K&C Science Report – Phase 2 Investigating the use of PALSAR for assessment in semi-arid environments of : The Murray-Darling Basin (MDB)

Anthony Milne, Anthea Mitchell and Rachel Melrose School of Biological, Earth and Environmental Sciences, University of , Sydney, NSW 2052, Australia. [email protected]

Ian Tapley Horizon Geoscience Consulting Pty Ltd, 12 Viewcrest Way, Sorrento,WA, Australia. [email protected]

Abstract - ALOS PALSAR data is used to analyse the flood 2006-2008 [1]. The results of this study showed that following dynamics of two semi-arid systems and to characterise and the release of an environmental flow into the Macquarie define wetland typologies that result from infrequent and highly Marshes, the following information could be obtained using a variable river flood regimes. The two sites, the Gwydir and the time series of PALSAR imagery: Paroo , are both located within the Murray Darling Basin • Spatial mapping of inundation extent over the period of of eastern Australia. The methods developed have the potential to provide cost effective monitoring of wetland condition in inland image acquisition; Australia, and to also supply useful baseline data on flood pulse • Identification of changes in surface water and soil moisture and vegetation response for the management of internationally content and distribution; significant Ramsar . • Monitoring of the changing wetland dynamics over the time; and, Index Terms—ALOS PALSAR, K&C Initiative, Wetlands Theme, • The discrimination of wetland vegetation classes using time- flood inundation, wetland condition series data.

I. INTRODUCTION The wet conditions in the during December 2007 and January 2008 presented an opportunity to While mapping the extent of flooded forests and wetlands refine techniques employing imaging radar for inundation in humid and tropical areas using radar has been readily mapping in semi-arid wetland environments and for assessing demonstrated, the detection and analysis of flood patterns in soil moisture changes. The study also showed that an semi-arid environments is less well known and understood. operational system for monitoring environmental flows in Flood events in these environments often depend on irregular semi-arid wetland environments using imaging radar is and infrequent rainfall events or on the release of possible. The full results of this investigation are described in environmental flows from upstream storage dams on rivers a three volume report, Trial of L-band radar for mapping where discharge is largely confined to in-channel rather than inundation patterns in the Macquarie Marshes [2]. to overbank flows. Sheet flooding does however occur. These patterns of flooding are found especially within the dispersive II. DESCRIPTION OF PROJECT or braided stream systems which characterise many of the catchment basins found within the northern section of the The first objective of this study, which is ongoing, is to use Murray Darling Basin (MDB) of Eastern Australia. ALOS PALSAR data to map changes in wetland hydrology and vegetation cover associated with land clearance for Results of using ALOS PALSAR data to monitor agriculture and to identify and monitor wetland morphological inundation patterns and vegetation response to flood events in features that result from periodic flooding as a result of heavy a semi-arid wetland environment, namely the Macquarie rainfall events. Marshes in Central New South Wales, were reported in ALOS Kyoto & Carbon Initiative, Science Team Reports, Phase 1,

1 The second objective is the development of an operational on both the quality of the natural environment and the system using ALOS PALSAR data for mapping wetland economic sustainability of the MDB. It is estimated that there typologies and assessing the effect of periodic flooding and are some 30,000 individual wetland sites within the basin, environmental flows on vegetation and soil response in most of which occur around farm dams and water courses on regional semi-arid wetland environments. private land. Sixteen wetlands are RAMSAR declared sites with another 200 listed in the ‘Directory of Important The two sites chosen for this investigation are the Gwydir Wetlands in Australia’ [6]. River near Moree where large areas of wetland habitat have been cleared for grazing, irrigation and dryland farming, and Efforts to manage and conserve the surface waters of rivers the in the far north–west of the State which in the MDB are hampered by limited scientific data regarding constitutes one of the last “wildland” or free flowing river the historical and contemporary flow and flooding patterns systems in arid Australia. Both are found within the MDB. and of the response of flora and fauna to the high natural variability of flow regimes that typify the lowland-dryland The Murray Darling Basin (MDB) (Figure 1) occupies rivers [7]. approximately one-seventh of the continental surface area of Australia or just over 1 million square miles. The Great A major strategy of the Wetlands Policy of the Dividing Range marks the eastern and southern edges of the Commonwealth Government of Australia is to “ Document the basin. The and its tributaries flow south and extent of the Commonwealth’s wetlands and identify priorities south west before joining the Murray system and discharging for conservation action and rehabilitation ” (Commonwealth into the Southern Ocean at Lake Alexandrina near Goolwa in Government of Australia, 1997). There is also a high . Many of the Darling related stream networks importance placed on establishing the ecological character and have their source in the arid and semi-arid landscapes of the flooding dynamics of the inland aquatic systems in order to Australian inland. manage and protect them into the future.

A. Gwydir Wetlands The Gwydir Wetlands are located in the Gwydir valley which lies to the north of the Macquarie Marshes, the site of the previous study. The wetlands include the Lower Gwydir and Gingham watercourses, both of which end in terminal floodplains, except during major floods when water may reach the nearby Barwon River. The Gwydir Wetlands support an estimated area of 102,000 ha of wetland vegetation and are recognized internationally for their significance as waterbird habitat and are listed in the Ramsar Convention. The wetlands and wider area also support significant grazing and irrigated agriculture industries [8].

(i) Work Approach This initial analysis focuses on identifying wetlands and the remnants of wetlands in an area partially cleared for agriculture and irrigated farming

Two PALSAR images were used in the study (Table 1). th The first image was acquired on the 25 January 2007, in the middle of summer at a time when a peak in river flow of Figure 1. The Murray Darling Basin and location of the Paroo and Gwydir around 3,000 ML/day was observed at nearby Pallamallawa Rivers, eastern Australia. (Source MDB) gauging station (Figure 2). The second PALSAR image was

acquired on 12 th June 2007 in winter, with water around 160 Freshwater is a vital resource in Australia, and its ML/day at Pallamallawa and 30 ML or less at the other availability is highly variable in semi-arid and arid zones [3]. gauging stations. The June image was preceded by Rapidly expanding water resource development in the MDB approximately three months of low river flows. has impacted natural flow regimes and the ecological integrity of many dryland rivers and their large floodplain wetlands [4], The images were co-registered and geo-referenced to the [5]. corresponding area on a SPOT-5 mosaic (Figure 3). Image-to

image-registration was performed using a 1 st order polynomial Declining river flows from reduced rainfall in recent with 50 GCPs and a RMSE of 0.74. Two test sites were decades together with the increased diversion of water for selected and subset from the PALSAR scenes. irrigation and excessive groundwater extraction, has impacted

2 TABLE I. ALOS PALSAR coverage of the Gwydir wetlands.

Figure 2. Daily river discharge (mean ML/day) for the Gwydir Wetlands as recorded at five gauging stations between January 2006 and September 2007. Acquisition dates of PALSAR imagery shown by arrows.

Figure 3. SPOT-5 mosaic of the Gwydir wetlands (NIR, green and red in R,G,B respectively) with the extent of ALOS PALSAR coverage overlain (41º; green outline).

3 (ii) Inundation mapping Areas of high soil moisture, storage dams for irrigation and ponding dams can be identified on the PALSAR imagery. Areas of open, clear water (including dams, ponds, creeks and irrigation reservoirs) are identified on SPOT-5 imagery as sites of very low albedo, with saturated soil and irrigated paddocks with crops being identified based on high visible green reflectance. In the corresponding PALSAR images for both test areas several sites of open water (dark response) are observed, see Figures 4 and 6.

Bright targets are highlighted in Figures 4 and 5 and represent areas of high dielectric content such as wet soil areas and water beneath the canopy along streamlines. Paddocks with high soil moisture are identified on the PALSAR images Figure 6. Gwydir wetlands Test Area #1: contrast stretching of PALSAR based on their bright response, and in particular, there is a imagery to highlight areas of open water and/or ground features with smooth, large bright area of high soil moisture in th e PALSAR image specular surfaces resulting in zero backscatter to the radar sensor. These areas from June 2007 in Figure 7. are shown in black on the derived masks. © JAXA/MET

Figure 7. Gwydir wetlands Test Area #2: contrast enhancement of PALSAR Figure 4. Gwydir wetlands Test Area #1: identification of open water in images to highlight rough, high dielectric surfaces, and water-beneath-canopy paddock dams (dark albedo – yellow arrow) and irrigated paddocks (green targets (red arrow). These areas appear white on the derived masks. There is tones - blue arrow) in SPOT-5 (bands 3:1:4 displayed as R,G,B respectively) a large area of high soil moisture (bright response) in the masked PALSAR and PALSAR HH-polarisation data for January and June 2007. Changing image from June 2007 (orange arrow). © JAXA/MET water levels in dams and irrigation paddocks show as black, specular surfaces in radar images (orange arrows). Bright areas along streamlines in the JERS-1 images indicate inundation beneath the tree canopy. © JAXA/MET (iii) Change detection Change detection was undertaken using the two PALSAR scenes for the Gwydir wetlands captured in June and January of 2007. Figure 8a illustrates the three-band colour composite for the Gwydir wetlands with January 2007:June 2007:January 2007 in R,G,B respectively, and Figure 8b illustrates the change between the two dates. In Figure 8a, the green areas are dominated by the June (winter) response and consist mostly of vegetation along streamlines and adjacent wetland vegetation and grasslands. The purple areas are dominated by the January (summer) response and relate to the majority of the agricultural area.

Only limited change is observed between the two dates, Figure 5. Gwydir wetlands Test Area #1: contrast enhancement of PALSAR images highlight rough, dielectric surfaces, and water-beneath-canopy targets with the most obvious differences in the agricultural areas (i.e., bright response). White areas on the masked PALSAR images (Figure 8). Some paddocks show an increase in backscatter (> correspond to areas of inundated trees and shrubs. © JAXA/MET 6 dB) in June, indicative of perhaps winter crops or irrigation, while numerous paddocks show lower backscatter (between 0 – 3 dB) indicative of drier ground or limited crop cover. The

4 areas of wetland and grassland show variable backscatter but Both the Paroo and Warrego Rivers are the focus for this are typically higher in June (increasing by 0 – 6 dB). research since they have extensive floodplain wetlands (Figure 9).

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Figure 9. The Paroo and Catchments in the Murray Darling Basin. (Source MDB).

The Paroo and Warrego catchments cover 7,400,224 and 6,290,533 hectares respectively. Both rivers are approximately b) 600 km long. They comprise a vast assemblage of braided channels, waterholes, swamps, claypans, mound springs,

shallow freshwater lakes and salt lakes [10], [11]. There are Figure 8a) PALSAR 3-band colour composite for the Gwydir wetlands: Jan two internationally recognised RAMSAR sites along the Paroo 2007: June 2007:Jan 2007. The purple areas are dominated by the January River (Ramsar Convention Secretariat, 2006) and numerous (summer) response while the green areas are dominated by the June (winter) sites in the catchments designated on the Directory of response; and b) Change detection between January and June 2007. A decrease in backscatter is observed over most of the agricultural areas (of the Important Wetlands in Australia [12]. order of 0.1 – 6 dB), while areas with higher backscatter are dominated by wetlands and grassland. © JAXA/MET The mapping of widespread floods in these river systems is important for many aspects of catchment planning including the estimation of flood potential using historic data, B. Paroo River sustainable grazing of pastures, flood risk modelling for flood One of the last unregulated rivers of the MDB is the Paroo mitigation, and catchment condition monitoring. For effective River in north-western New South Wales. The Paroo is flood mapping, monitoring and management, the timing, connected to the Warrego River through an array of duration, extent and drainage pattern of floodwaters need to be intersecting streams that congregate to form Cuttaburra Basin, examined. Land managers, both private and within a significant bird breeding area of swamp and marshland [9].

5 government, require information about these complex interactions to incorporate effective policies, planning and ii)Work Approach management to ensure cost effective and ecologically Given the extensive surface flooding and the attenuation of sustainable management of floodplain areas. the floodwaters which are stored in a “localised” network of riverine environments in the upper catchments, ALOS During the last week of February and the first week of PALSAR data is being used to map the inundation patterns March 2010, the upper catchments of the Paroo and Warrego and recession of floodwaters to evaluate whether this data river systems received record rainfalls from a monsoonal source can be used as an efficient monitoring and emergency trough centred over Northern Australia (Figure 10). response tool. Floodwaters from this rainfall event caused extensive flooding in the upper section of these rivers. Over the next three months Also, it will be evaluated to see the extent to which the the passage of floodwaters towards the with the fluvial systems that characterise the dominant wetland types Darling River saw most of the water trapped in the network of found in this area of the semi-arid MDB zone can be channels, billabongs and floodplain lake storages on the identified. These wetland types include; wetland freshwater Paroo. Little floodwater if any actually reached the Darling lakes; periodically-inundated floodplain freshwater lakes; River system 700 kms downstream. The flow however periodically-inundated non-floodplain (depressional) watered thousands of square kilometres of floodplain, reviving freshwater lakes; floodplain freshwater swamps; non- many ecosystems and riverine environments that had not floodplain (depressional) freshwater swamps; saline lakes and received water for over a decade [13]. saline swamps [14].

Preliminary analysis of PALSAR FBD data (Scene 381- 6550) acquired on 25 th May, 2010 of the Peery Lake region, which is downstream some 700 kms from the catchment areas shows that a range of wetland-riverine environments can be identified within this semi-arid area on L-band data. Peery Lake is a large overflow storage (Lat 30°45’ S, Long 143°30” E) and is located within and adjacent to the Paroo-Darling National Park, one of three reserves in the Paroo River system. The other reserves are Nocoleche Nature Reserve and are further north in south-western area of and will be the subject of future study. These three lake-reserves provide significant refugia for wildlife with diverse ecosystems and are major breeding grounds for more than 50 local and migratory waterbird species.

(ii) Inundation mapping Figures 11 - 14 show different stream patterns in the vicinity of Lake Peery carrying floodwaters. Some of the floodwaters appear dark due to surface reflection and are difficult to separate from bare sandy soils. However, most stream courses are lined with scattered trees and vegetation resulting in high backscatter when underlain with water.

(iii) Morpho-ecological mapping The visual identification of fluvial patterns such as are found in Figures 11-14 is a necessary first step to the characterizing and mapping of the different semi-arid wetland typologies. The latter however, will require a multi-temporal Figure 10. Flooding in eastern Australia depicted on MODIS, 14 th March 2010 dataset that extends along the length of the Paroo River system and rainfall totals for January-March 2010 (Australian Bureau of Meteorology). and be frequent enough to successfully separate out different riverine-ecological environments.

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Figure 11. L-Band ALOS PALSAR FBD and oblique photo (right) showing sheet-flooding where wide expanses of land are covered with shallow water. Trees lining stream channels give high radar backscatter as a result of double bounce. Dark areas represent open water intermingled with islands and scattered tree cover. © JAXA/MET

Figure 12. L-Band ALOS PALSAR FBD (HH;HV;HH in RGB) sub–area (left) and Landsat insert (right) for comparison showing largely in-channel flow from increased discharge. The “gallery” effect of trees lining the channel bank gives high radar return. © JAXA/MET

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Figure 13. L-Band ALOS PALSAR FBD (HH;HV;HH in RGB) sub–area (left) and oblique photo (right) showing overbank and floodplain inundation. Water is largely confined to the immediate stream valley and adjoining cut-offs and billabongs (Photo. Anthony Scott, 6 May 2010). © JAXA/MET

Figure 14. L-Band ALOS PALSAR FBD (HH;HV;HH in RGB) sub–area (left) and Landsat insert (right) of Lake Peery which is the largest overflow lake on the Paroo River. It is approximately 15km long and covers over 5,026 hectares when in flood. The lake is bordered by sedimentary ranges on the west and sand dunes and sand plains on the east and is a RAMSAR listed site. The Lake is fed by floodwaters passing down the Paroo River. © JAXA/MET

8 III. ONGOING WORK [9] Kingsford, R.T. and Porter, J.L., “Wetlands and waterbirds of the Paroo and Warrego Rivers.’ In ‘A Free flowing River: the ecology of the Paroo River”, Ed. R. T. Kingsford, pp. 23-50. Sydney: NSW National Multi-temporal data stacks can yield more information Parks and Wildlife Service, 1999. about changing surface dynamics than single scene [10] Timms, B. V. and Boulton, A. J., “Typology of arid-zone floodplain acquisitions and are necessary to capture environmental wetlands of the Paroo River (central Australia) and the influence of changes and help quantify bio-physical processes. Given the water regime, turbidity, and salinity on their aquatic invertebrate assemblages”, Archives of Hydrobiology, vol.153, pp. 1-27, 2001. severe 10 year drought Australia has been experiencing (2000- [11] Kingsford, R.T. and Lee, E., “Ecological character description of the 2010), there have been few flood events on inland river Paroo River Wetlands Ramsar site”, Department of Environment, systems that would permit the identification of wetland types Climate Change and Water NSW, Sydney, 2010. and none within the current lifetime of the ALOS sensors until [12] Environment Australia, “ A Directory of Important Wetlands in Australia”, Third Edition . Environment Australia, Canberra, 2001. early 2010. Where possible historical data from other sensors [13] New South Wales Office of Water (2010), ‘ Flood flows in the will be used to examine and supplement the historical record. Barwon-Darling River System ,’ Issue 8 | 14 May 2010. [14] Price, A. and Gawne, B., “The Development of Wetland Conceptual Twenty-five PALSAR scenes are currently being analysed Models for the Semi-Arid Zone – Final Report ”, A report prepared for the MDBA by the Murray-Darling Freshwater Research Centre, to further this investigation. These include images from pp1- 48, 2009. 2/10/2009 which is the driest date before the February-March 2010 flood. Other scenes cover the flood peaks (17/11/2010- Anthony Milne received his B.A degree in 17/02/2010) and the recession period (4/4/2010-20-08/2010). Geography from the University of New England, Also, an extensive fieldwork program has been initiated in Armidale in 1967; Honours Masters in Geomorphology, University of Sydney in 1974 order to survey vegetation communities and examine their and a PhD from the University of Colorado, resilience to the changing flood conditions and to validate Boulder, in 1977. image interpretation and analysis of the geomorphological He is currently a Visiting Professor of classes identified. Geography and Remote Sensing in the School of Biological, Earth and Environmental Sciences at the University of New South Wales, Sydney, ACKNOWLEDGEMENTS This work has been undertaken within the framework of the Australia and Remote Sensing Science Manager in the Australian Government JAXA Kyoto & Carbon Initiative. ALOS PALSAR data has sponsored Cooperative Research Centre for Spatial Information. He is also a Co-Director of Horizon Geoscience Consulting Pty. Ltd founded in 1992. His been kindly provided by JAXA EORC. research interests lie in radar remote sensing, vegetation assessment and the mapping of wetlands. REFERENCES Ian Tapley received his PhD in 1989 from the [1] Milne, A.K. and Tapley, I.J., “ Wetland monitoring of flood extent, Curtin University of Technology in Perth. Formerly inundation patterns and vegetation, Mekong River Basin, South-east a Principal Research Scientist with CSIRO Australia, Asia and the Murray-Darling Basin, Australia”, ALOS Kyoto & he is now a Co-Director of Horizon Geoscience Carbon Initiative, Science Team Reports, Phase 1, 2006-2008, Japanese Consulting based in Perth, . His Aerospace Exploration Agency, Japan, 10pp ., 2010. current interests lie in radar polarimetry and [2] Milne, A.K., Tapley, I.J, Mitchell, A.L., and Powell, M., “ Trial of L- interferometry for landcover mapping, landform band radar for mapping inundation patterns in the Macquarie definition and change detection. Marshes”, Volumes 1-3, Report for the NSW Department of Environment and Climate Change, Sydney, 280pp., 2008. [3] Puckridge, J.T., Walker, K.F., and Costelloe, J.F., “Hydrological persistence and the ecology of dryland rivers”, Regulated Rivers: Anthea Mitchell received her BSc degree in Research and Management, vol. 16 no. 5, pp. 385 – 402, 2000. Applied Geography in 1999 and PhD in remote [4] Timms, B.V., “Large freshwater lakes in arid Australia: A review of sensing in 2004 from the University of New South their limnology and threats to their future”, Lakes & Reservoirs: Wales, Sydney, Australia. She is currently a visiting Research and Management, vol. 6, no.2, pp. 183-196(14), 2001. research fellow with the Cooperative Research [5] Kingsford, R. T., and Thomas, R. F., “Changing Water Regimes and Centre for Spatial Information (CRC-SI) at the Wetland Habitat on the Lower Murrumbidgee Floodplain of the University of New South Wales. Her research in Arid Australia”, Report to Environment interests are in radar remote sensing, mangrove and Australia, NSW National Parks and Wildlife Service, Sydney, 2001. wetland dynamics and forest monitoring. [6] CSIRO, “Water availability in the Murray-Darling Basin .” Summary of a report to the Australian Government from the CSIRO, Murray- Darling Basin Sustainable Yields Project. CSIRO, Australia, 2008, 12pp. [7] Sheldon, F., Boulton, A. J., and Puckridge, J. T., “Conservation value Rachel Melrose is a PhD student in the School of of variable connectivity: aquatic invertebrate assemblages of channel Biological, Earth and Environmental Sciences at the and floodplain habitats of a central Australian arid-zone river, Cooper University of New South Wales. She has B.Sc and Creek”, Biological Conservation, vol. 103, no.1, pp. 13-31, 2002. M.Sc degrees from the University of Sydney in [8] Morrison, M.D., Bennett, J.W. and Blamey, R.K., “ Designing Choice spatial information sciences. Her current research is Modelling Surveys Using Focus Groups: Results from the Macquarie related to using L-band ALOS PALSAR data to Marshes and Gwydir Wetlands Case Studies”, Choice Modelling investigate flood dynamics in the Murray-Darling Research Report No. 5, University College, The University of New Basin. South Wales, Canberra, 1997.

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