View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Department of Agriculture and Food, Western Australia (DAFWA): Research Library Research Library Resource management technical reports Natural resources research 2005 Greenough region catchment appraisal Angela Stuart-Street M Clarke Follow this and additional works at: https://researchlibrary.agric.wa.gov.au/rmtr Part of the Agriculture Commons, Natural Resources Management and Policy Commons, Soil Science Commons, and the Water Resource Management Commons Recommended Citation Stuart-Street, A, and Clarke, M. (2005), Greenough region catchment appraisal. Department of Agriculture and Food, Western Australia, Perth. Report 268. This report is brought to you for free and open access by the Natural resources research at Research Library. It has been accepted for inclusion in Resource management technical reports by an authorized administrator of Research Library. For more information, please contact [email protected], [email protected], [email protected]. GREENOUGH REGION CATCHMENT APPRAISAL Compiled by Angela Stuart-Street and Mike Clarke December 2005 RESOURCE MANAGEMENT TECHNICAL REPORT 268 GREENOUGH REGION APPRAISAL ISSN 1039-7025 Resource Management Technical Report 268 Greenough Region CATCHMENT APPRAISAL Compiled by Angela Stuart-Street and Mike Clarke For the Northern Agricultural Region Catchment Appraisal Team December 2005 DISCLAIMER While all reasonable care has been taken in the preparation of the material in this document, the Western Australian Government and its officers accept no responsibility for any errors or omissions it may contain, whether caused by negligence or otherwise, or for any loss, however caused, sustained by any person who relies on it. Director General, Department of Agriculture 2005 GREENOUGH REGION APPRAISAL Summary • The Greenough Region encompasses almost the entire northern half of the Northern Agricultural Region. It covers nearly 1.9 million hectares, extending across eight shires and the City of Geraldton. The climate is Mediterranean with mild wet winters and warm to hot dry summers. • The Greenough Region is drained primarily by the Irwin, Greenough, Chapman and Murchison Rivers. Minor rivers of the Northampton Block include the Bowes, Hutt, Oakajee and Woolowar. • Sandplains collectively account for over half of the Greenough Region’s landscapes with Yellow Deep Sand the dominant soil, occupying 31 per cent. Loose, coarse, dry surface soils are prone to wind erosion and 53 per cent of soils have a high to very high wind erosion hazard. 33 per cent of soils are currently or likely to exhibit subsurface acidity in the next 10 years and 24 per cent of soils are highly susceptible to sub soil compaction. • Salinity risk varies across the Greenough Region. Future salinity risk on the Yilgarn Craton, within the Greenough Region, appears negligible. That is, areas of existing salinity are unlikely to expand or new areas develop. • Salinity risk in the Irwin Sub-basin is uncertain as there does not appear to be any net watertable change after nine years of monitoring. Large areas of the Northampton Block appear to have attained a groundwater equilibrium. The future salinity risk within the Carnarvon Basin is unknown at this time as no bores are sited in this area. • Salinity risk in the Perth Basin is extreme. Alarming rates of watertable rise have been observed in central parts of this basin for decades. • The 143,633 hectares of remnant vegetation accounts for only 8 per cent of what originally grew. This vegetation contains 44 species of priority flora and 32 species of declared rare flora. • In 2000-01, the gross value of agricultural production (GVAP) for the Greenough Region was estimated to be $305 M, nearly 7 per cent of the total GVAP of WA. On average over the past 5 years, farms in the Greenough Region have cropped the highest percentage of arable land annually than anywhere else in WA. A range of options for reducing land degradation is discussed. Factors such as soil type, annual rainfall, enterprise mix and financial structure will determine the most suitable approach for each farm business. GREENOUGH REGION APPRAISAL Table of Contents Summary ................................................................................................................... 3 Acknowledgments .................................................................................................... 5 1. Introduction.......................................................................................................... 6 1.1 Study area .................................................................................................... 6 2. Natural resource base ......................................................................................... 8 2.1 Climate ......................................................................................................... 8 2.2 Geology ...................................................................................................... 10 2.3 Soil-landscapes .......................................................................................... 12 2.4 Hydrology ................................................................................................... 18 2.5 Native vegetation........................................................................................ 21 2.6 Agricultural production................................................................................ 25 2.7 Land use..................................................................................................... 30 2.8 Demographics ............................................................................................ 32 3. Resource condition and future risk.................................................................. 33 3.1 Climate change impacts ............................................................................. 33 3.2 Land management hazards........................................................................ 35 3.3 Hydrological risk ......................................................................................... 36 3.4 Native vegetation condition and risks ......................................................... 45 3.5 Risks to agricultural production................................................................... 47 4. Management Options and Impacts.................................................................... 50 4.1 Land Management Options ............................................................................. 50 4.2 Water management .................................................................................... 60 4.3 Vegetation Management ............................................................................ 65 5. Publications — Department of Agriculture...................................................... 68 6. Further information and contacts..................................................................... 69 7. References ......................................................................................................... 70 Appendix 1: Soil groups of the Greenough Region............................................. 72 Appendix 2: Main soil supergroups of soil-landscape Zones within the Greenough region................................................................................................... 74 Appendix 3: Rare and priority flora of the Greenough Region ........................... 75 4 GREENOUGH REGION APPRAISAL Acknowledgments The members of the Greenough Region Appraisal Team responsible for this report are: John Bruce GIS mapping support Mike Clarke Team Leader, remnant vegetation and revegetation Phil Goulding GIS mapping support and data interrogation Lyle Mildenhall Surface water hydrology Gary Patterson Farming systems Frank Rickwood Surface water hydrology Damian Shepherd GIS mapping support and data interrogation Russell Speed Groundwater hydrology Angela Stuart-Street Soils, climate and report compilation Peter Tozer Agricultural production Thanks also to Ken Atkins and Kelly Poultney from the Department of Conservation and Land Management for providing information on rare and priority flora; to Chrissy Rob from the Department of Environment for information on surface water; to Susie Murphy-White and the Central Agricultural Region RCA team for a peer review of the report; to Peter Tille for compiling the Land Management Unit data extraction for the Greenough Region; and to Heather Percy and Tim Wiley for reviewing sections of the document. 5 GREENOUGH REGION APPRAISAL 1. Introduction The purpose of this report is to provide a ‘snap shot’ appraisal of the condition of the natural resources within the Greenough Region at a regional scale. The information provided here allows an assessment of the natural resource base, its condition and the current and future risks to which it may be subject. It also provides the currently recommended best management practices for those risks. Finally, the report also provides a resource of further information sources and contacts for more enquiries. 1.1 Study area The Greenough Region encompasses almost the entire northern half of the Northern Agricultural Region. It covers nearly 1.9 million hectares, extending across eight shires and the City of Geraldton. It is limited to the west by the Indian Ocean and to the north and east by the rangelands or extensive land use zone. To the south it meets the boundaries