Government of South Australia

South Australian Arid Lands NaturalResources Management Board

July 2009South Australian Arid Lands Natural Resources Management Board

Landscape processes of Moonaree Station: a pilot study

Gresley Wakelin-King

DISCLAIMER The South Australian Arid Lands Natural Resources Management Board, and its employees do not

warrant or make any representation regarding the use, or results of use of the information contained

herein as to its correctness, accuracy, reliability, currency or otherwise. The South Australian Arid Lands

Natural Resources Management Board and its employees expressly disclaim all liability or responsibility

to any person using the information or advice.

© South Australian Arid Lands Natural Resources Management Board 2009

LANDSCAPE PROCESSES OF MOONAREE STATION: A PILOT STUDY

GRESLEY WAKELIN-KING

July 2009

South Australian Arid Lands Natural Resources Management Board

This work is copyright. Apart from any use permitted under the Copyright Act 1968 (Commonwealth), no

part may be reproduced by any process without prior written permission obtained from the South

Australian Arid Lands Natural Resources Management Board. Requests and enquiries concerning

reproduction and rights should be directed to the General Manager, South Australian Arid Lands Natural

Resources Management Board Railway Station Building, PO Box 2227, Port Augusta, SA, 5700

Wakelin Associates Pty. Ltd. Geology – GIS – Geomorphology

2

Landscape Processes of Moonaree Station: A Pilot Study

Table of Contents

Summary 5

Part 1 – Introduction 7

Background 7

Aim, Output, Outcome 8

Study Area: Moonaree Station 8

Methods 11

Results: Assessment of Methods and Resources 14

Part 2 – Report to Landholders 25

Geology 25

Geomorphology and Landscape Process 39

Implications for Land Management: Summary 57

Part 3: Controls on Surface Water in SA Arid Lands 59

Low Priority Given to Understanding Drylands Catchments 59

Different Features of Drylands Rivers 61

Human Activities that Affect River Flow 64

References 67

Tables 1 Comparison of cost and utility of images for geomorphic mapping. 24

Figures 1 Location of Moonaree Station. 10

3

2 Landform-process units and field sites. 13

3 Narrow-scale comparison of air-photo, photomosaic, LANDSAT, and DEM images

for a small valley. 17

4 Broad-scale comparison of photomosaic, LANDSAT, ALOS, and DEM images for a

wide area. 19, 20, 21

5 Comparison of in-house photomosaics created from 800dpi scans of existing air

photos. 22

6 The Yardea Dacite. 25

7 Geological structure at Moonaree, shown by fracture-valley and hilltop trends. 26

8 Digital Elevation Model of the Gawler Ranges, showing the Acraman Impact

Structure and the regional fracture pattern. 27

9 Fracture spacing influences hillslope weathering and gnamma formation. 28

10 Observed outcrops of white claystone and weathering profile. 29

11 Near Gorge Creek, white claystone, mottled with weathering profile overprint. 30

12 Tertiary rocks and weathering profile. 32

13 Calcrete and silcrete. 33

14 Calcrete distribution at Moonaree. 34

15 Modern soil and sand, old and modern gypsum. 35

16 Distribution of gypsum and gilgai at Moonaree. 36

17 Elevation profiles of the southern sand sheet. 37, 38

18 Landscape elements. 39

19 A discontinuous drainage gutter in a rocky fracture-valley. 40

20 Chenopod plains in Belt Hill and Bond Paddocks. 41

21 Looking across the drainage axis of a chenopod plain in Mt Cooper paddock. 42

22 Bare, sheet-eroded patches along the stock route at Kallinta. 43

23 A swale with trees; a sketch of a line of discontinuous creeks. 44

24 A discontinuous creek in Mt Cooper Paddock. 45

25 Channel incision in Yeltabinna Creek. 46

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26 Catchments of the Moonaree creeks. 47

27 Gilgai pits. 49

28 One of Moonaree’s largest gilgai pits. 50

29 Gilgai in the bare ground around Cornish Well. 52

30 Downslope sediment transport in the rocky hilltops of Parkers. 53

31 A stock pad may concentrate runoff and promote erosion. 54

32 A deep gully system in Spearfelt traces upslope to a station track. 55

33 Gullying along station tracks. 56

34 Less accuracy in understanding remote catchments. 60

35 A gully formed along a station track in NSW. 65

Maps (A3 size) 1 Paddocks and major creeks. End pages

2 Station tracks and watering points (Landholders and SAAL-NRM only). End pages

3 Paddock boundaries over the LANDSAT image. End pages

4 Moonaree Digital Elevation Model as if lake-full to 200m ASL. End pages

5

LANDSCAPE PROCESSES OF MOONAREE STATION: A PILOT STUDY

Summary This pilot study aimed to map landscape processes (geomorphology) on a grazing

property, to gain new information contributing to sustainable rangelands

management. Moonaree Station (Alastair and Catherine McTaggart), in the Gawler

Ranges, was the chosen site. The method was an initial desktop and remote-

sensing study followed by field work and consultation with the landholders. The

project began in early February, field work was undertaken in mid-June, preliminary

results verbally presented to the landholders in late June, and project documentation

was completed to first draft by end August. The method worked well, however

affordable satellite images are not particularly suitable for geomorphic investigation of

this type, and in South Australia aerial photography is difficult to access. Timing of

field work proved to be a difficulty, as the landholders could not engage with the

project until after shearing, whereas the project had to be acquitted before the end of

the financial year; the time in the field and the post-field reporting were thus

shortened.

Method recommendations for subsequent work of this kind are 1) that an

arrangement be made with SA-DEH for access to stereo pairs of aerial photography;

2) that LANDSAT and ALOS be used for base map construction; 3) that strong

representations be made to State and Federal policymakers that range managers are

increasingly required to manage for whole-country goals (e.g. biodiversity), yet a

fundamental source of information (aerial photography) is no longer being affordably

supplied by government; 4) that project funding not be tied to the financial year; 6)

that extra time should be allocated (as non-project time interval: at no extra project

cost) between draft and final report to give landholders opportunity to comment.

Moonaree Station's landscape is high rounded hills of Yardea Dacite separated by

wide straight fracture-valleys, with playa lakes to the east and west. The geological

history is as follows: emplacement and later fracturing of volcanic rock (<1,600 and

<580 million years ago), partial submergence of the rocky hills by Lakes Gairdner

and Acraman, deposition of fluvial sediments in valleys, and deep weathering (~65-2

6

million years ago), and during the last ~6 million years, sand transport, soil formation,

and repeated episodes of valley sediment deposition and duricrust (calcrete and

silcrete) formation. The most recent events have been smaller increments of rising

and falling lake water levels (>2 million years), the arrival of Aboriginal people at

~40,000 years, and the commencement of European-style stock grazing in 1862.

Dominant landscape processes include: links between soil type and underlying

geology, differing degrees of runoff (rocky hilltops versus upper hillslope), the

importance of intense localised rainfall as landscape formation element,

discontinuous ephemeral stream processes in many of the valleys, channelised

streams in the longer valleys with bigger catchments, spatially discontinuous

development of gilgai soils, and landscape control of the groundwater amount and

salinity.

Implications for land management include: strong links between geology and

landscape productivity, particularly with respect to gilgai areas; gully erosion along

tracks; strong links between landscape productivity and the discontinuous ephemeral

stream landforms; grazing management and vegetation preservation as an important

factor in landscape maintenance; the random occurrence of rain-induced erosion

patches; the dominance of local subsurface conditions in the success (or otherwise)

of drilling for groundwater; the need for good information on track creation and

management; and the need for effective techniques of rangeland rehabilitation along

the old stock route.

This project demonstrates the strong links between landform and ecology, and the

diversity of landscape types in the Arid Lands. The information that came out of this

project has given the landholder new information about water quality issues, extra-

productive “sweet spots” in the landscape, gullying, rangeland rehabilitation, and the

relationships between grazing history, river type, and chenopod plain productivity.

Issues highlighted for further consideration generally in the SA Arid Lands include 1)

identification of land in near-original condition, 2) the need for low-impact track

creation and maintenance techniques, 3) links between palaeochannels and gilgai,

and 4) the potential loss of a valuable information source with reduced access to

aerial photography for land managers. Future projects of this type in different types of

country will add to the known landform-ecology relationships and expand the

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information which is specifically targeted to land management. As a general principle,

ecology starts with land and water, and geomorphology – landscape process – is

fundamental to both.

This report concludes with some general observations on management of surface

water (including groundwater extracted from alluvium) use in South Australia. At

present there is little legislative framework governing the use of surface waters in the

SA Arid Lands. Control of surface waters generally aims to ensure all users

(including the environment) have reasonable use of the resource. It is important to

recognise that dryland rivers and drainages do not necessarily operate in the same

way as perennial rivers, nor necessarily look like them: management policies should

be developed from understanding South Australia's creeks, rather than derived from

policies developed for temperate-zone rivers. Small discontinuous and/or ephemeral

creeks, such as are the dominant creek type on Moonaree, could be regulated by

limiting the amount of water captured in lower-order tributaries. Effective and fair

regulation is not straightforward. Further consideration should be given to

characterisation of the Arid Land’s waters. The ultimate aim of such regulation must

be defined: is it to preserve the status quo, to work towards some approximation of

pre-European function, or to balance ecological and economic requirements (which

in their turn must then be defined).

Part 1: Introduction

Background Plants and animals do not live in isolation from their physical surroundings, and

knowledge of an area’s landscape processes (the geological science of

geomorphology) should be a key component of any rangeland management plan.

Despite this, landscape is often dealt with descriptively, and its processes are not

well understood; rangeland monitoring tends to focus on plant communities rather

than effective landscape processes.

In the rangelands the most important physical element is water. Drylands rivers are

water’s most obvious manifestation, but they are not the only pathways of water

transport, nor do they behave in the same way as “normal” (perennial) rivers. Recent

8

innovators in rangeland management (Peter Andrews of Natural Sequence Farming;

Bob Purvis of Atartinga Station; Hugh Pringle and Ken Tinley of the Ecosystem

Management Project) have used drylands river processes to improve the condition of

their lands. Similar projects need to be undertaken in a range of landscapes so that

general principles can be extracted from landscape-specific solutions.

Aim, Output, Outcome This project aims to map and document landscape processes in a property in the

SAAL-NRM area. A suitable property would:

• be a sheep or cattle grazing property

• be without permanent natural surface water

• have a mixture of landscape types

• be available to be visited by the researcher for field work

• have a land manager or other knowledgeable person available for occasional

discussions with the researcher during field work;

• and ideally have a land manager or other knowledgeable person available to

provide some background information to the researcher at the project start.

The outputs are some maps, a GIS dataset, report to SAAL-NRM, report to the

landholder, and an industry newsletter report. The outcome is information

contributing to management plans and land condition monitoring on the property. The

project was completed by mid-2009.

Study Area: Moonaree Station Moonaree Station is in the Gawler Ranges, occupying the whole land area between

Lakes Acraman and Gairdner (Fig. 1), an area managed in pre-European times by

the Kokata and Wirangu peoples (Tindale 1974). The station is reached by graded

unsealed public road from Iron Knob. The public road continues north to Kingoonya

on the Trans-Australian Railway, but there are no other public roads on the property.

The nearest fuel is at Mt. Ive station, an hour’s drive south of the Moonaree

boundary. Moonaree is currently held by Alistair and Catherine McTaggart. The

property grazes sheep and a few cattle, and mustering is mostly by motorbike.

Paddock names and major creek names are shown in Map 1, and watering points

(dam and bore) and station tracks are shown in Map 2 (Landholders’ version only).

9

Early European exploration in the Moonaree region included Steven Hack in 1857

and Major Warburton in 1858, and the Moonaree Pastoral Lease was taken up in

about 1862 (Blisset, 1985). The McTaggart family settled at Nonning Station in the

Gawler Ranges in the late 1800s, and the Nonning Pastoral Company acquired

Moonaree sometime before 1923 (Anderson 1995). The Nonning Pastoral Co was at

one time Australia’s largest pastoral company. In the 1980s company broke up and

Moonaree passed to Mr. McTaggart. Moonaree Station lies on a road extending from

Iron Knob in the south to the Trans-Australian railway line to the north (near

Coondambo Station, Fig. 1), but there are not known to have been inter-property

stock routes through the station.

Moonaree Station is 2,466 square km in area, its perimeter is 426km, and it extends

a maximum of 57km east to west and 65km north to south. It is bounded to the east

and west by playa lakes, and to the north and south by belts of sandhills. Current

homesteads include Old Moonaree to the south of the property and Kangaroo Well

closer to the northern boundary. There are also a homestead paddock at Mt Harper

Well and a crutching shed at Belt Hill/Yeltabinna. According to Mr. McTaggart, all the

station shearing used to be at Old Moonaree, so stock were droved there from the

distant parts of the station along the main road (from Mt Cooper Dam to Beviss Well

and into the old homestead area). Beviss, Ram and Willigenda paddocks, part of the

shearing area, have had hard usage, as have Kallinta, Kallinta South, and Waurea

paddocks. Kallinta, Kallinta South, and Ram are management focus paddocks and

have had very low stocking levels for the last 20 years (A. McTaggart, pers. comm.,

2009). Some range rehabilitation (contour ripping) has been done by Mr McTaggart

in overgrazed areas along the main road in Beviss and Kallinta paddocks.

Moonaree Station is watered by surface dams and by wells, some of which supply

distant watering points. Some of the wells were created by drilling, but a number of

historical wells were dug by hand through surface alluvium and into rock. The

McTaggarts report that the character of the wells and dams is quite variable. Some

wells had good water for a while that then went salty or reduced in quantity; dams

may be brackish or fresh, clear or muddy. Most water is fairly brackish. Finding water

on the property is quite a challenge as it is not clear where to drill to get good quality

water.

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Fig. 1 Location, Moonaree Station, showing public roads and neighbouring properties. Playa lakes in

blue, study area (Moonaree Station) in yellow.

Moonaree is not overly troubled by feral pests. Foxes, rabbits, and feral plants

(African boxthorn, and Wards Weed) were reduced during drought, though rabbits

and foxes are now slowly increasing in numbers. There are a few dingos or wild dogs

getting through the local dog fence. There are no pigs or wild horses. There are a few

(300-400) goats; not many, in comparison to the rest of the Gawler Ranges. Mrs.

McTaggart says the goats don’t like to come over the sandhills along the northern

and southern property boundaries, and only a few come in by way of the salt lake

islands.

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Moonaree weather history (A. & C. McTaggart pers. comm. 2009) includes drought

during the 1980s, and big floods in 1997 when the lakes filled after several hundred

mm of rain (12 inches of rain in 4 hours). The creeks ran hard, washing away fences

and windmills, and Old Moonaree was completely flooded. There was a lot of

damage, especially in the south of the property. Yeltabinna Creek ran 15 feet deep,

and Garden Well and Jolly Creeks ran very high. A lot of erosion gullies were

created. A new cohort of Acacia trees has germinated in the creek lines; there

weren’t so many before the floods.

Other station issues include erosion along some old tracks, and the McTaggarts’

curiosity as to the causes of differences between paddocks on the property: Little

Gorge is one of the most productive, Belt Hill has a lot of stock deaths, and a whole

belt along the west has lots of flies, and the country is soft, good in a good year but

bad in a bad year (Dingo Hill, Kulgulya, Waurea, Bond Hill, Kallinta and South

Kallinta).

Methods The project hinges around the collection of field information, with a pre-field

component of stakeholder engagement and desktop information studies, and post-

field data analysis and report compilation.

Project aims and objectives (above) had been defined prior to project beginning. The

SAAL-NRM Water Projects Officer indicated a region of interest (the Gawler

Ranges),and the SAAL-NRM field officer identified two potentially suitable properties.

The properties were contacted, and Moonaree Station indicated willingness to be

involved. Preliminary discussions were held regarding the nature of the Station and

suitable time for fieldwork. As part of stakeholder engagement, phone discussions

were held with the field officer, and materials were prepared for presentation at the

Gawler Ranges Landcare meeting and the SAAL-NRM Arid Lands Muster.

Desktop information studies commenced with locating and obtaining paper copies of

the 1:250,000 scale topographic and geological maps (GAIRDNER SH53-15 and

YARDEA SI53-3), and obtaining paper or digital copies of relevant references

(Anderson 1995, Blissett 1985, Dickinson 1942, Williams & Gostin 2005, etc.).

12

The most important part of pre-field studies is landform mapping. Digital Elevation

Model data was obtained from the NASA SRTM (Shuttle Radar Topography Mission)

web site, and modelled using Global Mapper. Digital topographic data sets were

obtained from South Australian and Commonwealth departments, and a GIS

database collated (including resolution of datum issues: the SA government uses a

slightly unusual datum). Aerial photography was identified at the South Australian

Department of Lands. The original intention was to purchase the relevant aerial

photographs for examination with the high-quality in-house stereoscope, however

South Australia no longer possesses a photographic laboratory. An arrangement was

made to visit Mapland in Adelaide and examine photographs from their library in their

office. Preliminary landform units were identified and traced on transparent air photo

overlays. This information was then transferred to a base map. A number of base

map options were examined, including Quickbird, LANDSAT, ALOS, SPOT,

purchased orthorectified aerial photography, in-house orthorectified aerial

photography, and topographic dataset. Ultimately a combined GIS dataset,

comprising pan-sharpened LANDSAT, SRTM DEM, and topographic data was used.

The preliminary landform units (Fig. 2), with their provisional process assessment,

were compiled into maps and printed for use in the field. Fieldwork took place for two

weeks in early June. During fieldwork, the researcher visited sites identified from the

air-photo mapping (Fig. 2). Some sites were single-location examinations, and some

were traverses of up to 4 km. Geology, geomorphology, and some aspects of

vegetation were recorded descriptively and by photograph, and sites were located by

autonomous GPS. (Note that this study did not attempt to identify vegetation types,

however the general assessment was made of species diversity, population density,

and individual plant health.)

During fieldwork, stakeholder engagement took place: seeking information from the

local landholders about their property and what information might be useful to them,

discussion with neighbouring landholders, and a close-of-visit presentation to the

local landholders of information derived from mapping.

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Figure 2. Landform-process units identified by air-photo and satellite image interpretation prior to field

work (areas of colour), and sites examined in the field (red circles). The scope of the project did not

permit sufficient field work to turn this interpretive map into an actual map, so no description of the units

is presented here. This map was used to guide field work and is not meant to be a representation of the

results.

Post-field analysis comprised recompilation of the GIS dataset, including field site

locations, correlation between field observations and map elements, and data

management; revision of the geomorphology map and process assessment in light of

the field data; and documentation of the observed geomorphology and its

implications for land management.

This report consists of three parts: 1, the introductory material and (because this is a

pilot study) an assessment of the methods and resources; 2, analysis of the field

area; and 3, arising from this study and at the request of SAAL-NRM, a discussion on

surface water regulation in SA. The landholders’ report consists of the introductory

material plus Part 2 (pages 1-13, 25-58, and all four maps).

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Results: Assessment of Methods and Resources Constraints on Timing This pilot study was estimated to take five months to achieve a usable result, and this

was an appropriate amount of time. It was not enough time to produce a sufficiently

reliable map of landform process, particularly in view of the area’s unexpectedly

complex geology (see Part 2). Soils and vegetation specialists contributing to

fieldwork would have also been a useful expansion of the work. Approximately six

weeks was taken up exploring different options for landform visualisation, and in a

future project these questions would not need to be readdressed.

The time allocated in the field was two weeks (not counting travel time), and this was

enough to understand many of the processes, ground-truth the preliminary map, and

consult with and present to the landholders. The time in the field was hampered by

very rainy weather, which lost two days (bad access). Time allotted to field work does

not include the days spent in physical preparation before and after the field (gear &

vehicle overhaul, etc); this should be borne in mind when allocating project time.

More field time would have been better. The ideal field time for this 5-month project

would be a week at the beginning of the project to get an overview of the area and

consult with the landholder, and three weeks in the middle of the project for data

collection and information presentation.

There were conflicting time requirements in this project: the landholders’ work

timetable, and the firm dates for the project’s start and finish. The project began early

in 2009 and was required to be acquitted by the close of the financial year (30 June

2009). The landholders could not have the researcher on-property until after shearing

in late May; the field work happened in early June. Even with a two-week extension

for the draft report, the post-field analysis time was short.

Landholder engagement with this type of project will not happen if researchers come

on to the property at a time when they are not welcome; fieldwork must fit in around

shearing, crutching, lambing, and so on. However, fieldwork should not be scheduled

in the summer: hot-weather remote-area work involving foot traverses by workers not

deeply familiar with the country is very poor OH&S. Ideally, fieldwork should happen

sometime between autumn and early spring, at a time that suits the landholders –

15

however that’s the end of the financial year. This report recommends that a way be

found to untie project scheduling from ending with the financial year.

Landholder Feedback At the end of the fieldwork the Mr. McTaggart was taken to selected sites and the

results of the mapping discussed with him. Some labelled rock samples were left for

his information. He seemed quite interested and pleased but at the close of this

project I will have had no further discussion with him. Ideally, a project of this type

would have time built in between draft and final reports for the landholder to

comment on the project outcomes. I would be especially interested in hearing what

new information was most valuable for land management. The time built in would be

non-project time: a month (say) would elapse but no billable work would take place.

To put it another way, the project timeline would increase by (say) a month, but the

project budget would not increase by a month’s costs.

Aerial Photography and Satellite Imagery The existing published material covering the field area is limited to the 1:250,000

geological maps and their explanatory notes, a water resources report dating back to

the middle of last century, and a Historical Society paper on the family history

(Dickinson 1942, Anderson 1995). This small amount of information is all that can be

expected to be available for a remote rural area in Australia: research and publicly-

funded services concentrate around population centres. It is for this reason that field

studies are crucial to a project of this kind, as background data are scarce. Other

relevant information included references on the Acraman Impact Structure and on

South Australia’s palaeochannels (Keeling & Self 1996, Williams & Gostin 2005).

Geomorphological mapping on the regional scale, such as this, requires a method of

observing a broad swathe of country which also allows specific narrow-scale features

to be identified on the ground. In this way, landforms can be grouped into categories

and their distribution plotted on the map, and representative examples of the

landform can be selected for ground-truthing and detailed examination. For example,

a belt of sand dunes 50 kilometres wide can be mapped, and a specific sand dune

can be selected from the map, and identified in the field. Key features that identify

landforms and indicate landscape processes are shape, colour, and vegetation. The

medium of observation must therefore be accurate in its display of elevation, true-

16

colour, and sufficiently high-resolution; it must also be affordable. Aerial photography

(of the kind that once was routinely flown by State Departments of Lands, which gave

overlapping photographs) is the ideal medium for this type of work. The resolution is

very high (limited only by the magnification that the photograph is viewed under), the

colours reflect what can be seen on the ground (Fig. 3A, 3E), existing photography

covers the entire state, and with the use of a quality stereoscope the landform

shapes are accurately revealed.

More modern remote sensing techniques are often assumed to be superior to air-

photo interpretation, but this is not the case. Very few remote sensing techniques

accurately depict elevation, and without elevation landform cannot be determined.

Accurate elevation can be obtained with the use of Quickbird or LIDAR, but these

techniques are beyond the budget of a land-management project. Free SRTM digital

elevation data is available from NASA, however its elevation is only accurate to ± 2-

9 m. At this degree of accuracy, it is useful for regional overviews but not at all usable

for landform mapping (Fig. 3D). Similarly, very few remote sensing techniques show

true colour. Remote sensing which records within certain wavelength bands, and in

which bands are combined to simulate true colour in a single image, do not really

reflect the true colour of the soil or the vegetation (Fig. 3C). Finally, much remote

sensing has a very large pixel size, suitable for regional overviews but inappropriate

for detailed landform mapping. Some remote sensing has quite small pixels (for

example, Quickbird,) but again these techniques are quite expensive. The more

easily available and affordable LANDSAT has a 25 m pixel in most bands, and a 12.5

m pixel in the black and white panchromatic band.

Landforms were therefore mapped on to clear overlay sheets, using stereo pairs of

1:80,000 colour aerial photographs (film number 4874, flown in November 1994, 67

photographs in all). Sourcing these aerial photographs was unexpectedly difficult.

Aerial photography has routinely been flown over all of South Australia, and

negatives and existing prints are held by Mapland, at the Department of Environment

and Heritage. I had expected to be able to purchase prints, but South Australia no

longer has a photographic laboratory. Mapland will do an inkjet print from a scan of

the negative or of the existing photo, however an inkjet print is not of sufficiently high

quality to do geomorphological mapping. In addition, Mapland have not scanned the

negatives from these kinds of rural areas, deeming them to be too remote to be of

17

u

Figure 3 Comparison of a small uplands valley as seen by: A, 800 dpi scanned aerial photograph; B,

photomosaic made from the same scan; C, pan-sharpened LANDSAT bands 741; D, a DEM from

SRTM data has a 90m pixel. Field of view 2.4 km. E, the landscape view. Real-world colours and

shapes correspond better to air-photos than to LANDSAT. Better resolution of the air-photo allows

individual hillslopes and vegetation groups to be identified.

A B

C D

E

18

general interest. Scans of the negatives would therefore be charged for (an additional

$130 for each of the 67 photos over this study area). After some discussion, Mapland

staff generously allowed the researcher to visit their office for a week to examine their

existing photographs on-site.

Different options for obtaining air photos are examined in Table 1, and compared with

the cost of purchasing air photos in a state which still has a photographic lab. Of the

available options, examining Mapland’s photos on-site is the only economically

feasible one. However, it is a concern that Mapland is not set up to be a library, and

they might choose not to let people have access. A technically feasible solution is

purchasing Mapland negative scans and having them printed photographically

interstate, however the combined cost of negative scanning and interstate

photographic printing may be prohibitive for NRM projects. Finally, the Mapland office

is said to be downsizing, and the prints and negatives may be archived somewhere,

possibly with limited access. The combined cost structure, low priority assigned to

photos of remote rural areas, and lack of access to existing prints may remove this

valuable information from the orbit of land managers. There are no plans for

systematic acquisition of new digital aerial photography. Rather, new photography is

commissioned and paid for by government agencies, and organised through DEH.

This report recommends that discussions between the NRM boards and the

Department of Environment and Heritage make some provision for controlled access

to the existing aerial photograph prints. If Mapland can host the occasional visitor that

would work well; otherwise it is suggested that the existing airphoto prints be

archived at an appropriate venue such as the geoscience library at PIRSA.

This report also recommends that consideration be given to the issue of access to

aerial photography and orthophotography. Range managers are increasingly

required to manage for whole-country goals (such as biodiversity or feral animal

control), and certainly popular opinion can be very judgemental towards graziers and

pastoralists who are not seen to be looking after the country. Nonetheless here is a

primary tool for landscape interpretation which is no longer being supplied by

government for the remote areas. Strong representations should be made to State

and Federal policymakers that population density should not be the only determinant

of information supply.

19

Figure 4 Comparison of the central Moonaree paddocks as seen by different visualisations at basemap-

scale. A, Paddock map (superimposed over the budget photomosaic, see Fig. 4); B, aerial photograph

photomosaic; C, pan-sharpened LANDSAT bands 1,2,3; D, pan-sharpened LANDSAT bands 7,4,1; E,

LANDSAT panchromatic; F, DEM; and G, ALOS. Field of view 29 x 17 km.

B

A

20

C

D

E

21

The output of aerial photograph examination is 33 clear overlay sheets, marked with

unit boundaries and areas of interest, and a list of geomorphic units, described and

with preliminary process interpretations. The next stage is to compile the overlay

sheets by plotting the researcher-defined unit boundaries onto a base map. The base

map should cover the study area seamlessly, be georeferenced (usable in GIS and

able to give real-world coordinates for points on the map), and contain enough

information that matches may be made between base map and air photos.

The ideal base map would be orthorectified air-photo mosaics purchased from

Mapland, with the added advantage that this would be a valuable resource for the

landholders. However, these are not available over the South Australian Arid Lands.

Considering the issues described above about resolution, colour, and cost of satellite

imagery, it was decided to use LANDSAT bands 1,2,3 (attempting to produce

something like true colour) with the resolution sharpened by combination with the

panchromatic band. The LANDSAT was incorporated into a GIS database, and used

in combination with vector topographic data and the digital elevation model as a

multi-layered base map.

The LANDSAT was partially successful. The image was sufficiently clear that overlay

information could be transferred to it, and its ease-of-use in the GIS made it very

suitable for locating points of interest, plotting waypoints, etc. However, its colours

F

22

Fig. 5 Comparison of trial photomosaics over the central Moonaree paddocks (see Fig. 4A) created in-

house during this project. A) budget run photomosaic, B) best run photomosaic. The budget run used

scans of every other photograph (nos. 30 and 32) at ~25% overlap; the colours are uneven and piece

boundary ghosting is visible but the image would be suitable for basemap production. The best run used

scans of every photograph (nos. 30, 31, 32, 33). The colours are well-balanced to produce a nearly

seamless image, although at detail level it has a little less contrast. In both cases the photomosaic

process reduces image resolution, c.f. the original scans.

were not true colours (Fig. 4), making it difficult to relate LANDSAT features to units

defined on aerial photographs (the transfer from overlay to base map taking place

when the aerial photographs were no longer available). The end result was a map

B

A

23

(Fig. 2) partly defined on spectral characteristics not visible in the field, leading to

misinterpretation of the map features.

In light of the mismatch between LANDSAT and field observations, after field work

two trial versions of rectified photomosaic of part of the study area were created in-

house, one (best run: photos 30, 31, 32) with more overlap than the other (budget

run: photos 30, 32) (Table 1). These were successful and their geolocation properties

were good. They had a little ghosting at piece edges, and the less overlap version

had imperfect colour balance, but both were acceptable for basemap creation. Their

costs are shown in Table 1 and comparison is shown in Figures 4 and 5.

Photomosaicing decreases image resolution, so detailed work on airphoto scans is

best done on unaltered images (Fig. 3A, 3B).

For further projects of this type, this report recommends the use of panchromatic

LANDSAT, DEM, and vector topographic data as base map layers if unit boundaries

can be drawn while air photos are still available for comparison. Rectified and

georeferenced photo mosaics created in-house will be better than the LANDSAT,

and will also produce an image the landholder can use (for example, for an EMS

study); however it is more expensive. ALOS, a new type of satellite image, may also

be useful: although the example used during this project (250cm_2007_RGB_LCC)

was incomplete the false-colour was a better approach to real colour than other

satellite data (Fig. 2).

24

Table 1 Comparison of cost and utility of images for geomorphic mapping. Costs based on 67 photos, or

equivalent satellite coverage, at prices mid-2009 *On-site photo examination costs include transport to

Adelaide, one week’s accommodation and food. ** Note that a best-run photomosaic would call for

scans of all photos covering the study area, reducing the cost of the “print photos interstate” option to

$1,675.

Cost Image Type And Source Sufficient Reso-lution for Landform Mapping

True Colour

Sufficient Scale & Detail for Base Map

Georefe-renced

Per Photo $

Whole Project $

For Landform Mapping - Images of Parts of the Study Area:

for comparison, photos, existing lab, NSW Y Y N N 26 1,748

inkjet prints of existing scans (SA Mapland) Y Y N N 78 5,226

photos, scan negative, print interstate Y Y N N 155 10,385

photos, scan photo, print photo interstate ** Y (barely) Y N N 66 4.422

examine photos on-site SADEH* Y Y N N 1,680

new aerial photography SA DEH (for an area equivalent to a 1:100,000 map sheet)

Y Y N N 25,000 -35,000

For Basemap and GIS dataset - Images of All the Study Area:

LANDSAT panchromatic (black & white) N N partly Y 727

LANDSAT pan-sharpened bands 247 N N partly Y 1,680

Quickbird (stereo) Y Y Y 50,000

SPOT with 3-D Y N Y Y 9,688

SPOT N N Y Y 3,600

ALOS (stereo) Y N Y Y 1,320

SRTM digital elevation model N N partly Y 0

orthophotos from SA Mapland not available n/a n/a

best run N Y Y Y 10,834 rectified and georeferenced photomosaics made within the project, incl. scans **

budget run N Y Y Y 5,489

Topographic GIS (vector) N N partly Y 0

Google Earth N N partly N 0

25

LANDSCAPE PROCESSES OF MOONAREE STATION: A PILOT STUDY

Part 2: Report to Landholders

Geology

This section describes the geological origin of Moonaree’s rocks and sediments.

Land management implications are shown in italics, and summarised in the land

management section of this report.

Gawler Range Volcanics > 1,600 million years old

During the Proterozoic geological age, the Gawler Range Volcanics were laid down.

The Volcanics comprise a number of fairly similar silica-rich rock types, each with a

different name. Most of Moonaree’s hills are the Yardea Dacite, but there is a belt of

different rock types extending across Waurea, Kulgulya, Dingo Hill, 10 Mile, and part

of Charpatta Paddocks. All of the Gawler Range Volcanics are dense, hard rocks,

which are very fine-grained.

A fresh broken surface of

these rocks is a rich reddish-

brown colour, studded with

small (1-3mm) pale or dark

crystals of feldspar or epidote

(Fig.6). The outer surface is

usually weathered to a more

pale orange-brown.

Fig. 6 Chunks of the Yardea Dacite,

the most common rock type on

Moonaree Station.

26

Management implication – Groundwater: The rocks are dense and very fine-grained.

They are not porous and the only way these rocks can hold water is in fractures and

cracks.

Regional Fracturing and the Acraman Impact Structure, >580 million years old

During the Proterozoic geological age, earth movements created extensive fracturing

in the Gawler Range Volcanics (Fig. 7). This is expressed in the landscape as valleys

(along the fractures) and hilltops (where the rock is less fractured, it is more resistant

to erosion). These structures trend towards 0º and 35º (north and north-northeast).

Another, larger fracture system trends 320º (northwest). These fractures predate the

Acraman impact.

Figure 7. The influence of geological structure on Moonaree landscape is strong, as shown by the

trends of the fracture-valleys (dark lines) and the hilltops (gray lines).

27

Management implication – Groundwater: These fractures permit water to be stored

in, and flow through, the volcanic rock.

580 million years ago, a meteorite or comet struck the earth west of the present

Gawler Ranges. At that time the land surface was approximately three kilometres

above its present level. The impact shattered the Gawler Range Volcanics most

strongly in the central crater zone, forming what is now Lake Acraman and its

surrounding flat plain, and the outer crater rim, forming what is now the Yardea

Corridor (Fig. 8). In these places, the broken rock has been more easily weathered

and removed, so the landscape is less hilly. The impact also added some curved

fractures elsewhere. Fist-sized debris landed as far away as the Flinders Ranges,

and the catastrophic effect of the impact is thought to have influenced the course of

evolution of Earth’s early life (Williams & Gostin 2005).

Figure 8 Digital

Elevation Model (DEM)

showing a regional view

of the Gawler Ranges

and its fracture pattern.

1, Lake Gairdner; 2, the

Acraman Impact

Structure; 3, the Yardea

Corridor (black dashed

line); 4, like the Yardea

Corridor, this curved

feature (black dashed

line) lacks hills. Picture

is ~150 km wide. Lowest

elevation (lake level) is

purple to deep blue, with

rising elevation climbing

through the colours

green-yellow-red-purple,

to highest hilltops at dark

blue to light blue.

1

2

3

4

28

Management implication – Gnamma Waterholes and Hilltop Domes: The same

fracture systems that are expressed on the landscape scale are also visible in a

much smaller area (Fig. 9A). Where fractures occur close together and the rock is

broken into small pieces, it weathers more rapidly. Rock fragments are transported

away from the fractured area, leaving a small depression in which soil collects and

vegetation grows (Fig. 9B). The soil acidity and moisture speeds up the weathering

process, and the small depression becomes bigger and deeper. In this way a wide

and relatively shallow hole (a gnamma) is created, in some cases becoming a

waterhole: a reliable water source for human and animal use.

Where fractures are widely spaced (tens to hundreds of meters apart) the rock is

resistant to weathering and can form a broad unvegetated dome on the hilltop or

hillside. (Sometimes rock domes weather by spalling or onion-skin weathering, where

5-20 cm thick sheets break free from the underlying rock.) Very little vegetation

grows on a rock dome, and it will be a high-runoff area during rain. Vegetation on

hillslopes beneath such domes would benefit from the increased runoff, though there

is also an increased risk of erosion during heavy storms.

Figure 9 A) Closely-spaced fractures on a hilltop in Crown Paddock, oriented north-northeast, northwest,

and east. B) Rock rubble has weathered away from closely-spaced fractures, leaving a soil-filled hole

which can eventually form a gnamma.

A B

29

Tertiary sediments: white claystone (65 million years to 2 million years ago)

At Moonaree a number of outcrops of white claystone were seen (Fig. 10), the best

being on the banks of Gorge Creek, 100m from the Outside fence in Gorge Paddock

Fig. 11), and beneath the gypsum layers in the gypsum field at Parkers Outside

Paddock. The claystone is crumbly-looking, bright white, slightly sandy, and cut by a

network of very fine ?quartz veins. The white claystone is normally very poorly

exposed and hard to see, and also hard to distinguish from the weathering profile

(see below).

Figure 10 Observed occurrences of white claystone (dark pink triangles) and weathering profiles (pale

orange triangles), plotted on a Digital Elevation Model which assumes a lake level at an elevation of 200

metres above sea level (dark grey). The current Lake Gardener shoreline is at 130 metres ASL.

During the Tertiary geological age, earth movements and variations in the local

climate caused sea level to rise and fall many times. In the Gawler Ranges area,

30

large creek systems extended from the ocean back as far as Glendambo. These old

creek systems (or “palaeochannels”) are now marked by chains of salt lakes.

Elsewhere in southern South Australia, these palaeochannels are known to contain

dolomitic (magnesium-limestone) shales grading in colour from dark grey to bright

white (Keeling & Self 1996). With wetter climates and higher sea levels, lake levels

would have been higher than they are today. If the Moonaree white claystone is

similar to the channel sediments found elsewhere in South Australia, it is likely to

have been deposited during these high lake-level times. Locations of the observed

outcrops are consistent with being deposited in water-filled lakes (Fig. 10).

(Note: during fieldwork it was thought this white claystone might have been related to

the Great Artesian Basin, but further investigation indicates this is unlikely.)

Figure 11 A 4m high bank of white sandy

claystone, overprinted by brown, red, and

dark purple-red of the weathering profile.

Location is 100 m from the station track,

along Gorge Creek, near the

northeastern fence of Gorge Paddock.

Management implication – Gilgai

Soils: The palaeochannels are

strongly associated with swelling

clays (smectite and palygorskite)

(Keeling& Self 1996). These

types of clay crystal are much

bigger wet than dry, and are an

important component of shrink-

swell soils like gilgai. Since gilgai

soils are prominent on Moonaree

Station, the distribution of these

swelling clays (Fig. 16) will

influence paddock productivity.

31

Tertiary weathering profile, ironstone (buckshot) gravel, and silcrete (65 million years to 2 million years ago)

At some time during the Tertiary geological age, there have been episodes of strong

weathering. Long exposure, warm climates, and plenty of groundwater will change

the chemistry of the rocks close to the earth’s surface, leaching out some substances

(like quartz) and concentrating others (like iron). The result is a weathering profile:

bleached white clays, in places heavily mottled with iron oxides. This can be best

seen at the claystone outcrop (Fig. 11), but there are places where the dacite is so

heavily weathered that it also looks like white claystone (for example Jolly Creek in

garden well paddock).

Management implication – Groundwater: The weathering profile will penetrate most

deeply where the rock is most fractured. The chemical changes taking place during

weathering are likely to partially fill the fractures, decreasing fracture permeability. In

this way locations that look promising for putting down wells (like the intersection of

two fracture-valleys) might have surprisingly poor results. The extent of the

weathering profile may strongly influence groundwater availability and quality,

however further investigation is required to answer this question.

In some places the iron oxides are so concentrated in the weathering profile that they

form bands of very hard, very dark red to almost black, siliceous ironstone (Fig. 12).

This ironstone breaks into small shiny dark pebbles (sometimes called “buckshot

gravel”) which are found in patches on the surface of some paddocks, especially

Little Gorge and Parkers.

Under certain conditions of groundwater chemistry, silica from quartz dissolved out of

the weathering profile gathers together and recrystallises, cementing together or

even completely replacing the sediment it surrounds. The result is a silcrete: a very

hard fine-grained pale rock often used for making stone tools in pre-European

Aboriginal technology (Fig. 13D). No outcrops of silcrete were observed during this

fieldwork but some is known to exist at Crown and Woolly Paddocks, and there is a

large silcrete outcrop at the lake margin on Mount Ive Station (Fig. 13C).

32

Figure 12 Tertiary rocks and weathering profile. A, white claystone mottled with dark red iron oxides of

the weathering profile; B, heavily weathered dacite; C, heavily weathered rock that might be claystone or

might be dacite; D, buckshot gravel cemented by iron oxides; E, well-rounded silcrete pebbles with a

characteristic highly-polished surface.

Tertiary sediments (65 million years to 2 million years ago) Ironstone and silcrete fragments, eroded from their original places in the weathering

profiles, can be transported in creek systems, becoming smooth, water-worn pebbles

over time. Sometimes these old creek sediments can become re-cemented into new

rocks. Highly-polished silcrete pebbles and re-cemented buckshot gravel (Fig. 12 D,

E) were found in a few places.

Management implication –Groundwater: The sediments indicate that the sub-surface

geology of Moonaree is likely be complex. This would contribute to the difficulty in

predicting the location of good-quality groundwater.

Tertiary to modern calcrete (65 million years ago up to the present day)

Calcrete is a rock similar to limestone. Like the silcrete, it precipitates from

groundwater and cements or even replaces the sediments that the groundwater is

surrounding. It requires different conditions of groundwater chemistry, but the

E

C

B

B

A

D

33

groundwater must be very high in dissolved calcium and carbonate. Calcrete is hard

and usually white (but less bright than the claystone) to pale pink or tan. The outer

surface of calcrete nodules and rocks has a slightly grainy, matte appearance.

Figure 13 A, calcrete; B, dirt-covered calcrete pisoliths surrounding something that is now weathered

away (possibly dacite rubble), leaving a mass of hollow spheres; C, an unusual silcrete from Mt. Ive, in

the form of hollow spheres, possibly silica replacing a calcrete rock similar to B; D, a stone tool made

from fine-grained silcrete.

Calcrete occurs all over Moonaree, from the hilltops to the valley bottoms. It has no

relationship to higher lake levels (Fig. 14). It occurs in a variety of forms (Fig. 13): as

sheets cementing rocks or dacite rubble, as rubble at the break of slope between

bare rock and rocky soils on hillslopes, as layers of nodules close to the ground

surface (best visible as white patches on station tracks), and as chips or veins

through the soil profile (“calcareous earths”). The silty soils associated with calcrete

are a slightly pale orange and are hard underfoot.

Calcrete and silcrete can form over the top of each other, and the complex

relationships at Moonaree indicate that there have been several episodes of calcrete

and silcrete formation.

C

A

B

A

D

34

Figure 14 Widespread distribution of calcrete outcrop (blue crossed boxes) or calcareous soils (blue

wavy lines) has no relationship to previous higher lake levels. (Digital Elevation Model shows the lake

level at 200 metres above sea level (dark grey); the current Lake Gardener shoreline is 130 m ASL).

Pleistocene to modern gypsum (2 million years ago up to the present-day)

Gypsum (calcium sulphate) is widespread on Moonaree. Its most common

occurrence is as high-salinity groundwater in some wells and dams, and a few creek

channels (notably in Crown Paddock, near the Yeltabinna fence, where a

hyperconcentrated brine was precipitating gypsum at the sediment-water interface).

Its next most common occurrence is as kopi (also known as “seed gypsum”), fine (<

1mm) lens-shaped crystals. Typically these are pale tan-coloured accumulations,

very light and soft underfoot, described by the landholder as “something your

motorbike would get bogged in”. Kopi forms above the groundwater surface, in or

above the soil profile. Older deposits of kopi can consolidate and harden (gypcrete),

such as the bench of old kopi a few hundred metres from the creek channel in Crown

Paddock. Gypsum that precipitates over a long period of time below the

groundwater’s surface forms narrow, long (>10 cm) semi-transparent bladed crystals

35

with swallow-tail twinning. These can be found either deep in the soil (exposed when

a dam is deepened, such as Mount Cooper dam), or in the wet sediment of the lake

(Fig. 15E). ”Desert rose” is a special kind of gypsum crystal that probably forms in a

narrow zone of fluctuating groundwater level at the lake’s edge. Its crystals are large

(0.5-5 cm) but lens-shaped and may gather in semi-circular flower-like structures. A

layer of desert rose crystals (like those at the Parkers Outside inlet) indicates a

previous lake shoreline.

There have probably been many lake-full episodes during the Ice Ages. At the end

of each, while the lake was gradually drying up, water salinity would have increased

and gypsum precipitated within the lake and around the lake edges. The distribution

of gypsum at Moonaree is related to higher lake levels (Fig. 16).

Figure 15 A, modern soil

derived from dacite; B,

slightly silty quartz sand; C,

old consolidated kopi

(gypcrete); D, older gypsum

blade crystals; E modern

gypsum blade crystals dug

from the lake’s edge.

Management Implications – Groundwater: The presence of gypsum crystals in an

area, or its position in the old lake (Fig. 16) may indicate decreased chance of good-

quality groundwater. However, it is also possible that high-salinity brine underlies the

whole station. Hydrological investigation would be useful to answer this question.

Pleistocene to modern soil and sand (2 million years ago up to the present-day)

Much of the soil at Moonaree is derived from the local dacite rock. It is (like the rock)

coloured a deep red-brown (Fig. 15A), and is fairly coarse in its grain-size. Pure

dacite soil is firm but not hard underfoot. It is easy to drive over (not bulldusty, not

soft, only a little greasy when wet). Dacite soils support a rich variety of chenopod

vegetation.

E

C

BA

D

36

Figure 16 Previous high lake levels may control the distribution of gypsum (surface occurrence, white

blazes; subsurface occurrence, white crossed boxes) and soils containing swelling clay (gilgai, green

circled diamond; soft crunchy soil, green wavy lines; hard-water dams, green boxes). (Digital Elevation

Model shows the lake level at 200 metres above sea level (dark grey); the current Lake Gardener

shoreline is at 130 metres ASL).

Management Implication – Plants: The type of soil, and depth of soil, has a clear

influence on plant type. Rocky, thin, poor soils of the hilltops support spinifex but

rarely chenopods, and the boundary between the two plant groups is usually sharp.

Hillslope soils may support chenopods but they will be small and sparse if the

underlying rock is close to the surface, or if the soil is full of dacite rubble. Soils with

more fine silty material and less rubble have thicker stands of bigger bushes. There

were several different types of chenopod assemblages on different chenopod plains.

A survey with a plant specialist and a soils specialist would be informative.

Pleistocene to modern sand (2 million years ago up to the present-day)

A wide belt of sand extends east-west across the southern paddocks of Moonaree,

visible in the LANDSAT as blue-and-white colour. It is mostly medium-fine quartz

37

sand which has been blown hundreds of kilometres from the west. It is softly sandy

underfoot, fine-grained enough to bog vehicles. It supports hardy specialist plants like

spinifex and mallee, and makes poor grazing country. The belt of sand is in the form

of a flat sand sheet, with high narrow dunes trending east-west, covering the dacite

except for the highest hill crests. Sand is thickest to the east of dacite hills, where it is

sheltered from wind. The sand sheet is shallow in places, but piled high along its

northern margin, where it faces into Moonaree (Fig. 17). The sand is generally stable

although there are some patches of erosion near dune crests and on the steeper

dune slopes near the northern margin. Closer to Lake Acraman, in the west of

Mulcaree, the sand has a greater proportion of dacite. This is visible in the LANDSAT

as brown-and-white colour. It is much more firm underfoot than the quartz sand.

Management Implication – Feral Animal Control: According to the landholders, sheep

and goats are disinclined to travel over quartz sand, and they attribute the relatively

goat-free status of Moonaree to the sand belts north and south of the station. The

dacite sand however is firm under foot, and is not such a barrier. Where dacite sand

extends almost through the quartz sand (for example, west of Mulcaree, or far east of

Morinippi), an opportunity may exist for goats to enter the station. The LANDSAT

image (Map 3), which shows the difference between quartz and dacite sand, can be

used to suggest where such a pathways exist.

Management Implication – Erosion Control: the northern edge of the sand belt has

the potential to become susceptible to erosion. At the moment, it is held in place by

the combination of protecting hills and anchoring vegetation. Where vegetation is

depleted, it shows signs of mobility (erosion), and in places the sand is creeping

northwards over the chenopod plains. If the sand sheet was to encroach northwards,

paddock productivity would decline. Preservation of sand dune vegetation should be

considered, possibly including fire management (controlled, small, cool, patch burns

in the highly flammable spinifex + mallee country).

Figure 17 (next page) The Moonaree southern sand sheet. A) Sand elevation profile along the track

south to north through Mulcaree; yellow dots match landmarks noted at the bottom of the profile. B)

LANDSAT view of southwestern Beviss; green lines are fences and the yellow line is the path of the

sand profile shown in C. The sand sheet is a blue and white colour, the dacite hills are dark and the

chenopod plains are brown. Note the dune crests (look like ripples) near the sand sheet edge. C) Sand

profile southwest to northeast through the southwestern corner of Beviss.

38

B

A

Kittles high gate track Sprft Dam dacite hills gate dogleg Dam

fence sand profile edge dogleg

C

39

Geomorphology and Landscape Process

This section describes the landscape processes currently operating on Moonaree’s

landforms. Land management implications are shown in italics, and summarised in

the land management section of this report.

The Moonaree landscape consists of the following elements (Figs.18, 20):

• rocky hilltops, forming more or less high domed hills, where bare rock is exposed; characteristically the vegetation includes spinifex and sometimes small trees

• upper hillslopes, where not much rock is exposed but where the soil is dominated by dacite sand and abundant large chunks of dacite rubble; rock is probably only shallowly buried; vegetation is thinly-spaced chenopods and sometimes small trees

• low rubble hills, without exposed rock; the soil is dominated by dacite sand and abundant rubble; rock is probably only shallowly buried; vegetation is thinly-spaced chenopods

• lower hillslopes, with some rubble in the dacite-sand soil; vegetation is more closely-spaced chenopods; grades into chenopod plains

Figure 18 Landscape elements (Gorge Paddock).

rocky hilltop upper lower chenopod

hillslope hillslope plain

40

• chenopod plains, wide flat spaces, more or less densely occupied by chenopods; soil is silt and dacite sand with little or no rubble; the central drainage lines are typically discontinuous small creeks, or unchannelled swales

• sand sheet with dunes, near the lake edges, and in a belt along the southern station

• narrow rocky valleys between closely-spaced hilltops; created by weathering along the regional fractures (see Geology above); drainage lines are small, discontinuous gutters flanked by closely-spaced small trees (Fig. 19)

• the larger creeks (especially the creeks that flooded in 1997: Jolly, Yeltabinna, Garden Well, Old Homestead) are arroyos with steep sides, typically 1-4 meters deep and 5-20 metres wide

Figure 19 In a small rocky fracture-valley (Dingo Hill Paddock), the central drainage is only sometimes

contained within a channel: this small creek is discontinuous (alternates between channelised flow and

unchannelled sheetflow). Arrow shows end of channel; flow towards camera along arrow path.

Salt Lakes

When the lakes are dry, gypsum crystallises on the lake floor and is sometimes

blown into the eastern shore, forming shoreline dunes of very pale fluffy gypsum

sand. When the lakes are full, the prevailing westerly wind creates waves and

currents along the eastern shoreline. This is why the western shorelines of Lakes

41

Acraman and Gairdner have a rough outline on the map, whereas the eastern shore

lines have been smoothed by wave action.

Fig 20 Chenopod plains. A) Belt Hill Paddock: Lower hillslope with rubble and chenopods merging down

to chenopod plain (see Fig. 21) in distance (small white dot below hills is white ute for scale). B)

Chenopod plain in Bond Paddock has a surface that is very often wet: the cryptogam crust is very thick

and dark, and there are mosses and liverworts. (White ute in the distance for scale.)

A B

42

Chenopod-covered Lower Hillslopes, and Chenopod Plains: “Sponge Country”

On air-photos and satellite images, Moonaree looks like it’s mostly rocky hills, but on

the ground the landscape is dominated by wide, low-gradient vegetated land: lower

hillslopes and chenopod plains. Red soil partly covered by closely-spaced chenopods

rises gently towards the surrounding hills (Fig. 20A). The hillslopes and plains have

soil dominated by dacite sand and silt, with a variety of differences and supporting

different plant communities. Pure dacite soil is firm but not hard underfoot;

calcareous soil is hard underfoot; kopi (gypsum sand) is very soft and fluffy; and soil

containing swelling-clays is soft underfoot and sometimes has a slightly crunchy

crust. Some chenopod plains had evidence of being frequently wet at the surface: the

cryptogam crust was very thick, dark, and wrinkled, and there were moisture-loving

plants (mosses and liverworts) growing between the shrubs (Fig. 20B).

In many chenopod plains where you’d expect to find a creek in the valley centre,

there is no visible drainage network (Fig. 21).

Figure 21 Looking across the drainage axis of a Mt Cooper Paddock chenopod plain, there is no visible

creek. The dip in the road (right of the photo) is damp and tiny salt crystals (?gypsum) are forming in the

wheel tracks.

43

Management Implication – Paddock Productivity: The lack of organised drainage is a

key factor in paddock productivity. Rainwater and hillslope runoff stays around

instead of heading off down the channel – water has the best possible chance of

infiltrating the soil. The relatively closely-spaced chenopod vegetation, and the shape

of that vegetation (bushy right down to the ground level) also promotes water

infiltration, by placing barriers across downslope flow. The lower hillslopes and

chenopod plains act like giant sponges, and as a result there is good growth of

vegetation. Where vegetation is completely lost, there is no barrier to water runoff.

Water is not retained, vegetation does not germinate, and sheet erosion is likely (for

example along the stock route in Kallinta Paddock, Fig. 22).

Furrowing rehabilitation works were undertaken by the landholders who report

successful plant establishment after ~20 years. The works were not able to be laid

out along surveyed contour lines. Contour furrowing in the Western Catchment of

New South Wales has been shown to be most successful where contour elevations

are most accurate. It is likely that the Moonaree works would have had more success

sooner had surveying been available to assist the landholders.

Figure 22 The stock

route in Kallinta

Paddock has bare

patches along it, and

sheet erosion is

demonstrated by the

remnant soil

pedestal (isolated

plants, lower right).

Furrowing

rehabilitation works

have been

undertaken (where

Adrian is standing),

and the landholders

report some

vegetation growth

after ~20 years.

44

Discontinuous Ephemeral Creeks

In some hillslopes and plains, the drainage axis can be seen as a line of scattered

Acacia trees around a poorly-defined swale (a swale is a depression that holds

water, but which is not as clearly-marked in the landscape as a creek channel or a

gully) (Fig. 23A).

Figure 23A) A swale with trees is the only sign of central drainage in the chenopod plain of Belt Hill

Paddock. Backpack and pink notebook for scale, swale extends the full photo width at the backpack

location, there are no clear banks. B) Sketch of a line of discontinuous creeks down a drainage line:

channels are separated by unchannelised sheetflow zones (light blue arrows). Looking from above,

arrows show flow direction, orange shapes are the banks of the channel. As water flows over the

chenopod plain, it is sometimes it is gathered into a channel. At the downstream end of the channel it

spreads out as sheetflow again.

In other places, the drainage is a little more organised, forming short discontinuous

creeks, sometimes singly, sometimes one after the other in a line separated by

channel-free sheetflow areas. In each of these discontinuous creeks there is an

B

A

45

Fig. 24 A discontinuous creek in Mt Cooper Paddock, near the road crossing at Yeltabinna Creek..

A Looking upstream along the

beginning of a discontinuous

creek. Water flowing down the

centre of a chenopod plain gathers

enough energy to trigger erosion.

The hammer (for scale) is between

two plunge-pools, and small creek

channels pass to right and left of

the camera.

B Looking downstream along the

central creek channel. It is shallow and

the banks are not sharply defined. This

channel is close to the station track at

the north of Mt Cooper Paddock.

C Looking downstream along the end of a

discontinuous creek. Water flowing down the channel

from B (above) disperses over the chenopod plain as

the channel gets more and more shallow and

eventually disappears. The shrubs here have very

water-rich leaves.

46

upstream eroding end, a central channel, and a downstream distributary end (Fig.

23B, 24). In other landscapes the downstream end of a discontinuous creek is a

floodout (a richly-vegetated “sweet spot”) but at Moonaree the floodouts are not

strongly visible, probably because the downvalley slope of the drainage lines is so

strongly influenced by non-fluvial processes.

Management Implications – Channels & Decreases in Paddock Productivity:.

Discontinuous creeks are common across Moonaree and there is no reason to think

they aren’t a natural part of the landscape. (For example, few are found in high-

erosion areas: stock routes, piospheres.) However, in other parts of the world, where

discontinuous creeks become eroded and the channel either deepens or lengthens,

water that was once retained in the floodplain goes straight into the channel and

paddock productivity decreases (Figs.25, 29, 32).

This kind of erosion can happen when a valley-floor is scoured by extreme rainfall

events. It can also happen under more normal rainfall if the valley-floor resistance to

erosion is weakened by vegetation loss through overgrazing or drought. Keeping the

valley-floors well-vegetated will help to keep the discontinuous creeks from joining up

– which will help keep the valley-floors well-watered.

Fig. 25 Yeltabinna Creek in Ten-Mile Paddock. After channel incision (possibly during the 1997 floods)

water has less chance to accumulate in the chenopod plain, and trees along the drainage line may find it

difficult to survive.

47

Large Creeks: big flows, channel incision, channel relocation

The longest creeks, or creeks with the biggest catchment areas, are most likely to

gather enough water to carry large flows. Other factors include 1) the path of a

storm’s most intense fall will cross some catchments and not others, and 2) rain that

falls on rocky (high-runoff) ground will quickly find its way to a channel, but rain that

falls on “sponge” ground will not travel far. In the 1997 floods, the landholders report

that Garden Well, Jolly, Old Homestead, and Yeltabinna Creeks ran very high. Two

are the longest creeks with the biggest catchments, and two are shorter with small

catchments but collect water from high-runoff rocky areas (Figure 26, Maps 1, 3).

Moonaree’s main creeks are not well-connected. Instead of the channels being

continuous from hills to lakeshore, they may be discontinuous even along the main

drainage axis (for example, Crown Paddock). Some channels are deeply incised with

clear banks (for example, Jolly Creek), others show evidence of recent channel shifts

(Boolatta Creek in Little Gorge). Moonaree’s creeks are not stable landscape

features. This makes Moonaree a little unusual: most landscapes are governed by

river landform development, but Moonaree is more influenced by hillslope processes.

Figure 26 Catchment areas of the Moonaree creeks. 1, Yeltabinna; 2, Garden Well; 3, Jolly; 4, Old

Homestead; creeks that were flooded in 1997.

4

3

2

1

48

Gilgai

Gilgai soils have clay chemistry resulting in shrink-swell characteristics (see the

Geology section above). When the ground is wet, gilgai soaks water like a sponge.

When it is dry, it shrinks and cracks. It can be very rich and biologically productive.

There are many different kinds of gilgai. On Moonaree there are gilgai pits in Little

Gorge, Gorge, Kallana, Kallana Outside and White Well Outside Paddocks (and

probably others too). In Gorge, North Kallana and Kallana Outside there is stony gilgai as well as gilgai pits.

Gilgai pits are roughly circular depressions in the ground (ranging from less than a

metre to 100s of meters in diameter, Figs. 27, 28), centred around crabholes (very

deep cracks that open up after the wet ground dries out). Stony gilgai is a step-like

arrangement of rocky steeper ground and flattish muddy cracked ground. The cracks

or crabholes are the key characteristic of the gilgai. The shape of the ground – the

pits or the steps – helps to trap the first flush of rainwater, which drains into the open

crack. The water deeply penetrates and soaks the ground, which swells and heaves.

The heave creates the pit or the stony steps. In this way the gilgai are self-sustaining

landforms. The water-retaining nature of the gilgai supports dense vegetation. At the

time of this study, the gilgai pits were distinguished by a rich crown of bright grasses

(Fig. 27). The chenopods were often larger, or more closely spaced, or had more

water-soft leaves in the gilgai pits.

Distribution of gilgai around the property probably relates to previous high-lake levels

(Fig. 16). It is likely that the swelling-clay soil elements are blown to nearby hilltops

and washed downhill by rain, so isolated occurrences of gilgai may be found

elsewhere also. Other influences on the size of gilgai structures include soil depth to

bedrock, and mixture of coarser elements (such as dacite sand).

Management implications – Paddock Productivity: The landholders report Little

Gorge Paddock as being the one of station’s best paddocks, and it is also a paddock

very rich in gilgai pits. Observations during this study indicated gilgai pits were highly

productive ( more biomass, greater species diversity, higher number of desirable

species; Fig. 27). It is likely that paddock productivity is high where many gilgai are

49

Fig. 27Gilgai pits. A, the inside of a small

gilgai pit in Gorge Paddock, with pale

grasses around the edge and a deep open

crabhole below the hammer. Moisture-loving

vegetation (possibly nardoo) is now dried-out

and dead (brown-grey colour) between the

grass and the bottom of the photo. B, A

moderately large gilgai pit in White Well

(ringed by bright grass, Adrian for scale).

Heavy local rainfall has eroded sediment

from the upper hillslopes (rocky foreground,

and bare hillslope in the distance). The

sediment has washed into a shallow valley

and a gilgai pit has formed in this local area

of deeper soil. C, The hillside across the

valley from this fence is dotted with large

gilgai pits, shown by the patches of pale

grass (White Well Paddock).

A

B

C

50

Figure 28 Along the

fenceline in Gorge

Paddock, one of the

biggest gilgai pits on

Moonaree Station is

hundreds of metres in

diameter (bright grass).

Trees and very large

crabholes are in the pit’s

centre, where the track

dips. On the other side of

the fence, near the

watering point, there are

few signs of gilgai

function as well as little

vegetation.

51

present. Future management plans may benefit from noting gilgai distribution about

the property. Future vegetation monitoring sites should include some gilgai country.

Management Implications – Maintenance of Paddock Productivity: Some rangeland

managers consider that vegetation plays a key role in maintaining gilgai processes.

Certainly there are places in western New South Wales where loss of vegetation

along stock routes has been accompanied by a decrease in the visible signs of gilgai

processes (fewer crabholes, less ground “heave”). Similar situations may exist on

Moonaree, in Gorge and Spearfelt Paddocks (Figs. 28, 29). Preservation of a

minimum level of vegetation on gilgai landforms is likely to be important for

preserving their function and productivity. At present, there are no accepted

techniques for rehabilitating gilgai-pit country (although contour furrowing has been

shown to be useful in some circumstances for stony gilgai country in western New

South Wales).

Management implications – Station Tracks: Very large gilgai (such as Fig. 28) are

likely to be uncomfortable driving in all weathers. Sloppy and boggy when wet, when

dry they will be uneven and thick vegetation will conceal sump-busting holes. If

erosion starts along the track (see below) and drains into the central crabhole, the

result will be a two-headed gully extending away from the crabhole on either side. No

matter how much material erodes from the track, the crabhole will not fill up (they are

incredibly big). For the same reason, dumping road base into the hole may not be

effective either. It’s probably easier just to drive around them.

Heavy Rain and Local Hillslope Erosion: Moonaree’s Dominant Landscape Process Today

In most properties, region-scale slopes and rivers are the dominant influences, so

modern-day landscape change usually relates to pre-existing river landforms. At

Moonaree, the hillslopes are all local (originating in the dacite fracture pattern), and

the valley slopes have largely been controlled by local hillslope sediment deposition

and low-gradient old lake sediments. River landforms are a relatively minor part of

the landscape, and the creeks are generally only poorly-connected so flow events

tend to have only local affects.

52

Hillslope processes dominate modern day landscape change in Moonaree, and the

active agent for geomorphic change on hillslopes is heavy rain.

Hilltops:

Intense cloudbursts falling on bare rocky hilltops can give rapid runoff. In many parts

of Moonaree the rocky hilltops have a belt of dense vegetation at their base, where

the plants have received the benefit of the extra runoff. In other parts of Moonaree,

the break of slope between rocky hilltop and upper hillslope (see Fig. 18) is marked

by common outcrops of calcrete, which also indicates a flush of groundwater.

Figure 29 Gilgai at Cornish Well in

Spearfelt paddock. A, Hammer

handle sticking out of a deep

crabhole. B, Although there are

many crabholes, there are no gilgai

pits in this heavily grazed area.

A

B

53

Dacite soils, and clays and silt blown onto the hills during dry seasons, are washed

downslope by rain storms. If the rain is particularly strong, or if vegetation has been

reduced (for example, by lightning-strike fire in the spinifex), the rocky hilltop can

exhibit moderately severe local erosion. In some hilltops the spinifex grows in

contour-parallel bands and traps some of the downward-moving sediment (Fig. 30).

Sometimes, the downslope movement overwhelms the hillside vegetation and a little

patch of sediment forms lower down (Fig. 30). If the clay chemistry is right a gilgai pit

will form in this patch.

Upper Hillslopes:

The upper hillslopes, with their thin vegetation and rocky soils, are not likely to

absorb much rain. If a lot of water is shed during heavy rain, local patches of erosion

may be created and sediment deposition will take place on the lower hillslopes and

chenopod plains (for example, at White Well Paddock, Fig. 27 B.). Short sections of

discontinuous creeks along hill bases may be activated.

Lower Hillslopes and Chenopod Plains:

Chenopod plains will absorb most rain and runoff, as long as the vegetation and the

gilgai are in good condition. However, creek channels running through the chenopod

plains will tend to capture water and funnel it away.

Figure 30 Contour parallel bands

of spinifex (arrowed) trap

sediment in a convergent valley in

Parkers Paddock. Arrow shows

direction of runoff flow. A wedge

of sediment (*) has been washed

from higher in the hillslope at

some previous time.

*

54

Management Implication – Keeping Hillslope Processes Dominant: A little excess

runoff from place to place, or from time to time, giving localised patches of erosion

and sediment deposition or short discontinuous creeks, is a natural part of this

landscape. Moderately large channels at the downstream end of the largest creek

systems are also to be expected in this landscape. The important point for Moonaree

is to avoid creating conditions in the lower slopes and chenopod plains where

repeated runoff may trigger erosion, creating channels or joining discontinuous

creeks to create longer, deeper channels.

Factors which may promote erosion and channel formation are loss of vegetation

(Fig. 22), stock pads (Fig. 31), and station tracks (see below). Vulnerable locations

include stock routes, watering points, and convergent slopes (where several hillsides

face towards each other and the valley between receives extra runoff, Fig. 30, 31). A

combination of factors can make an area especially vulnerable, such as at Cornish

Well, where a substantial gully system (Fig. 32) has formed in an area where a track

down a convergent slope leads to a poorly- vegetated watering point.

A really extreme rainfall event will

also promote erosion and channel

formation, regardless of range

condition, however good range

condition will mitigate against erosion

in most weather conditions.

Fig. 31 A stock pad down the centre of a

convergent slope may become a focus for

erosion. Hammer for scale.

55

Figure 32 A

deep and

actively-

expanding

gully system

can be traced

upslope to an

old track

near Cornish

Well,

Spearfelt

Paddock (and

see Fig. 29).

Management Implications – Gullying Along Station Tracks: Graded and ungraded

station tracks are naturally predisposed towards gullying because barriers to flow

(like vegetation) have been removed, and hillslope water is concentrated between

track edges. In addition tracks are sometimes located where they intercept hillslope

runoff, gathering large amounts of runoff (and incidentally starving the downslope

vegetation of water).

Gully erosion along tracks in Moonaree is moderately common (noted in Parkers

Outside, White Well Outside, Charpatta, Beviss, Bond Hill, Belt Hill Paddocks). Most

gullies erode upslope from some low point such as a creek crossing or the central

low point of some plain (Fig. 33A, B). Some in gullies erode in two directions into a

central point within the gully itself, like someone pulling themselves up by their own

bootstraps. This is probably related to deep cracking in the valley sediments (see

Gilgai above).

Most of the gullies are not large, but nonetheless they use station resources in

grading for track maintenance. Some gullies are very large and represent a real risk

56

to vehicles, or station tracks have had to be relocated (for example White Well

Outside). The biggest concern is if these gullies become actively-eroding large

networks, such as the one in Spearfelt Paddock (Fig. 32). Such gully networks can

considerably reduce or destroy paddock productivity, and are extremely difficult to

rehabilitate. Examples elsewhere are known to be kilometres in length.

C Figure 33 Gullying along station tracks. A) Charpatta

Paddock, gully draining towards centre of chenopod

plain; B) gully draining towards creek, Kumburta

Paddock (hat for scale); C) Beviss Paddock, a

double-headed gully draining in towards its own

central point. One gully head is in photo foreground,

the other is shown by white arrow.

BA

57

Effective techniques for track placement, design and maintenance are not within the

scope of this report, however should be an important part of the SAAL-NRM

information resources made available to land managers.

Implications for Land Management: Summary

The statements in this report do not imply any criticism of past or present managers of Moonaree

Station or SAAL-NRM.

Groundwater is most likely to be carried in fractures through the volcanic rocks, and

in the younger sediments of the fracture-valleys. However, weathering and sediment

deposition during higher lake-levels in the geological past has created a complex

groundwater situation in which quality and supply are variable. Map 4 and Fig. 16

may indicate areas affected by heavy weathering and gypsum deposits, however it

should be noted that this project’s mapping component was intended to provide an

overview only. Groundwater flows down from hills to lake, and flow is more rapid

where the ground surface is steeper (Dickinson 1942). Local variations in slope will

also therefore add complication to the groundwater picture. Local aquifers in wide flat

areas are more likely to be slow-flowing and stagnant. Those closer to steeper

hillslopes may be more quickly freshened by rain on the hillslopes. Finally,

landholders observe that fresh water is usually above saline water – this is likely to

be a result of the greater density of saline water. Fresh water isn’t weighted down

with dissolved gypsum, so it floats on top of the saline water.

Gilgai soils are an important part of Moonaree’s productivity. Map 4 and Fig. 16 may

also indicate where gilgai soils are most likely be found.

The principal soil components are dacite sand, silt, clays (including swelling clays),

quartz sand, gypsum and calcrete. Vegetation is strongly related to soil types, from

the relatively poorly productive spinifex communities (in quartz sand and in rocky

hilltop areas) to the highly productive chenopod plains in the wide, low- gradient

valleys. Although superficially similar to each other, many of the chenopod plains

have different soils and different plant communities.

58

The wide belt of sand across the south of Moonaree is not very productive country

but may play a role in keeping feral goats off-station. The sand is currently stabilised

by underlying hills, and by vegetation; loss of vegetation may lead to sand

encroachment across more productive country.

The chenopod plains are the most important landform on Moonaree Station. Their

lack of connected drainage makes them into giant “sponges”, which is the heart of

their productivity. Short discontinuous creeks are common throughout Moonaree, but

long continuous channels are not common. Valley-floor erosion, creating new

channels or joining together short shallow creeks into long deep channels, will

decrease or destroy productivity in the chenopod plains.

Vegetation is an integral part of the landscape processes that maintain gilgai

landforms and protect chenopod plains. It is not only important to preserve vegetation

for its own sake, but also because the loss of vegetation means the loss of landscape

processes which allow the vegetation to grow.

Gully erosion down tracks is present in many places in Moonaree. While not currently

a serious problem (except in Spearfelt), such erosion has the potential to seriously

degrade landscapes. Information on effective track creation and maintenance should

be available to all landholders.

The loss of vegetation along stock routes and near watering points is a common

problem throughout the rangelands. Because the loss of vegetation may change the

landscape processes, the land may not effectively recover without intervention.

Rangeland rehabilitation processes such as contour furrowing are most likely to be

successful and economically viable if information on successful techniques is

available to the landholders, and if the landholders have access to accurate

surveying when installing the rehabilitation works.

59

LANDSCAPE PROCESSES OF MOONAREE STATION: A PILOT STUDY

Part 3: Controls on Surface Water in SA Arid Lands

The Great Artesian Basin is not the only important water resource in South Australia:

surface waters in drylands rivers are also a resource worth regulating and

conserving. Though subordinate to waters from the Great Artesian Basin in amount,

surface waters nonetheless supply a substantial part of the South Australian Arid

Land area. The grazing industry relies on small ephemeral creeks to water stock

(either directly via earth tanks and dams, or indirectly as recharge for bores drilled

into alluvial sediments). The tourist industry relies on surface waters for visitor

services and to underpin the beauties of the landscape which the visitors come to

see. Aboriginal homelands need surface waters for human services and cultural

values. Most significantly, all over South Australia, surface waters are the key

element supporting ecosystems.

Legislation regulating the use of surface waters generally aims to ensure all

stakeholders (including the environment) have reasonable access to the resource. At

present there is little legislative framework governing the use of surface waters in the

SA Arid Lands. In Australia, much existing legislation focuses on the extraction of

irrigation water from large perennial river systems. Regulation of ephemeral creeks

tends to be by simple rules of thumb. In New South Wales, landholders are allowed

to build earth tanks (dams) on first- and second-order stream channels. In the

Northern Territory, the owner/occupier of the property can extract water from a

watercourse for stock without a license; permits are required for earthworks that halt

or divert water, but rural dams <3 m high or with catchment <5 km2 are exempt.

Western Australia appears to be in the process of formulating new water

management plans.

60

Low Priority Given to Understanding Drylands Catchments Regulation of arid land surface waters is hampered by a generally poor

understanding of drylands rivers. There is a general assumption that drylands rivers

work in the same way as “normal” (by which is meant: temperate-zone, perennial)

rivers, except they don’t work most of the time. The very words we use show that our

understanding is grounded in our European heritage: “waterway”, for example, or the

definition of “river” in Australia’s own Macquarie Dictionary as “a considerable natural

stream of water flowing in a ... channel”.

Figure 34 The degree of accuracy given to understanding catchment in remote SA is much less than

that given to populous places. A) Detailed capture of drainage divides in the Fleureau Peninsula:

catchments (pink) and subcatchments (blue). B) Basins for all of SA; the area shown in A) is included

(pink and blue). The water basins defined for the less populated parts of South Australia are not

hydrologically correct. For example, the Gairdner basin groups together many smaller drainage

networks, including some offshore ones, and the Lake Frome basin (orange) lumps together Lakes

Frome, Callabonna, Blanche, and Eyre.

A B

61

It is understandable that population centres and large water resources have the lion’s

share of organisational attention, however the result is that organisations (such as

SAAL-NRM) which have to manage the largest area of land in the State have to do it

with the least information. For example, online maps of South Australia’s surface

water basins have catchments and drainage divides in great detail for e.g. the

Fleurieu Peninsula (Fig. 34A), whereas the basins for the arid lands are not even

correct (Fig. 34B). Similarly, aerial photography can be purchased from existing

scans of negatives from areas close to Adelaide, whereas there are no resources

available to scan negatives of remote lands, thus doubling the cost. SA inkjet prints

of remote-area air-photos are six times more costly than actual photo prints from

states with existing facilities.

South Africa, a nation equally concerned with managing arid lands, has recently

begun to upgrade its surface water regulation. Their water board has begun by

attempting to characterise the rivers. However, they have been told to use the basins

that were defined (based on unknown criteria) some decades ago. These basins

don’t correspond with the hydrological reality, so the task has been difficult and the

results are unlikely to be worth the resources spent to achieve them.

Different Features of Drylands Rivers Drylands rivers are qualitatively different from temperate-zone rivers, with processes

and landforms that may not be recognisable in terms of “normal” rivers. They are

working when they are dry: the vegetation:landform relationships continue to affect

landform even when the water is gone. The markers for waterway health are

different.

Overland Flow, Not Flow Through Soil In a temperate river, rain falling on hillslopes infiltrates and makes its way to the river

by horizontal flow through the soil. A channel downstream from a dam will receive,

through the soil, some of the water that fell uphill from the dam. In the rangelands,

the soils often seal after only a little rain, and overland flow – surface runoff – plays a

much larger part in delivery of water to the river network. A channel downstream from

a dam will probably receive nothing of the rain that fell uphill from it. A regulation that

allows damming of every second-order channel in a river will not trap most of the

62

water in a perennial setting, but in an arid-zone river it could sequester most of the

catchment’s water.

Arid Rivers Often Discontinuous Australian rangeland rivers are often discontinuous. What seems to be a string of

small insignificant creeks in flat country can actually be a “discontinuous ephemeral

stream” (Pickup 1995, Bull 1997, Wakelin-King & Webb 2007) – where the river

landforms are repeating sequences of gullies, channels, and then unchannelled

floodouts. The idea that a flat bit of ground without a channel can be a river reach is

not commonly accepted in catchment management circles, yet discontinuous

streams, separated by floodouts, are a very common landform in some parts of arid

Australia. They are the dominant fluvial landform in Moonaree.

The NSW Water Act allows dams to be placed across first- or second-order

channels. The channels are defined according to features displayed in listed

1:100,000 topographic map sheets. The problem with this is that the cartographers

don’t recognise the discontinuous nature of the creeks, so drawing a single drainage

network as two. Dams thrown across what are effectively third-order channels are

threatening the viability of a downstream terminal wetland. There is the potential for

water-rights disputes in the future.

Arid Rivers Depend on Episodic Flow Drylands rivers and their ecologies are designed to cope with flow variability. The

occasional large floods that push high volumes of water far downstream or across

the floodplains are just as valuable (sometimes more valuable) as smaller flows.

Retaining floodwaters (for example, to irrigate crops) is not “good use of water

otherwise wasted”, it deprives downstream ecosystems of their most important flow

events. Dams which release excess water as a small trickle over a long time favour

local ecosystems at the expense of distant ones. This is an ecological issue as well

as a industry water rights issue.

Floodouts Floodouts are functional equivalents to riparian zones: they mediate erosion, store

nutrients, are valuable ecological niches, and play an important role in maintaining

63

river health (Wakelin-King 2006, Wakelin-King & Webb 2007). However, lacking

channels, they aren’t well-known in the professional sphere as fluvial landforms.

They may not be recognised as deserving the same protection from erosion or the

same access to Landcare funding.

Banded Vegetation Banded vegetation is a natural runoff-runon landform-ecology link that is common in

some parts of arid Australia. Some examples include the mulga grove country in

Central Australia, or the hillslopes bordering the Finke River (Wakelin-King 1999).

Where there is banded vegetation, water flows as sheetflow across the slope. This

landform has no place in the list of known fluvial landforms, but it transmits water and

has relevance to groundwater recharge, erosion management, road alignment

placement, and land use planning.

Erosion Can Propagate Downstream Generally, where erosion is triggered by some human activity, the erosion

propagates upstream. Stream rehabilitation manuals are written around this

sequence of events. In western NSW, there appear to be clear cases where an

erosion trigger causes channel incision to propagate downstream instead. For

example, at a creek crossing, a river-level dip in the road was replaced by a raised

causeway with culverts transferring flow under the road. The culvert sizes were

based on a temperate-zone expectation of the likely flow, and the result was flow

concentration and erosion. The channel deepening proceeded downstream where it

has killed the riparian vegetation and triggered lateral floodplain gullying. This

downstream direction of action is not an accepted feature of stream rehabilitation, but

it is consistent with the processes which create discontinuous ephemeral streams

(see above).

Monitoring Waterway Health Standards for monitoring waterway health often use indicators such as water salinity

and turbidity, or the heath and species diversity of fish or aquatic invertebrates.

These are not relevant for rivers and creeks over an enormous part of Australia.

Other indicators need to be developed for dry creeks, and for creeks that are dry

along most of their length but which have semipermanent waterholes. The non-wet

bits need to be managed also – this is an incredibly important yet almost totally

64

overlooked land management issue. Potential indicator factors could include riparian

and floodout vegetation, herpetofauna, and bird life (though obviously for all these

allowance for local drought history must be made). Other factors such as landform

stability may also be relevant, as long as some understanding of the river’s natural

processes is a starting point.

Human Activities that Affect River Flow

Dams impound water. Most dams have a way to get rid of excess water: some have

pipe outlets which release a little water slowly, others have bywash channels. Both

systems have advantages and disadvantages. Dams that are thrown across flat

country, collecting in wide shallow basins, will lose a lot of water through evaporation.

Water-capture earthworks, for example low ridges (bunds), divert floodplain water

into the channel, usually upstream of a dam. Waterspreading and waterponding

divert floodplain water from its course, either spreading it across another section of

floodplain, or collecting it in shallow ponds. In either case, the aim is to encourage

water to infiltrate the floodplain, rather than drain to the channel and be conducted

away. Contour furrowing re-establishes vegetation on overgrazed areas. Where

successful, it reduces runoff, which may reduce water entering channels and could

be a useful control for erosion. Success of the furrowing technique needs accurate

surveying and tailoring of the program for local conditions.

The above activities can be viewed in two ways. On the one hand they are valuable

rangeland management techniques which increase productivity and in some cases

are rehabilitation works which may restore rivers to something like their pre-

European state. On the other hand they may deprive downstream users of water that

might otherwise have come to them. There seems to be little attention given at the

moment to the water-rights implications of some rangelands works. Resolving the

issue may be complex: what is the logical starting point? The downstream user’s

customary flow pattern, as of some recent date? In that case an upstream user may

be prevented from repairing pre-existing damage. (For example, if an upstream reach

had incised due to vegetation removal from overstocking, the downstream reach

might get more water. If the upstream reach floodplain is rehabilitated by

waterponding, the downstream reach gets less water yet the river as a whole

becomes more healthy.) Knowing the pre-European state of a river would provide a

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good starting point. Historical data can be ambiguous or hard to find; understanding

river processes is likely approach. However, more research is needed.

Road construction and creek crossings are often triggers for downstream erosion,

through flow concentration and gully initiation. In NSW the Road Transport Authority

was only required to manage erosion along its 50m easement: that is, anything

outside that easement is not their business. This is clearly not an ideal regulatory

environment, as it encourages the displacement of erosion problems to the easement

edge, rather than resolution of the problem. All over the Australian rangelands,

station tracks also commonly concentrate flow and evolve into creeks (Figure 35) or

initiate gully networks. These are hard to rehabilitate once formed. Continued

investigation into, and support for, effective track construction and maintenance

techniques should take place.

Figure 35 Aerial photograph of a long straight gully (dark line) developed from a station track in NSW.

There is no natural surface drainage in this paddock (a mud gilgai plain, mottled orange and brown

ground surface). Red scale bar = 1.6 km.

Recommendations for Surface Water Management

Small creeks and ephemeral rivers should be recognised as important contributors to

the economy and amenity of South Australia’s rural sector, and as critical

underpinnings of rangeland biodiversity. Regulation might be required to protect the

interests of all users.

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Management organisations should understand that dryland rivers and drainages do

not necessarily operate in the same way as perennial rivers, nor necessarily look like

them. Dryland fluvial landforms include discontinuous ephemeral streams, floodouts,

and banded vegetation. Management policies should be developed from

understanding South Australia's creeks, rather than derived from policies developed

for temperate-zone rivers. As a first step, basic data should be collated about the

types of river, and the true catchment boundaries around them. Historical information

on stock route locations, pastoral ownership, and regional stocking rates would also

be useful.

As a preliminary measure, the regulations limiting size of dam capture that are used

in NSW (dams of 1st or 2nd order channels) or the NT (dam <3m high or across

catchment <5 km2) may be useful. However, they should be applied with some

judgement. The stream order rule shouldn’t be tied to a cartographer’s judgement as

to what constitutes a single drainage; the <5 km2 rule shouldn’t apply to a tiny

stream. Neither rule should apply to every single small lower-order catchment of a

larger river, as that will cut off most of the water.

The authority that builds roads should have some incentive to care about erosion

outside the road easement.

Measures to rehabilitate gullied station tracks, and to build and maintain erosion-free

tracks, should be sought.

An awareness of downstream water rights, and their relationships with rehabilitation

techniques such as waterponding and waterspreading should be part of discussions

on surface water regulations. This is a complex issue and not one that will be

resolved in a hurry.

Water rights should include support for ecology and biodiversity as well as human

needs.

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References

Anderson, Ruth. 1995 The McTaggarts; stories of a pastoral dynasty. Online extract , SA History

Conference ( 2005) www.history.sa.gov.au, from The McTaggart Story : five generations of pastoralists.

Openbook Adelaide.

Blissett, A.H., 1985. Gairdner, South Australia : Sheet SH/53-15. 1:250,000 geological series -

explanatory notes. Geological Survey of South Australia, Adelaide.

Bull, W.B., 1997. Discontinuous ephemeral streams. Geomorphology 19: 227-276.

Dickinson, S.L., 1942. The Moonaree Station saline ground waters and the origin of the saline material.

Transactions of the Royal Society of South Australia 66: 32-45.

Keeling, J.L., & Self, P.G., 1996. Garford Palaeochannel palygorskite. MESA Journal 1: 20-23 (South

Australian Dept. Mines & Energy, Adelaide)

Pickup, G., 1985. The erosion cell - a geomorphic approach to landscape classification in range

assessment. Australian Rangeland Journal 7: 114-121.

Wakelin-King, G.A. 1999. Banded mosaic ("tiger bush") and sheetflow plains: a regional mapping

approach. Australian Journal of Earth Sciences 46: 53-60.

Wakelin-King, G.A. 2006. Landscape history controls vegetation ecology: formation of mid-creek

floodouts in western NSW (abstract, poster). Australian Rangelands Conference, Renmark, SA, 3-7

Sept. 2006.

Wakelin-King, G.A. & Webb, J.A., 2007. Threshold-dominated fluvial styles in an arid-zone mud-

aggregate river: Fowlers Creek, Australia. Geomorphology 85: 114-127.

Williams, G.E., & Gostin, V.A., 2005. Acraman – Bunyeroo impact event (Ediacaran), South Australia,

and environmental consequences: twentyfive years on. Australian Journal of Earth Sciences 52: 607 –

620.

Map 1: Moonaree Paddocks and Major Creeks

Moonaree Paddocks and their names (in black) and the major creek lines and their names (in blue)

Map 3: Moonaree LANDSAT view

Moonaree station viewed in LANDSAT 721pan, with paddock boundaries in green. Dacite hilltops are very dark brown, or purplish-

brown. Dacite sand and soil is mid-brown in colour. The southern sand belt is pale blue (quartz sand), or brownish and bluish (dacite

sand, near Lake Acraman), with dark hilltops emerging from the sand. Speckled dark brown and pale blue in Morinippi and Morinippi

Outside shown a thin veneer of quartz sand over dacite rock.

Lake Acraman

Lake Gairdner

Map 4: Moonaree as if the lakes were full to 200m ASL

Digital Elevation Model of Moonaree station viewed as if the lake levels were at 200m ASL (current shoreline is at 130m ASL). The grey

area would have been under water, and only the main hilltops and higher central valleys would have been dry land. The areas with

observed gilgai or swelling-clay sols are shown in green stars. Lake-full episodes in the wetter climates of previous geological ages are

likely to have governed rock weathering and sediment deposition, influencing today’s water quality and paddock productivity.