in comparison to Narran Lakes. All acts of within the temporal and spatial scales of the lower migration reflect compromises between competing level (<2 years, <10 km) would be food species and and conflicting factors. Examination of the above lignum. Lignum growth and clump morphology are kinds of ecological factors at this scale should determined by hydrological attributes within the include comparison of lignum with other shrubs and temporal and spatial scales of the focal level. Dead bushes that may otherwise provide suitable nest growth contributes to the tangled structure of the sites within the larger landscape, and comparison bush, providing the environment within which the of (the availability of) potential food species, and next new growth event will be contained. This life the presence of potential predators, as well as the history cycle of a typical lignum clump certainly particular spatial configurations of these aspects, as occurs within the time period of the lower level, mentioned above.

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To return to the question posed above in and their corresponding future states, and consideration of hydrological factors at the same hydrological characteristics. A monitoring scale, To what extent are the properties of the programme should therefore be designed to Narran Ecosystem generally within the landscape, explicitly accommodate the possibility of interactions so that its utility may be revealed through landscape- between rates of change in morphological scale considerations? All of the above factors characteristics and all hydrological characteristics, – physical, hydrological, and ecological – obviously at least over the temporal scale of the focal level have the potential to interact in complex ways at all within Narran Ecosystem itself. Examining these scales. The strength and nature of these interactions kinds of interactions over a broader spatial scale will shape any answer to this question. The following may be impractical, and far less important than section speculates on the likely importance of a understanding the same interactions at the number of these interactions, providing guidance Ecosystem themselves. for issues considered important in the design of a The population dynamics of lignum within the monitoring programme. Ecosystem are certainly constrained and influenced Table 2 summarises the three categories of factors by morphological characteristics. The clumps only described thus far at the three scales of interest. grow within areas of very dense channel topography, Interactions across hierarchical levels are discussed and many of these areas are subject to rapid and in the following sections. Interactions between dramatic morphological and hydrological change. factors across different hierarchical levels are not As mentioned above however, within the channel considered. networks, hydrology almost certainly drives change in morphology, with little effect in the other direction. 6.4.4 Interactions among physical, Accordingly, a monitoring programme should focus hydrological, and ecological factors on directional interaction between characteristics of hydrology and the population dynamics of lignum. As mentioned above, a general hypothesis when considering interactions among the three factors Physical or hydrological factors are vastly less likely is that physical factors precede and constrain to directly constrain or influence any of the other hydrological factors, which in turn precede and ecological factors given in Table 6.9. constrain ecological factors. This will be presumed to occur at all three hierarchical levels described in Table 6.10: Fact sheets produced for Narran the following, although a number of exceptions to ecosystem project this scheme are noted. The interaction described in the following are summarised in Table 6.10. 1. The Narran ecosystem 2. Oral history Focal Level 3. Landuse in Narran Physical morphology obviously constrains hydrology 4. Physical features at all levels, and, at the same time, it is the hydraulic 5. Geomorphology processes themselves that largely determine 6. Environmental history physical morphology at this spatial scale. Within the 7. Narran and the regional Wetlands: use of larger lakes, morphology almost entirely constrains radiometric data hydrology, with little interaction in the other 8. Soils direction. Outside the lakes and within the channel networks, hydrology almost entirely determines and 9. Hydrology – wetting and drying constrains morphology (mediated perhaps through 10. Hydrology – nolumes such things as variation in soil types, and of course 11. Hydrology – modelling elevation), again with relatively little interaction in 12. Vegetation index and floro-geomorphic regions the other direction. In both cases however, these 13. Vegetation – trees interactions will be primarily immediate and direct, 14. Vegetation – lignum such that the hydrological factors entirely reflect their physical constraints (in the lakes) or vice 15. Vegetation – groundcover versa (in the channel networks), and interaction 16. Zoned vegetation communities between the two is implicit in the distinction between 17. Zooplankton these two categories. One interaction that may 18. Fish nevertheless be unpredictable through separate 19. Waterbirds consideration of the two categories is that between 20. Waterbirds in the Murray-Darling basin rates of change in morphological characteristics,

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Lower level of influences 6.5 Knowledge exchange The physical processes of erosion and deposition Knowledge Exchange (KE) and science certainly both influence and constrain all communication is a process of linking science with hydrological processes, and yet the same physical natural resource managers and local communities. processes are entirely driven by hydrology. It is an inclusive two-way process designed to Any details regarding these complex, two-way encourage successful scientific outcomes along interactions would certainly enhance understanding with community ownership of these as well as the of the overall functioning of the Narran Ecosystem inclusion of local knowledge. for ibis recruitment, and thus should be considered within a monitoring programme. Three types of Knowledge Exchange activities occurred for the Narran Ecosystem Project and Interactions between both physical and hydrological these have focused on community, industry and factors and the ecological factors are likely to scientific audiences. The detail of these activities is reflect the above considerations at the focal level, provided below. in primarily being upon the life history response of lignum, while having negligible impact upon other ecological factors. Nevertheless, these 6.5.1 Community and industry fact sheets fine-scaled interactions between such factors as Twenty fact sheets have been written and widely deposition or erosion and the life history responses distributed through various community groups and of lignum are likely to be far less important than federal and state natural resource management coarser responses between overall morphological departments. The fact sheets provide specific detail change and population dynamics at the level above. on a range of topics (table 6.10). Therefore, it is recommended that these interactions be ignored at this level. 6.5.2 Oral history Upper level of influences ‘Changing channels: Life on the Narran’

All manner of interactions may play very significant An edited volume combining the knowledge of local roles at the broadest spatial and temporal scales. community members linked to the Narran regional Overall topography and geology would certainly and that derived from the Narran Ecosystem Project constrain hydrology, but given the extraordinary has been produced. The oral histories of twenty local flatness of most of inland Australia, this constraint Narran River residents were taken in 2004. These will not be particularly significant for the present were then transcribed and their memories arranged concerns. Far more significant are likely to be into chapters for a book. Within each chapter, a the interactions between the weather and the section of scientific relevance has been added with asynchronicity of hydrological behaviour across graphs and figures as required. The science has broad spatial and temporal scales. been written in such a way to be understandable Interactions between both physical and hydrological to people without a scientific background, without factors and ecological factors are certainly likely to losing its message. The Narran Ecosystem and it be very strong and enormously complex at these residents form a complex interaction. This book broader scales. Since these interactions are those has attempted to incorporate as many components that have evolutionarily determined the ecology of of that interaction as was possible, making it a ibises, lignum, food species, predators, etc., they comprehensive and very readable document. may well lie beyond the scope of any practical The list of contributors include: monitoring programme. Any attempts simply to understand the evolutionary ecology of these (groups Ross Slack-smith, Ted Fields senior, Rory and Joan of) species would be a significant first step, and Treweeke, Michael Treweeke, Allan Hall, Elizabeth should certainly provide sufficient information for a Wallace, Robert and Anne Senior, Barry and Ruth comprehensively informed first draft of a conceptual Tibbey, Helen and Rick Hall, David Gleeson, Tim model, without need for understanding dynamic Remond, Donald and Pam Crothers, Henry and processes leading to that ecological state. Robyn Crothers and Kate Bucknell. The table of contents for the Narran book – ‘Changing channels: Life on the Narran’ is provided below.

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Introducing the Narran residents Adams J., Tyson D. (2004). Local knowledge of the 1. Introduction: The Narran Lakes Narran Lakes: Oral history as a line of evidence 2. The Narran: The physical environment in ecological understanding. Proceedings of the 3. People and the river 4th Australian Stream Management Conference: linking rivers to landscapes. Department of Primary 4. Plant life Industries, Water and the Environment, Hobart, 5. Fish Tasmania. 6. Birds 7. Other animals Murray O., Rayburg S., Thoms M., Neave M. (2004). Variations of wetland patch characteristics 8. Introduced plants and animals under different inundation levels using remotely 9. Floods and flows sensed data: preliminary results from the Narran 10. Water resource development Lakes, NSW. Proceedings of the 4th Australian 11. To the future Stream Management Conference: linking rivers to landscapes. Department of Primary Industries, 6.5.3 Newsletters Water and the Environment, Hobart, Tasmania. Newsletters have been prepared since the beginning Rayburg S., Neave M., Thoms M., Mesley E. of the project, with the first being produced 29 May, (2004). A preliminary investigation into the 2003 and the last on 11 November, 2006. They are influence of changing stream network patterns available on the Narran Ecosystem Project website. on the distribution of water in the Narran Lakes Eleven have been produced in total. Ecosystem. Proceedings of the 4th Australian Stream Management Conference: linking rivers Western Division Newsletter, February 2005. to landscapes. Department of Primary Industries, ‘Management benefits intended from study of Water and the Environment, Hobart, Tasmania. Narran’. [www.agric.nsw.gov.au/reader/wdn] Written by Ann Milligan. Thoms M.C. (2003). Floodplain-river ecosystems: lateral connections and the implications of human interference. Geomorphology 56: 335–349. 6.5.4 Scientific papers Thoms M.C., Parsons M. (2003). Identifying spatial Published and temporal patterns in the hydrological character Cossart R., Thoms M. & Rayburg S. (2006). The in the Condamine-Balonne River, Australia, using infilling of a terminal flood plain-wetland complex. multivariate statistics. River Research & Applications International Association of Hydrological Sciences, 19: 443–457. 306: 389–398. Ogden R.W., Thoms M.C., Levings P.L , (2002). Murray O., Thoms M. & Rayburg S. (2006). The Nutrient limitation of plant growth on the floodplain diversity of inundated areas in semiarid flood of the Narran River, Australia: growth experiments plain ecosystems. International Association of and a pilot soil survey. Hydrobiologia 489: 277–285. Hydrological Sciences, 306: 277–286. Sheldon F., Thoms M.C., Berry O., Puckridge J. Rayburg S., Thoms M. & Lenon E. (2006). Unravelling (2000). Using disaster to prevent catastrophe: the physical template of a terminal flood plain- referencing the impacts of flow changes in large wetland sediment storage system. International dryland rivers. Regulated Rivers: Research and Association of Hydrological Sciences, 306: 304–313. Management 16: 403–420. Webb M., Reid M. Capon S., Thoms M., Rayburg S. and James C. (2006). Are flood plain wet-land plant In preparation or planned communities determined by seed bank composition or inundation periods? International Association of James, C., Capon, S et al. Growth and biomass Hydrological Sciences, 306: 241–248. allocation of Muehlenbeckia florulenta seedlings in relation to water level, sediment type and ontogeny. James C., Capon S., White M., Rayburg S. and Thoms (Paper in preparation – close to completion.) M. (2006). Spatial variability of the soil seed bank in a heterogeneous ephemeral wetland system in semi- James, C., M. Thoms and G. Quinn. Zooplankton arid Australia. Plant Ecology, 190, 205–217. dynamics from wetting to drying in a complex ephemeral floodplain wetland. (Paper in preparation Thoms, M., Rayburg S., Murray, O., Capon S., James – close to completion.) C., (2005). The wetting and drying of a floodplain wetland. Riprap 29, 20–21.

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Capon, S.J., James, C.S. et al. Environmental Other written outputs heterogeneity and vegetation diversity in a large Cassandra James and Samantha Capon – Provision terminal wetland system. (Paper in preparation.) of plant specimens to National Herbarium of New James, C., S. Capon et al. Plant interactions South Wales. in a semi-arid ephemeral wetland. (Paper in Cassandra James – Advice to L. Smith and D. preparation.) Nielsen at the Murray Darling Freshwater Research Capon, S.J., James, C.S. et al. Effects of flood pulse Centre on floodplain vegetation for Lower Balonne characteristics on plant community development from Scoping Report. the soil seed banks of a large heterogeneous wetland Samantha Capon – NSW Scientific Advisory in semi-arid Australia. (Paper in preparation.) Committee – invited submission on status of Capon, S.J., James, C.S. et al. Factors influencing coolibah / blackbox woodlands in northern basin, the character and condition of tree patches in the January 2007. Narran Lakes Ramsar site. (Paper planned.) Samantha Capon – John Duggin, UNE – information Capon, S.J., James, C.S. et al. Relationships between about distribution and abundance of lippia for recent and long-term flood history on lignum research project, late 2006. shrubland characteristics in a large semi-arid Samantha Capon – Margaret Brock and Daryl wetland. (Paper planned.) Nielsen – water quality data, 2005 . M. Webb – The influence of inundation period on development and productivity of flood plain-wetland Other papers plant communities. (Paper in preparation.) Narran Lakes Scoping Study part 1 and 2 (August 2002) Ecological summary of work planned (2003). Rayburg, S. Thoms, M., In review. Channel network characteristics of anastomising distributary river systems: methods and field evaluation. Water 6.5.5 Community presentations Resources Research, submitted November 2006. • Lower Balonne Community Reference Group Padgham M., Thoms M., (2007). Large-scale, 30 May, 2003 coherent rainfall systems, the Madden-Julian • Lower Balonne Area Community Reference Oscillation, and flow volumes in Australia’s Murray- Group meeting 1 May 2003 Darling Basin, to be submitted to the Proceedings of • Lower Balonne CRG meeting 30 May 2003 the National Academy of Sciences of the U.S.A. • Lower Balonne CRG meeting 3 July 2003 Padgham M., Thoms M., (2007). A protocol for • Narran Community Reference Panel 8 relating global-scale climatic variation to localised September 2003 ecological responses, to be submitted to the Proceedings of the National Academy of Sciences of • Narran Community Reference Panel 16 the U.S.A. September, 2004 • Narran Community Reference Panel meeting, Padgham M., Thoms M., (2007). A robust statistical East Mullane, May 2005 technique for determining climatic causation, to be submitted to the Journal of Ecology. • Narran Community Reference Panel meeting Lightning Ridge June 2006 Padgham M., Thoms M., (2007). The decline of • Narran Community Reference Panel meeting waterbirds, the decline of river flows, and the Nov 06.doc changing climate of eastern Australia, to be submitted to Global Change Biology. • Narran Ecosystem Community field days • May 5 2005 held at East Mullane. Talks provided Padgham M., Thoms M., (2007). The Madden-Julian on the day include: Oscillation as the most important climatic cycle for inter-annual variation in river flows in Australia’s – Channel Network Murray-Darling Basin, to be submitted to Journal of – Environmental History Climatology. – Fish Communities – Hydrology – Narran Ecology overview – Narran Mesocosm Experiment

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– Narran Zooplankton Regional groups – Remote Sensing and GIS • Lower Balonne Ministerial Advisory Committee – Vegetation April 2006 – Waterbirds • NSW Regional Advisory Committee at Narran Lake Nature Reserve, 16–17 February, 2007. • 31 May 1 June 2006 (presented at the Lightning (meeting of DEC – The Riverbank Program, Ridge Bowling Club) Western CMA conservation and water – Environmental History management programs, Cultural Heritage, – Remote Sensing NPWS) – Soils Project Steering Committee meetings – Waterbirds • 29 June 2005 – Zooplankton • 28 April 2006 • 29 November 2006 (presented at the Lightning • 6 October 2006 Ridge Bowling Club + a bus trip to the Lakes with approx 25 people in attendance): 6.5.7 Scientific presentations and – Birds of the region conferences – Bird overview Australian Society for Limnology, University of – �nowledge Exchange Adelaide, 2004 – Hydrology Diversity in ephemeral wetland systems – a spatial – Vegetation ecology study in North-West NSW, Australia – Cassandra James and Melissa White.

6.5.6 Industry presentations Local knowledge as a line of evidence in understanding dryland aquatic ecosystems – Janey Federal Adams. • National Water Commission April 2006 • Department of Environment and Heritage April Australian Society for Limnology, Hobart, 2006 November 2005 • Murray Darling Basin Commission May 2006 Are floodplain-wetland plant communities determined by seed bank composition or inundation • Murray Darling Basin Commission Natural periods? Munique Webb. Resources Committee November 2006 • Murray Darling Ministerial Council December The physical diversity of inundated areas in 2006 floodplain ecosystems – Orla Murray.

State Departments Australian Society for Limnology, Albury- Wodonga, September 2006 • NSW Dept. Natural Resources June 2006 Diversity and Dynamics of vegetation in a dryland • NSW Dept. of Environment and Conservation floodplain wetland – Cassandra James. June 2006 Physical complexity in floodplain wetlands – Scott • Queensland Dept of Natural Resources and Rayburg. Mines February 2006 • Queensland Dept of Natural Resources and The changing complexity of floodplain wetland Mines October 2006 ecosystems – an example of the Narran Ecosystem – Martin Thoms • Queensland Dept of Natural Resources and Mines July 2004 4th Australian Stream Management Conference, Launceston, Tasmania, 2004 Local knowledge of the Narran Lakes: oral history as a line of evidence in ecological understanding – Janey Adams

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Variations of wetland patch characteristics under Diversity in ephemeral wetland systems – a spatial different inundation levels using remotely sensed study in North-West NSW, Australia – Cassandra data: preliminary results from the Narran Lakes, James NSW – Orla Murray. Technical Reference Group Meetings Canberra, A preliminary investigation into the influence May 2006 – presentations included: of changing stream network patterns on the distribution of water in the Narran Lakes Ecosystem • Driver of change hydrology – Scott Rayburg. • Ecological response 2004 flood event • Physical Template International Association of Geomorphology – Large Rivers Group Meeting, Lyon France,  • Technical Reference Group – Ecological June 2007 Response May 2006 Is what you see what you get? different approaches, • Narran Ecosystem Project Technical Reference different scales, provide different perspectives of Group Meeting May 25–26 floodplain depositional histories – Robert Cossart • Technical Reference Group notes May 2006

Scales and ecosystem functioning: the Narran Other Scientific Conferences floodplain wetland —Martin Thoms Catchments to Coast, Society for Wetland Scientists International Association of Hydrological Conference, July, 2006 – Dust to dust: the dramatic Sciences – Dundee, UK. July 2006 life of plant communities in a large terminal wetland system in semi-arid Australia – Samantha Capon Zoned vegetation communities: a product of seed bank or����������������������������� inundation? –��������������������������� Munique Webb University of Canberra, postgraduate presentation.

The dirt on floodplains – Erin Lenon ‘Getting down and dirty: the environmental history of a terminal floodplain’ September 2006. Robert The diversity of inundated areas in semi-arid flood- Cossart plain ecosystems – Scott Rayburg 36th International Binghampton Geomorphology Deposition within a terminal floodplain – Robert Symposium, Geomorphology and Ecosystems, Cossart Buffalo, N.Y., USA. 2005. Channel network change International Association of Hydrological in a complex distributary system: the Narran Lakes Sciences, Perugia, Italy July 2007 – Scott Rayburg Environmental change: inferences from sediments 6th International Conference on Geomorphology, in a terminal floodplain wetland complex – Robert Geomorphology in Regions of Environmental Cossart Contrast, Zaragoza, Spain. 2005. Spatial and temporal patterns in channel network change in a The decline of waterbirds, the decline of river flows, terminal wetland impacted by landuse change and and the changing climate of eastern Australia water resource development Scott Rayburg. —Mark Padgham A national Floodplain Workshop was hosted by 10th International Symposium on Regulated the Narran Ecosystem Project in September 2006 Streams, Stirling, UK. August 2006 at the University of Canberra. This workshop was attended by over 90 people, a list of the presenters Diversity and dynamics of vegetation in dryland are provided below. floodplain wetlands. Part 1: Trees and shrubs – Samantha Capon • Craig Boys. Fish-habitat associations in a large dryland river of the Murray-Darling Basin, Diversity and dynamics of vegetation in dryland Australia floodplain wetlands.” Part 2: Herbs and forbs —Cassandra James • Samantha Capon. Resilience and Fragility of Dryland Floodplain Vegetation Resilience 7th INTECOL International Wetlands • Peter Cullen. The knowledge agenda for Conferences, Utrecht, July, 2004 floodplain rivers Germination responses to flooding in desert • Ben Gawne. Organic matter dynamics in floodplain plants – Samantha Capon lowland rivers

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• Jonathon Marshall. Water management,persista nce,distribution and quality of waterhole refugia in dryland rivers. • Tony McLeod. The Living Murray • Michael Reid. Easing the working river squeeze. Detecting the effects of environmental water allocations on floodplain wetlands • Neil Saintilan. Wetland conservation and management in NSW • Martin Thoms. Busting some myths of Australian floodplain river ecosystems • Jim Thorp. The riverine ecosystem synthesis –� A conceptual model and research framework • John Tibby. Floodplain rivers and wetlands. Pre-impact conditions and nature of change • Klement Tockner. Emerging issues in floodplain research

6.5.8 Media Ralph Ogden and Janey Adams – ‘New interactive website invites storytelling about Narran Lakes’, 2 October 2003

Ogden, Wilson, Quinn and Thoms – ‘New study to throw light on water needs of the Narran Lakes’, 13 June 2003

Janey Adams – ‘Researchers interviewing long-time residents about the Narran River and Lakes’, 20 July 2004

Samantha Capon – Telephone interview with Outback Radio, 2004

The Black Opal Advocate. ‘Website for Narran science’, July 2006.

The Black Opal Advocate.’Narran the jewel of the inland’, 6 December 2006

The Black Opal Advocate. ‘Floods critical to save inland waterbirds from extinction’, 6 December 2006

Canberra Times, double page cover story on Narran, 21 May 2007

73

Appendix 1: Groundcover Species List

Family Species Name Family Species Name AIZOACEAE Glinus lotoides CHENOPODIACEAE Chenopodium pumilio AIZOACEAE Trianthema triquetra CHENOPODIACEAE Chenopoidum auricomum ALISMATACEAE Damasonium minus CHENOPODIACEAE Einadia nutans AMARANTHACEAE Alternanthera denticulata CHENOPODIACEAE Enchylaena tormentosa AMARANTHACEAE Alternanthera nana CHENOPODIACEAE Halosarcia pergranulata AMARANTHACEAE Alternanthera nodiflora CHENOPODIACEAE Maireana appressa AMARANTHACEAE Amaranthus macrocarpus CHENOPODIACEAE Rhagodia spinescens ASTERACEAE Aster subulatus CHENOPODIACEAE Salsola kali ASTERACEAE Brachyscome basaltica CHENOPODIACEAE Sclerolaena bicornis var. horrida ASTERACEAE Calotis multicaulus CHENOPODIACEAE Sclerolaena birchii ASTERACEAE Calotis scapigera CHENOPODIACEAE Sclerolaena convexula ASTERACEAE Centipeda cunninghamii CHENOPODIACEAE Sclerolaena decurrens ASTERACEAE Centipeda minima CHENOPODIACEAE Sclerolaena divaricata ASTERACEAE Conyza bonariensis CHENOPODIACEAE Sclerolaena muricata ASTERACEAE Conyza sumatrensis CHENOPODIACEAE Sclerolaena stelligera ASTERACEAE Eriochlamys sp. A CONVULVULACEAE Convolvulus graminetinus ASTERACEAE Euchiton sphaericus CONVULVULACEAE Cuscuta campestris ASTERACEAE Pseudognaphalium luteoalbum CONVULVULACEAE Evolvulus alsinoides var. villosicalyx ASTERACEAE Rhodanthe stricta CYPERACEAE Cyperus difformis ASTERACEAE Senecio runcifolius CYPERACEAE Cyperus eragrostis ASTERACEAE Soliva anthemifolia CYPERACEAE Cyperus pygmaeus ASTERACEAE Sonchus oleraceus CYPERACEAE Eleocharis acuta ASTERACEAE Xanthium occidentale CYPERACEAE Eleocharisp pallens BORAGINACEAE Heliotropium supinum CYPERACEAE Isolepis australiensis BRASSICACEAE Lepidium sp. CYPERACEAE Schoenoplectus BRASSICACEAE Sisymbrium irio dissachanthus CAMPANULACEAE Wahlenbergia sp. ELATINACEAE Bergia ammannioides CARYOPHYLLACEAE Spergularia rubra ELATINACEAE Elatine gratioloides CARYOPHYLLACEAE Stellaria angustifolia EUPHORBIACEAE Chamaesyce drummondii CHENOPODIACEAE Atriplex leptocarpa EUPHORBIACEAE Chamaesyce sp.B CHENOPODIACEAE Atriplex limbata EUPHORBIACEAE Phyllanthus virgatus CHENOPODIACEAE Atriplex spongiosa FABACEAE Aeschynomene indica CHENOPODIACEAE Chenopodium auricomum FABACEAE Cullen cinerum CHENOPODIACEAE Chenopodium desertorum FABACEAE Cullen tenax subsp. desertorum

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Family Species Name Family Species Name FABACEAE Sesbania cannabina POACEAE Sporobolus mitchellii FABACEAE Trigonella suavissima POACEAE Thyridolepis mitchelliana GENTIANACEAE Centaurium spicatum POLYGONACEAE Muehlenbeckia florulenta GERANIACEAE Geranium solanderi POLYGONACEAE Persicaria lapthifolia GOODENIACEAE Goodenia heteromera POLYGONACEAE Polygonum plebeium HALORAGACEAE Haloragis glauca POLYGONACEAE Rumex crispus HALORAGACEAE Myriophyllum verrucosum POLYGONACEAE Rumex crystallinus HYDROCHARITACEAE Vallisneria sp. PORTULACACEAE Portulaca filifolia JUNCACEAE Juncus aridicola PORTULACACEAE Portulaca filifolia LILIACEAE Bulbine bulbosa PORTULACACEAE Portulaca oleracea LILIACEAE Bulbine semibarbata RANUNCULACEAE Ranunculus pendulus LYTHRACEAE Ammannia multiflora RANUNCULACEAE Ranunculus pentandrus LYTHRACEAE Lythrum wilsonii ROSACEAE Potentilla supina MALVACEAE Abutilon oxycarpum SCROPHULARIACEAE Glossostigma diandra MALVACEAE Abutilon theophrastii SCROPHULARIACEAE Limosella australis MALVACEAE Lavatera cretica SCROPHULARIACEAE Mimulus gracilis MALVACEAE Malva australiana VERBENACEAE Verbena macrostachya MALVACEAE Malva verticillata (charophyte) Chara spp. MALVACEAE Malvastrum americanum (charophyte) Nitella spp. MARSILEACEAE Marsilea drummondii NYCTAGINACEAE Boerhavia dominii ONAGRACEAE Ludwigia peploides subsp. Montevidensis OXALIDACEAE Oxalis sp. PLANTAGINACEAE Plantago debilis PLANTAGINACEAE Plantago sp. POACEAE Dactyloctenium radulans POACEAE Diplachne muelleri POACEAE Echinochloa colona POACEAE Echinochloa inundata POACEAE Enneapogon polyphyllus POACEAE Hordeum leporinum POACEAE Lachnogrostis filiformis POACEAE Panicum queenslandicum POACEAE Phragmites australis POACEAE Poa fordeana POACEAE Poa sp. POACEAE Schismus barbatus

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Appendix 2: Tree Species List

Family Species Name Mimosaceae Acacia homalophylla Mimosaceae Acacia oswaldii Mimosaceae Acacia salicina Mimosaceae Acacia stenophylla Myoporaceae Eremophila bignoniiflora Myoporaceae Eremophila mitchellii Myoporaceae Eremophila sturtii Myoporaceae Myoporum deserti Myoporaceae Myoporum montanum Myrtaceae Eucalyptus camaldulensis Myrtaceae Eucalyptus coolabah Myrtaceae Eucalyptus largiflorens Myrtaceae Eucalyptus populnea Rutaceae Geijera parviflora Sapindaceae Atalaya hemiglauca

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APPENDIX 3: Methodology and Management Implications Methodology and Management • Predict the responses of selected components Implications of the Narran Lakes ecosystem to alterations in flow regime under different water resource development and long-term climate change 1. Introduction scenarios. These predictive models would The Narran Floodplain Ecosystem is a significant emphasise the links between flow regime and floodplain wetland complex located in inland biota through habitat availability and changes in Australia. It is an ecotone that regulates aquatic ecological processes such as primary productivity. – terrestrial interactions across a Riverine landscape • Evaluate the ecological significance of the Narran that extends from SW Queensland into northern Lakes in the regional context of wetlands within New South Wales. These ecosystems respond to the northern Murray Darling Basin. both natural and human induced disturbances over • Develop a conceptual model that links physical a range of scales – from organism-level responses, and biological responses of the Narran Lakes through population and community changes and ecosystem to past and future changes in water finally ecosystem-level changes. The nature of resource development, land-usage and climate. these changes depends on the organism or group of organisms or ecosystem component in question. Additionally, there will be a lag time before an The approach taken ecosystem response can be detected in floodplain The focus of Narran science project was water bodies and the extent of this lag time will interdisciplinary in nature, in that it required the again depend on the component in question. For collaboration of different scientific disciplines. For many of the more familiar organisms (large fish, this study, the disciplines of ecology, geomorphology riparian trees), there would be a considerable lag and hydrology were brought together to address the time, with the effects of changing water regimes research aims of the project. possibly taking decades to be detected. Previous works in the lower Balonne floodplain Studies of inland floodplain wetlands like the Narran and that on the Narran lakes all acknowledge the have tended to ignore their multi-scaled functioning complexity of the physical environmental and its and the requirement for an interdisciplinary and ecology. The ecosystem structure and behaviour integrated approach to study these ecosystems. of the Narran ecosystem expresses many internal They therefore provided limited information and and external influences — geomorphological, knowledge on how these systems function over hydrological and ecological — that interact closely. a range of scales. The Narran Ecosystem project While the importance of this interaction has been was established to investigate the responses of this recognised, issues of how to study complex and key ecosystem to variations in the flow regime at variable ecosystems, like Narran, are prescribed different scales. The project was based upon a series in any text book or manual. In addition, there of initial conceptual models of the key ecological have been few large interdisciplinary studies of functioning of Narran Ecosystem and it takes such ecosystems. Successful interdisciplinary an interdisciplinary approach to the study of this studies require that the separate disciplines gain floodplain ecosystem. a common understanding of the nature of the This integrated project recognises the importance of problem at hand, and identify the scales of relevant the Narran floodplain, lakes and the river network, subsystem components, the underlying processes or which make the Narran Ecosystem. It also notes phenomena, and the important variables involved. the importance of viewing the Narran Ecosystem Conceptual frameworks are useful tools to order as part of a mosaic of floodplain ecosystems within phenomena and material, thereby revealing the Murray-Darling Basin and beyond. Three scales patterns and processes. Recent interdisciplinary of investigation were used to study the Narran ecosystems studies (Dollar et al., 2007; Hughes et Floodplain Ecosystem – the landscape scale, the al., 2007; Parsons and Thoms, 2007) all recommend regional or catchment scale and the local scale. the establishment of a conceptual framework Specifically, the project aimed to: with which to base research activities on. A conceptual framework can help different disciplines • Determine the physical and biological responses work together in an integrated way by ordering of the Narran Lakes ecosystem to variations in phenomena and materials and, thereby, revealing the flow regime. patterns (Rapport, 1985).

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The basis for the Narran science framework depends on the context provided from above and the recognises the key aspects of the driver, template, integration of processes from below—the same basic altered state and the ecosystem response (Figure drivers could produce different forms within different 1). Drivers create, maintain or transform structural constraining contexts. Interpreting the relationship and functional features of an ecosystem. Drivers between downward constraint and upward include biotic activities and abiotic disturbances integration of explanation is critical in interpreting such as floods. The template is the entity the driver complex ecosystems like floodplain wetlands. (s) act (s) upon. Templates are bounded spatially by The approaches taken to investigate the Narran the research question and they can be both abiotic Floodplain Ecosystem were therefore organised and biotic. The physical surface of a floodplain or around this framework with methods organised lake bed is an abiotic template while vegetation is an to provide information on the initial and altered example of a biotic template. The interaction between template, drivers and ecosystem responses. a driver and the template produces an altered state This report therefore provides information on the or template. The inundation of a floodplain surface methods for each of these components of the (template) by floodwaters (a driver) produces a science framework. wetted floodplain landscape which represents an altered template or state. The ecosystem responds to the formation of this altered state. 2. Methods for the Physical Frameworks, like the Narran science project Template framework have been used to demonstrate, among A variety of methods were employed in the other things, modes of change in heterogeneity characterisation of the physical template of the (Pickett et al., 2003) but such models are not Narran Ecosystem. These included the collection generally spatially explicit. For our framework we and analysis of remotely sensed imagery (e.g., use a multi-level framework to allow integration Landsat, aerial photography and LiDAR data) and between processes operating at different scales field surveys (e.g., ground based DGPS, soil surveys). (Figure 1). This structure accommodates feedback Five basic areas of investigation were incorporated responses, allowing biotic consequences to into this portion of the study. These include: contribute to the altered state. It also allows for 1. an initial determination of the extent of the consideration of downward constraint by higher Narran Lakes Ecosystem and its associated levels and upward integration of processes from wetlands; lower levels – an important factor in hierarchically organised systems like floodplain ecosystems. 2. the construction of a digital elevation model of The relative importance of downward constraint the Narran Lakes Ecosystem; and upward integration is different at each level 3. the determination of the physical and chemical of organisation. The higher levels are controlled properties of the surface soils within the Narran predominantly by downward influence, while Lakes Ecosystem; features at lower levels are more manifestations of 4. characterising the extent and change in the upward influence. At all levels the altered state, river channel network within the Narran Lakes Ecosystem through time; and, Figure 1: The conceptual framework for the study of the Narran floodplain complex. 5. a consideration of the environmental history of the Narran Lakes Ecosystem over geologic timescales.

2.1 Wetland mapping Ecosystem Driver Scale one response The location and extent of the wetlands along the Narran River (including the Narran Lakes Abiotic Ecosystem) were determined using two approaches. Template Altered template First, a set of large format Landsat images (for 1990 Biotic and 2000) were obtained which spanned the area from St. George in the north to Dubbo in the south.

Ecosystem These were combined with topographic maps to Driver response identify the wetlands along the Narran River and the Scale two Abiotic extents of these wetlands were determined using Template Altered image interpretation techniques. An independent template Biotic verification of these extents was obtained using

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geophysical data obtained from Geoscience the LiDAR flight (deep waterholes along the Narran Australia. This involved the use of radioactive River and the deepest part of the Northern Lake). isotopes of Uranium, Thorium and Potassium to The combined horizontal and vertical accuracy highlight wetland areas. The wetlands identified of these data is on the order of 8–10 cm absolute using the satellite images all showed a high (relative to the true elevation above sea level) but concentration of radioactive Potassium relative to approximately 1 cm internal (one point relative to their surroundings and so it was possible to use this the next). Technical details about the operation and element to characterise the extent of these wetlands the correction and processing of LiDAR data are based on elevated Potassium levels. A further benefit available in Wehr and Lohr (1999) and Cobby et al. of this analysis was that it enabled the differentiation (2001). In order to calibrate the LiDAR data, ground of wetlands that filled from flows down the Narran survey points are needed and the DGPS survey was River and those that filled from rainfall. Narran used for this purpose. This represents an order River flows are exceptionally rich in radioactive of magnitude more data than is typically used for Potassium so wetlands that filled from this source this purpose resulting in a highly accurate LiDAR had very high levels of this element relative to their data set. Each of these topographic data sets were surroundings. Meanwhile, wetlands that filled then used to produce DEMs (using the software QT from rainfall had intermediately high Potassium Modeler) with the LiDAR data DEM serving as the levels and non-wetland areas had very low levels of basis for all subsequent physical and hydrological radioactive Potassium. Further details on the use of research. Once completed, the LiDAR derived DEM radioisotopes in determining sediment sources is was used to produce a set of hyposmetric curves presented in Pickup and Marks (2000). for the Northern and Narran Lakes. This process necessitated several key steps: 1) the surface area 2.1.1 Accompanying datasets and volume of each lake was determined at 10 cm 1. Narran River Wetlands (ArcGIS Polygon increments using QT Modeler; 2) these data were Layer showing the extents of all major plotted against water surface elevation in excel; 3) wetlands along the Narran River) the ‘full’ level of each lake was determined as the point at which surface area remained relatively constant with increasing flow depth while the volume 2.2 Topography continued to increase; 4) the validity of the maximum Three topographic data sources were utilised in this size of each lake was later verified using known flood study. The first was the 9 second DEM of Australia, extents (as determined from historical flood extents which was derived from spot heights taken from derived from Landsat data) and hydraulic modeling 1:100,000 scale topographic maps and has a spatial (using Mike21). resolution of 250 m. The horizontal and vertical accuracy of these data is greater than 1 m. This 2.2.1 Accompanying datasets was the only data available for the Narran Lakes 1. Narran_DEM (LiDAR derived DEM of the Ecosystem prior to 2003. Second was a 20,000 point Narran Lakes Ecosytem). differential GPS (DGPS) survey conducted in 2003 by 2. Narran_veg (LiDAR derived vegetation the Queensland Department of Natural Resources height layer for the Narran Lakes and Water. This was the first detailed survey of the Ecosystem). Narran system and has a variable spatial resolution (ranging from 1 m along survey lines to more than 200 m between survey lines) and a horizontal and 2.3 Soils vertical accuracy of less than 1 cm. These data are highly accurate but failed to cover the entire Narran 2.3.1 Soil Surveys Lakes Ecosystem. Notable omissions were the Two soil surveys were incorporated in this study. bulk of the floodplain and much of the Northern The first consisted of samples taken from sites Lake as long as the southern overflows of the main positioned on a regular grid with an average spacing Narran Lake. Only the central portion of the main of 1,800 m between each sample point. For the Narran Lake was adequately covered by these second survey, soil samples were collected at data. The third data set was a LiDAR aerial survey locations where vegetation surveys had been carried of the Narran system comprising approximately out. In total, 163 soil samples were collected, 130 650,000,000 data points with a spatial resolution of from the grid pattern and the remaining 33 from the approximately 1 m2 flown in October 2004. These vegetation sites. At each site, a 10 m quadrat was data were supplemented by a small set of DGPS established and surface soil was collected at each measurements (about 1,000) to account for areas corner and the centre of the quadrat. inundated (LiDAR cannot penetrate water) during

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2.3.2 Soil Analysis 2.3.4 Accompanying datasets A number of physical and chemical properties of 1. Narran_soil.xls (spatial locations and the surface soils were determined. These include physical and chemical properties of the the full grain size distribution, pH, organic matter soil samples collected in the Narran Lakes content, liquid and plastic limits, colour, and a series Ecosystem). of geochemical properties including aluminum, barium, calcium, cobalt, copper, iron, lead, 2.4 River channel network magnesium, manganese, phosphorous, potassium, The river channel network of the Narran Lakes sodium, strontium, titanium, and zinc. Soil texture Ecosystem was investigated using a set of three was measured by determining the clay, silt and aerial photographic mosaics (1969, 1992 and 2003). sand fraction of samples using an ASTM 152H soil Although other aerial photographic runs were hydrometer (ASTM, 1985) and the full grain size available, these all contained some flooded areas spectrum was determined using a laser particle size thereby obscuring portions of the network. The three analyser. Soil colour was determined for both moist chose photo-mosaics were all completely dry and are and dry samples using the Munsell Soil Colour Chart, therefore directly comparable (in terms of visibility and pH was measured with an INOCULO CSIRO soil of the network) to one another. The images for each pH test kit. Organic content was estimated as loss on 1:50,000 aerial photographic run were imported into ignition (LOI) at 550°C for 2.5hrs. Consistency limits of ArcGIS and the channel network was digitised. The samples were investigated using the liquid and plastic resultant polygon layers were then used to compute limits, these were measured using the Casagrande the overall area of channel during each time period. Apparatus and glass plate as described by Sowers This allowed for comparisons of network gain or (1965). Geochemical properties were determined loss between periods. In addition, the 1969 and using a variety of techniques depending on the 2003 digitised channel networks were overlayed to chemical property in question. determine if individual channels had changed their 2.3.3 Data Analysis size, shape or position between time periods. The net result is a map that illustrates locations were the For each of the soil variables identified above, the network was unchanged between 1969 and 2003, values were entered into a table in ArcGIS 8.2 along areas were the network was present in 1969 but not with their geographic position in the landscape. In in 2003, (network contraction) and areas were the addition, for each sample point, the elevation, height network is present in 2003 but was not present in of the surrounding vegetation and the frequency of 1969 (network expansion). inundation (defined as the number of times inundated during the last 30 years by the largest annual flood) Further analysis of the river channel network were determined. A radial basis function was then included a characterisation of river types following applied to each variable using the geostatistical a new technique developed by Rayburg and Thoms analyst function in ArcGIS 8.2 to derive a soil surface (in press). Only the most recent channel network map for each of the soil properties. (2003) was investigated in this way. This allowed for the determination of overall network complexity The soil character across the study area was further and diversity within the Narran Lakes Ecosystem. examined through a range of multivariate statistical Details of this approach and its outcomes can be analyses. A similarity matrix of Gower’s similarity found in Rayburg and Thoms (in press) and will not be coefficients was first calculated using all soil variables discussed further here. and this matrix was used to test between-geomorphic region differences using the analysis of similarity 2.4.1 Accompanying datasets (ANOSIM) routine in the PRIMER computer package 1. 1969 Network (ArcGIS polygon layer (Clarke and Warwick 1994). In addition, Semi- showing the extent of the channel network Strong-Hybrid Multidimensional Scaling – (MDS; in 1969). Belbin, 1993) was used to represent the similarity matrix graphically. A stress level of less than 0.2 2. 1992 Network (ArcGIS polygon layer indicated that the ordination solution was not random. showing the extent of the channel network Relationships between different soil variables and in 1992). the independent variables of site elevation, flood 3. 2004 Network (ArcGIS polygon layer frequency and vegetation height and the position showing the extent of the channel network of samples in the multi-dimensional space were in 2004). determined using Principal Axis Correlation – PCC – (Belbin, 1993) and only those variables with an R2 greater than 0.8 were considered.

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2.5 Soil cores 2.5.3 Laboratory sampling 2.5.1 Field Sampling Sediment cores were split longitudinally in a dark room, under red light conditions to avoid light Twelve sediment cores were extracted from the contamination. One half was sealed in black northern section of the Narran Floodplain-wetland polyethylene tubbing and stored for sediment complex (Figure 2). Three cores were extracted dating. The remaining half was used for physical from each geomorphic region (Clear Lake, Back and chemical analysis. To attain a detailed Lake, long Arm, and Floodplain). Field sampling was lithofacie profile the exposed face was cleaned and conducted in April/May 2005 during a period of no smoothed with stainless steel blades. Based on inundation of the complex. the lithofacie profile, sub-samples were collected from each unit for physical and chemical analysis. 2.5.2 Core Extraction Samples were oven dried for 72 hours at field Sediment cores, up to a depth of 14 meters, were temperature (~32°C), disaggregated and dry sieved extracted using a piston driven coring rig (Geoprobe (<2 mm) prior to analysis. Macro-Core Soil Sampler). Cores were extracted in 1.4-meter lengths in-cased in a steel housing 2.5.4 Stratigraphy using an undersized cutting tool to allow for The stratigraphy of each core was described expansion of the clay sediments (Figure 1.2). Lengths using a modified lithofacies classification scheme were sealed in black polyethylene tubbing before the incorporating that of Lewin (1996) and Miall (1985) removal of steel housing to avoid light contamination (Table 1). Lithofacies were based on texture, (Figure 3). Cores were transported intact to the layering, basal contact, colour and presence of laboratory to minimise sample disturbance and/or nodules and lenses. Sediments were classified as deterioration. Drilling data including: target depth, mud, sandy mud (<50% sand), muddy sand (>50% length short, depth achieved, and measured sample sand) and sand. Basal contacts were described as amount were recorded. Environmental variables sharp or gradual with structural patterns such as including resistance to drilling and water tables were laminating and cross bedding also noted. Specific also recorded. characteristics such as lenes, nodules, carbonates, organic matter and mottling were also recorded. Figure 2: Location of sediment cores (n=12) Sediment colour was determined from dry samples extracted from the Narran Lakes Floodplain- using the Munsell Soil Colour Chart. wetland complex. Three cores were extracted from the geomorphic regions of Clear Lake, Back Lake, Table 1: Lithofacies classifications used in this Long Arm and Floodplain. study modified from Maill (1996) and Lewin (1985).

Facies Code Lithofacies Sedimentary structures M Mud Layer, Lens Sm Sandy Mud Layer, Lens Ms Muddy Sand Layer, Lens S Sand Layer, Lens Ca Carbonate Scattered particles No Nodules Scattered particles

2.5.5 Grain size analysis Sediment samples were extracted from each identified lithofacies unit for grainsize analysis. Multiple samples were extracted from each unit with a depth of greater than 200 mm. Samples were collected from the centre of each core cross section to avoid possible contamination on the outer edges of the core. All samples were dried to a temperature of 63°C and then passed through a 2000 µm sieve

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Figure 3: Extraction of sediment cores using a piston driven coring rig. Sediment cores were extracted in 1.4-meter lengths encased in steel housings using an undersized cutting tool. Cores are sealed in black polyethylene tubbing before the removal of steel housing to avoid light contamination and transported back to laboratory for sampling.

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to remove the coarse fraction. This fraction was 2.5.8 Sediment dating weighed and tested for carbonates. The remaining Sediment dating was determined by Optical samples were used for particle size analysis using Simulated Luminescence (OSL) and Isothermal a 1 g sub-sample. Organic matter and carbonates Luminescence (ITL) methods. These dating were removed from the sediments using 10% HCL technique is a well-established methods for and organic matter was removed by 30% H O 2 2 determining the burial time (time elapsed since (Battarbee et al. (2001). Grain size analysis was quartz or feldspar grains were last subject to conducted using a Malvern Mastersizer 2000 sufficient heat or light) of Quaternary deposits (Atkin particle sizer using the parameters between 0.2 µm 1998). Dating was undertaken using single grains – 2000 µm. Disaggregation of clays was assisted by analysis techniques. Samples were selected for 20 seconds of ultrasonic dispersal prior to analysis. dating following the completion of data analysis. Samples were selected for OSL from 5 cm below the 2.5.6 Geochemical extraction surface depositional unit to remove the possibility The geochemistry of the sediment samples of light penetration due to cracking of surface soils. from each lithofacies unit was also determined. Due to the extreme age of the initial samples ITL Geochemical analysis was conducted on the <63µm dating was used to establish the remaining dates. fraction (silt and clay) of the sediment sample WHY. An additional 3 dates were established on sediment Fifteen geochemical variables were measured core Back Lake ‘b’ using ITL. All samples were from each sub-sample (Table 2) at the ALS Chemex taken from the centre of each core cross section laboratories using geochemical digestion – four acid to avoid possible light contamination on the outer (near total) – ICP Atomic Emission Spectrometry edges of the core. (ICPAES). All sample preparation and analysis was conducted Table 2: List of stable and soluble elements at the CSIRO OSL/ITL laboratory in Canberra. determined for the geochemical analysis of the Sample preparation was designed to isolate pure <63µm fraction of sediments extracted from the extracts of 180-212 µm light safe quartz grains Narran Lakes Ecosystem. following standard procedures (e.g., Aitken 1998). Treatments were applied to remove contaminant Stable Elements Soluble Elements carbonates, feldspars, organics, heavy minerals and acid soluble fluorides. The outer ~10µ m alpha- Aluminium (µg/g) Barium (µg/g) irradiated rind of each grain was removed by double Titanium (µg/g) Calcium (µg/g) etching each sample in 48 % Hydrofluoric Acid.

Strontium (µg/g) Copper (µg/g) Burial doses were determined from measurement of the OSL signals emitted by single grains of Lead (µg/g) Iron (µg/g) quartz. The etched quartz grains were loaded on to Cobalt(µg/g) Potassium (µg/g) custom-made aluminium discs drilled with a 10 x 10 array of chambers, each of 300 µm depth Magnesium (µg/g) and 300 µm diameter (Botter-Jensen et al., 2000). Manganese (µg/g) The OSL measurements were made on a Risø TL/OSL DA-15 reader using a green (532 nm) Sodium (µg/g) laser for optical stimulation, and the ultraviolet emissions were detected by an Electron Tubes Ltd. Phosphorous (µg/g) 9235QA photomultiplier tube fitted with 7.5 mm of Hoya U-340 filter. Laboratory irradiations were conducted using a calibrated 90Sr/90Y beta source 2.5.7 Nutrients mounted on the reader. The pH and electrical conductivity of these sediments Equivalent doses (De) were determined using a were also determined. For this a conductivity and pH modified SAR protocol (Olley et al. 2004). A dose- probe with a 1:5 sediment to water ratio. Percentage response curve was constructed for each grain. The organic matter and percentage carbonate content OSL signals were measured for 1 s at 125°C (laser were measured through loss on ignition with at 90% power), using a preheat of 240°C (held for organics being removed through loss on ignition 10 s) for the ‘natural’ and regenerative doses, and a at 550oc for 2.5 hours, and carbonates removed pre-heat of 160°C (held for 10 s) for the test doses through ignition at 1000oc for 1 hour following (0.5 Gy). The OSL signal was determined from the removal of organic matter (Heiri et al. 2001).

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initial 0.1 s of data, using the final 0.2 s to estimate 2.5.10 Multivariate statistics the background count rate. Each disc was exposed The data set used for multivariate statistics included to infrared (IR) radiation for 40 s at 125°C prior to twenty-seven sediment variables and three hundred measurement of the OSL signal to bleach any and eighteen samples. A suite of multivariate IR-sensitive signal. analyses was preformed on the assembled data Grains were rejected if they did not produce a matrix in the PATN statistical analysis package measurable OSL signal in response to the 2 Gy (Belbin 1993) and PRIMER V6.0 statistical analysis test dose, had OSL decay curves that did not package (Plymouth Marine Laboratories). Initially, reach background after 1 s of laser stimulation, or an association matrix was derived using the produced natural OSL signals that did not intercept Gower metric distance measure, which is a range the regenerated dose-response curves (‘Class standardised measure recommended for non- 3’ grains of Yoshida et al. 2000). The ‘central age biological data sets containing different units of model’ of Galbraith et. al., (1999), has been used to measure (Belbin, 1991). Subsequent ordination, determine an over-dispersion parameter ( d) for principal axis correlation, and analysis of similarity each De distribution. d is calculated as the relative (ANOSIM) were undertaken on the Gower Metric standard deviation of the single-grain De distribution association matrix. Similarity percentages (SIMPER) after taking into account the measurement were preformed on the initial assembled data matrix. uncertainty for each grain (Galbraith et al. 1999). Ordination was used to produce a graphical If measurement uncertainty were the only source representation of the data set and investigate the of spread in a distribution then d would be 0 %. interrelatedness of samples. Ordinations were Olley et al., (2004) suggest a d value <~22 % to be preformed in two dimensions except where the indicative of uniform bleaching prior to deposition, stress level was >0.2 and where they were preformed and for such samples they recommend use of the in three dimensions. The data set was ordinated central age model to calculate a De. Where d using Semi-Strong-Hybrid-Multidimensional-Scaling >~22 % Olley et al., (2004) recommend use of the (SSH) (Belbin 1991). Stress levels for all ordinations minimum age model to calculate a De. were less than 0.2, indicating that the representation Burial doses were determined from measurement of the data points was not random (Clarke and of the ITL signals emitted by large aliquots of Warwick, 2001). Ordinations were mapped using the quartz, mounted on stainless steel discs using a priori grouping of levels of organisation (outlined silicon oil. Equivalent doses (De) were determined in section 3.2.1) using the ITL SAR protocol of Murray and Wintle Principle axis correlation (PCC) was used to identify (2000). A dose-response curve was constructed relationships between a priori groups and the for 8 aliquots of each sample, with sample Des position of sediment variables in ordination space. calculated as the weighted average of all aliquots, A Monte Carlo permutation test (Belbin 1993) was excluding single outliers. Lithogenic radionuclide preformed to test the significance of correlation activity concentrations were determined using high- values. Variables with an R2 value greater than resolution gamma spectrometry (Murray et al. 1987), 0.8 were considered to have a strong association with dose rates calculated using the conversion with sediment character and those with an R2 factors of Stokes et al. (2003). Attenuation factors value between 0.5-0.79 were considered to have were taken from Mejdahl (1979). Cosmic dose rates a moderate association with sediment character. were calculated from Prescott and Hutton (1994). Variables with an R2 value less than 0.5 were considered to have no association with sediment 2.5.9 Data analysis character. Combinations of standard descriptive sedimentological, univariate and multivariate A one-way ANOSIM (Clarke 1993) was conducted on statistical analysis were used. The purpose of this the Gower association matrix to test for similarities section is to describe the multivariate techniques between a priori groups (geomorphic region, used, a justification for the use of multivariate sediment cores, depositional unit and nested statistics in geomorphological studies was outlined combinations). ANOSIM compares the similarity in the literature review (chapter 2). Descriptive and among samples within groups with the similarity univariate techniques and application of multivariate among samples between groups and generates techniques are outlined in the analysis section of an R statistic between 0 and 1. The probability relevant chapters. of observed results being determined by chance alone was determined by comparing variance determined under 1000 Monte Carlo randomisations (simulations under a null hypothesis) (Manly 1997).

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One thousand randomisations is regarded as an impacts on the hydrology of the Narran Lakes acceptable minimum for significance testing at the Ecosystem was undertaken through an investigation 0.05 probability level (Marriott 1979). An R statistic of all climate records within the Condamine-Balonne <0.3 implies little or no separation among the catchment. In each case, moving averages and groups; R 0.3 to 0.75 indicates that the groups are regression analyses were used to determine if there different but overlapping and R>0.75 indicates a were any distinct trends in rainfall for the mean clear separation of groups (Clarke and Gorley 2001). annual rainfall itself and for the deviation of yearly rainfall from the mean. In addition, each rainfall SIMPER analysis (Clarke and Warwick 2001) was record was compared to the Southern Oscillation also used to determine the percentage contribution Index to investigate how rainfall responded to El Nino each variable makes to the dissimilarity within a and ENSO events within the region. priori groupings. Mean dissimilarity between groups composition was conducted on groups of difference 3.1.1 Accompanying datasets as highlighted by ANOSIM (R<0.3) to determine which variables are associated with differences 1. Narran_Climate.xls (spreadsheet with between levels of investigation. the complete climate records for Walgett, Lightning Ridge and Brewarrina). 2.5.11 Accompanying datasets 1. Narran Cores (ArcGIS polygon layer 3.2 Flow data showing the locations of the 12 soil cores). There are three principal gauges on the Narran 2. Narran_Cores.xls (summary sheet with all River and these are located at: Dirranbandi (on the of the physical and chemical properties of Queensland side of the border and the first gauge on each core with depth). the Narran River, record length 1964-present); New Angledool (the first gauge on the New South Wales side of the border, record length 1931-present); and Wilby Wilby (the closest gauge to the Narran 3. Methods for Hydrological Drivers Lakes Ecosystem, record length 1964-present). An additional gauge is located at Narran Park (the Determining the hydrological drivers of the Narran northern end of the Narran Lakes Ecosystem) but Ecosystem required an analysis of historical this gauge has only a short record and is prone to and simulated flow data and climate data. The backwater effects from the Narran Lakes. Therefore, investigation into the hydrological drivers was this study employed data only from the first three subdivided into two key areas of investigation. stream gauges. For each gauge, the data were These were: plotted to determine the sequences of floods over 1. an analysis of existing climate data to determine the period of record. For individual flood events, the historical rainfall patterns and to identify discharge at each gauge was compared to give an potential long term trends in rainfall (and thus assessment of transmission losses between gauges. streamflow) in the Condamine-Balonne Basin Flood frequencies and recurrence intervals were and the local Narran Lakes Ecosystem region; determined for each gauge with the New Angledool and, gauge providing the longest record and therefore the best estimate of these two indices. These data 2. the collation and analysis of all existing flow are useful in determining the mean, maximum and records on the Narran River to look for patterns variability of flows, ascertaining the relative severity in stream flow through time. of wet and dry periods within the gauging record and classifying flood events into useful categories (large, 3.1 Climate medium and small) with respect to flow inputs into Climate data were gathered for the three long- the Narran Lakes Ecosystem. term climate stations surrounding the Narran 3.2.1 Accompanying datasets Lakes Ecosystem: Walgett, Lightning Ridge and Brewarrina. Each of these stations has rainfall 1. Narran_flow.xls (complete flow records and temperature records extending from 1898 to for Wilby Wilby, New Angledool and present thereby enabling an assessment of long- Dirrinbandi). term climate patterns adjacent to the Narran Lakes Ecosystem. In addition, a more through consideration of climate patterns and their potential

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3.3 Flood frequency the largest recorded flood extent over the period of 34 years. The second index uses only the data from Eighty three cloud-free MSS, TM and ETM+ images 1981 to present as both wetting and drying were of the Narran Lakes Ecosystem were acquired for considered. This index measures the number of the period February 1971 to February 2004. These times any particular pixel was uniquely inundated images include the “before and after” of every flood over this period. That is, the index assigns a value of the Narran Lakes Ecosystem since 1981, one of ‘1’ to a pixel if it was dry in the previous image image per year (which is all that was available) from but is wet in the subsequent image. This index, 1971 to 1980 and two extended drying sequences (a therefore, incorporates notions of antecedence series of images from the beginning of the flood until and reflects the persistence of water in various the lakes were completely dry) spanning the periods parts of the landscape. from 1988-1992 and the 2004 event. These images were reprojected to the Geodetic Datum of Australia 3.3.1 Accompanying datasets 1994 (GDA94), Universal Transverse Mercator (UTM) zone 55 S, an appropriate localised projection that 1. Narran_FF (ArcGIS raster layer showing minimises spatial distortions. The images were then the flood frequency of the various parts geometrically rectified using a 1:250,000 topographic of the Narran Lakes Ecosystem). map as a reference. Twenty ground control points were used and the RMS errors were kept below one 4. Methods for the altered template pixel length (30 / 50 m). Determining the influence of hydrological drivers Water-covered pixels were identified by performing on the Narran Ecosystem involved the analysis of a density slice on TM and ETM+ Band 5. This near- satellite imagery to determine the actual inundation infrared band (1.55–1.75µm) returns very low patterns within the floodplain wetland systems values for water, as at this wavelength virtually all and the development of a predictive water balance radiant flux is absorbed. Conversely, vegetation model for Narran. This component of the project and soils have a very high return. The resultant was subdivided into three key areas of investigation. images showed water as deep black, and soils These were: and vegetation as bright areas. Classification was 1. a determination of how inundated patch accomplished by using an ISODATA algorithm. character varies within and between flood events; This divided the scenes into wet and dry pixels. 2. a spatially explicit assessment of the frequency of The binary rasters were then converted to vector flooding within the Narran Lakes Ecosystem as a format for ‘cleaning’, whereby cloud elements, whole and its component parts; and, artificial water storages and unrelated inundated areas were removed. Additionally, expert knowledge 3. the development of a coupled hydraulic- was used to reconnect estranged channels where hydrologic model that incorporates all of the an evident link had been lost through rasterization. projects team knowledge of the physical and This process was undertaken to increase the overall hydrological character of the Narran Lakes accuracy of the flood maps. Ecosystem into a predictive modelling tool.

The data existed in two levels of spatial resolution, 4.1 Inundated patch character due to the nature of the sensors that acquired them: 50 m for older MSS imagery (pre 1988) and 25 m for Fourteen near cloud-free Landsat Thematic Mapper TM and ETM+ imagery (1988-2004). In order to allow (TM5) scenes were obtained covering two flooding accurate cross comparison of the data, another set and drawdown sequences that took place from of degraded TM and ETM+ images were created by December 1995 to February 1997 and from February reducing their pixel resolutions by 50%, bringing to December 2004. Total discharges of 496 000 ML them in line with the 50 m resolution of the MSS data. and 26 000 ML were recorded for the 1995-97 and 2004 floods respectively immediately upstream The images were then used to compute two of the study area. These floods have a 20 and 50 measures of flood frequency. The first measure is percent probability of occurrence, respectively, in the number of times an area was inundated by the any one year based on a Log Pearson annual series. largest annual flood extent. That is, the raster layer Antecedent conditions for each flood were relatively for the largest flood extent during each year from dry and consisted of a few pools of stagnant water 1971–2004 was input into ArcGIS and assigned a in the channel entering the wetlands equating to value of ‘1’. Raster calculator was then used to sum areas of ~31 ha and ~25 ha respectively. All images these wet extents. The resultant raster records the were geometrically corrected to Geodetic Datum number of times any particular cell was wet during of Australia 1994 (GDA94), Universal Transverse

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Mercator (UTM) zone 55S by cubic polynomial not random (Clarke and Warwick, 1994). In order rectification. Image-to-image rectification was to reduce the possible influence of flood size this used with the base satellite image being rectified statistical routine was undertaken with and without to a 250K digital topographic map. A minimum of the total surface area inundated and patch number 20 ground control points (GCPs) were collected for as variables. Relationships between the different each scene and all RMS errors were kept below one inundated-patch variables and the position of each pixel (30 m). A Band 5 (1.55–1.75 μm) density slice image in multi-dimensional space were determined was performed on all images as this near infrared using Principal Axis Correlation (PCC; Belbin, 1993) (NIR) band shows very high absorption of radiant and only those variables with an R2 greater than flux for water and significant reflection for vegetation 0.8 were considered. and bare soils. This analysis delineates a sharp boundary between land and water. In some cases, 4.1.1 Accompanying datasets where the above method produced unsatisfactory 1. Narran_patches.xls (summary results, an unsupervised ISODATA classification spreadsheet illustrating the inundated (maximum number of classes: 235; iterations: 24) patch character in the Narran Lakes was performed and classes were grouped into Ecosystem in response to flooding). water and dry classes. The resultant rasters were converted to vector format for “cleaning” and editing 4.2 Water balance modelling (i.e., connection of channels where expert knowledge suggested connection would exist, removal of water 4.2.1 Data Sources tanks, clouds, errors and inundated areas unrelated to the Narran River inflow). Vectors were then The development of a coupled hydraulic-hydrologic converted to signed 32-bit integer grids for use in the model is a data intensive process, requiring spatial pattern analysis program FRAGSTATS Version information on climate, river flows, topography, 3.3 (McGarigal and Marks, 1995). A series of spatial inundation extents, infiltration (into the lake bed) metrics were obtained and analysed with FRAGSTATS and transmission losses. The sources, applications using the 8-cell rule such that diagonally touching and methods employed in utilizing or creating the pixels were considered as one patch. Metrics data for this study are summarised in Table 3. Of analysed include number of patches, area, shape the seven major data types included in the study, index and a proximity index. A full explanation of each three were sourced from existing records (rainfall, metric is given in (McGarigal and Marks, 1995). evaporation and discharge) and four were newly derived or created (topography, transmission losses, Four measures of diversity were calculated to lake infiltration and flood extents from 1981 to 2004). provide a reflection of the overall distribution of the different inundated patch character – in this case: The topographic data were acquired using a LiDAR area, shape and proximity. The measures calculated aerial survey flown by AAM Hatch Australia in were Margalef Richness Index (DMg), Shannon October 2004. The LiDAR dataset included over Eveness Index (DSe), Shannon Weiner Diversity Index 650,000,000 data points spanning an area of about 2 (DSw), and the Simpson Diversity Index (DSi) (Zar, 650 km with one data point per square meter 1984). Combined, these indices provide a measure of and internal positional and vertical accuracies of abundance and components of diversity of individual ~ 1 cm. More than 20,000 points were used to inundated patches calculated from each image. calibrate the LiDAR data, sourced from a 2003 Queensland Department of Natural Resources and The character of flood plain inundation during Mines differential GPS survey which had positional the two flood events was examined via a range of and vertical accuracies of <1 cm. At the time of multivariate statistical analyses. Initially, a similarity the aerial survey, small areas of the Narran Lakes matrix of Gower’s similarity coefficients was Ecosystem were inundated (in particular, there calculated using the area of inundation, number of were several deep pools along the Narran River). As patches and the four diversity measures for each LiDAR is unable to penetrate water a differential GPS flood image and this similarity matrix was used to survey was conducted to fill these gaps. test between flood differences using the analysis of similarity (ANOSIM) routine in the PRIMER Transmission loss data were calculated from a computer package (Clarke and Warwick, 1994). series of four flow gauges along a 172 km stretch Semi-Strong-Hybrid Multidimensional Scaling of the Narran River. The Narran River has no (MDS; Belbin, 1993) was used to represent the major input tributaries along this section and similarity matrix graphically. A stress level of less discharge decreases in the downstream direction. than 0.2 indicated that the ordination solution was Transmission losses (due to infiltration and

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evaporation) were calculated as the long-term mean largest pool of data that could be used to ascertain difference in flow between each gauge, temporally the inundation response in each lake complex to corrected for the travel time of water between floods of various magnitudes, at different times of each gauge. The net result is a value for water loss year and with different antecedent conditions. per kilometre of river length. This value was then In addition, the inclusion of two long drying subtracted from flow data recorded at the long-term sequences allows for the calibration and validation gauge closest to the Narran Lakes Ecosystem (the of the loss component of the model and, therefore, Wilby Wilby gauge) to derive an input flow at the provides accurate information on the residence point of entry into the system. time (and future antecedent conditions) of water within the system. Data on lake infiltration volumes and known flood extents were obtained from satellite imagery. Eighty Upon acquisition, each image was reprojected to two cloud-free Landsat MSS, TM and ETM+ images the Geodetic Datum of Australia 1994 (GDA94), of the Narran wetland were acquired for the period Universal Transverse Mercator (UTM) zone 55 S, February 1972 to April 2004. These images provide a which is an appropriate localised projection that snapshot of the system before and after every flood minimises spatial distortions. The images were event since 1981 along with two extended drying geometrically rectified using a 1:250,000 topographic sequences. The optimal time for image acquisition map as a reference with a minimum of twenty was determined as two weeks before the arrival ground control points (usually water storage tanks or of water and a month after the cessation of flow road junctions). The individual and total RMS errors into the system, however, limitations in the return for each geo-rectified image were about one pixel period of the satellites (±16 days) means there is length (30 or 50 m depending on the resolution some variability around this optimum. This image of the satellite). acquisition strategy was adopted to provide the

Table 3: Data considerations for the constituents of the coupled hydrologic-hydraulic model.

Data Type Data Source Data Considerations Data Use

Rainfall Bureau of Thiessen polygons constructed from three Input into water balance Meteorology surrounding rainfall stations with greater than 100 model years of data (Walgett, Lightning Ridge, Brewarrina)

Evaporation Bureau of Amalgam of several surrounding evaporation Input into water balance Meteorology records to form a continuous 60 year record of and hydraulic models pan evaporation; data were corrected for open water evaporation by using Bureau of Meteorology correction factors for the appropriate location

Soil losses Derived Computed by comparing input flow volumes (from Input into water balance the Wilby Wilby gauge) to the standing water model volumes for each flood as determined by overlaying the inundated areas determined form the satellite imagery with the LiDAR DEM.

Transmission Derived Computed by assessing the losses (by distance) Input into water balance losses between three flow gauges along the Narran River. model

Discharge NSW Dept. of 40 years flow gauge data from the Wilby Wilby Input into water balance Infrastructure, gauge approximately 45 km north of the study site and hydraulic models Planning and Natural Resources

Topography LiDAR Dedicated flight over the study site, data set Input into hydraulic model includes 650,000,000 points with 1 point per m2. Data accuracy of 8 cm, data precision of 1 cm.

Known flood Landsat Landsat imagery was collected before and after every Calibration for the extents imagery flood event from 1981-2004 as well as two drying hydraulic and water sequences with images gathered every 1–2 months balance models. until dry. Total data set includes over 80 images. Computation of soil losses.

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Water-covered pixels were identified by performing 4.3 Modeling Approach a density slice on Landsat MSS, TM and ETM+ Band A hydraulic-hydrologic modeling approach was used 5. This near-infrared band (1.55-1.75 µm) returns to develop a water balance model that reconstructs very low values for water because virtually all radiant the inundation history of the Narran Lakes flux is absorbed at this wavelength. Conversely, Ecosystem and that has the capability of predicting vegetation and soils have a very high return. The the impacts of natural and anthropogenic changes resultant images showed water as deep black on hydrology (timing, frequency and duration of areas and soils and vegetation as bright areas. inundation). Given the paucity of existing data on the Classification was accomplished using an ISODATA nature of flow within the Narran Lakes Ecosystem, algorithm within Erdas Imagine that divided the the history of inundation and even the sizes of the scenes into wet and dry pixels. lakes, a hydraulic modeling approach was deemed The binary rasters (i.e., the classified images) were a necessary first step to developing a water balance then converted to vector format for ‘cleaning’, model for the system. The hydraulic model provides whereby cloud elements, artificial water storages two critical pieces of data: first, it elucidates the and unrelated inundated areas were removed. flow pathways by which water moves across the Additionally, expert knowledge was used to landscape; and second, it provides a quantitative reconnect estranged channels where an evident link accounting of the proportion of water that travels had been lost through rasterization. This process down each pathway in response to variable input was undertaken to increase the overall accuracy of flows. These data provide the core of the hydrologic the flood maps. An example of two final flood images model in that they define the quantity of water that for the Narran Lakes Ecosystem are presented travels to each lake in response to a given flood in Figure 3. These finalised polygon extents were event. Although the hydraulic model provides verified based on field observations undertaken invaluable information on flow pathways and can be during the 2004 flood event and its drawdown used to predict the extent and duration of inundation phase. These observations indicate a high level of it is computationally intensive, with a single years agreement between water identified in the satellite worth of data requiring 6–7 weeks of model run images and that observed on the ground. time. In comparison, the hydrologic model is computationally simple and capable of running over The final raster flood extent files were overlayed on 100 years of flow data in several minutes. the LiDAR topography map. This allowed for a highly Thus, this model can more easily be used to accurate determination of both the surface area and reconstruct the timing, magnitude and duration of volume inundated within the Northern and Narran flooding in the Narran Lakes Ecosystem (since the Lake complexes. The volumes determined were beginning of gauge data along the river in 1964) and coupled with discharge, evaporation and to model a variety of flow scenarios that seek to transmission loss data to ascertain the volume of ascertain how climate change and/or water resource water lost to the soil during each flood event since development will impact on future inundation 1981. Although there was considerable variability patterns within the system. due to antecedent conditions, time of year, etc., a mean value for overall soil moisture loss was 4.3.1 Hydraulic Model determined (range: 300-1100 L m-2; mean: 624 L m-2). This result was compared to anecdotal The hydraulic model for the Narran Lakes data provided by agricultural land holders who Ecosystem was constructed within a commercially observed comparable soil losses on their properties. available software package, MIKE21, created by the Danish Hydraulics Institute (DHI). The Mike The flood extents determined from the satellite family of products has a long history and Mike21 imagery provide the calibration and validation has been widely applied within both scientific and data sets used in both the hydraulic and environmental consulting communities to address hydrologic modelling phases of this project. a range of hydraulic modelling, assessment and/or These “known” flood extents are compared to prediction issues. Mike21 is a 2D depth-averaged those produced by each model to verify model hydraulic model that solves the Reynolds-averaged performance with respect to predicting the Navier-Stokes equations. The governing equations quantity, distribution and residence time of water for the model can be written as: in both lake complexes.

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where Equation 1 is the local continuity equation and resolution of the bathymetry layer, along with the Equations 2 and 3 are the horizontal momentum velocity of flow, determine the Courant number that equations for the x and y flow components, must be below one for the model to run successfully. respectively. In these equations: t is time; x, y and Thus, the spatial resolution of the bathymetry layer z are Cartesian coordinates; u, v, and w are the determines the ideal time step which was set at downstream, lateral and vertical components of eight seconds for this study, yielding a maximum velocity, respectively; S is discharge; ρ is the density Courant number of 1.0007. of water; and g is the acceleration of gravity. The second category of input data for Mike21 are The inputs into the Mike21 model for the Narran the calibration factors that include bed resistance Lakes Ecosystem occupy four distinct categories and eddy viscosity. The bed resistance is given by including: domain and time parameters, calibration the Manning equation and can be either constant factors, initial conditions and boundary conditions. or spatially variable. Given that the primary output Domain and time parameters refer to two types for this modeling exercise is relative discharge of data – the bathymetric data and the simulation past particular points of interest, the accurate length and time step. The bathymetry for the determination of velocity within the Narran Lakes model was derived from the LiDAR dataset. In its Ecosystem was not necessary and, in addition, original form this dataset was too detailed for the was not verifiable due to a lack of available data. model, generating model run times on the order Thus, a constant value of Manning’s n was used of one model day per actual day. To reduce the run and shown to produce both a stable model and times it was necessary to reduce the resolution predicted inundated areas commensurate with of the bathymetry layer. Several resolutions were those observed on the remotely sensed imagery. The attempted with the final resolution selected eddy viscosity within Mike21 can be based on either according to the competing ideals of minimum run a flux or velocity based formulation. The velocity times and the preservation of all potential flow based formulation is more accurate but can create pathways within the system. The optimal spatial instabilities in the model. However, the accuracy of resolution of the bathymetry layer was 25 m which the eddy viscosity term was deemed of sufficient maintained all of the important topography within importance that a velocity based formulation was the system while improving run times to about eight adopted in this study. A constant value for eddy model days per actual day. The second component viscosity was chosen based on early calibration and within this input category is the simulation length validation model runs that showed close agreement and time step. These parameters have significant between the observed and predicted distributions of impacts on the both the length of modeling runs and water within the Narran Lakes Ecosystem. the overall stability of the model. The simulation The 2004 flood event was used to calibrate the length selected for this modeling exercise coincided hydraulic model. This event lasted approximately with the largest recorded flood in the Narran Lakes three months, with a total discharge of ~45,000 ML, Ecosystem since 1964. This flood (1983–1984) was classifying it as a small flood within the Narran exceptionally large and had three distinct flood peaks Lakes Ecosystem. The short-duration of the event separated by several weeks to months of minimal enabled multiple model runs to proceed over a to no flow. To minimize run times all intervening relatively short period of time, thus facilitating the periods of minimal or no flow were removed, thereby calibration of several input parameters the most producing a flood of reduced duration but with important of which were eddy viscosity and bed realistic peak flow levels and rise and fall times. resistance for which both single value and spatially Even with the reduced simulation length, the final variable models were trialed. Once the hydraulic model run took more than six months to complete. model input parameters were finalised, the model The second time parameter to be set within a was validated using the 1994 flood event, which Mike21 model is the time step. The time step and the

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lasted approximately 126 days, had a total discharge Figure 4: Comparison of input flows to those down of ~145,000 ML (or approximately the mean annual the main flow pathway to Clear Lake. a) discharge discharge) and inundated both the Northern and plot for the input flow and the flow down the main Narran lake complexes. This event, therefore, was pathway to Clear Lake; b) relationship between the classified as a medium sized flood. The validation flows into theN arran Lakes Ecosystem and that results showed close agreement between the down the main flow pathway to Clear Lake (the predicted and observed inundated areas (± 5%). grey line represents the maximum flow that can travel down this pathway); and c) the mathematical The initial conditions necessary for a Mike21 model relationship between input flows and flows down include an initial water surface level and an initial x the main pathway to Clear Lake. and y component of velocity. Given that the Narran Lakes Ecosystem dries periodically and was dry prior to each model run, both of these parameters were set to 0. Thus, the model is acting on a dry basin and predicts the movement of water into and through the system as each modeled flood progresses.

The final input parameters included in a Mike21 model are the boundary conditions of the water level and/or discharge. These two parameters are tied and either one can be used to route flow into the system. The input flows included in this study were derived from the flow gauge at Wilby Wilby, approximately 45 km upstream of the Narran Lakes Ecosystem corrected for transmission losses as previously described.

Once calibrated and validated, the hydraulic model was used to simulate a single large event of sufficient magnitude and duration to activate all possible flow pathways within the Narran Lakes Ecosystem. Thus, the simulation event both identified the flow pathways and provided a mechanism for quantifying relationships between input flows and those along each primary, secondary and tertiary flow path. In total 28 locations were extracted from the hydraulic model for further analysis and these defined all the major and minor pathways of flow through the system. An example of how the relationship between input flows and the flow down a major flow pathway is derived is presented in Figure 2.1. This illustrates one of the more important flow pathways; the main pathway by which water is routed into the Northern Lake complex. Importantly, this pathway has a maximum flow transport capacity (a threshold flow value of 10 m3 s-1) above which all additional flow volumes 3.3.3 Hydrologic (Water Balance) Model are routed down alternate flow pathways to the Narran Lake complex. Alternative flow pathways into The water balance for a lake or wetland can be the Northern Lake complex are only triggered in the written as: largest floods (i.e., those above 25 3m s-1) and flows into the complex cease when the lake becomes fully inundated at which point all water is diverted into the Narran Lake complex. where V is the volume of the lake, t is time, Q is inflow discharge,T is transmission loss, I is infiltration into the lake bed,P is precipitation and E is evaporation. The water balance for the Narran Lakes Ecosystem includes all of these major parameters with the two storages, the Northern

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Lake complex and Narran Lake complex, being The flow input from Step 10 is then routed into modelled independently but with linked flow inputs. the Narran Lake complex and a water balance is computed using Steps 5–9 with one exception; rather The linked water balance model for the Narran than striping water off the input flows to account for Lakes Ecosystem is computed in the following lake bed infiltration and internal transmission losses iterative fashion: (Step 5) a standard loss of 1,100 L m-2 is applied to 1. the transmission-loss-adjusted inflow discharge this complex. Although this value is at the top of the from Wilby Wilby is routed into the top end of the range defined for lake bed infiltration, it captures Narran Lakes Ecosystem; both lake bed infiltration and transmission losses 2. a check is made of the input flow level against and because a large proportion of the water that threshold values for each of the flow pathways flows into the Narran Lake complex flows overland into the system; rather than in channels these combined losses are quite large. 3. for any pathway on which the commence to flow level has been exceeded, the proportion of The water balance model was calibrated and the input flow that travels down the pathway is validated using the 50:50 method. In this method, determined from the relationships defined by the one half of the known flood extents (1981–1992) were hydraulic model (refer Figure 5 for an example of used to calibrate the model while the remaining this procedure); known flood extents (1993–2004) were used to validate the model. There was a high level of 4. the total flow input into the Northern Lake (via all agreement between the calibration and validation functioning flow pathways) is determined (note: data and the model outputs for both the Northern the flows into the Northern Lake complex are and Narran Lake complexes with both complexes determined first because once this lake fills it reporting an r2 of nearly 0.9 for the actual to alters the amount of flow delivered to the Narran predicted surface area inundated when all known Lake complex); flood extents are considered. The time series of 5. the input flows into the Northern Lake complex predicted against actual inundated surface areas for are adjusted for lake bed infiltration and internal both lake complexes are presented in Figure 5. transmission losses by subtracting a fixed volume of 250 ML and an additional 12.5% of the Figure 5: Time series of predicted versus flow down each pathway; actual flood extents. a) theN orthern Lake; 6. the running discharge (i.e., the cumulative and b) Narran Lake. discharge for a given flood event) is calculated based on the adjusted input flows; 7. the volumetric daily loss/gain is computed as the rainfall minus evaporation (times a correction factor for open water evaporation) multiplied by the surface area of standing water from the previous time step; 8. the adjusted Northern Lake volume is determined by first querying the current standing water volume of the lake to see if it is full. If so, all additional flow inputs are routed to the Narran Lake complex. If not, the new volume of the lake is computed by taking the volume of the lake during the previous time step minus the loss/gain value plus the input discharge; 9. the adjusted discharge is converted into a surface area based on the hypsometric curves for the Northern Lake complex; 10. the flow to the Narran Lake complex is determined by subtracting the total input discharge at the top of the system from the (pre-adjusted) flow into the Northern Lake.

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These plots show a high degree of correlation of error is also possible in the actual flood extents between the actual and predicted flow levels with all as derived by the satellite imagery. Although the of the major and minor inundation and drying events band five density slice technique is an established being captured by the model. In addition, there is no method and field observations were conducted to systematic error in the model in that the actual verify several flood extents in 2004, there is still the inundation level exceeds the predicted as often as the possibility of mis-classifying wet soils as inundated predicted exceeds the actual. Therefore, the long soils using this technique. In addition, the inundation term predicted flow levels are highly compatible with that occurs from secondary flood peaks can often those that actually occurred and the total predicted be obscured by the tremendous vegetative response and actual lake volumes for the period of record are to inundation that occurs within the Narran Lakes nearly identical for both lake complexes. Ecosystem. Thus there is the possibility of error both within the input and calibration data for the water 4.3.4 Uncertainty balance model. However, despite these numerous There are many potential sources of uncertainty sources of error, the close correlation between the within the water balance model that could account actual and predicted inundated areas indicates that for variability in the predicted to actual surface the model is robust and capable of predicting the areas. Effectively, every input parameter within inundation within the Narran Lakes Ecosystem with the model has a level of uncertainty within it, a high degree of accuracy. although some input parameters are significantly more uncertain than others. The highest levels of 4.3.5 Accompanying datasets uncertainty are found within the infiltration and 1. Narran_Model_Scenarios.xls (summary transmission loss parameters. Because there are spreadsheet showing the results of the no data available on these values within the Narran hydrologic model for 4 climate and water Lakes Ecosystem they are used largely as calibration resource development scenarios). factors with their limits defined according to the previously described procedures. The precipitation and evaporation data also have a degree of 5. Methods for Ecosystem Response uncertainty, particularly with respect to the daily values occurring directly over the lakes. Although Vegetation the data themselves are of high quality, the spatially The methods used to address the aims of the variable nature of both precipitation and rainfall vegetation ecology component of the Narran within this semiarid environment means that the Ecosystem Project included both field surveys actual value over each lake could be considerably and glasshouse experiments. Due to issues of scale different (on a daily basis) than that derived from and complexity, different survey methods were the Thiessen polygon approach. However, these employed to examine each of the main components errors will be mitigated over the longer term as the of the extant vegetation, i.e. tree communities, average rainfall and evaporation over the area are lignum shrubland and understorey vegetation. relatively constant. Therefore, the overall impact on The major field survey activities conducted during the model results will be negligible for the long term the project were: but could be significant over the scale of several days to several weeks. An additional level of uncertainty 1. the Vegetation Survey (focusing primarily on applies to the evaporation data in the conversion groundcover communities), of pan evaporation to open water evaporation. As 2. the Lignum survey and no evaporation data are available over the lake 3. the Tree Patch Survey. surfaces, this correction is based on standard Bureau of Meteorology data and therefore may Glasshouse experiments were also conducted, also be inaccurate over short timescales. The input primarily to examine the soil seed bank and its flows to the system are another potential source of responses to flooding. Two major mesocosm error, particularly during the largest flood events. experiments were conducted during the project. Although the Wilby Wilby gauge is rated to have The first of these examined the composition good quality data, some of the water in the Narran and structure of the soil seed bank in relation to River flows overland during the largest flood events various habitat types within the study area and the and is beyond the extent of the rating curve for the second experiment investigated plant community Wilby Wilby gauge. The gauge discharges recorded development and productivity from the soil seed during these events, therefore, do not necessarily bank in response to a variety of annual flow regime represent the total discharges potentially entering scenarios. A further glasshouse experiment the Narran Lakes Ecosystem. Finally, a small degree was conducted to examine the growth of lignum

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seedlings in response to different hydrological 5.1.2 Survey methods conditions and soil types. Detailed methods for each Field surveys were conducted in November 2004, of these activities are provided below as well as a list following the recession of floodwaters, and again in of relevant datasets that accompany this report. The May 2005 following 6 months of drying. As conditions aims and objectives of the vegetation ecology of the did not change significantly during the project, no Narran Lakes Ecosystem Project are described in further surveys were conducted. At each site, a 50 m the final report of that project and are not explored x 50 m quadrat was positioned. In November 2004, further here. all trees within each quadrat were recorded and an estimate of lignum cover was recorded where 5.1 Vegetation survey present. In both November 2004 and May 2005, groundcover surveys were made by recording the The methods for the vegetation survey were derived % cover of all species occurring within 10 1m x 1 m from the experience of team members and previous quadrats randomly located within the larger 50 m x surveys of comparable study areas such as the 50 m site. Soil samples were also collected within Cooper Creek floodplain. It should be noted that the each survey site as per the methods used for the vegetation survey was designed and conducted prior broader Narran soil survey (described elsewhere to the availability of the more detailed topographical in this report). and inundation history data (i.e. LiDAR and Landsat analyses) produced during later phases of the 5.1.3 Accompanying datasets Narran Ecosystem Project. Future surveys would benefit from utilising this information to select 1. Star Pick Locations within Reserve.xls additional sites representing a more complete (locations of all star pickets within the range of patches of differing geomorphic and Narran Nature Reserve). hydrological characteristics. 2. VegSurvey_SiteData.xls (locations, % lignum cover and soil characteristics for 5.1.1 Site selection all survey sites). Sites were chosen to represent a broad range of 3. VegSurveyTrees_Nov04.xls (counts for geomorphic habitats, soil types and flood histories each tree species within each site). within the study area using the best available information at the time. Inundation maps produced 4. VegSurveyData_Nov04.xls (species list for by Neil Sims and Martin Thoms during previous November 2004 survey, % cover of each studies of the region were used to delineate four species in each quadrat for November broad flood frequency zones: 2004 survey, cover index (summed cover %’s for each species in each site in 1. Frequently flooded (i.e., Clear Lake and Narran November 2004 survey, species presence Lake centres), (1) and absence (0) for each site in 2. Moderately flooded (i.e. Back Lake and edges of November 2004 vegetation survey). Narran Lake), 5. VegSurveyData_May05.xls (species list for 3. Infrequently flooded (i.e,. lower floodplain areas) May 2005 survey, % cover of each species and in each quadrat for May 2005 survey, cover index (summed cover %’s for each species 4. Rarely flooded (i.e., higher floodplain areas). in each site in May 2005 survey, species In each of the major drainage regions of the study presence (1) and absence (0) for each site area (i.e. the northern lakes and the southern in May 2005 vegetation survey). Narran Lake), three random sites were then selected for each of these flood frequency classes. 5.2 Lignum survey An additional three sites in each region were also selected within the neighbouring terrestrial land A range of methods for surveying the character, systems (recognised as that area beyond the red population structure and condition of lignum soil boundary and largest known flood extent). shrubland were trialled during the Narran A further three sties were located randomly within Ecosystem Project with varying degrees of success. the known bird colony area. This produced a total Those described here are considered to be the most of 33 sites. These were located in the field using useful in terms of the information yielded and the GPS and marked with labelled star pickets for ease with which they can be applied. repeat surveys. A list of star picket locations for Locations for the lignum survey were chosen to vegetation survey sites is provided in the datasets cover patches of lignum shrubland occurring across accompanying this report. a broad range of flood histories, from the bird colony

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in Back Lake to areas at the drier extreme of its 5.3.1 Site selection distribution. Only areas with lignum cover >10% were We begun by mapping mature tree patches within included. Sites were selected haphazardly within the the study area based on a set of criteria formulated field for the final lignum survey as it was conducted using the expert knowledge of team members from prior to relevant analyses of Landsat imagery. Future a range of disciplines. Mature tree patches were surveys would benefit considerably by including a defined as those areas greater than 50 000 2m large number of sites to represent a larger range of within the extent of the largest recorded flood event patches with known flood histories determined from that had greater than 60 % density of vegetation inundation maps and hydrologic modelling produced points higher than 3 m (as recorded by LiDAR). This by the Narran Ecosystem Project. mapping was conducted in Arc GIS using LiDAR and Landsat layers. Four random sites within each of 5.2.1 Survey methods the 15 resultant tree patches were then selected to The final survey was conducted in May 2005 which characterise each patch. Sites were located in the was the first field trip when a wide range of lignum field using GPS. patches became accessible following the inundation event of 2004. At each survey location, five random 5.3.2 Survey methods 5 m x 5 m quadrats were delineated. Within each At each site a 25 m x 25 m quadrat was delineated. quadrat the % cover of lignum was then estimated Within each quadrat, all trees were then counted and the number of lignum clumps were recorded. and a variety of variables recorded for each tree. Clumps rather than individuals were counted as Variables included: species, height, dbh (diameter lignum shrubs often grow very close together in at breast height for all stems >1 cm diameter), a tangled form and it is difficult to differentiate reproductive status (i.e. flowering, fruiting), between individuals, particularly in frequently developmental stage (i.e., mature, pole, sapling flooded areas. The following morphological or seedling for eucalypts, based on descriptions characteristics were then recorded for each clump: contained in George et al. (2005), or mature, juvenile, height, perimeter, % green, presence of leaves, seedling for other species). An index of tree health presence of flowers and sex if present. The presence ranging from 0 (i.e., dead with no leaves) to 5 (healthy of seedlings within each quadrat was also noted. with a large, intact canopy) was also recorded for Ten random measurements were also taken at each each tree. This index was based on canopy area and survey location with a soil moisture probe. % of canopy with leaves and was calibrated amongst field workers at the commencement of the survey. 5.2.2 Accompanying datasets Canopy cover at each site was measured by taking 1. LignumSurvey_SiteData.xls (coordinates readings from a spherical densiometer at 10 random and mean soil moisture measurements for locations within the quadrat and the % cover of each survey location). leaf litter was recorded within 10 random 1m x 1m 2. LignumSurveyData.xls (data for each quadrats at each site. Soil samples were collected lignum clump surveyed in each quadrat for each site as per general soil survey methods and summary data for each survey location described elsewhere in this report. and quadrat). 5.3.3 Accompanying datasets 5.3 Tree Patch survey 1. Tree Patches.shp – ArcGIS shapefile. 2. TreePatchSurvey_SiteData.xls (coordinates Patches of mature tree communities are relatively for each survey site and canopy cover, soil rare within the Narran Lakes study area and random and leaf litter data). sites selected for the original vegetation survey did not cover a sufficient range of wooded areas 3. TreePatchSurveyData.xls (the complete to characterise the composition, structure and dataset including all measured variables condition of tree communities. Consequently, we for every tree recorded within each site developed an approach to surveying trees in this within all patches). wetland that utilised the detailed site information obtained via LiDAR and analyses of Landsat imagery. 5.4 Mesocosm 1 experiment The first mesocosm experiment was designed to characterise the composition and structure of the soil seed bank and investigate any spatial patterns relating to habitat types. A complete description of this study can be found in James et al. (2007).

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5.4.1 Site selection Trays containing vermiculite were also monitored during the experiment to detect seeds that may Seven hydro-geomorphic habitats were pre-defined have been dispersed by wind into experimental based on broad differences in geomorphology, trays. However, none were observed during the hydrology and dominant perennial vegetation. This experiment. samples. was done prior to any analysis of Landsat of LiDAR data in the project and was based on previous work 5.4.4 Accompanying datasets and field observations. The habitats were: 1. Mesocosm1Data.xls – species list and 1. The Narran River channel, number of seedlings of each species 2. The Narran River bank, germinating in each experimental tray 3. Clear Lake centre, during the experiment. 4. Clear Lake shore, 5.5 Mesocosm 2 experiment 5. Back Lake, The second mesocosm experiment was conducted 6. Lignum floodplain and to examine the diversity and productivity of plant 7. Chenopod floodplain. communities developing from the soil seed bank in response to a range of annual flood pulse scenarios. Table 1 in James et al. (2007) provides a complete description of each of these habitat types. Three 5.5.1 Site selection and soil collection sites were then randomly selected from each habitat type. Soils for the second mesocosm experiment were collected from all of the wetland sites (i.e., not 5.4.2 Soil collection terrestrial sites) used in the vegetation survey, excluding the 3 bird colony sites, during November Three replicate sediment samples were collected 2004. At each site, aggregate samples were from locations approximately 100m apart within each collected by taking sufficient soil cores (10 cm site. Each sample comprised 10 random sediment diameter and 5 cm deep) from scattered locations cores (10 cm diameter and 5 cm depth) taken from within the 50 m x 50 m quadrat to fill a 10 L within a 10 m2 quadrat and aggregated in a single bucket. Samples were dried and stored until the bag. Samples were collected from December 2003 – commencement of the experiment. January 2004. Samples were dried, sorted to remove large debris, mixed and stored until the experiment 5.5.2 Experimental procedure commenced. Soil samples from each site were sieved to remove 5.4.3 Experimental procedure coarse material, mixed and sub-sampled for distribution amongst 13 pots (175 mm diameter A seedling emergence experiment was conducted and 175 mm deep). Each pot was first filled with a outside at the Northern Basin Laboratory of the thin layer of vermiculite (3 cm deep) followed by a Murray-Darling Freshwater Research Centre in mixture of steam sterilized mixed clay soil collected Goondiwindi, Queensland. For each replicate soil from the study area and river sand. Divided soil seed sample, two plastic trays (16.3 cm x 11 cm) were bank samples (0.7L per pot) were placed on top of filled to a depth of 2.5 cm. One of these trays was this substrate in a 4 cm deep layer, leaving 2 cm to subjected to a waterlogged treatment, in which soil the top of the pot. Each pot was then individually was kept wet throughout the experiment and the placed within a larger pot (225 mm diameter and other to a submerged treatment by placing it within 230 mm deep) to conduct watering treatments. a larger 4 L plastic box and flooding it to a depth of 10 cm. Trays were placed randomly on two large Nine of the pots for each site were subjected to wire frames and covered with thick clear plastic to annual watering treatments as follows: minimize disturbance by rainfall. Trays were rotated 1. 6 month summer flood with fast drawdown, regularly (every 3 weeks) during the experiment. 2. 6 months summer flood with slow drawdown, 3. 3 month summer flood with fast drawdown, The experiment was run for 5 months from 4. 3 month summer flood with slow drawdown, late summer to the middle of spring 2004 so 5. 6 month winter flood (drawdown not relevant as that sediments were exposed to a range of still submerged at 12month harvest time), temperatures. Seedlings germinating in trays 6. 3 month winter flood with fast drawdown, were harvested upon flowering and before further 7. 3 month winter flood with slow drawdown, seeds were added to the soil. Where necessary, 8.12 month flood and 9. 3 month summer flood seedlings were transplanted and grown in pots until with fast drawdown and 3 month winter flood with flowering occurred and identification was possible.

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fast drawdown. A further 4 pots were subjected 5.6.1 Experimental procedure to 6 month long watering treatments: 1. 6 months Lignum plants were grown from seeds planted in submerged, 2. 3 month summer flood with fast trays of damp soil in a glasshouse in Melbourne, drawdown, 3. 3 month winter flood with slow Australia during September 2004. Achenes were drawdown and 4. rainfall only. Flooding was imposed collected during a flood event in 2004 from multiple by filling larger containers with water (creating inundated lignum plants in the study area. After a flood depth of 75 mm above soil samples) and three months of growth in damp conditions, maintaining these water levels regularly as required. 200 seedlings were randomly selected and re-potted Fast drawdown was achieved by emptying larger in individual 30 cm lengths of 750 mm diameter containers of water and allowing sediments in PVC tube with gauze attached at one end to contain the smaller pots to subsequently dry naturally. In sediment whilst allowing the uptake of water from pots where slow drawdown was required, water in larger buckets in which tubes were positioned larger pots was gradually emptied over a period to conduct watering treatments. A thin layer of of 4 weeks (i.e. a quarter of the water emptied vermiculite was placed in the bottom of each tube each week). All pots were subjected to simulated followed by steam-sterilised clay collected from rainfall delivered by hose and using a rainfall gauge the field site in one half of the tubes and a mixture to measure weekly amounts comparable to that of 50% sterilised clay and 50% river sand in the received in the field during that year as reported by remaining tubes. Seedling heights, root depths and the Bureau of Meteorology for Walgett. Pots were leaf numbers were recorded for all seedlings prior to randomly arranged on tables in the glasshouse and re-potting. An additional 10 seedlings were randomly re-randomised regularly during the experiment. harvested to obtain initial measurements of selected An additional 3 pots filled with sterilized soil and biomass and growth variables. Four seedling tubes river sand but not including seed bank material of each sediment type were then placed in each were also included to account for seedlings that of 25 larger buckets and kept moist by regular may have germinated from seeds dispersed into watering with a hose for a period of two weeks to the glasshouse. Of these, one was continuously allow seedlings to acclimatise before commencing submerged, one waterlogged and one only watering treatments. subjected to rainfall. Only algae and one seedling of Cyperus eragrostis emerged in these pots during The glasshouse experiment was conducted over a the experiment. period of 6 months from January 2005 at which time the large buckets containing individual seedling tubes All plant material was harvested from pots after were drained of any residual water and randomly 6 months for the latter 4 watering treatments and assigned to one of five watering treatments: deep after 12 months for the first 9 watering treatments. flooding, shallow flooding, waterlogging, damp For each pot, individuals for each species were or drying. The damp treatment was included as a counted as they were harvested and plant material control and buckets assigned to this treatment were was divided into aboveground and belowground watered every second or third day as required to keep components for each species. Biomass values were soil surfaces in seedling tubes moist but ensure that then obtained for each component by drying plant seedlings experienced neither flood nor drought material to a constant weight at 105°C. stress. The three flooding treatments were imposed by filling the large buckets with water from a hose 5.5.3 Accompanying datasets to a depth of 15 cm over the soil surface of seedling 1. M2Data_12mnthHarvest.xls – species list, tubes in the deep flooding treatment, 5 cm in the seedling counts and aboveground and shallow flooding treatment and to the same level as belowground biomass for each species in the soil surface in the waterlogged treatment. Water each pot of the experiment from the levels were maintained throughout the experiment. 12 month harvest. No further watering was applied to buckets assigned to the drying treatment and sediments were 5.6 Lignum establishment experiment allowed to dry out naturally during the course of the experiment. Buckets were randomly arranged in the This glasshouse experiment was conducted to glasshouse and re-randomised at regular intervals examine survival, growth and morphological throughout the experiment. responses of lignum seedlings to various hydrological conditions in broadly differing Five seedlings in each watering treatment-sediment sediment types. type combination (i.e., one from each bucket) were harvested at each of 4 times: 30, 60, 120 and 180 days. For each harvested seedling, maximum plant

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height and root depth, the number of leaves and the Narran Project. The procedure is based upon stems and the presence of adventitious roots were simple quadratic estimators applied to sum-of- recorded. Total leaf area was obtained for each squared residual error responses. An unconditional harvested plant via image analysis (Bioscan™ Image sum-of-squares estimator function is a very good Analyser, Monash University, Victoria, Australia). approximation to a maximum-likelihood estimator Shoot, root and leaf components were dried to a with maximum posterior density (Box and Jenkins constant weight at 105 ˚C to obtain biomass values. 1976). It also has a quadratic form about the minimum, at least in theoretically general cases 5.6.2 Accompanying datasets (i.e., those where a single parameter does exist). 1. LEEData.xls – recorded and calculated Having calculated both correlation coefficients, and variables for all seedlings harvested squared residual errors, for a range of lags, any during the experiment. hypothetically causal relationships must satisfy the following four conditions: Waterbirds (i) The response of correlation coefficients must exhibit a smooth continuous response defining 5.7 Data sources a single extremum (and to exclude, for example, Bird data are drawn from the eastern Australian quasi-periodic oscillations); aerial bird survey (Kinsford et al. 1999, Braithwaite et (ii) The response of sum-of-squares functions must al. 1986), conducted every October since 1983. Data exhibit a single region wherein p-values for were available up to 2005, so all statistical tests are correlations are below specified significance based upon n = 23 annual samples. (p = 0.05 here);

All meteorological and hydrological data were taken (iii) A quadratic regression (with statistically from 1960 onwards. For all analyses not involving significant 2nd-order coefficient) fitted to the bird counts, the full time series (1960-2005) were this region to must yield a single value of lag used, with all p-values calculated assuming n = 23 corresponding to the minimal error; and samples, for direct comparison with those involving (iv) A 1 – p confidence interval must be established bird counts. around this minimal-error lag, , defined by values of the quadratic sum-of-squares Daily rainfall records were taken from every available response, for which, station maintained by the Australian Commonwealth Bureau of Meteorology. Numbers of operating stations vary over the years, but there are currently 854 stations operating within eastern Australia , (63 in the Northern Territory, 197 in Queensland, where λ is the temporal lag, n is the number of 307 is New South Wales and the Australian Capital observations used to calculate the values of S2, Territory, 108 in South Australia, and 179 in Victoria). and . For each day, rainfall is averaged from all stations within each one-degree grid square (defined by Figure 6: Location of the Murray-Darling Basin integer boundaries), with cross-spectral coherences within eastern Australia with points showing (see below) calculated from the averaged data locations of all gauging stations used to estimate covering 365 days. total flow volumes within the basin. Hydrological data were obtained for as much of the real coverage of the MDB as possible (Figure 6), from the state authorities of Queensland (Department of Natural Resources and Water), New South Wales (Department of Natural Resources), and Victoria (Department of Sustainability and Environment). A total of 456 gauge sites were used (96 from Queensland, 317 from New South Wales, and 43 from Victoria).

5.8 Estimation of temporal lags Temporal lags were calculated between climatic, hydrological, and ecological processes using the following procedure developed specifically for

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The confidence interval will ideally lie within A cross-spectral distance was defined, and cross the region established above (step ii); if it lies spectra calculated between every (source) point, beyond this region, it must lie entirely within and all (destination) points lying at that (integer) the obviously quadratic region of the response distance within the south-eastern quadrant of each function. source (Figure 7). There were thus three variables for each analysis: the distance between which cross- Note that values of n are in all cases reduced by one spectra were calculated, and the lower and upper to reflect the degree of freedom required for different limits of spectral period between which coherences values of the lag. Thus, n = 23 – 2 – 1 = 20 degrees of were averaged. freedom are presumed, even in relating 45 years of flow and coherence data. For several combinations of these three variables, maps of cross-spectral coherence were generated 5.9 Cross-spectral coherence across the eastern Australian continent. Mean coherences were assigned to each source point, The coherence analyses are based on the measure representing the mean coherence with all points lying of cross-spectral coherence (Jenkins and Watts the specified distance to the south-east (Figure 7). 1968). A cross spectrum is taken between two distinct time series, rather than a lagged version Exponential smoothing filters were applied to of the same series, as is the case for conventional these coherence maps, using weights of e-0.2d, for spectral analyses. If is the auto-covariance d≤2°. Contiguous bands of relatively high coherence of the series x, for a lag of k, then the spectral were delineated with a combination of two 3rd- density of x is, order edge-detection filters. These identify locally minimal (negative) curvatures, calculated across both 3- and 5-point spans. Edge points are identified

as points at which both filters exhibit local minima. The cross-spectral density is the analogous The filters also provide a direction to the interiors expression, using the cross-covariance, . of high-coherence bands (i.e., the direction in which The cross-spectral coherence, , is then, curvature progresses from positive to negative), enabling identification of all points interior to these identified edges (cf example in Figure. 4.2).

Figure 7: Schematic illustration of the calculation For each frequency, ω, this measure is effectively of cross-spectral coherences. Cross-spectra are a cross-correlation coefficient in the domain of generated from each source point (red box) to all frequency, with high values representing a high south-eastern destination points at the specified covariance between the two series at that frequency. distance. Two distances are illustrated, showing We utilised mean values of cross-spectral coherence how the number of points increases with increasing taken between defined lower and upper limits of distance. Lines illustrate a select few of the spectral period. Averages were calculated only connections between the source and destination from those components having positive phase points. Coherence at each source is the mean relationships, i.e., representing a destination point cross-spectral coherence with all destination point. leading a source point (these generally comprise around 90% of data within the frequency range considered). Spatial separations between points are discussed in the following section.

5.10 Spatial coherence analyses Spectral analyses require continuous data, yet many meteorological stations, particularly throughout the more arid, remote regions, have not recorded daily data throughout the study period (1960-present). Rainfall records were therefore aggregated into grid boxes (points) of 1° of latitude and longitude, defined by integer boundaries, to increase the likelihood of continuous records for each point.

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Measures of annual coherence throughout the birds is 13 days (day 275 = November 2nd). There are eastern continent were thus obtained by averaging thus 275 – 238 = 37 days unaccounted for within the the coherence of all points lying within the identified additions of lags. This value is, however, less than bands of relatively high coherence. Maps were any of the confidence limits for the individual terms, generated from the 365 days of rainfall prior to the and has been ignored within the figure. bird survey, which was assumed to occur on Oct There was no significant relationship between flow 15th. The three variables, of cross-spectral distance, volumes and coherence averaged throughout the and lower and upper limits of spectral period, were entire eastern continent, although there was a single varied to determine the combination that yielded the pronounced minimum. This lack of significance was highest correlation between annual coherences and perhaps not surprising, considering that the MDB the avian abundances. occupies a much smaller portion of the eastern These analyses were insufficiently precise to permit continent than the bird survey region. In relating flow application of parameter estimation techniques, as volumes to coherence, therefore, mean coherences described above. For example, distances were varied were taken from within the MDB only. Doing so between 1 and 10°, with these ten values being able yielded a relationship between lag and residual to provide only a rough estimate of the distance error that exhibited a single, highly significant yielding the maximal correlation. Values derived minimum. Flow within this figure should thus be from these analyses, and used throughout all considered as relating to this sub-portion of the subsequent analyses, were a cross-spectral distance entire coherence map. of 10°, with coherences averaged between spectral periods of 13 and 21 days. The most important consideration throughout these analyses was, 6. Management Implications however, that the results be not overly sensitive to This section discusses the major management the particular combination of values used. This was implications of the key findings of the activities indeed the case, with the maximal correlation being described above. More detail concerning these in the centre of a broad region of high values (e.g., findings is given in the final report of the Narran similar results pertain for all distances between Lakes Ecosystem Project. Management implications 7 and 10°, and limits of spectral period taken from are discussed for the physical template, hydrological 7 days upwards). drivers, each of the main vegetation components, i.e., groundcover communities, lignum shrubland Having established these three values, a lag was and tree communities and waterbirds. introduced by calculating coherences from rainfall data finishing at some date prior to Oct 15th. Values up to this day (i.e., day 288) were used, with 6.1 Physical Template the resultant response of squared residual errors The physical template of the Narran Lakes exhibiting a single, pronounced minimum. We Ecosystem could only be accurately defined interpret the existence of this single, minimal-error using LiDAR data. Existing DEMs of Narran were lag to support the validity of the prior search for either too coarse (e.g., the 90 m DEM of Australia) the values of cross-spectral distance, and limits of or incomplete (e.g., the QDNRM DGPS derived spectral period. DEM). The high degree of morphologic complexity (especially the extensive network of over 8,000 river 5.11 Correlation between coherence and channels) and the dense vegetation (specifically flow volumes lignum) meant that a remotely derived DEM was the only practical way of capturing the topography. This In correlating mean values of coherence with mean lesson is also relevant to most floodplain-wetlands annual flow volumes, any range of dates may be in Australia which are typically characterized by used to reference the calculations. To avoid problems highly complex morphologies and dense vegetative thus arising, we calculated the lag of flow behind networks. This data source also enabled a highly the bird counts (13 days), and the lead of flow ahead sophisticated hydraulic modeling exercise to be of the coherence that best explains the bird counts, undertaken on the Narran Lakes Ecosystem. This i.e. the coherence calculated at 75 days behind the simply could not have been accomplished without bird counts. The lead of flow thus calculated is 25 ± this data set. Thus, future investigations into 62 days. Tracing back from the bird survey (October floodplain-wetland character in Australia should 15th bird = day 288), through coherence (288 – 75 consider the benefit of LiDAR as a data source and, = day 213), and forward, leads to the flow being were feasible, these data should be collected. calculated for the year ending at 213 + 25 = day 238 (September 26th), while the lag of flow behind the

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Soils in the Narran Lakes Ecosystem are spatially Knowledge of the timing, magnitude and duration variable both in terms of their physical and of inundation (derived from the hydrologic model) chemical composition. These soils are derived from can be coupled with information about hydrologic sediments that originate upstream in the Maranoa patch dynamics and ecological response models and Condamine sub-catchments. The stability of to manage flows to meet particular ecological sediment delivery through time, and the slow rate of objectives. For example, decisions about the need accretion within the Narran Lakes Ecosystem indicate for top-up events (e.g., to maintain a breeding event) that this feature is and has been a functional wetland or providing a maximum flow peak (e.g., to wet the habitat for many millennia and should remain largest floodplain extent to induce vegetation growth) as such (sedimentologically speaking) for many can be made by coupling the flow and ecological millennia to come. As a closed basin, the Narran response models. Lakes Ecosystem is a repository for sediments A robust and detailed hydrological model for derived from upstream. Consequently, monitoring floodplain wetlands is a key tool for future water sedimentation in the basin can provide an indicator of management initiatives. Such a tool provides changes in sediment delivery from upstream. the data upon which ecological evaluations and The channel network in the Narran Lakes Ecosystem predictions can be made and provides evidence is dynamic with marked change over time. Alterations for evaluating the consequences of particular in the channel network have implications for the water management plans. To this end, it is a delivery of water and sediment to the system and recommendation that coupled hydrological driver- also may have wider ecological impacts (as channels ecological response models are derived for all are key habitats within the Narran Lakes Ecosystem). critical floodplain-wetland areas within the Murray Recent trends in channel network complexity show Darling Basin. an overall reduction in the amount and diversity of channels over the last two decades. If these trends 6.3 Groundcover plant communities continue, the viability of the Narran Lakes Ecosystem as an aquatic habitat may be compromised. It is 6.3.1 Flow-related responses important, therefore, to monitor the state of the Groundcover vegetation in the Narran Lakes network in coming years to see if this reduction in ecosystem was found to be species-rich (c. 100 network complexity and extent is within the range of species) and substantially different to that observed natural variability or is a systematic decline driven by in neighbouring terrestrial landsystems. Many increased sediment loads or decreased flow inputs to annual and perennial forbs, grass and sedge species the Narran Lakes Ecosystem. maintain large, long-lived soil seed banks and groundcover communities are therefore likely to 6.2 Hydrological Drivers exhibit some degree of resilience to environmental Although there has been no obvious climate change fluctuations. Surface water hydrology, however, over the Narran Lakes Ecosystem over the period has an overriding influence on the development of record, current climatic predictions do entail an of plant communities from these soil seed banks increase in temperature (and hence evaporation) and and also interacts with the physical template to a decrease in rainfall over the coming years. These affect the composition and structure of soil seed changes will need to be monitored to maintain an banks themselves. Managing flow regimes to accurate picture of the water balance in the Narran promote spatial and temporal heterogeneity in Lakes Ecosystem in the future. Flow modeling in the inundation patters is therefore central to maintaining Narran Lakes Ecosystem, however, shows that the groundcover vegetation diversity at both local and impact of water extraction upstream far outweighs landscape scales. even the most severe climate change potential At a local scale, high diversity and productivity of in terms of overall impact on flow magnitude groundcover species will mostly be promoted by and duration in the Narran Lakes Ecosystem. short to moderate periods of submergence (~ 1–3 To ascertain the true impact of future water months) followed by long periods of waterlogged or management decisions, the hydrologic model for damp soil (~ 3–6 months). In contrast, long periods of the Narran Lakes Ecosystem needs to be regularly submergence limit both the productivity and species updated with new information as it becomes richness of groundcover communities although available. This might include new climate change some plant groups are favoured by such conditions, data, new development or water sharing options e.g., charophytes and perennial hydrophytes such and/or new inundation (and drawdown) patterns as Vallisneria spp. and Myriophyllum spp.. Plant which can be used to further refine the models community responses to patterns of flooding underlying equations.

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and drying are also dependent on soil seed bank Table 4: Exotic species recorded in the vegetation composition which varies amongst different and/or the soil seed bank during the Narran Lakes hydrogeomorphic habitat types. Soil seed banks Ecosystem Project. in frequently flooded habitats, e.g., the centre of Species name Common name Clear Lake, contain less germinable seeds of fewer species than surrounding wetland habitats and plant Abutilon theophrastii swamp lantern communities establishing in such sites in response Aster subulatus bushy starwort to inundation are likely to comprise fewer species Conyza sumatrensis tall fleabane than those in neighbouring areas regardless of the duration of submergence or waterlogging. The Cuscuta campestris golden dodder replenishment of soil seed banks in these habitats Cyperus eragrostis umbrella sedge however may depend on frequent small to medium Echinochloa colona barnyard grass sized flood events that result in reproductively successful germination events. Conversely, Gamochaeta calviceps cudweed infrequently inundated areas at the periphery of the Gnaphalium polycaulon cudweed floodplain have comparatively species-rich soil seed Heliotropium supinum heliotrope banks from which productive plant communities Hordeum leporinum barley grass are likely to establish in response to even short periods of soil waterlogging. The composition of Malva verticillata curled mallow these communities also differs substantially from Potentilla supina cinquefoil those in frequently and moderately flooded habitats. Phyla canescens lippia Protecting large floods that inundate such areas is thus critical to promote heterogeneity of groundcover Rumex crispus yellow dock community types at a landscape-scale and also Schismus barbatus Arabian grass to enable the replenishment of soil seed banks in Sisymbrium irio London rocket infrequently flooded areas through both hydrochory Soliva anthemifolia dwarf jo-jo and reproductive output of local germination events. Sonchus oleraceus sowthistle 6.3.2 Exotic species Spergularia rubra sandspurrey At the time of the surveys and experiments Verbena officinalis common verbena described here, exotic species appear to be relatively Xanthium occidentale Noogoora burr rare in the soil seed bank and vegetation of the Narran Lakes ecosystem, although extensive areas of lippia (Phyla canescens) were observed in the shore vegetation of Clear Lake in areas not included and field surveys will probably be most informative in the vegetation survey. In total 21 species were if conducted at such times. Useful and easily observed during the project (Table 4). In the soil seed measured survey indicators might include species bank, germinable propagules of exotic species are richness, % cover and identification of dominant most prevalent in frequently inundated sites, e.g., the species and % cover and identification of exotic centre of Clear Lake and Narran Lake, suggesting species. Analyses of such indicators however must that propagules may disperse into these areas by take into account variation in flood attributes (i.e., floodwaters. Establishment and growth of these duration of submergence, duration of waterlogging, exotic species from the soil seed bank, however, seasonal timing) related to measured responses. appear to be limited by long periods of submergence Survey sites established during the Narran Lakes and slow drawdown of flood waters. Consequently, Ecosystem Project will provide an initial network of there is a potential for exotic species to become sites for monitoring as baseline data for these is now more prolific in frequently flooded habitats if flood available (see accompanying datasets). Results of events with short durations of submergence occur LiDAR, Landsat image analyses and the hydrological more commonly. model since produced by this project should also be interrogated however to select additional sites 6.3.3 Monitoring representing habitat types not currently included or sites where long-term changes to flood history are Monitoring the condition of groundcover vegetation likely to have occurred. communities in the Narran Lakes ecosystem is likely to be best achieved through a combination of Periodic investigation of soil seed bank composition field surveys and soil seed bank studies. Vegetation and structure may also be useful for detecting composition and structure are at their most diverse species declines or additions (e.g., potential species and complex following the recession of floodwaters invasions) over time. Soil seed bank monitoring

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might target frequently flooded areas (e.g., the State policy should recognize the variation in the centre of Clear Lake and Narran Lake) in order to character of lignum shrubland throughout its range monitor the abundance of propagules belonging to as this is likely to be an important determinant of its exotic species. Sites known to have species-rich ecological function (e.g., provision of breeding habitat plant communities following flooding, e.g., the bird for waterbirds). colony area of Back Lake, may also be a priority for monitoring temporal trends in soil seed bank 6.4.3 Monitoring composition and structure. Monitoring of lignum shrubland should consider both the overall extent of this community and 6.4 Lignum shrubland the extent of patches of varying character. Given the hypotheses developed in the Narran 6.4.1 Flow-related responses Lakes Ecosystem Project, particular attention The results of the Narran Lakes Ecosystem should probably be directed towards monitoring Project indicate that the distribution, character and the boundary of lignum shrubland at the condition of lignum shrubland within the study area frequently flooded end of its distribution to detect are closely related to surface water flows. While encroachment of open water areas. Potential mature individuals of lignum are clearly tolerant methods for this might include analysis of remotely of a wide range of environmental conditions, sensed data, however, further research is required to including flooding and extended periods of drought, test such techniques. hypotheses developed during the project suggest that alterations to long-term patterns of flooding 6.5 Trees may result in changes in the distribution of lignum patches of varying character at the landscape-scale, 6.5.1 Flow-related responses with potentially important ecological consequences. Patches of mature trees within the Narran Lakes The character of lignum patches varies along a flood Ecosystem appear to be the least resilient component history gradient from high-densities of many small of the vegetation and are also in the most degraded lignum clumps occurring in infrequently inundated condition at present. High proportions of the 3 main areas to areas with high cover comprising few large tree species, Eucalyptus camaldulensis, E. coolabah lignum clumps in moderately inundated areas and A. stenophylla within the study area are dead or such as in the bird colony area of Back Lake. In under stress and it is highly likely that this mortality frequently flooded areas such as the centre of Clear results from a lack of sufficient flooding in these Lake, lignum shrubland is absent and experimental areas. To prevent further mortality and promote results suggest that this may be due to limitations on recovery of stressed individuals, preserving flows seedling establishment resulting from flood stress. which inundate tree patches must be a management Reductions in flood frequency and duration may priority for the Narran Lakes Ecosystem. therefore result in a migration of lignum patches of varying character and possible encroachment of open 6.5.2 Monitoring water areas. This may have numerous implications for waterbirds such as a decline in the quality of Sites established for the tree patch survey in the historical breeding areas and reductions of open Narran Lakes Ecosystem Project provide a solid water feeding areas. Further research is required to baseline for monitoring tree community condition test these hypotheses more thoroughly (see below). in the study area. Rapid assessment methods could include observations of the % of each species at each 6.4.2 Clearing site within broad condition categories, e.g., dead with no leaves or bark, dead with bark, very stressed with Clearing of lignum shrubland, via chaining or few leaves, moderately healthy and very healthy. burning, has been conducted in dryland floodplain- It would be appropriate to time such assessments wetland systems throughout the northern Murray- with changes in environmental conditions, e.g., Darling Basin. While both Queensland and New substantial rainfall or flood events, however, care South Wales vegetation policies include restrictions would need to be taken in interpreting causality until on such activities in areas defined as wetlands as a long-term dataset was established. Monitoring well as within specified buffer zones and riparian the condition of individual trees would also be areas, lignum shrubland is generally treated by both informative and help determine individual tree states as a single vegetation category and clearing responses to various conditions. This could involve limits based on plant size are not included as they selecting representative individuals of each major are for trees such as Eucalyptus camaldulensis.

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developmental stage for each common species in the case, any interventions that disrupt the kind different tree patches and monitoring more specific of qualitative hydrological response that would indicators, e.g., canopy area, % canopy with leaves, occur under a given climatic state may negatively degree of epicormic growth etc. affect waterbird populations. In the absence of any contrary evidence, any such impacts must at least 6.5 Waterbirds by hypothetically considered as consequences of any and all modifications of hydrological processes. There are three primary implications for the management of waterbird populations both within 6.5.3 Temporal Lags the Narran Lakes region and the larger landscape A much more clear and direct implication of the beyond, as follows. establishment of the inter-connections between 6.5.1 Climate climate, hydrology, and avian abundance, concerns the importance of temporal lags mediating these, The Narran Ecosystem Project has demonstrated and indeed any, large-scale processes. In almost that climate is the major determinant of inter-annual all previous studies, temporal lags have been variations in waterbird abundance throughout implicitly presumed, yet given only the most cursory Eastern Australia. Any study of waterbirds, whether treatment. Not only are temporal lags vitally for direct management of populations, or any other important, but the establishment of a statistically reason, therefore must explicitly take account significant, single value for the temporal lag of climatic variability in order to understand mediating any two large-scale processes should variations in abundance at any scale. The climatic be a prerequisite for any hypothesised causal descriptors developed for the Narran Ecosystem connection. We assert that any and all studies aiming Project were exploratory and, while providing to investigate hypothetically causal connections very strong descriptive ability, remain in need of between large-scale processes, be they climatic, further development. Thus not only should climate hydrological, or ecological, must follow something be taken in to account in studying and managing very much like the protocol developed in the Narran waterbird populations, but understandings of the Ecosystem Project. The simple assertion that climatic mediation of waterbird abundances must two processes are maximally correlated at one be developed in line with management requirements. particular lag is grossly inadequate and ought not In particular, the scale of any action designed to be acceptable. We proffer a single caveat that there address waterbird populations will necessitate may be some cases where data are of insufficient understanding the effects of climate upon bird temporal resolution, yet most large-scale processes abundance at that scale. in the enormously climatically variable continent 6.5.2 Hydrology of Australia are climatically mediated in some way or other, and climatic data are very readily Inter-annual variations in waterbird abundance available. Two non-climatic processes may be are related to climate; inter-annual variations in quantified through scant data, yet the inclusion of amounts of available water are relate to climate; a climatic inter-connection enormously improves and inter-annual variations in waterbird abundance the ability to adhere to our protocol. All analyses of are related to amounts of available water. This avian abundance relied upon a mere 23 data, yet last connection reflects not only the redundant extremely (statistically) powerful conclusions were connection through climatic mediation of water, but possible throughout. the independent component of hydrology as affected by all processes other than climate, particularly those arising through human agency within the water cycle. The management implications of this finding within the context of the present findings are not entirely clear at present (see Future Research, below), but certainly may not be ignored for that reason. In the absence of any contrary evidence, one must presume that waterbirds have evolved to intimately track the dynamic relationships between climate and hydrological processes, and quite likely possess a highly detailed knowledge of both landscape topography, and the hydrological networks that permeate the landscape. This being

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Murray-Darling Basin Commission

GPO Box 409 Canberra ACT 2601 Tel 02 6279 0100 Fax 02 6248 8053 www.mdbc.gov.au