Gulf Water Study Limmen Bight & McArthur Rivers Region Front cover: Waterhole downstream from Jandanku, (Bauhinia Spring) Isolated waterhole on Tanumbirini Creek Ronnie Raggett and Lewis Raggett at Wee-ak on the McArthur River. GULF WATER STUDY Limmen Bight River at the Nathan River Road crossing. WATER RESOURCES OF THE LIMMEN BIGHT AND MACARTHUR RIVERS REGION REPORT 17/2009D U. ZAAR DARWIN NT © Northern Territory of Australia, 2009 ISBN 978-1-921519-65-9 2 ACKNOWLEDGEMENTS This project was co-funded through the Australian Government’s Water Smart Australia Program and the Northern Territory Government Department of Natural Resources, Environment the Arts and Sport. I would like to thank my colleagues who provided help on this project: Peter Jolly (now retired) who instigated this project; Des Yin Foo for his generous support as our team manager; Anthony Knapton, my co-worker on this project who provided technical and field assistance; Steve Tickell and Danuta Karp for their technical advice; Lynton Fritz for his outstanding cartographic skills in drawing up the map; Sean Lawrie, Daniel Low Choy, Ian Mc Masters and Phil O’Brien for their efficient field work and Renee Ramsay for her production of the GIS and collation of the DVD. I take pleasure in also thanking members of our technical working group; Max Gorringe, manager of Elsey Station, Frank Shadforth, manager of Seven Emu Station and Glenn Wightman – ethnobiologist who all kindly took the time to provide advice at our meetings. All were always ready to help. I am very much indebted to the local people in the region. There is little recorded surface water data in the region so the information provided by locals has been vital to the project. I thank the station owners and managers; Alec Anderson, Bill Bright, Bill Darcy, David Daniels, Jimmy Mawson, Tim and Judy Mc Farlane, Chris and Christine Shilling, Rhett Walker the Parks and Wildlife rangers; Shaun Evans, Ben Senge, Eddie Webber, Stewart Woerle and from the minerals sector Simon Fell-Smith, Tim Lewis and Bruce Maycock. Indigenous people with links to the region provided not only excellent field guidance but also a cultural perspective. The memory of some of the older people has been extraordinary. I thank Alec Anderson, Katie Baker, Donald Blitner, Les Hogan, Roy Hammer, Bruce Joy, Stephen Johnston, Harry Lansen, Daphne Mawson, Dulcie Mawson, Wailo Mc Kinnon, Billy Miller, Ronnie Raggett and Stephen Roberts. I would like to thank Mabunji Aboriginal Resource Association and their chairman Frazer Baker, and the Northern Land Council who provided liaison assistance with indigenous knowledge. I humbly thank all these people as it has been no less than fascinating to learn about water in the Gulf. Lynton Fritz Technical working group Field guides, Vanderlin Island SUMMARY This report provides details of the groundwater and Dry season surface water resources of the Limmen Bight River Region and the McArthur River Region of the Gulf as depicted on the accompanying two water resource maps. These are two of five regions which make up the mapping area of the Gulf Water Study (Figure 1.1). The study was co-funded by the Australian Government Water Smart Australia Program and the Department of Natural Resources, Environment, the Arts and Sport of the Northern Territory Government. The purpose of this work is to provide readily accessible, easily understandable and user friendly information products on water resources in the region. The project was undertaken with the dual perspective of western science and indigenous knowledge and both are represented in the products of this study. It is hoped that common understandings will develop between Indigenous people and land managers about water in the region. The key aim is to provide a fundamental data set to guide development of water resources in the region maintaining healthy groundwater and rivers as well as the ecosystems which depend upon them. Each map region encompasses cattle stations, Aboriginal land and National Park. The town of Borroloola, located in the McArthur River Region, services the two regions. Domestic water supplies are sourced from groundwater, springs, river water and rainwater. The main industries of the regions are cattle grazing, tourism and mining. Cattle are watered by groundwater, river water, natural waterholes and dams. The groundwater resources of the two map regions have been classified into seven aquifer types: • Sedimentary Rocks with intergranular porosity (yields 1.0 – 10 L/s) • Fractured and Karstic Rocks – regional scale aquifer (yields 0.5 - 10 L/s) • Fractured and Karstic Rocks – local scale aquifers (yields up to 10 L/s) • Fractured and Weathered Rocks – carbonate rocks (yields 0.5 – 10 L/s) • Fractured and Weathered Rocks – carbonate rocks (yields 0.5 – 5 L/s) • Fractured and Weathered Rocks (yields 0.5 – 5 L/s) • Fractured and Weathered Rocks with minor groundwater resources (yields 0 - 0.5 L/s) Few bores exist in the Sedimentary Rock aquifer and water quality can be marginal. It lies on the eastern coast of the McArthur River Region map. The Fractured and Karstic regional scale aquifers lie in the south-west of each map. The aquifers are situated in Cambrian aged limestone formations, namely the Anthony Lagoon Beds and Gum Ridge Formation. The latter is equivalent to the Tindall Limestone. These regional scale aquifers cover an area from Tennant Creek to Mataranka and provide the key groundwater resource in the western Gulf region. As part of the Gulf Water Study this entire aquifer was modelled. This work was undertaken by A. 2 Knapton (2009) and a report is available. The fractured and karstic local scale aquifers are small in extent in the two map regions and have yet to be tested. The dominant aquifer type of the regions occurs in fractured and weathered rocks. The better yielding carbonate aquifer is situated within the Karns Dolomite and lies in the eastern McArthur River region. It provides baseflow to the Wearyan River. Bores commonly yield 3 L/s. Other fractured and weathered carbonate aquifers occur in hard old (Proterozoic) rocks which predominantly rely on fracturing for aquifer development. Fractures are targeted for supplies. Non carbonate fractured and weathered rocks with yields typically between 0.5 – 5 L/s are associated with sandstones. Of particular interest is the Abner Sandstone located in the Borroloola area where yields up to 10 L/s have been achieved, however, the formation has not been extensively drilled elsewhere. It is possible that these high yields are a localised feature. With the dominant aquifer type in the region being fractured and weathered rocks with local scale aquifers only small spring discharges are observed, generally less than 40L/s. The springs host dependent ecosystems often denoted by lush vegetation pockets. These are refuges for terrestrial and aquatic wildlife. River flow has been classified on the maps according to the minimum recorded flow at the end of the Dry season during a dry period. There are three categories that describe river flow; • River with a minimum flow of between 10 and 100L/s at the end of the Dry season • River with permanent waterholes and minimum flows up to 10 L/s at the end of the Dry season • River which is dry at the end of the Dry season Only short river reaches are listed under the first category. They include the upper McArthur River, upper Rosie Creek and other discharge channels from localised springs often associated with faults. Although most of the rivers in the region cease to flow by the end of the Dry season some rivers maintain large pools such as those along the McArthur River and Batten Creek. The largest permanent lake across the two regions is Lake Eames. It is located on Vanderlin Island. Indigenous knowledge on specific sites has been provided by traditional owners and is documented in this report. Many of the sites are shown on the map. Indigenous people believe that the Spirit Ancestors created their environment as well as a charter that is the Law for existence and through this law all land, water, plants, animals, natural phenomena, people and the Spirit Ancestors (Dreamings) are inextricably connected. It is through these intricate connections that indigenous people relate to water and everything else. Water sites not only have a physical entity and a purpose in the connected environment but also social, emotional, cultural and spiritual significance. Effective management of land and water therefore involves consideration of all these realms. Understanding how indigenous people relate to land and water enables the documented knowledge on waterholes to be put into perspective. Much can be learnt from their holistic view as it engenders responsible land and water management. 3 Aside from the map and this report other products from the Gulf Water Study include a GIS, posters and photographic and video collection which are all available on a data DVD. 4 TABLE OF CONTENTS ACKNOWLEDGEMENTS ....................................................................................................................... 1 SUMMARY .............................................................................................................................................. 2 Table of Contents .................................................................................................................................... 5 List of Figures.....................................................................................................................................