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Whyalla Conservation Park is located in the Hundred of Cultana, north-eastern Eyre Peninsula, 10 km north of Whyalla and approximately 70 km south-south-west of Port Augusta, adjacent to the Lincoln Highway (Map 1).
The Park is a long sided rectangle, 1 011 hectares in area, comprising Section 14 of the Hundred of Cultana and is fenced on all boundaries.
The Park is roughly divisible into two sections, an eastern plain vegetated with Western myall, Bluebush (Maireana sedifolia), Bladder saltbush (Atriplex vesicaria) woodland, and a western portion dissected by a series of low lying hills supporting Narrow-leaved fuchsia bush (Eremophila alternifolia), Lobed-leaved hop-bush (Dodonaea lobulata) and Tall or Rock sida (Sida calyxhymenia).
The most outstanding topographic feature of the Park is Wild Dog Hill, in the north-west corner, a sandstone outcrop rising abruptly from the surrounding plain, and exhibiting interesting rock structure and flora (Lewis, 1974 p 20-21).
Main access to the Park is from the Lincoln Highway 10 km north of Whyalla, just south of the Port Bonython turn off.
Alternatively, access can be gained via Iron Knob road - turn off at the Speedway and follow the road to south-west corner of the Park and onto the western boundary road.
Signs on the Lincoln Highway on both the southern and northern approaches to the Park are placed 400 metres before the entrance to give notification of the entrance onto the southern boundary road.
Internal roads are unsurfaced. There is no access for caravans. Use of roads following heavy rain causes considerable damage and is discouraged. The Park may be closed to vehicle access following heavy rain.
Other tracks cross the Park at:
1) the dam site and ETSA power lines from the southern boundary to the northern boundary road.
2) from Wild Dog Hill to the northern boundary road.
3) from the south-western corner, along the western boundary and then to Wild Dog Hill. This road follows part of the fire break cut in 1975.
The land surrounding the Conservation Park is pastoral lease, used for sheep grazing to the north, east and west. Immediately south of the Park is an area of land controlled by BHP. Large areas of it are currently not used for any purpose. Beyond this area steelworks and other associated industries are located just north of Whyalla, 8 to 10 km south of the Park. In 1982, SANTOS established a gas fractionation plant at Port Bonython near Point Lowly. While this plant is approximately 10 km from the Park, the turn-off from the main highway to this plant is opposite the mid-point of the eastern boundary of the Park.
Recently, a new electricity sub-station has been installed immediately outside the Park on the northern side. This sub-station feeds power to both the Point Lowly area and to the City of Whyalla.
Urban development is confined within the limits of Whyalla. A small quarrying operation takes place at Mt Laura. The Whyalla waste disposal landfill has been recently relocated to one of the used quarry sites in this area.
An area, opposite the eastern boundary of the Park, is set aside for a variety of industrial purposes and is known as Cultana Industrial Estate (Lewis, 1974 p 20). A recreation area adjoins the western boundary of this area. This is owned and managed by the Left Hand Club of Whyalla and is known as Tregalana Park.
The climate of the Whyalla region is dominated by the Sub-tropical High Pressure system. In summer, this system exists as a series of cells, which progress from west to east at about latitude 38oS to 40oS in the Great Australian Bight. In winter, this system moves northward, and centres at about the latitude of Marree (29oS). This seasonal movement of the Sub-tropical high causes dry continental air to blow over the area for most of the year.
This pattern is varied by monsoonal lows in summer which can bring heavy rain. These tropical lows are most commonly from north-west Western Australia, with lows from Queensland being less common. These tropical lows are responsible for the heaviest rainfall events in the region. In winter, frontal depressions from the Southern Ocean bring showers.
It is a dry area, with an annual average rainfall at Whyalla of 271 mm (1906 to 1990) and an estimated annual potential evaporation of 2400 mm (Laut et al., 1977). Whyalla averages 65 rainy days per year. The remaining 300 days are, on average, clear and sunny and this contributes to high evaporation rates. There are no recorded figures for evaporation at Whyalla, the figures for nearby Minnipa are included as indicative values.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Total | |
| Temperature Mean Max oC | 28.8 | 28.5 | 26.7 | 23.8 | 20.2 | 17.5 | 16.8 | 18.2 | 20.6 | 23.4 | 25.7 | 27.3 | 23.1 |
| Temperature Mean Min oC | 18.6 | 18.9 | 17.2 | 14.1 | 10.8 | 8.3 | 7.3 | 8.1 | 10 | 12.5 | 15 | 16.8 | 13.1 |
| Rainfall Mean mm | 18 | 24 | 18 | 19 | 28 | 25 | 23 | 24 | 25 | 26 | 22 | 19 | 271 |
| Rainfall Median mm | 8 | 11 | 11 | 15 | 21 | 16 | 18 | 23 | 19 | 20 | 18 | 14 | 256 |
| Humidity 3pm Mean | 45 | 47 | 48 | 46 | 53 | 55 | 54 | 49 | 46 | 42 | 43 | 40 | 48 |
| Minnipa Evaporation mm | 350 | 293 | 250 | 165 | 109 | 69 | 76 | 100 | 142 | 211 | 274 | 324 | 2363 |
| Rain Days | 3 | 3 | 3 | 5 | 7 | 7 | 8 | 8 | 7 | 6 | 4 | 4 | 65 |
Temperatures increase as one goes inland, and those experienced in the Park are probably 2 or 3 degrees above those experienced in Whyalla. On the coast, summer temperatures are typically in the high 20s with some days in the mid to high 30s. Days over 40oC are infrequent. Winter temperatures are generally mild, with daily maxima in the mid to high teens.
Wind direction is predominantly southerly due to the sea-breeze effect generated by the warmth of inland South Australia and the contrast with the cool waters of Spencer Gulf. This sea-breeze effect extends up to 20 kilometres inland.
Whyalla Conservation Park is located within the Western myall plains country of north-east Eyre Peninsula. While geomorphologically similar to much of central Eyre Peninsula, the region is distinguished by its particularly well developed Western myall/chenopod communities.
The region is defined to the south by the distinct zone of transition from Western myall to Mallee and by an associated change in land use from extensive livestock grazing to cereal cultivation. Laut et al. (1977), identify it as one of the four major environmental regions of South Australia.
Although generally of low, undulating relief, the Park itself has been classified as a part of the North Whyalla Hills (Crawford and Forbes, 1969). This geomorphic unit extends from False Bay and the City of Whyalla in a north-north-westerly direction for approximately 35 kilometres. The highest peaks in these hills are Mt Laura (176 metres) and Mt Whyalla (233 metres).
The western parts of these mounded hills rise to 70 - 100 metres, the western aspect of some being marked by sandstone outcrops. Wild Dog Hill, isolated in the north west corner of the Park, is by far the most prominent feature of the landscape. Rising sharply from the surrounding plain to a height of 90 metres, its northerly aspect features a series of spectacular sandstone faces.
The eastern portion of the Park slopes gently away from the hills in a north-easterly direction. The area is relatively low lying and flat, at 20 to 40 metres above sea level, merging into an extensive plain which is known as Long Sleep Plain.
Drainage channels
Natural drainage channels are poorly defined, generally being marked by regions of heavier native vegetation and pest plant growth. However, they have been accentuated in some areas by the construction of artificial drains. Drainage from the hills in the Park is in two main directions, south east along constructed drains towards a dam located on the southern boundary of the Park and westward into neighbouring Middleback Station.
Regional landscape
From the higher elevations of the Park, extensive views of the regional landscape well beyond the Park boundary can be obtained. To the north and south, the scene is dominated by the more prominent peaks of the North Whyalla Hills as previously described.
To the west, across an extensive plain of Western myall woodland, can be seen, in the distance, the prominent escarpments and steep strike ridges of the Middleback Ranges.
A complex of features dominate the landscape to the east of the Park. Spencer Gulf, with False Bay arching away to the east towards Point Lowly can be observed beyond the northern edge of the Whyalla Steel Works with the Flinders Ranges on the eastern side of Spencer Gulf in the background. The first of the two major upland areas can also be observed in this direction. The prominent face of the Simmens Plateau which extends from Point Lowly to beyond Lincoln Gap is clearly visible, rising to a height of 300 metres. The Plateau is bounded to the east and west by faults which are largely obscured by scree. It is the remnant of a much older more extensive tableland. Yet further to the east, bordering Upper Spencer Gulf in the region of Backy Point is an irregular hilly area, the Douglas Upland and Cultana Group.
The hills of the Park are formed from the Pandurra formation and have an age of between 1 600 and 1 000 million years. The major rock formation of the Park is Wild Dog Hill (90 m), which consists of red or purple medium grade sandstones with some conglomerate.
The formation dips in a shallow way towards the north east. Trig Hill (95 m) which is the highest part of the Park is in this same formation. The remainder of the Park is covered by alluvial material which consists of sands and clays.
The soils of the Whyalla Conservation Park result from the interaction of parent material, slope and climate. The work of Megan Lewis (1972) and the Environmental Impact Statement for the adjacent Tioxide site (Dames and Moore, 1990) confirm that the soils of the Park are typical of the semi-arid regions of Australia.
The presence of lime nodules in the subsoil is due to the re-deposition of these salts following leaching from the surface layers. Soils in the area are alkaline due to the low rate of leaching which is possible under a regime of low rainfall and high evaporation. Typical pH values found by Lewis (1974 p 39) were 6.5 -9.0.
There is a close association between soil type and vegetation. The soils map is based on Lewis's vegetation map and indicates that four major soil types can be recognised in the Park.
i Skeletal soils on the upper slopes of hills.
ii Sandy clay where Bladder saltbush is the dominant under-shrub.
iii Clay sands where Bluebush is the dominant under-shrub.
iv Sandy loam where Black oak (Casuarina cristata) groves occur.
There is a good coverage of soil lichens especially in soil types 2 and 3. These soil lichens have important functions.
i They fix atmospheric nitrogen and thereby increase the soil fertility.
ii They absorb rainfall and decrease run-off.
iii They bind the soil surface and thereby reduce erosion.
Laut et al. (1977) indicated that ground water in this area is very rare because of the underlying geology.
Fire History
The Whyalla Conservation Park had no known recent fire history up until 1974 (Lewis, 1974 p 23). NPWS have records of a small fire of approximately 40 hectares on the western boundary in January 1975 (Map 5). The source of the fire is unknown. A fire break was constructed to contain this fire. The size and age of the Western myalls in the rest of the Park indicate there may not have been a fire in the area for at least 350 years.
Fire Hazards
Fire is not a particular problem in the Park most of the time because of the fire-resistant nature of much of the vegetation, relatively simple topography and low fuel loads.
The dominant Western myall, although occurring in association with a fire resistant understorey of bluebush and saltbush, is itself killed by fire. The Park contains significant stands of this species which are a valuable natural asset which should be protected from fire where possible. Highly flammable annual grass (Stipa spp.) and herb (mainly Wards weed (Carrichtera annua)) growth following good seasons could well pose a threat to mature Western myall trees. There is potential for cured annual grass to be ignited by lightning or human activity.
A brief fire prevention plan should be prepared for the Park outlining a mechanism whereby fuel loads and conditions are assessed at the beginning of each fire season and protection and suppression measures put in place. This will be carried out in association with SAMFS and NPWS as is the normal procedure.
