Land Resources Study of the Carnarvon Land Conservation District and Part of Boolathana Station, Western Australia

Research Library Land resources series Natural resources research 1992 Land resources study of the Carnarvon Land Conservation District and part of Boolathana Station, Western Australia M R. Wells C D M Keating J A. Bessell-Browne Follow this and additional works at: https://researchlibrary.agric.wa.gov.au/land_res Part of the Agriculture Commons, and the Natural Resources Management and Policy Commons Recommended Citation Wells, M R, Keating, C D, and Bessell-Browne, J A. (1992), Land resources study of the Carnarvon Land Conservation District and part of Boolathana Station, Western Australia. Department of Primary Industries and Regional Development, Western Australia, Perth. Report 9. 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 Land resources series by an authorized administrator of Research Library. For more information, please contact [email protected]. M.R. Wells, C.D.M. Keating and J.A. Bessell-Browne Editor: L.J. Snell LAND RESOURCES SERIES No.9 August 1992 DEPARTMENT OF AGRICULTURE Baron-Hay Court South Perth 6151 WESTERN AUSTRALIA ISSN 1033-1670 AGDEX 526 07178-1 The authors: M.R. Well and C.D.M. Keating, Research Officers, and J.A. Bessell-Browne, Technical Officer, Land Assessment Group, Division of Regional Operations, Department of Agriculture, Western Australia Present addresses: M.R. Wells Environmental Capability 7/27 York Street Subiaco 6008 WESTERN AUSTRALIA C.D.M. Keating 187B Riverton Drive Shelley 6155 WESTERN AUSTRALIA J.A. Bessell-Browne Regional Operations Department of Agriculture Baron-Hay Court South Perth 6151 WESTERN AUSTRALIA National Library of Australia Cata- loguing-in-Publication entry Wells, M.R. Land resources study of the Carnarvon Land Conservation Dis- trict and part of Boolathana station, Western Australia. Bibliography. ISBN 0 7309 5075 1 1. Land use-Rural-Western Australia-Carnarvon Region. 2. Land use-Western Australia- Carnarvon Region. 3. Conservation of natural resources-Western Australia- Carnarvon Region. I. Keating, C.D.M. (Colma .Derlua Monica), 1960 -.II. Bessell- Browne, J.A. III. Western Australia. Dept. of Agriculture. IV. Title. (Series: Land Re- sources Series; No.9). 333.76099413 © Chief Executive Officer of the Department of Agriculture, Western Australia 1992 LAND RESOURCES SERIES No.9 2 Summary A survey of the land resources of 36,343 ha covering the Carnarvon Land Conservation District and an adjoining portion of Boolathana station was conducted to assist future land use planning and management. This report describes the soil, landform and vegetation conditions of land units shown on an accompanying 1:50,000 scale map. These land units are components of land systems previously mapped at 1:250,000 scale for the Carnarvon Basin by Payne et al. (1987). As part of the study, further, more detailed land resource mapping and land capability assessments were conducted at specific locations. Land use planning and management considerations arising from that work have been extrapolated to the broader scale mapping herein covering the entire study area. The three major land use issues of concern are: • grazing or stockholding on special leases: • land release for horticulture; and • future urban development. The report provides a framework against which current and future land uses can be examined in relation to their compatibility with the condition and capability of the land resources. It is primarily intended as a reference document for people concerned with land use and land management decisions within the area. These include the Carnarvon Land Conservation District Committee; the Department of Agriculture, Western Australia, rangeland advisers; land use planners and land administrators. 3 LAND RESOURCES SERIES No.9 Contents 4 LAND RESOURCES SERIES No.9 Objectives Location Introduction The objectives of this study were to Carnarvon is situated just south of assist in future land use planning the Tropic of Capricorn, and management within the approximately 960km north of Carnarvon Land Conservation Perth on the North West Coastal District and an adjoining portion of Highway. The study area (Figure Boolathana station (Figure 1). The 1) covers 36,343 ha and extends study area is characterized by from Oyster Creek, about 4 km extensive tracts of sparsely south of Carnarvon township, to vegetated very low relief terrain Bejaling Shoals some 28 km to with saline, erodible soils which are the north. The western boundary susceptible to flooding. Within the is the Indian Ocean and the inland area there are examples of serious boundary is formed by Blowholes land degradation resulting from land Road, the North West Coastal use activities which have been Highway, and the approximate inappropriate for the environment. boundary of the Carnarvon Shire’s town planning scheme The survey was initiated in mid (Drake and Smith 1987). 1987, in response to a request from the Carnarvon office of the The major part of the study area Department of Agriculture, to assist (about 25,170 ha) covers the in the resolution of a number of Carnarvon Land Conservation recurring land use issues and to help District as gazetted on March 13, prevent further land degradation. 1987. The district encompasses The major issues were: leasing of the township of Carnarvon, the Crown land for grazing or irrigated plantations along the stockholding, additional land margins of the Gascoyne river, release for irrigated horticultural some conservation reserves, and crops and land requirements for large areas of Crown land mainly urban expansion. north of the river which are, or have been, subject to short term The work comprised a field survey special leases for grazing or to describe and map, at 1:50,000 stockholding. scale, the soil, landform and vegetation resources of the area. In The remaining 11,170 ha are addition, an assessment was made covered by pastoral leases, of the capability of the land to mainly Boolathana station, north sustain rangeland grazing by sheep of the Land Conservation District. and cattle. This was determined by This northern area was included the same methods as used for in the study at the request of the pastoral stations within the Carnarvon Shire because it Carnarvon Basin (Payne et al. contains land with potential for 1987), but based on the land unit urban and industrial uses should a mapping and the area'’ current deep water port be developed at erosion status and vegetation Bejaling shoals (Claughton 1986). condition. Within key areas, shown on Figure Climate 1, more detailed mapping at scales An understanding of the climate of 1:10,000 to 1:25,000 and within the study area is important associated land use capability to land use planning and assessments were done. Full results management. Climatic factors of this work are presented strongly influence the risk of land elsewhere (Wells and Oma 1987; degradation since the principal Wells, Oma and Holm 1987; Wells agents of erosion are flooding and 1989 and Wells and Bessell-Browne wind. Regeneration of land 1990). The principal land use following disturbance is also planning and management influenced by climatic factors. All considerations arising from these forms of agricultural land use rely works have been collated here using on plant growth which is a 1:50,000 scale mapping to provide primarily determined by climatic a regional framework in which conditions. To a lesser extent, current and future land use can be urban development can be examined. influenced by climate 5 LAND RESOURCES SERIES No.9 Figure 1. The study area showing locations of detailed surveys. LAND RESOURCES SERIES No.9 6 through market demand for more favoured microclimatic conditions. The area's climate is classified by Beard (1976) as 'semi desert Mediterranean' using the classifica- tion methods of Bagnouls and Gaussen (1957). The area is characterized by hot summers and mild winters and fits the common defi- nition of' arid' because insufficient rain falls for cropping in any season, mean annual rainfall is below 250 mm and zero rainfall can be recorded in any month. The following discussion of temperature, rainfall and winds has been mainly summarized from the reports of Payne et al. (1987) and Johnson (1974) which in turn are based on Bureau of Meteorology data. Temperature Mean monthly maximum and minimum temperatures recorded at Carnarvon are given in Figure 2. Figure 2. Mean maximum and mean temperatures at carnarvon. Source: Maximum temperatures are high- Bureau of meterology data cited in Payne et al. (1987). est in February (32°C) and lowest in July (21.9°C). Inland areas have higher maximum temperatures and lower minimums because of the absence of the ameliorating effect of diurnal sea breezes. Close to Carnarvon, the warm winter climate and absence of frosts enables the established horticultural plantations to produce, with irrigation, a wide variety of tropical and tem- perate zone fruits and vegetables. Carnarvon is particularly important as a source for much of the State's out-of-season vegetable supply. Rainfall The average annual rainfall is about 230 mm with an evaporation potential of 2,180 mm. Most rain falls in winter months when rain bearing fronts from the Indian Ocean interact with mid-level tropical disturbances approaching from the north-west. Irregular cyclonic storms may however, precipitate heavy rain during late summer. Mean monthly rainfall recorded at Brickhouse station, near the eastern boundary of the study area, is shown in Figure 3. Figure 3. Mean monthly rainfall at Brickhouse station. Source: Bureau of Meterology data cited in Payne et al. (1987). LAND RESOURCES SERIES No.9 7 In such an arid environment, rainfall is the limiting factor in plant growth. Even in the wettest years rainfall never approaches the area’s evaporation potential, so that plant growth is confined to limited periods of available soil moisture following rainfall.

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