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1988

Salinity in Western Australia : a situation statement

V T. Read

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Part of the Forest Management Commons, Hydrology Commons, and the Soil Science Commons

Recommended Citation Read, V T. (1988), Salinity in Western Australia : a situation statement. Department of Primary Industries and Regional Development, Western Australia, Perth. Report 81.

This report is brought to you for free and open access by the Natural resources research at Research Library. It has been accepted for inclusion in Resource management technical reports by an authorized administrator of Research Library. For more information, please contact [email protected]. ISSN 0729-3135 August 1988

Salinity in Western Australia A Situation Statement

Prepared by Viv Read

Resource Management Technical Report No.81 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

Disclaimer

The contents of this report were based on the best available information at the time of publication. It is based in part on various assumptions and predictions. Conditions may change over time and conclusions should be interpreted in the light of the latest information available.

 Chief Executive Officer, Department of Agriculture Western Australia 2001 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

Select Committee on Salinity

The Select Committee on Salinity was established by the Legislative Council of the Parliament of Western Australia in November 1987 to inquire into and report on salinity in Western Australia giving particular regard to: • what action has, or is being taken, to assess the magnitude of the problem; • what form of action can, or should, be taken to control salinity; • what legislative of administrative acts or incentives to the private sector are necessary or desirable to assist further in controlling or eradicating salinity.

Members appointed to the Select Committee were the Honourable David Wordsworth (Chairman), the Honourable Doug Wenn (Deputy Chairman), the Honourable Tom Butler and the Honourable John Caldwell.

SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

Summary

Introduction

Investigations into the salinity problem in Western Australia began early in the 20th century. Early concerns were not about agricultural land but about the quality of water supplies for railway steam engines.

Today land salinisation is a major form of land degradation in the agricultural areas of the State. It is a problem that both the landholders and the community must address.

This submission reviews past research on salinity; details the development of salinity in the agricultural areas and presents an assessment of the area of land that could in future be affected by salinity unless land management practices change; gives an estimate of the cost of salinity to the community; summarizes the current research being done by the Department of Agriculture and offers suggestions on how implementation of ameliorative and preventive measures might be achieved.

Past Research

Research and investigations into salinization of land and streams in Western Australia began in the 1920’s. In a paper published by Wood in 1924 it was recognized that removal of native vegetation and development for agriculture was the prime environmental disturbance that caused the salinity problem.

During the 1930’s it was established that the source of salts stored in Western Australian soils was the rainfall. Salt deposition via rainfall was found to range from more than 200 kg/ha/year near the west coast to 18 kg/ha/year near the west coast to 18 kg/ha/year at inland sites such as Merredin.

The hydrological processes responsible for mobilizing the stored salts and transporting them to the soil surface were described during the 1950’s and 1960’s. In the past twenty years these processes have been quantified and management strategies developed which will ameliorate current salinity or prevent future salinity.

It is now well accepted that salinity is caused by deep percolation of a relatively small quantity of water (20-80 mm year) which mobilizes the stored salts and causes the watertable level to rise. Once the saline watertable reaches one to two metres below the soil surface capillary action transports sufficient salts into the root zone to be deleterious to the growth of non-salt tolerant plants.

Extent of Salinity

Since 1955 there have been five surveys of the area of once productive agricultural land affected by salinity. Because the response to the question relies on an historical knowledge of the state of the land these surveys become less reliable with time. However, they do provide an insight into the expansion of land salinization in the State.

In 1955 there was 73,500 ha of land affected - 0.5% of the cleared area. By 1984

iv SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT some 255,000 ha or 1.6% of the cleared area was affected. It is estimated from the expansion rate that 315,000 ha would be affected in 1988.

Regionally based Research Officers of the Department were asked to assess the potential for salinization in their regions. Given current land use practices the Officers estimate that there is a potential for some 2.4 million ha of agricultural land to become affected by salinity. The time scale for realization of this potential is estimated to range from 10 to 200 years with a large proportion of it developing over the next 30 years.

Cost of Salinity

Based on an average gross value of production of $140.50 per hectare per annum the annual production loss due to salinity is currently estimated to be $44.2 million.

If the predicted’ salinity potential were realized the annual gross value of production lost in. terms of 1988 dollars would be $344 million.

These figures include only direct costs and do not account for loss of water supplies, capital investments, more rapid machinery deterioration and loss of amenity.

Current Salinity Research

The salinity research programme of the Department aims to identify and quantify the causal agents of salinity and determine appropriate catchment management strategies to obtain production from the affected area, prevent spread of the affected area and reduce off-site effects of salinity.

The research programme is broadly sub-divided into five major areas: • Catchment hydrology • Land drainage • Saltland agronomy • Waterlogging • Agroforestry

The submission summarizes 41 current research projects.

Saltland Management

The Department has developed, and advocates, a catchment approach to saltland management. It is patent that there are no simple solutions to land salinity; the solutions lie in addressing the landscape water balance by reducing recharge and increasing discharge. Control of the landscape water balance must be achieved while maintaining the productivity of the land, be that productivity in terms of agricultural produce, water resource or public amenity.

Techniques have been developed to manipulate the landscape water balance and to obtain production from salt affected land. These are slowly being adopted by

v SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT landholders.

Encouraging Adoption of Salinity Control Measures

Landuse management strategies developed by the Department for salinity control are at least as economic as current practices. However, additional costs are often incurred in the initial implementation of these strategies due to fencing, tree establishment and change of watering points for example.

Taxation relief is available for some control measures such as fencing and establishing trees on recharge areas.

Incentive payments for undertaking salinity control measures are made in Victoria. These payments contribute to fencing costs and establishment of trees, salt tolerant vegetation and perennial pastures.

Implementation of salinity control measures on a catchment basis requires that the hydrologically significant areas of the catchment be defined. This definition is a specialists task and, for instance, in Montana specialist teams have been established to assist groups in developing catchment management plans. The cost of these teams is met jointly by the State and the landholder. With the enthusiasm for action generated by the Soil Conservation District movement there is a place for such teams in Western Australia.

Research into salinity is currently well ahead of implementation. While there is a continuing need or research, particularly into remote means of catchment definition, the urgent need is for extension and technical support to assist implementation of control measures.

vi SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

Table of Contents

1. Introduction...... 2

2. Historical Review ...... 3

3. The Cause and Nature of the Salt Problem...... 13

3.1 Source of the Salt - Rainfall ...... 13

3.2 The Accumulation in Soil of Salt from Rainfall ...... 13

3.3 Soils, Topography and Hydrology ...... 14

3.4 Soil Factors Influencing Salt Accumulation ...... 14

3.5 Parent Material and Naturally Saline Soils ...... 14

3.6 The Influence of Topography on Soil Salinity...... 15

3.7 Slope...... 15

3.8 Dissection ...... 15

3.9 Micro- topography...... 16

3.10 Hydrology and Salinity ...... 16

3.11 Effect of Land Use on Salinity ...... 17

3.12 Salt Movement and Accumulation in Soil and Groundwater ...... 22

3.13 Effect of Soil on Salt Movement and Accumulation...... 22

3.14 Salt and Water Imported in Groundwater...... 22

3.15 Movement of Water Under Pressure...... 23

3.16 Capillary Rise and Critical Depth ...... 25

4. Extent of Salinity in Western Australia...... 26

4.1 Australian Bureau of Statistics 1984 Saltland Survey ...... 26

4.2 Previous Results 1962-1979 ...... 26

4.3 The 1984 Survey and Results...... 26

4.4 South West Division...... 26

4.5 Southern Agriculture Division...... 26

vii SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

4.6 Central Agriculture Division ...... 27

4.7 Northern Agricultural Division ...... 27

4.8 Eastern Goldfields, Central and North West Divisions...... 27

4.9 Results Summary ...... 32

4.10 Discussion of Survey Results ...... 32

4.11 Conclusions...... 40

4.12 Regional Assessment of Potential for Land Salinization...... 40

4.13 Northern Agricultural Region ...... 40

4.14 Current Status ...... 40

4.15 Potential Area...... 40

4.16 Strategies ...... 41

4.17 Central Agricultural Region...... 41

4.18 Current Salt-Affected Areas...... 42

4.19 The Potential Area Which Could Become Saline ...... 42

4.20 Time to Develop the Full Potential...... 43

4.21 Strategies Available for Saltland Control ...... 44

4.22 Great Southern Region...... 50

4.23 South West Region...... 53

4.24 South Coast Region ...... 56

5. The Cost of Land Salinization ...... 58

6. Salinity Research 1987/1988- ...... 59

6.1 Catchment Hydrology ...... 59

6.2 Land Drainage...... 63

6.3 Saltland Agronomy ...... 64

6.4 Waterlogging ...... 67

6.5 Agroforestry...... 67

7. Saltland Management, The Catchment Approach ...... 71

viii SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

7.1 Water is the Real Problem ...... 71

7.2 Problem Definition...... 72

7.3 The Importance of Catchment Management...... 72

7.4 Management of Recharge Areas ...... 72

7.5 Strategic Clearing...... 72

7.6 Replanting Trees and Shrubs ...... 73

7.7 High Water Use Crops and Pastures ...... 73

7.8 Tillage Practices to Maximize Crop Water use and Minimize Run-off...... 74

7.9 Fertilizer Regimes to Maximize Crop Water Use ...... 74

7.10 Management of Discharge Areas...... 74

7.11 Drainage ...... 75

7.12 Trees as Pumps...... 75

7.13 Production from Halophytes...... 75

7.14 Site Severity...... 76

7.15 Waterlogging and Flooding ...... 77

7.16 Salt Content and pH of Soil...... 77

7.17 Salt Tolerant Plants for Grazing ...... 77

7.18 Conclusion ...... 79

8. References ...... 80

ix SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

1. Introduction

“The alternations of salt pools and fresh streams, even in the same channel, have puzzled exploring parties, but will hereafter be easily accounted for, and probably the cause made useful, like all the bountiful and various provisions of Providence, to mankind.” So wrote Nathaniel Ogle of the country east of the Darling Range in 1829. Ogle was referring to the inherently saline landscape of Western Australia. Large areas of the State were saline before the advent of European man on the continent. Since colonization, and the development of some 160,000 square kilometres for agriculture, further areas of once productive land have been lost to “normal” agricultural practice because of the accumulation of soluble salts close to the soil surface.

Land salinity not only affects farmers’ incomes, it impinges on the whole community. Salinity has rendered unusable many of the State’s water resources, it has destroyed the habitat of many freshwater species and has ruined the amenity of numerous natural environments. Salinity is one of the major forms of land and environmental degradation in the State.

Research on the salinity problem in Western Australia began early in the 20th Century and the cause of land salinity is now well documented; treatments which will arrest the spread or prevent future occurrence have been developed and are being tested; methods are available to obtain economic production from salt affected areas and the interaction between salinity and waterlogging has been described.

Ameliorative or preventative measures will only be successful if they are adopted on a whole catchment basis. Because catchments can be large and not controlled by one owner, the landholder who needs to impose the treatment may not receive the benefit. This presents problems of social and economic equity which can only be addressed through the desire of the community at large to protect the land resource.

This paper reviews past research on salinity; details the development of salinity in the agricultural areas and presents an assessment of the area of land that could be affected in future unless land management practices change; gives an estimate of the current cost of land salinity to the community; summarizes current research being done by the Department of Agriculture and offers suggestions as to how implementation of ameliorative and preventative measures might be achieved.

2 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

2. Historical Review

Wheat production in Western Australia started soon after colonization (Figure 1), but the area planted did not increase significantly until the period 1900 to 1930.

Figure 1. Area sown to wheat in Western Australia - 1940 to 1977. (W.A. Yearbook, 1975).

Saltland in the cereal growing areas received little attention until about 1910, and then it was as a result of the Railways Department’s concern about salty water supplies and not the Department of Agriculture (Wood, 1924). The first record appeared in 1907 as a reply printed in the Journal of Agriculture under the heading “Does clearing increase salt in the ground?” The reply indicated that a farmer’s query had been referred to the Government Analyst for attention and the answer stated that it had been “pretty conclusively proved” that the removal of trees affected water supplies because rainfall passing through the soil took salts with it. It was considered that to prevent salting it would be necessary to replant a very high proportion of the trees that had been removed.

3 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

In 1917 the Royal Commission on the Mallee Belt and Esperance Lands made reference to soil salt concentrations in the Esperance region, and disclosed a difference of opinion concerning what level was liable to be of serious consequence for agriculture. Overseas authorities were quoted in many cases to support both the proponents and the opponents of land release.

Paterson (1917) outlined in considerable detail the manner in which salts accumulated in the soil and factors influencing the level of salt which was significant for crops. He presented the results of soil analyses from the Salmon Gums area and concluded that about a third of the area was suitable for settlement, a sixth doubtful and a half had too much salt to be put to profitable use. However, the Commission strongly criticized Paterson’s Report and advocated land release.

Sutton (1927) described the results of applying stable manure and sheep manure to saltland on a property at York, but the first article of any consequence concerning saltland was by Teakle (1929) who reviewed overseas and local work on soil salinity and discussed causes of the problem in Western Australia. He described three ways in which salts could be distributed in the landscape after its deposition, which he believed was from rainfall: • Sufficient rainfall and suitable topography enabled salts to be drained from creeks and thence to the ocean. • In dry areas, salts were only leached to a certain depth where they accumulated. • Where the drainage was reasonable, creeks became salty and saline springs and seepage patches developed following clearing.

Overseas reclamation measures were suited only to very valuable land and he suggested that drainage or the application of stable and sheep manure were suited only for small patches.

In an appendix to Teakle’s article, C.A. Gardner described plants usually found on salt prone soils and suggested that saltbush could be planted on saline areas.

Thus by 1929 it had been recognized that: • The salt problem was at least partly due to cyclic salt, that is salt brought in with the rainfall. • Salt problems were more prevalent in areas where rainfall was low. • Occurrence of salt was influenced by topography and soil type. • Removal of the natural vegetation was the basic cause of salt encroachment. • Possible treatment measures included drainage, surface mulches, the use of salt tolerant plants, and soil management to maintain a surface cover of growing plants. It had also been observed that one approach to preventing salt encroachment was to replant the hills with trees.

Teakle proposed three general categories of saltland; seepage areas, waterlogged valleys, and dry land areas in which seepage and waterlogging played no part. In 1931, Prescott further refined the list of causes of the salt problem when he

4 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT concluded that soils in which salt occurred naturally in appreciable amounts were found primarily in those areas receiving, on average, less than 5 mm of rain per wet day.

The 1930’s and 1940’s were periods of intense soil survey activity in the agricultural areas. The prediction of Paterson in 1917 concerning the likelihood of salt problems developing in the Salmon Gums area proved to be substantially true and the resulting problems with saltland led to extensive soil surveys in that area. Other surveys were done in the Lake Brown area, the Lakes District, the East Pingrup-Lake Magenta area, and the 3500 Farms Scheme area to the south east of Southern Cross (Teakle and Burvill, 1938; Teakle, 1939; Teakle et al., 1940; Burvill, 1945 and Burvill, 1947). Details of the soil survey in the Salmon Gums district remain to be published (Burvill, private communication). Teakle (1953) in a later survey in the Many Peaks district reported that under natural conditions soils in somewhat higher rainfall areas also stored salt in their profiles. The surveys led to a more detailed understanding of the extent and nature of the salt problem in Western Australia.

The period of soil survey activity coincided with a time of increasing incidence of soil salinity on farm land. Teakle and Burvill (1938) reported that in the Carnamah, Wubin and Moulyinning areas saltland developed 10 to 20 years after agricultural development and there were numerous references to farmers reporting increasing flow of streams, increasing seepage and rising groundwater. This period was approximately 10 to 20 years after the main early increase in cropped area (Figure 1).

Concern for the salt problem in the late 1940’s led to the appointment of a CSIRO officer to report on the salt problem (Pennefather, 1950). He reported that the most important occurrence of salting in the Western Australian wheatbelt was associated with waterlogging of relatively flat valleys which contained much of the best wheat lands and he considered that a further 280,000 to 400,000 hectares was threatened. As insufficient data were available on which to base advice on the effective control of waterlogging, he recommended that investigations into the nature of the problem and methods of treatment should be undertaken.

The investigations were to also provide a better understanding of other aspects of salting, such as hillside seepages and the increasing incidence of saline surface and underground waters. Aspects to be studied were: • The development of saltland and its present extent. • The soils and geology in relation to saltland. • The nature and extent of waterlogging in valleys. • Water and salt movement under: (a) salt tolerant plants (b) dewatering plants (c) afforestation and control of clearing (d) subsoiling (e) surface drainage

5 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

(f) sub-surface drainage, perhaps including pumping (g) natural reclamation and water spreading which would have to be accompanied by a lowering of the watertable.

In 1950 Wellington Dam water quality received attention and the Minister of Works approved the formation of a Purity of Water Committee for Wellington Dam (Samuel, 1972).

A Senior Soil Research Officer was appointed to the Western Australian Department of Agriculture in 1953 with the prime responsibility of investigating the salt problem.

The Annual Report of the Soil Conservation Service, Department of Agriculture in 1954 gives an account of the Wellington Dam Catchment as follow: • There is evidence that clearing does have an effect on salinity of water. • There is considerable variation in the salinity of seepage water even under similar degrees of clearing and development. • There is a tendency for seepage to increase in salinity as the winter progresses.”

Many of the early results were reported by Smith (1962) who showed that highly saline groundwater existed at shallow depths beneath salt-affected wheatbelt valleys. Piezometric studies indicated that the water was under pressure and tending to flow to the soil surface, and that the groundwater extended, but at a greater depth, beneath the non-saline land on the valley sides. Soil surface treatments such as cultivation and application of a sand mulch were shown to reduce the concentration of salt at the soil surface, but attempts to reclaim saline areas by means of normal cultivation methods and normal plants, such as cereals and annual ryegrass, indicated that these methods were only likely to be suitable for mildly affected areas having perhaps 20 per cent of their area as scattered bare saline patches. On more severely affected areas special salt tolerant forage plants needed to be sown and a programme of research to identify suitable plants and develop methods for their establishment and management was embarked upon. This programme is still continuing.

In the late 1950’s and early 1960’s, work by the CSIRO Division of Soils provided detailed information on wheatbelt soils in areas not covered by earlier soil surveys (Bettenay, 1961; Bettenay et al., 1962; and Mulcahy and Hingston, 1961). These studies provided explanations for saltland occurrences in particular situations. They drew attention to the effect of clearing of the valley floors, and of intake areas around granite rocks in the development of watertables in wheatbelt valleys. Mulcahy and Hingston (1961), indicated the topographical and pedological situations where seepages were likely to occur and mapped the sandy outwash areas which appeared to be associated with salinity in some broad valley situations.

The 1970’s were periods of intense land and stream salinity survey, research and decision-making in Western Australia.

A salinity survey was conducted in the Collie irrigation area (10,700 ha) by the

6 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

Department of Agriculture in 1970 following farmers’ concern about the quality of irrigation water. The survey found that some 160 to 200 hectare of irrigated land was salt affected.

In 1972 CSIRO set up the Collie Salinity Advisory Committee under the auspices of the Australian Water Resource Council (Darling Range group, 1982), and in 1973 the Minister for Works, at the request of the Minister for Environmental Protection, asked that the Kelsall Committee be formed to advise on salinity aspects of forest management in the woodchip licence area. Meanwhile the Hunt Steering Committee was established by the Bauxite Policy Committee to advise (inter alia) on “... studies, investigations and trials to evaluate the soil salinity characteristics of the various catchment areas and quantify the effect of mining” (Darling Range study group, 1982).

In 1973 Peck and Hurle quantified the salt balance of the landscape in areas receiving more than 400 mm annual rainfall. They estimated that loss of chloride in stream flow (salt flow) from forested catchments in south western Australia was only slightly greater than the total annual input (salt fall) from rain and dust. However they indicated that, salt flow from catchments in which a significant area of the forest vegetation has been cleared for farming in much larger and exceeded salt fall by up to 690 kg/ha/yr. They stated that the removal of the forest vegetation had increased groundwater discharge of whole catchments by amounts ranging from about 10 to 130 mm/yr.

Characteristic times for equilibration of C1 input and loss on farmed catchments were estimated to range from 30 to 400 years.

The Annual Report of the Soil Conservation Service (1974/75) under the title of “Wellington Catchment” indicates that “... regular testing of water from Wellington Dam by the Public Works Department since 1968 has shown that all samples contained more than 400 mg/L and two in three had more than 800 mg/L TDS.”

The overall trend has been for salinity of Wellington Dam water to increase by 4.3 mg/L TDS per year (Department of Agriculture 1974). Various suggestions were advanced to halt or reverse the salinization process including introduction of clearing bans. A survey of farms in the Wellington Catchment was carried out at the request of the Environmental Protection Authority and the result showed that a ban on further clearing of alienated land would prevent only a small number of farmers from achieving economic viability (Department of Agriculture, (1975).

In 1976 the Hunt Steering Committee reported to Cabinet (Darling Range Committee 1982); Malcolm and Stoneman (1976) published the third saltland survey; and a ban on clearing of Wellington Dam Catchment proclaimed by D.H. O’Neil, Minister for Public Works.

A seminar entitled “Land Management and Water Quality” held in Perth in 1976 examined research into the effects of land use on stream salinity and stream turbidity in South Western Australia. The papers presented in this seminar were essentially aimed at providing the technical basis for predicting the effects of clearing and revegation on salt export from catchments.

7 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

In 1977, the Advisory Committee on Purity of Water published a study of the effects of recreation in catchments on salinity (Advisory Committee, 1977); the Salinity Research Committee and Western Australian Water Research Council formed and the Department of Agriculture published “Saltland and what to do about it” (Malcolm, 1977 revised 1983).

In 1978, the Government proclaimed legislation extending clearing bans to the Mundaring, Denmark and Kent catchments; the Hunt Steering Committee published “Research on the effects of bauxite mining in the Darling Range” (D. Sachs and E. Harvey, 1978); the Technical Advisory Group to the Department of Conservation and Environment recommended to the Environmental Protection Authority that bauxite mining be allowed in irrigation water catchments but should not extend east of the 1100 mm isohyet.

In 1979, investigations of the Whittington interceptor system of salinity control was published (Water Resource Information Note, 1979); and Greenwood and Beresford (1979) used the ventilated chamber technique to study the evaporation from vegetation in landscapes developing secondary salinity.

In 1980 an international seminar “Land and Stream Salinity” took place at Murdoch University. The seminar and the associated workshop was sponsored by the W.A. Government to provide a forum for discussion and exchange of ideas between engineers and research scientists with experience of salinity problems in many parts of the world.

George (1980) monitored 200 ha of land in the Collie irrigation area to provide information on the salt and water balance. The results showed that the phosphate content in the run-off waters varied between 0.05 and 0.4 mg/L which was 5 to 40 times the level in the applied irrigation water.

Early in 1981, Nulsen in his hydrological studies on wheatbelt catchments in the Wongan-Ballidu Shire concluded that preferential water flow was of prime importance in the hydrology of the area under natural vegetation. Removal of the natural vegetation and its replacement with annual crops and pastures will destroy a majority of the preferred pathways and drastically alter the hydrological pathways. Nulsen suggested that the conventional approach to modelling using frontal flow hydraulics (Darcy’s law, etc.) was not valid and more realistic methods must be used to express the flow dynamics.

Late in 1981 the Federal Government embarked on a study of the Nation’s water resource needs and problems to the end of the century. The a study aimed to identify water resource development and management issues which have a potential to impede plans for national development. A Steering Committee, chaired by Mr K.D. Green, was established and expert consultants were chosen to conduct each section of the study.

CSIRO consultants were asked to study the salinization of Australia’s soil and water resources as a result of man’s activities. In particular to: • Assess the current extent of both dryland and irrigation induced salinity problems in Australia, and expected future trends.

8 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

• Assess current and future effects of land salinization on the quality of water resources, highlighting particular regional problems and trends. • Estimate present economic, environmental, and social costs associated with salinity problems. • Estimate the current and likely future cost of the management of the problem; and • Evaluate policies and practices currently employed in the management of the problem, and identify options and needs (including data and information) for future management strategies.

In 1982 the Department of Agriculture, in co-operation with a Mollerin farmer and the manufacturers of a desalinator, Osmotron Australia, examined the performance of a reverse osmosis desalinator to provide stock water from a saline supply. The desalinator accepted water of 10,000 mg/L total dissolved salt at the rate of 40 kL per day and produced fresh water of about 350 mg/L at a rate of about 11 kL per day.

In 1983 Peck et al. published “Effect of man on salinity in Australia” as a part of the Federal Government study of the Nation’s water resources needs and problems. In late 1983 the Water Research Foundation of Australia, in co-operation with Alcoa of Australia Limited, Centre for Water Research at the University of Western Australia, Hardie Iplex Plastics Pty. Ltd, Murdoch University, Primary Industry Association of Western Australia (Inc.), Westralian Farmers Co-operative Ltd and Western Mining Corporation Ltd conducted a seminar of water quality and its significance in Western Australia. The seminar included invited and research papers from recognized experts and the message of the seminar was “Today’s research, tomorrow’s practice”.

A Research for Development Seminar, titled “Forage and Fuel Production from Salt Affected Wasteland” sponsored by the Australian Development Assistance Bureau, was held at Cunderdin in May 1984.

The Seminar included invited papers from recognized international research workers on: • Salt affected wastelands, nature and distribution. • Salt tolerant plant resources. • Production from salt-affected soils. • Establishment problems and methods. • Utilization, management and social aspects.

The seminar provided an information base for new initiatives in salinity treatment and control. The country reports illustrated the global extent and nature of salinity problem and the dearth of knowledge concerning potential productivity of salt-affected land. It concluded that plants and techniques are available to obtain forage and fuel production from saline land; salt-affected land need not be regarded as wasteland; the challenge is to make better use of this resource.

The interaction between salinity and waterlogging was firmly established by Barrett- Lennard in 1984. He suggested that it may be possible to grow wheat on marginally

9 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT saline land provided waterlogging is controlled. On the other hand, crops rapidly die on saline land subject to waterlogging. The cost of waterlogging induced production losses to Western Australian agriculture was estimated to be $19 million per year.

Land salinization research received a boost in 1985 with the appointment within the Department of Agriculture of two additional research officers. One officer, based at Merredin, was appointed to examine the hydrology of salinized catchments in the eastern wheatbelt. The other officer, was directed to examine alternative agricultural practices in the higher rainfall in the south west which would reduce recharge to groundwater.

In 1985 additional research was funded through the National Soil Conservation Program (NSCP) and research grants from the Reserve Bank Rural Credits Development Fund the Wheat Industry Research Committee of Western Australia, the Australian Wool Corporation and the Australian Meat and Livestock Corporation. The NSCP project studying potential solutions to prevent salinization in the Jerramnungup area commenced.

A Wheat Industry Research Committee funded project, based at Narrogin, aimed to delineate landscape units which contribute the most water to recharge saline groundwaters.

Other research highlights were: • The application of remote sensing and geophysical methods to delineate the causal factors in the appearance of salinity and to identify the potential for spread unless there is a change in land management.

The project involved staff from the Department of Agriculture, Geological Survey of Western Australia, CSIRO, Department of Lands and Surveys, Geoterrex and Tesla 10.

The use of airborne electro-magnetic induction to determine saline areas and areas at risk to salinization showed promise. Surveys were done in the East Perenjori Catchment and in part of the Kent River Catchment.

Intrusive dykes were shown to play an important role in causing saline seepages in the Great Southern. The dykes, or their weathering products, restrict groundwater flow causing water to accumulate upslope which often results in saline seepages. • LANDSAT was being used in an attempt to identify areas affected by salinity. This project was centered on the Wongan-Ballidu Shire and was done jointly by the Department of Agriculture and CSIRO with funding from the Australian Wool Corporation.

The NSCP funded a CSIRO project aimed at using the spectra of soils and an airborne multi-spectral scanner to identify saline areas and areas at risk to salinity. • A variety of Atriplex amnicola was identified which volunteered readily and produced more dry matter than other varieties A. amnicola is the preferred

10 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

species of Atriplex to establish on many saline areas because it has been shown to withstand high grazing pressure without a fall in production. Species such as A. paludosa and A. undulata, which are easily established, lose production after several years of grazing. However the problem with A. amnicola was that it was difficult to establish from seed. The Australian Meat and Livestock Corporation funded a project aimed at overcoming establishment problems with A. amnicola. • Drainage of various types - shallow surface drains, deep open drains, deep tube

drains and aquifer pumping - has been successful to varying degrees in rehabilitating saline and waterlogged land. With the exception of shallow surface drains, the drainage systems are expensive.

In addition the following research for salinity control was reported by the Division of Resource Management and the Commissioner of Soil Conservation 1985/86.

Salt/waterlogging interaction in wheat; waterlogging and growth of wheat in the field; grazing value of salt tolerant shrubs; indicator plants for identifying saline and/or waterlogged sites; screening of Atriplex species and ecotypes for production from salt affected land.

The Annual Report of the Commissioner of Soil Conservation and Division of Resource Management 1986/87 indicated that the majority of farmers recognized that the primary cause of land salinization was increased recharge after clearing. Strategies have been developed to reduce recharge which include tighter cropping rotations, use of perennial pastures and tree planting. Farmers were adopting these strategies and many intended to, contingent upon progress with farm physical redevelopment. The report added that farmers were becoming increasingly aware of the role of geological anomalies, such as dykes, in dictating where saline seeps occur. There was an increased demand for geophysical survey to define these anomalies but the Salinity and Hydrology Research Branch was not able to satisfy the demand with the current resources.

A special issue of the Journal of Hydrology titled “Hydrology and Salinity in the Collie River Basin, Western Australia” edited by Peck and Williamson was published in 1987. This publication summarized the ten years of research that CSIRO and the Water Authority of Western Australia had done in the Collie River catchment.

In 1986/87 the Steering Committee for Research on Land Use and Water Supply reported that a major new initiative in water catchment rehabilitation was the formulation of a joint project of integrated catchment management for the upper Denmark River catchment. The Water Authority, the Department of Agriculture, the Department of Conservation and Land Management and the landholders have combined to develop a catchment plan which aims to reduce stream salinity while increasing farm productivity.

The project will involve: • Soil surveys to classify land suitability for a range of high water using vegetation options (both forestry and agronomic). • Evaluation of the economics of various options.

11 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

• Development and integration of individual farmer plans into an overall catchment management plan.

Research highlights in salinity and hydrology during 1987 were: • The North Stirlings Land Reclamation project established in June 1986. The project is jointly funded by the National Soil Conservation Program, the Department of Agriculture and the Geological Survey of Western Australia. Drilling by GSWA has determined the nature of the tertiary basin on which the agriculture of the area is practised. The basin appears to be closed thus the only outlet for water is via evaporation. Salt storage in the basin is extremely high and groundwaters are extremely saline. The Department of Agriculture has determined an appropriate land use for the landscape elements within the North Stirlings and has established a 3 km strip demonstrating the land use options. • The application of geophysical techniques of magnetometry and electromagnetic induction to several catchments in the Great Southern. Interpretation of the output from these methods shows promise as a means of identifying recharge zones and areas of salinity hazard. This project is being conducted jointly by the Department of Agriculture and Geological Survey of Western Australia. The Wheat Industry Research Council of Western Australia has contributed funds. • The release of two volunteering lines of Atriplex in 1987. Both lines are palatable and productive. Research on Atriplex expanded into the cooler, wetter regions of the State and the production achieved at sites on the south coast has been outstanding. Problems of establishment in areas subject to waterlogging have been evident and it is hoped that a redesign of the seeding niche will prove beneficial. • Trees planting on the margin of a salt affected valley at Boundain (east of Narrogin) have been effective in lowering the watertable by up to 2 metres. The Boundain site has some hydrologic characteristics which have contributed to the success of the trees, but the result indicates that in some circumstances relatively low density (80 stems/ha) plantations can be effective in containing saline discharge areas.

Salinization in irrigation areas has long been a problem in Western Australia but has received very little attention. The State Government made a commitment to increase research into irrigation research in 1986. The increase in research effort in the irrigation areas required that some resources be diverted from research on land salinization in rain fed agricultural areas. Resources were diverted from research on land drainage and this area is no longer researched by the Department of Agriculture.

12 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

3. The Cause and Nature of the Salt Problem

Salinity in Western Australia is a problem that has continued to increase in extent and severity. Surveys published by Burvill (1956), Lightfoot et al. (1964), Malcolm (1974) and Henschke (1979) have shown that the total area of saltland has increased with the amount of land cleared. Since the clearing rate has declined, there is now an increasing proportion of cleared land which is being affected. Attempts to prevent salting, or to design treatments for restoring the productivity of saltland, require a clear understanding of the problem. The following indicates the factors involved in salinity in Western Australia. Qualitative knowledge has been available for many years although it is only recently that detail has become adequate to develop viable solutions. 3.1 Source of the Salt - Rainfall

Rainfall was first suspected as a source of soil salts in Western Australia by Wood (1924). A special committee of the Royal Society of Western Australia obtained data on the salinity of rainfall at various centres during 1926, Table 1 (Wood and Wilsmore, 1928). Since that time a great deal of information has become available concerning the role of rainfall in the development of salinity problems.

The salts found in rainfall come in part from the bursting of bubbles on the ocean. As extremely fine droplets of sea water are formed and evaporate, they leave minute particles of salts which are easily transported into the upper atmosphere by wind, (Mason, 1962). Some atmospheric salts also come from aeolian dust (Hutton and Leslie, 1958) and when falling to the soil surface are referred to as ‘dry fall’.

The amount of salt deposited by rainfall is a function of the quantity of rain and its salt concentration. The salinity of rainwater ranged from 27.7 mg/L NaC1 at Perth to 13.5 mg/L at Condon for coastal sampling sites. A difference in rainfall at these sites resulted in an overall deposition of salt of 240 and 43 kg/ha/year respectively. Inland areas received as little as 10 kg/ha/year.

Teakle (1937) reported data for NaC1 in rainfall at Merredin and Salmon Gums Research Station between 1933 and 1936. The annual average deposition of salt was about 30 kg ha at Salmon Gums and 18 kg/ha at Merredin. It was calculated that if all the salt deposited was accumulated in the soil it would take more than 200 years at Merredin and about 120 years at Salmon Gums to raise the salt concentration of 0.3 m depth of soil by 0.1 per cent salt (g NaC1 per 100 g soil). No attempt was made to separate dry fall from rainfall in Teakle’s study but the highest salt accessions occurred during the wettest months. 3.2 The Accumulation in Soil of Salt from Rainfall

Based on the amount of salt falling in rainfall in Western Australia Teakle (1937) concluded that there was no need to postulate that the salt in Western Australia soils and waters had its origin in the Miocene sea which existed 40 million years ago. He calculated that for Salmon Gums it would take only 37,000 years to raise the soil to its present 0.6 per cent salt to a depth of 15 m and only 35,000 years to raise the soil

13 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT at Merredin to 0.35 per cent salt from rainfall alone. (The growth of plants such as wheat is affected at levels approaching 0.2 per cent NaC1). Although this calculation made no allowance for possible loss of salt by deep drainage or recycling of salts locally through dust, the time since the retreat of the Miocene sea was many times these periods, making cyclic accumulation an adequate explanation for the present levels of soil salt.

A similar conclusion was reached by Dimmock et al.(1974), for the Bakers Hill area where, at the current accession rate of salts, 17,000 years was needed to accumulate the measured salt storages if no loss occurred from the system, an assumption which may not be valid. 3.3 Soils, Topography and Hydrology

Once salt arrives on the landscape, either in rainfall or dry fallout, its movement determines whether sufficient accumulates in certain sections of the landscape to cause damage to plants. Prescott (1931) listed the major factors affecting soil salinity as the amount and character of rainfall, the soil texture and the local topography. The factors which determine where, how much and how quickly salt moves are soils, topography and hydrology. 3.4 Soil Factors Influencing Salt Accumulation

For the Lakes District soil survey (Teakle, Southern and Stokes, 1940) and the 3500 farms area soil survey (Teakle, 1939), it was reported that heavier soils were the saltier, there being a good correlation between heaviness - or clayiness - and salinity. In these cases the higher levels of salts were believed to be a result of the reduced percolation of water and leaching of salt through the fine textured soils into the groundwater.

Other soil surveys of low rainfall areas in Western Australia showed lower salinity in sandy surfaced as distinct from fine textured soils (Teakle, 1939; Teakle et al., 1940; Burvill, 1945). However, Teakle (1938), has also indicated that in the 375 to 625 mm rainfall zone red-brown earths of sandy to loamy texture over clayey subsoil with decomposing rock at depth have accumulated salt in the clayey subsoil.

It may be concluded that although primary salt is mainly associated with finely textured soils, there are, in the lower horizons of some coarser textured soils, appreciable amounts of salt likely to be mobilized following clearing. These salts are important in the development of surface salinity problems (Malcolm 1983). 3.5 Parent Material and Naturally Saline Soils

In some areas of the world soils have formed from highly saline sedimentary rocks. The original igneous parent material of the Archean Shield in Western Australia contains little chloride. Some areas of Western Australia, particularly along the south coast, have soils derived from Tertiary sediments which are high in connate salt. Wind action in the region of salt lakes has been shown by Bettenay (1961), to have led to the formation of sheets of highly saline soil material comprising aggregates of clay, silt and sand blown from the lake beds. These saline and fine textured soils are

14 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT not readily leached and cause problems in the growth of normal agricultural crops.

The pallid zone materials in the lateritic profile have been shown to store appreciable quantities of salt. They comprise, in many cases, a considerable depth of medium to fine textured soil material and have therefore act as a major soil water storage and rooting medium (Dimmock et al., 1974). 3.6 The Influence of Topography on Soil Salinity

Soil surveys of the Lakes District and the Many Peaks District were some of the earliest attempts at classifying soils in relation to topography in Western Australia (Teakle et al., 1940 and Teakle, 1953). Naturally saline soils mainly occurred in the lowest parts of the landscape. Studies by CSIRO in the central wheatbelt have provided a clarification of the relationships of the soils to climate and topography. In his original studies Mulcahy (1959), studied the topographic relationships of soils near York, and a detailed study of landscape evolution by Mulcahy and Hingston (1961) concerned the development and distribution of soils in the York-Quairading area. This area was expanded by Mulcahy (1967), in his study of landscapes and soils in south-western Australia when he divided the whole of the south-west into zones of different drainage effectiveness. Bettenay and Mulcahy (1972) reported on the valley types in the south-west drainage division. 3.7 Slope

In their study of lateritic profiles in the Darling Range, Dimmock et al., (1974) found that the amount of salt stored in the profile was not markedly different for different positions in the landscape and increased as rainfall decreased for all slope positions. In this case a lack of slope effect resulted because there was a comparable depth of soil suitable for salt storage at each of the sites studied and at each slope position. By contrast, in the Belka Valley Bettenay et al., (1964) showed that soils of the valley slopes contained less salt per unit volume because there was a shallower depth of soil.

Malcolm (1983) reported that saline areas tend to be associated, not only with the floors of broad flat low grade valleys, but also with changes in slope whether these occur along the course of the valley or at the junction between the valley sides and floors. 3.8 Dissection

There are two reasons for the degree of dissection of the landscape being important in the development of saline soils: firstly, the degree of dissection determines largely the capacity for salts to be leached from the landscape and into the river system; secondly, the degree of dissection directly affects the depth of soil formation. The importance of truncation and dissection in land salinization was clearly illustrated in the studies of Bettenay and Mulcahy, (1972). The upper landscapes are usually the remnants of the old plateau, comprising coarse textured soils with sandy and gravelly surfaces overlying finer textured subsoils often of great depth. When the plateau is dissected, successive layers of the old laterite profile are truncated; consequently soils may be formed either on the remnants of the old laterite profile, or on the

15 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT products of erosion which form pediments downslope of the erosional surfaces (Stephens, 1946). In some cases the transported material lies on top of old eroded surfaces. All of the major river systems tap ancient drainage lines with salt lake chains in their upper reaches. Downstream of the salt lake chains, the valleys are successively more sharply incised and steeper. These are stages in the rejuvenation of drainage of the old uplifted plateau.

The inter-relationships, which develop between the various soil surfaces and layers in the landscape, during dissection and truncation of the old plateau and erosion of the country rock, is partly responsible for the location of saline areas.

In 1986 five hydrologically distinct zones were recognized within the East Perenjori Catchment which were grouped as provinces (Henschke and Ferdowsia, pers. comm.). • lateritic uplands • sandplain slopes • pediment slopes • valley flanks • valley floor

It was concluded that geomorphic/landscape surfaces could be aggregated into zones of particular hydrological activity which relate to the causes and development of soil salinity.

3.9 Micro- topography

Crabholes (gilgais) are depressions of one to several metres diameter, and up to half a meter deep, which occur in some fine textured soils. Teakle and Burvill (1938), drew attention to the fact that the rims of many gilgais were salt affected and Charley and McGarity (1964) also found the rim to have much higher nitrate and chloride levels than depressions. It was postulated that when water was in the gilgai capillary action was such that evaporation occurred at the rims and salts became concentrated in that position. 3.10 Hydrology and Salinity

The salt lake system in the Western Australian wheatbelt has been discussed by Bettenay (1961). Valley types in south-western Australia were described by Bettenay and Mulcahy (1972). From these studies it was concluded that salinity problems were related to the valley types and gradients. Downstream from the salt lake system the grade of valleys increases and, as Morrissey (1974) pointed out for the Blackwood River, a reverse longitudal salinity profile can develop compared with normal river systems. The salinity of the Blackwood River decreases as it gets closer to its mouth because of fresh in-flow near the higher rainfall areas near the coast.

Bettenay et al., (1962) in their study of the Belka Valley found that groundwater was present under much of the valley and its salinity increased from the highest points in the landscape to the base of the valley system. The main aquifer bearing the water

16 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT appeared to be in the zone of decomposed rock underlying both the pallid zone material and the alluvial deposits in the valleys. Where the overlay of relatively impermeable material was thin in the lower landscape the groundwater found its expression in saline soils and lakes. Localized groundwater flow systems cause the seepage areas which occur beneath spillways of sand, around the base of breakaways and at the junction between the transitional zone and the country rock (Mulcahy and Hingston, 1961).

In 1981 the Department of Agriculture began establishing a number of catchment studies aimed at treating salinity as a landscape problem. Research on each catchment aimed to identify and quantify the hydrological processes causing the salinity problem.

In the Cuballing catchment, seismic survey showed the catchment topographic divide and groundwater divide to be co-incident while a magnetic survey revealed the presence of several major dykes striking normal to the drainage line. Two of these dykes were retarding groundwater flow out of the catchment and were contributing to the surface salinity problems, Agronomic and engineering treatments have been imposed on the catchment to address the problem.

Henschke pers. comm. used aerial photo interpretation and transects of soil EC and measures of soil hydraulic conductivity to identify saline discharge areas in the East Perenjori Catchment. The in-situ constant head-permeameter determination of soil hydraulic conductivity showed deep sandy earths to be the most likely zones for recharge to groundwater.

Siewert pers. comm. used a network of piezometers to determine the hydrology of the Mallee Road Sump. She showed that a perched water table develops above the crabhole zone earlier in the season than it develops in other landscape zones. Thus the area upslope of the gilgai zone was considered to be contributing to recharge. The watertable in the sump has been rising at 0.5 m per year since clearing resulting in salinzation of the floor of the sump.

Engel (pers. comm.) used geophysical techniques and drilling to define recharge and discharge areas on a number of catchments. Results of their studies showed that electro magnetic indication has the potential to rapidly map the distribution of salt storages in lateritic profiles and interpretation of these profiles can assist in defining areas of hydrological significance.

George (1986, pers. comm.) studied sandplain seep development and its impact on regional groundwater system in the eastern wheatbelt. He found that perched groundwater develops at the interface between the deep yellow sands and underlying pallid zone clays. The water moves laterally until it flows to the surface where the sands shallow out. He concluded that perched aquifers were responsible for local salinization and regional groundwater recharge. 3.11 Effect of Land Use on Salinity

The earliest indications that removing native vegetation caused salinity came from concern about the quality of railway water supplies (Bleazby, 1917), Bleazby noted

17 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT that the common overseas practice of ringbarking vegetation on water supply catchments to increase water yield was followed in Western Australia by increased stream salinity. In other cases salinity was noted where there was agricultural development in the catchment of railway reservoirs. It became the practice to preserve the catchments of reservoirs in order to protect them from salinity.

The influence of vegetation removal on soil salinity was discussed by Paterson (1917). He claimed that forest scrub influenced salt behaviour by using water and thereby stopping salt rising, not by using salt. After land was cleared the salt was assumed to move from the high ground to the low ground by surface and underground flow. Teakle (1928) and (1929), also discussed the importance of clearing in causing the salt problem. Roots under forest, he claimed, prevented the movement of salt to the surface because they absorbed the moisture too rapidly. The importance of vegetation removal was thus recognized very early in the development of the salt problem.

Williamson and Bettenay (1979), studied the change in groundwater levels and run- off salinity in a catchment at Bakers Hill following replacement of perennial vegetation with annual crops and pasture. After clearing the groundwater levels increased at 0.8 m/year. When the potentiometric level of groundwater approached the soil surface there was a major increase in the salinity of run-off, indicating contribution from saline groundwater.

The effect of the water and salt yield of catchments of replacing natural vegetation with annual crops and pastures has been studied in considerable detail for high rainfall areas in Western Australia (e.g. Peck and Hurle, 1973). These studies indicate a similar hydrologic regime to low rainfall areas but with a quicker response time. Figures 2 and 3 illustrate the water and salt balance in the high and low rainfall areas under natural vegetation and following clearing.

18

SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

SALT BALANCE SALT BALANCE Yearly Input Yearly Output Yearly Input Yearly Output Salts Deposited Salts carried Salts Deposited Salts carried on Landscape by Streamflow on Landscape by Streamflow

Salts are slowly accumulating in low rainfall areas as there A slight excess of salts are leached from the landscape by are insufficient groundwaters to move salts in the day sub moisture which seeps through gravels and subsoil clays to soils through the landscape to the stream. The salts which the groundwater and finally to the surface stream system. are discharged come from the shallow soils.

SALT STORAGE SALT STORAGE

The Darling Range Over the centuries salts stor landscape has a high ages approaching and often exceeding 50 times those in potential to store salts in its deep soils. In the high rainfall the western regions have areas, however, sufficient developed. Although highly variable, peak concentrations water moves through the soils and back to the stream of salts usually occur 5 to 10 to stop any major metres below the surface, accumulation.

TYPICAL AVERAGE SALINITIES TYPICAL AVERAGE SALINITIES

Rainfall StreamfIow Rainfall Streamflow 15-2Omg/L TDS 120-200 mg/L TDS 8 to10 mg/L TDS 80 to 150 mg/L TDS Soil Salinity Groundwater Soil Salinity Groundwater 200 to 400mg/L TDS 150 to 250 mg/L TDS 3000 to 15000 mg/L TDS 1500 to 3000 mg/L TDS

Figure 2. Water and salt balance in the high and the low rainfall area prior to Clearing (The salinity problem of south-west rivers, Public Works Department of Western Australia, 1979).

20 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

SALT BALANCE SALT BALANCE Yearly Input Yearly Output Yearly Input Yearly Output Salts Deposited Salts carried Salts Deposited Salts carried on Landscape by Streamflow on Landscape by Streamflow

Two to three times the yearly input of salts are usually In excess of 20 times the yearly input of salts are discharged discharged after clearing in high rainfall areas. As the after clearing in low rainfall areas. Rising water tables inter- salinity of additional groundwaters discharged is low, average Sect zones of very high soil salinity which increases the

SALT STORAGE SALT STORAGE

The additional leaching of Because of the high salt salts following clearing is The storage and relatively slow likely to significantly deplete rate of leaching, high salt salt storage in less than 50 storages can be expected for years. hundreds of years.

TYPICAL AVERAGE SALINITIES TYPICAL AVERAGE SALINITIES Rainfall StreamfIow Rainfall Streamflow 15-20 mg/L TDS 120-200 mg/L TDS 8 to10 mg/L TDS 5000 to 6000 mg/L TDS Soil Salinity Groundwater Soil Salinity Groundwater 200 to 400 mg/L TDS 150 to 250 mg/L TDS 3000 to 15000 mg/L TDS 6500 to 7500 mg/L TDS

Figure 3. Water and salt balance following clearing in the high and low rainfall area (The salinity problem of south-west rivers, Public Works Depariment of Western Australia. 1979).

21 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

3.12 Salt Movement and Accumulation in Soil and Groundwater

It has been established that appreciable amounts of salt were stored in many Western Australian soils before agricultural development. In certain areas the salts were present at the surface in sufficient quantities to have an adverse effect on plant growth. In other cases there was sufficient salt present in soils with susceptible physical characteristics for the salts to concentrate at the surface under agricultural use. Other areas contained less salt and what was present was likely to be leached after clearing.

An essential feature of salinity problems is that sufficient salt accumulates in the surface or root zone layers of soil to reduce or inhibit the growth of normal crops and pasture plants. Consideration therefore must be given to the way in which salts move and accumulate in the soil and groundwater. 3.13 Effect of Soil on Salt Movement and Accumulation Reference has already been made to the effect of soil characteristics, such as texture, on the distribution of salts in the landscape before clearing. The same factors affect salt distribution under agricultural use. Salts move in solution in soils by either mass transport or diffusion. Mass transport occurs when the water in which salts are dissolved moves within the soil in response to pressure gradients. Diffusion occurs when there is a concentration gradient within the soil solution. Diffusion is normally much slower than mass transport but Doering et al., (1964), have suggested that there may be back diffusion from high surface salt concentrations in arid regions during summer if the surface remains sufficiently moist in the presence of a shallow watertable. When salt movement in the soil is occurring because of movement of a wetting front Bernstein and Fireman (1957) showed that there tends to be a high concentration of salt in the wetting front. The greater the initial salt content of the soil the less efficient was the movement of salt by the wetting front. It is also likely that movement of salt through undisturbed soils in the field will be less efficient because water may move along preferred paths and the salt will be more intimately mixed with the soil fabric. Nulsen (1980), however, reports that in a ped, a natural soil aggregate of about 0.05 to 0.1 m diameter, salt is at a higher concentration in the outside than the centre of the ped when the ped is taken from a salt accumulating area. Reverse distribution occurs in leaching situations. 3.14 Salt and Water Imported in Groundwater A major factor influencing the accumulation of soluble salts in soils is the transport of salts in the groundwater. In his study of the soils of Australia, Prescott (1931) observed that the distribution of salt, lime and gypsum in soil indicated downward leaching of soluble material as the dominant factor in soil maturation. When the watertable was in capillary reach of the soil surface the process was reversed. When water evaporates at the soil surface or is used by plants, the salts accumulate at the soil surface or in the root zone respectively. Talsma (1966), observed that in irrigation areas in Australia the development of salinity problems relates to the presence of a permanent watertable.

22 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

3.15 Movement of Water Under Pressure

Where water enters a particular layer of soil material or a rock crevice faster than it can escape, pressure will develop within that water-bearing layer. In a thick layer of relatively low permeability there will be pressure differences within the layer itself which indicate the directions in which water is tending to flow. If water is discharging from the layer faster than it is being recharged there will be a drop in pressure in the layer.

Movement of groundwater in Western Australian landscapes was studied by Smith (1962). He showed that there were extensive groundwaters beneath the valley and that these approached the surface in saline areas. The groundwaters rose in the test wells to heights greater than the depth at which water was first encountered during boring, indicating a degree of confinement of the water and that water was tending to flow towards the soil surface. There was also a gradient of increasing salinity from the highest point in the landscape to the valley floors. The hydraulic gradients indicated that water was tending to flow within the water bearing layer from the high country towards the valley floors.

The movement of salt and water through a wheatbelt landscape has been discussed in general terms so far but Bettenay et al., (1964), have examined the hydrology and salinity of soils and landscapes in the Belka area in considerable detail. As in the York-Quairading area, the soils highest in the landscape tend to be those formed on the old laterite profile. These soils the Ulva association) have high permeability and water moves down the profile and forms a watertable perched on the duricrust layer - see Figure 4. If the duricrust intersects the surface the water seeps out and form a saline area.

Finer textured soils of the Booraan, Merredin, Collgar and Belka associations tend to shed or retain water rather than allow it to leach their profiles. Salt therefore accumulates (Bettenay et al., 1964). These soils overlie massive heavy clays of low porosity and permeability. The authors state that “the permeability of these materials is extremely low and would prevent any significant seasonal accession of water to the aquifer from above. However, in response to the positive pressure of capillarity and the evaporation gradient towards the surface, there is a slow upward movement of saline water through the aguiclude”. In the valley floors, because the confining material is shallower, salt accumulation from the groundwater in the aquifer occurs at the soil surface.

Movement of saline water in the aquifer along the valley is stated to amount to only centimetres in a year but, in general, Bettenay et al. found the aquifer to be responsive to rainfall. If the aquifer was saturated the response to rainfall was rapid. If the aquifer was not saturated there was a delay between the commencement of rainy periods and the registering of rainfall events in piezometers. The most rapid loss of pressure at the lower end of the aquifer was noted where the aquiclude was cut by salt pans.

23 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

24 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

In discussion of the soils of the Belka valley, Bettenay and Hingston (1964) described earlier stream levees and fine textured flood plains which had developed on the valley floors but have subsequently been modified by wind action. They describe these soils as characteristically secondary solonchaks formed by the intrusion of saline groundwater. The soils comprise low sandy ridges winding through extensive clay plains.

The degree to which water, arriving at a particular part of the landscape, either enters the soil and downwards, enters the soil and moves laterally, or flows over the top of the soil, depends on the relationship between the rate of rainfall and the rate at which the water can enter and move downward in the soil. If the downward water movement in soil is slower than the rate at which water is arriving there will be an accumulation of free water in the soil and a tendency for water to move laterally. Once the possibilities for lateral flow have been saturated, water will accumulate in the soil and may run out onto the soil surface. 3.16 Capillary Rise and Critical Depth

Teakle et al., (1940) pointed out from the results of their soil survey in the Lakes District that it was apparent that soil salinity was not necessarily related to the proximity to salt lakes, but rather to the texture and structure of the soil and to the depth of the saline watertable. A saline watertable at shallow depth prevents effective leaching of salt from the soil, even in irrigation areas (Basco and Fekete, 1968) and causes secondary salinization of soil horizons above the groundwater.

Teakle and Burvill (1945) reported many instances where the saline watertable has risen from 6 m or more before clearing, to within 1 to 2 m of the surface. They regard 1.5 to 1.8 m as a critical depth for soil salinization. Pennefather (1950) referred to records showing that the watertable in Western Australian wheatbelt valleys was at 4.5 to 9 m soon after clearing - recent results show it is often now at about one or two metres. Nulsen (1981) found that the critical depth of a saline watertable for wheat production in Western Australia was within the range 1.8 to 2.4 m. Barley could be grown with watertables as shallow as 1.5 m.

25 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

4. Extent of Salinity in Western Australia

4.1 Australian Bureau of Statistics 1984 Saltland Survey

At various intervals since 1955 farmers in Western Australia have been asked to estimate the area of once productive land on their farms which is no longer productive due to salinity. Because the response to the question relies on an historical knowledge of the original condition of the land the accuracy of the survey becomes increasingly questionable with time. Perhaps it would be more appropriate to ask the question “What is the total area of salt affected land on your property?”

Despite the limitations, the surveys of 1955, 1962, 1974, 1979 and 1984 do provide some insight into the growth of the land salinity problem in the State. 4.2 Previous Results 1962-1979

In 1955 the estimate of saltland was 73,504 ha (0.5 per cent of cleared land; by 1962 this had increased to 123,591 ha (0.68 per cent of cleared land). In 1974 it was 167,294 ha, representing 1.17 per cent of all cleared land and by 1979 there were 263,752 hectares of once productive land reported as salt affected.

Henschke (1979) expressed concern about the dramatic rate of increase in the total area of saltland for the period 1974-1979, and suggested that it was unrealistic. He indicated that increased publicity on saltland in the previous few years could have led to increased farmer awareness of salt encroachment. 4.3 The 1984 Survey and Results

The 1984 survey was conducted by the Australian Bureau of Statistics using the same question as in the 1974 and 1979 survey (“the area of salt-affected land at March 31, 1984 which was previously used for crops and pasture”). The information is collated on a Shire basis enabling comparison with the previous surveys.

The following summarizes the extent of the salt problem in the agricultural land division. Table 1 and Table 2 summarizes relevant information for the all southern statistical divisions. 4.4 South West Division

In this Division 230 farmers reported salt-affected land on their farms, compared with 240 in the 1979 survey. The worst affected Shire was Boddington with 1.04 per cent of cleared land affected. Boyup Brook had the biggest number of farmers reporting some area of saltland (99). The average area of saltland on each affected farm was highest for Manjimup Shire with 35 ha.

Comparison with 1979 survey showed that Boyup Brook reported the biggest increase with 361 ha (Table 3). 4.5 Southern Agriculture Division

In this Division 1103 farmers reported saltland compared with 1140 in 1979. The

26 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT worst affected Shires were Tambellup with 4.19 per cent of cleared land affected and Katanning with 4.03 per cent. The average area of saltland on each affected farm was highest in Lake Grace with 120 ha and Dumbleyung with 114 ha. The largest increases since 1979 were in the Shires of Wagin (1951 ha), Kojonup (1484 ha) and Cranbrook (1210 ha). The biggest decrease was reported in the Shires of Dumbleyung (2174 ha), Kent (1089 ha) and Tambellup (880 ha) (Table 3). 4.6 Central Agriculture Division In this Division 1472 farmers reported saltland in 1984 compared with 1729 in 1979. Shires for which returns indicated the highest proportion of saltland to cleared land were: Tammin (5.64 per cent); Goomalling (4.00 per cent), and Dowerin (3.95 per cent). Shires with the biggest number of farmers reporting some area of saltland were Narrogin with 84, Brookton with 75 and Beverley with 72. The average amount of saltland on each affected farm was highest for Tammin (148 ha), Kondinin (119 ha) and Dowerin (112 ha). Comparison with the 1979 survey showed that Narrogin and Kuhn reported the biggest increases with 1634 and 1215 ha respectively. Decreases were reported in the Shires of Quairading (2004 ha), Corrigin (1354 ha) and Wyalkatchem (1139 ha). 4.7 Northern Agricultural Division In this Division 811 farmers reported saltland in 1984 compared with 983 in 1979. Shires with the highest proportion of saltland to cleared land were Wongan-Ballidu (4.80 per cent), Morawa (4.15 per cent) and Moora (3.47 per cent). Shires with the biggest number of farmers reporting some area of saltland were Dalwallinu (114), Wongan-Ballidu (105) and Moora (95). The average amount of saltland on each affected farm was highest for Wongan-Ballidu (147 ha), Morawa (133 ha), Coorow (129 ha) and Dalwallinu (125 ha).

Comparison with the 1979 saltland survey showed that the biggest increases occurred in the Shires of Dalwallinu (2162 ha), Dandaragan (690 ha) and Morowa (635 ha). The biggest decreases were reported in Shires of Mullewa (6294 ha), Perenjori (4586 ha), Wongan-Ballidu (1798 ha) and Moora (1312 ha). 4.8 Eastern Goldfields, Central and North West Divisions In these three Divisions 164 farmers reported saltland in 1984, compared with 141 farmers in 1979. The worst affected Shires were Dundas with 0.44 per cent of cleared land affected and Ravensthorpe with 0.42 per cent. Esperance, with 111 positive respondents was the Shire with the biggest number of farmers reporting some area of saltland. The average amount of saltland on each affected farm was highest for Dundas (147 ha) and Ravensthorpe (35 ha). Comparison with the 1979 survey showed that the biggest increases occurred in the Shires of Esperance (1130 ha) and Dundas (481 ha). A decrease was reported only in Shire of Yilgarn (213 ha).

27 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

Table 1. Saltland and clearing data for shires and farms from farmers’ estimates 1984

Statistical division Shire Number of Total area Area of Number of Area of Saltland Average area active of active cleared holdings saltland cleared of saltland holdings holdings land reported (km2) land (%) per affected (km2) (km2) saltland farm (ha) Perth Armadale 166 38 33 - - - - Cockburn 162 12 10 2 0.02 0.20 1 Gosnells 99 15 14 - - - - Kalamunda 213 17 15 - - - - Kwinana 38 11 8 - - - - Mundaring 118 111 87 9 0.21 0.24 2 Rockingham 80 76 59 1 0.08 0.14 8 Serpentine-Jarrahdale 243 326 292 4 0.19 0.06 5 Swan 434 351 241 10 0.24 0.10 2 Wanneroo 239 115 64 - - - - Other 30 1 - - - -

Southwest Augusta-Margaret R. 355 808 602 1 0.10 0.02 10 Boddington 83 767 625 27 6.47 1.04 24 Boyup Brook 301 2,095 1,732 99 12.74 0.74 13 Bridgetown-Greenbushes 254 672 539 13 1.20 0.22 9 Bunbury 12 12 12 - - - - Busselton 354 806 712 18 3.74 0.53 21 Capel 181 395 337 9 0.65 0.19 7 Collie 78 212 185 5 0.74 0.40 15 Dardanup 158 303 263 9 1.38 0.52 15 Donnybrook-Balingup 330 582 507 7 0.10 0.02 1 Harvey 331 762 639 13 2.56 0.40 20 Mandurah 11 26 19 - - - - Manjimup 538 1.039 821 11 3.89 0.47 35 Murray 258 694 605 15 3.66 0.60 24 Nannup 91 412 304 3 0.13 0.04 4 Waroona 128 324 288 - - - -

Southern Albany 576 2,693 2,178 18 1.36 0.06 8 Agricultural Broomehill 88 1,120 1,043 46 19.49 1.87 42 Cranbrook 227 2,563 2,078 99 35.31 1.70 36 Denmark 232 468 353 4 1.04 0.30 26 Dumbleyung 140 2,335 2,230 50 57.26 2.57 114

28 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

Statistical division Shire Number of Total area Area of Number of Area of Saltland Average area active of active cleared holdings saltland cleared of saltland holdings holdings land reported (km2) land (%) per affected (km2) (km2) saltland farm (ha) Gnowangerup 414 8,189 7,215 96 34.87 0.48 36 Katanning 118 1,474 1,375 62 55.44 4.03 89 Kent 191 4,062 3,636 44 34.49 0.95 78 Kojonup 304 3,325 2,726 150 35.68 1.31 24 Lake Grace 295 7,243 6,353 96 115.44 1.82 120 Plantagenet 556 3,214 2,689 152 29.33 1.09 19 Tambellup 98 1,337 1,187 54 30.32 2.55 56 Wagin 145 1,849 1,681 97 70.48 4.19 73 West Arthur 202 2,119 1,760 91 29.69 1.69 33 Woodanilling 78 1,048 924 44 28.61 3.10 65

Central Beverley 172 1,233 1,580 72 30.45 1.93 42 Agricultural Brookton 120 1,363 1,252 75 43.33 3.46 58 Bruce Rock 124 2,638 2,426 57 47.29 1.95 83 Corrigin 148 2,507 2,336 65 57.72 2.47 89 Cuballing 103 932 801 53 10.15 1.27 19 Cunderdin 114 1,940 1,817 70 42.49 2.34 61 Dowerin 114 1,649 1,553 55 61.47 3.95 112 Goomalling 124 1.681 1,486 60 59.37 4.00 99 Kellerberrin 101 1,867 1,742 56 60.97 1.87 119 Kondinin 146 3,614 3,268 51 60.97 1.87 119 Koorda 96 2,326 2,034 42 46.00 2.26 109 Kulin 194 4,233 3,856 41 29.75 0.77 73 Merredin 138 3.002 2,709 50 37.92 1.40 76 Mount Marshall 146 6,484 3,541 34 22.57 0.64 66 Mukinbudin 98 2,971 2,452 19 8.68 0.35 46 Narembeen 148 3,752 3,505 60 53.40 1.52 89 Narrogin 143 1,467 1,344 84 46.32 3.45 55 Northam 230 1,139 1,004 61 9.31 0.93 15 Nungarin 41 1,016 895 14 10.14 1.13 72 Pingelly 102 1,309 1,202 58 23.77 1.98 41 Quairading 107 2,072 1,909 58 23.77 1.98 41 Tammin 63 1,156 1,072 41 60.50 5.64 148 Toodyay 150 952 773 20 3.18 0.41 16 Trayning 72 1,482 1,335 25 16.98 1.27 68 Wandering 74 1,021 816 35 18.63 2.28 53 Westonia 70 2,172 1,819 15 8.57 0.47 57 Wickepin 129 2,091 1,835 54 52.30 2.85 97

29 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

Statistical division Shire Number of Total area Area of Number of Area of Saltland Average area active of active cleared holdings saltland cleared of saltland holdings holdings land reported (km2) land (%) per affected (km2) (km2) saltland farm (ha) Williams 144 1,732 1,554 57 14.44 0.93 25 Wyalkatchem 76 1,307 1,180 37 19.81 1.68 53 York 158 1,473 1,329 50 13.74 1.03 27

Northern Carnamah 86 1,744 1,390 36 40.16 2.89 112 Agricultural Chapman V 137 3,226 2,495 22 16.54 0.66 75 Chittering 219 799 668 15 2.44 0.37 16 Corrow 119 2,644 2,050 42 54.29 2.65 129 Dalwallinu 186 5,600 4,848 114 142.75 2.94 125 Dandaragan 208 4,119 3,207 19 8.82 0.28 46 Gingin 189 1,762 1,215 4 0.44 0.04 11 Greenough 193 1,694 1,479 7 1.33 0.09 19 Irwin 50 1,261 1,019 1 0.10 0.01 10 Mingenew 62 1,907 1,691 18 11.06 0.65 61 Moora 166 4,596 2,947 95 102.14 3.47 107 Morawa 127 3,399 2,368 74 98.32 4.15 133 Mullewa 141 8,946 4,215 49 54.68 1.30 112 Northampton 175 7,623 2,887 29 11.19 0.39 39 Penenjori 138 6,599 3,229 73 88.78 2.75 122 Three Spring 106 2,501 2,106 30 25.65 1.22 86 Victoria Pla ins 161 2,464 2,074 78 51.32 2.47 66 Wongan-Ballidu 163 3,571 3,216 105 154.23 4.80 147

Other Dundas 66 34,983 1,249 3 5.56 0.44 185 Esperance 523 10,929 9,078 111 37.73 0.42 34 Ravensihorpe 216 4,098 3,277 26 9.23 0.29 35 Yilgarn 161 9,361 4,942 24 - - - Yalgoo 21 25,181 - - - - - Carnarvon 184 43,512 19 - - - -

30

SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

4.9 Results Summary

The Shire for which returns indicated the highest ratio of saltland to cleared land was Tammin with 5.65 per cent. Wongan-Ballidu, Wagin, Morawa, Katanning and Goomalling followed with between 4 and 5 per cent. Six Shires have between 3 and 4 per cent and 13 between 2 and 3 per cent. Twenty Shires have between 1 and 2 per cent and 40 Shires have less than 1 per cent of saltland as a proportion of cleared land.

Comparison with the 1979 saltland survey shows that the number of farmers reporting saltland declined by 18 per cent in South West Division, 3.6 per cent in the Southern Agricultural, 15 per cent in the Central Agricultural, 17 per cent in the Northern Agricultural and 12 per cent in Eastern Agricultural. There was an average reduction per shire of 751 ha in the Northern Agricultural Division and 26 ha in Central Agricultural Division. The other Divisions showed an average increase per Shire of saltland in this period. 4.10 Discussion of Survey Results

There was an average reduction per Shire of 751 ha in the Northern Agricultural Division and 26 ha in the Central Agricultural Division. The other Divisions showed an average increase in the area of saltland (Table 3). Figure 4 shows the change in the area of saltland in Western Australia over the period of 1955-1984.

The results beg the question of why in some Shires farmers reported decreases in saltland, while in others they reported marked increases. Similar variant trends occurred between the 1962, 1974 and 1979 surveys.

Malcolm (1974) indicates that the possible causes of differences between 1962 and 1974 saltland surveys include the influence of season on the apparent severity of saltland. Henschke (1979) mentions that the increased publicity on saltland in the past few years well could have led to increased farmer awareness of salt encroachment. The Australian Bureau of Statistics believes that the form design may have caused a decrease in the number of holdings reporting saltland in 1984 (personal communications).

Figure 5 shows changes in the area of cleared land in Western Australia in the period 1930-1984. The continued clearing of large areas of land from 1945 onwards has predisposed lower lying areas to an increase salt encroachment.

32

SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

Table 2. Shows the totals of holdings, clearing and saltland in statistical division in the Saltland Survey 1984-85

Statistical division Number Total area of Area of Number of Total area of Saltland Cleared land % of active active cleared land holdings saltland (km2) cleared land area of holdings holdings holdings (km2) reported % (km2) saltland Perth 1.822 1,037 824 26 0.74 0.06 77 Southwest 3,463 9,900 8,190 230 37.36 0.50 83 Southern Agricultural 3,664 42,939 37,428 1,103 578.81 1.55 87 Central Agricultural 3,645 63,081 54,425 1,472 1,008.16 1.85 86 Northern Agricultural 2.626 64,437 43,104 811 864.24 2.00 67 Eastern Goldfields 972 59,371 18,710 164 57.61 0.31 27 Central and North West 205 68,693 19 - - - <1 Total: Reported by salt-affected farms 1,397 309,502 162,536 3,806 2,546.92 1.6 56 Total: Western Australia 16,890 1,139,697 162,679 3,807 2,546.90 1.6 14

34

SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

Table 3. Saltland Survey Data: 1974, 1979 and 1984

Shire 1974 1979 1984 AN AN AN Boddington 101 6 252 25 647 27 Boyup Brook 538 60 913 95 1,274 99 Bridgetown 61 5 166 20 120 13 Collie 24 3 136 17 74 5 Manjimup 10 2 58 11 389 11 Murray 100 4 339 3 366 15 Total SW 957 93 2,800 240 3,090 203 Albany 108 18 42 8 136 18 Broomehill 1,658 42 1,723 49 1,949 46 Cranbrook 971 61 2,321 79 3,531 99 Dumbleyung 4,235 50 7,900 58 5,726 50 Gnowangerup 2,857 62 2,370 81 3,487 97 Katanning 3,4907 61 6,233 78 5,544 62 Kent 2,127 37 4,538 56 3,449 44 Kojonup 1,770 110 2,084 138 3,568 150 Lake Grace 7,724 85 11,686 106 11,544 96 Plantagenet 874 97 1,764 161 2,933 152 Tambellup 2,205 43 3,912 - 63 3,032 54 Wagin 3,168 81 5,097 94 7,048 97 West Arthur 1,416 64 3,152 121 2,969 91 Woodanilling 1,644 47 2,591 47 2,861 44 Total Sth Ag 34,271 853 55,500 1,140 57,777 1,100 Beverley 2,016 59 2,934 70 3,045 72 Brookton 2,148 58 5,078 84 4,333 75 Bruce Rock 2,353 57 5,066 70 4,729 57 Corrigin 5,207 60 7,126 77 5,772 65 Cuballing 1,037 40 992 55 1,105 53 Cunderdin 3,829 68 4,437 84 4,249 70 Dowerin 3,057 51 6,512 57 6,147 55 Goomalling 3,746 73 5,019 85 5,937 60 Kellerberrin 2,761 54 4,057 75 3,825 56 Kondinin 2,676 50 5,300 69 6,097 51 Koorda 4,567 48 5,252 62 4,600 42 Kulin 2,133 35 1,760 51 2,975 41 Merredin 2,297 50 3,443 63 3,792 50 Mt Marshall 1,497 20 1,712 40 2,257 34 Mukinbudin 817 15 1,201 20 868 19 Narambeen 3,572 59 4,738 81 5,340 60 Narrogin 1,850 64 2,998 84 4,632 84 Northam 537 45 742 59 931 61 Nungarin 668 11 1,015 20 1,014 14 Pingelly 1,753 46 3,058 53 2,377 58 Quairading 4,726 66 8,070 76 6,066 61

36 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

Shire 1974 1979 1984 AN AN AN Tammin 3,138 39 5,962 41 6,050 41 Toodyay 239 13 506 33 318 20 Trayning 1,684 22 1,584 34 1,698 25 Wandering 631 26 1,445 39 1,863 35 Westonia 332 7 735 16 857 15 Wickepin 2,776 47 4,877 55 5,230 54 Williams 265 29 936 59 1,444 57 Wyalkatchem 1,724 30 3,120 46 1,981 37 York 1,127 43 1,934 71 1,374 50 Total Cent Ag 65,173 1,285 101,600 1,729 100,816 1,472 Carnamah 4,394 57 4,733 44 4,016 36 Chapman V 530 13 1,477 31 1,654 22 Coorow 4,410 45 5,762 48 5,429 42 Chittering 31 5 500 22 244 15 Dalwallinu 9,028 111 12,113 123 14,275 114 Dandaragan 130 6 192 12 882 19 Gingin 41 3 81 8 44 4 Greenough 209 7 70 5 133 7 Mingenew 1,237 20 1,301 22 1,106 18 Moora 7,140 105 11,526 116 10,214 95 Morawa 4,528 67 9,197 99 9,832 74 Mullewa 3,258 41 11,762 64 5,468 49 Northampton 1,091 26 2,056 34 1,119 29 Penenjori 8,046 85 13,464 97 8,878 73 Three Springs 2,514 31 2,622 35 2,565 30 Victoria Plains 4,018 77 5,105 95 5,132 78 Wongan-Ballidu 12,602 123 17,221 128 15,423 105 Total Nthn Ag 63,215 722 99,200 983 86,424 811 Dundas 242 - 75 4 556 3 Esperance 2,622 - 2,643 80 3,773 111 Ravensthorpe 244 - 736 27 923 26 Yilgarn 452 - 722 28 509 24 Total Eastern 3,560 - 4,300 140 5,761 164 Total W.A. 167,294 ? 263,752 4,269 254,690 3,807

A = Area of saltland in ha. N = Number of holdings reporting saltland.

37 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

38 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

39 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

4.11 Conclusions

According to farmers’ estimates in 1984, there was 254,692 hectares of salt-affected land in Western Australia which had previously been used for crops and pastures. The area represents 1.6 per cent of cleared land. This is a 0.15 per cent decrease from the 1979 and a marked increase from the 1974.

The worst affected Shires were Dalwalinu and Wagin. Dundas, Tammin and Wongan-Ballidu had the highest average amount of salt per affected farm, and Morowa had the biggest increase in saltland in the period of 1979-1984. 4.12 Regional Assessment of Potential for Land Salinization

Surveys of the area of agricultural land affected by salinity have been carried out by the Australian Bureau of Statistics since 1955. However, because these surveys rely on farmers’ prior knowledge of the condition of their land there is increasing unreliability of the data with time.

Over the last seven years the Department of Agriculture has placed specialist salinity research staff at district offices. These researchers are familiar with their areas and were asked to assess the current and potential areas of soil salinity in each of the five Department of Agriculture advisory regions in the South West Land Division, 4.13 Northern Agricultural Region

The region covers that area serviced by the Geraldton, Three Springs and Moora offices of the Department. 4.14 Current Status

Australian Bureau of Statistics 1984 survey reported 86,400 ha of previously productive land now salt-affected. The most severely affected areas are the broad, low gradient valleys in the Shires of Carnamah, Coorow, Dalwallinu, Moora, Morawa, Mullewa, Perenjori and Wongan-Ballidu. Shires with a greater degree of landscape dissection (e.g. Chittering) or with more recent development of sand plain soils (e.g. Dandaragan) have low levels of land salinization. 4.15 Potential Area

Surveys done in association with Soil Conservation Districts in the region indicate that valley salinity is the major problem with the potential for all valley soils to become salinized. These are virtually all cleared and constitute up to 15% of the area of some of the eastern catchments.

In a detailed study of a 13,900 ha catchment east of Perenjori, valley floors constitute 13% of the catchment. Current watertable depths in this valley -range between 1 and 3m. A further 9% of this catchment was classified as valley flanks with current problems of ephemeral waterlogging and the potential to develop saline seeps. A total of at least 17.5% of this catchment has a potential salinity risk under current land use practices.

40 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

Little salinity has developed on the West Midland sandplain. However, there have been recent outbreaks near Coomallo Creek and, given the experience of the Esperance sandplain, the West Midland sandplain may have a large potential salinity problem.

On the basis of the above it is estimated that the potential area at risk of salinization is some 600,000 ha.

A significant proportion of this potential will be realized under current land use practices within the next 20 years. 4.16 Strategies

Current

These are generally being implemented on an individual basis with little co-ordination within catchments. - • Drainage - deep open drains. • Trees - mainly on the margins of salt-affected land. • Salt tolerant shrubs - reasonable adoption in the eastern areas where the economics have been demonstrated. • Higher water use rotations - increasing growing of lupins on sandy soils.

Preferred strategies

Generally, water management on a co-ordinated catchment basis with emphasis on dealing with problems in the early stages of degradation is the preferred treatment strategy.

Water management to emphasize surface water control on slopes and valleys to reduce waterhogging. Design of drains in valleys needs to be improved to minimize silting and ensure adequate capacity to handle large storms. This will involve increased culvert capacity at roads and railways and careful management of disposal areas.

Improved soil surface management systems to maintain ground cover and soil structure and to encourage leaching of salt.

Intensive and well maintained tree plantings in and around emerging sandplain seepages. 4.17 Central Agricultural Region

The region includes the ten Shires of the Campion Zone and the four Shires of the Lakes region. It also includes 11 Shires from the Avon region excluding Dalwallinu and Wongan-Ballidu, which fall outside the Central Agricultural Region. Data used are from the 1984 Australian Bureau of Statistics census.

41 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

4.18 Current Salt-Affected Areas

Northam Advisory area 40,698 ha Merredin Advisory area 24,888 ha Lake Grace Advisory area 26,388 ha Total salt affected 91,974 ha

The most severe salinity problems in the Central region occurs between the 450 mm and 350 mm isohyets. This zone lies to the east of the Meckering line which separates the active drainage system of the Darling Ranges from that of the central wheatbelt. The Shires of Tammin, Goomalling and Dowering are the most seriously affected having 5.55, 4.06 and 3.98% of their arable area saline.

Two major types of secondary salinity occur in the Central Agricultural region. Valley floor salinity is responsible for most of the problems in the abovementioned areas. However to the east, below the 350 mm rainfall isohyet, sandplain seeps are the main salinity problem. 4.19 The Potential Area Which Could Become Saline

The salinity potential of the Central region can be estimated from either extrapolating existing A.B.S. data, using quantitative water balances or from qualitative field observations.

Existing survey data

Five saltland surveys have been carried out since 1955 (i.e. 1955, 1962, 1974, 1979 and 1984). The data suggests that saline land has increased from 0.5% to 1.64% of the cleared land. If it is assumed that the current growth can be approximated by a straight line, then this growth rate is 0.04% per year (Figure 6).

The discrepancy caused by the results of the 1979 survey, and subsequent decline in 1984, is not generally supported by farmers observations. Most report a rapid growth of salinity in the 1960’s, followed by sustained growth throughout the 1970’s and 1980’s. Although some suggest that their saltland area has stabilized over the last few years, little proof exists.

Continued growth at or about 0.04% per year would increase the total area affected to 4.15-5.40% by 2050, and perhaps as high as 10% by 2150. Owing to the lack of data sets, and quality control over the surveys, it is probably unreasonable to extend this method beyond 2050.

In the central region, an increase of saltland by a factor of 3 or 4 would result in some Shires being between 10-20% salt affected, especially in the severely affected zone in the eastern portion of the Avon district. However salinity spread in the eastern wheatbelt may not be as significant owing to the greater depth to the watertable in many catchments.

42 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

Water balances

Groundwater systems and watertable levels are currently changing in response to the clearing of native vegetation and consequent decrease in evapotranspiration caused by new agricultural systems. A knowledge of the hydraulic properties and behaviour of aquifers before clearing and at present, can be used to calculate water balances for groundwater systems.

Little is known about the time required for catchments to reach a new equilibrium. However, Peck and Hurle (1973) suggests it may be of the order of 100’s of years in the Darling range to 1000’s of years in the central and eastern wheatbelts. From knowledge of the recharge rates and areas, and discharge rates and areas, an estimate of potential area to be affected can be calculated.

Current estimates suggest recharge rates are two to three orders of magnitude greater than before clearing. Using estimates of discharge rates from saline soils, it is suggested that 10-20% of the landscape could be prone to groundwater discharge and salinity.

Observations

Field observations in severely saline catchments corroborate that up to 20% of the catchment is required to balance the incoming recharge. Examples can be seen in the Wongan-Ballidu, Tammin and Wickepin Shires.

In these catchments severely saline soils occur across the entire valley floor, and have moved upslope at the head of major valleys. This may be what could be expected in many central wheatbelt valleys and eventually in all valleys unless management strategies are adopted to control its spread. 4.20 Time to Develop the Full Potential Salinity will continue to develop as a result of the need for groundwater systems to balance increased recharge caused by clearing. This growth in the area of groundwater discharge will continue until recharge is balanced by discharge. This may take 100’s to 1000’s of years to achieve.

A reduction in this time scale will only occur if recharge reduction or discharge enhancement measures are adopted. The area of saltland will then reflect a compromise associated with the effectiveness of these methods. In the Northam Advisory District the saline area is expected to expand rapidly, as most of the major valley systems, currently free of salinity, are underlain by shallow groundwater tables. Evidence of watertable rates of rise from the Narrogin area, which is environmentally similar, suggest increases of between 0.1-0.5 metres per year, across the entire landscape. In the drier, eastern wheatbelt, rates of rise appear to be much slower. However, with only two years of monitoring available no clear trend has emerged. The greater depth to watertables (often up to 10 m below regional valley soils) suggests salinity will not be a major problem for many years. Some valleys do show groundwater

43 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT levels closer to the surface and will therefore become affected sooner. A planning time frame would place major salinization in the central wheatbelt within the next 0-100 years and within the eastern wheatbelt between 50-200 years. 4.21 Strategies Available for Saltland Control

Farmers in the Central Agricultural region have not adopted many salinity control or soil conservation measures. This is due to a lack of any immediate financial incentive and the current state of the rural economy. However, many are aware of the options available and have experimented with one or two of them. A pre-occupation with the idea that one strategy will solve the salinity problem, and a lack of any thorough understanding of processes involved, has restricted the adoption of remedial measures.

It is the lack of understanding about the processes and time frame involved, that causes much of the problem. Farmers are used to responding to trial results, with, more or less, conclusive answers. Salinity problems do not respond instantly to management changes. This makes it difficult for a farmer who must alter an existing practice to accept that a long term benefit will be produced. It is just as difficult for researchers to demonstrate success, since the time scales involved, and degree of land use change needed are both large, and expensive to implement.

The nett result is that the only management procedures currently being adopted are ones which have a quick response time. These are often ineffective and expensive. Groundwater pumping and large dozer built earthworks are good examples. Others such as sandplain seep drainage using tube drains, lupin-wheat rotations and tree belts are both economic and effective.

Ones being adopted in the Central Region

Management type Adoption & Success a. Saltland agronomy 6 6

b. Eucalyptus replanting - on saline areas 1 3

- on recharge areas 2 ?

c. Groundwater pumping 1 4

d. Tube drainage 1 2

e. Open drainage - 3 3

f. Large dozer built banks 4 2

g. Reverse bank seepage interceptors 2 7

h Soil ameliorants 6 8

* Adoption and success both scored, 0-10 (10 very good - 0 poor).

There are some notable exceptions to this list, namely rotation management and historical soil conservation earthworks. Rotations for recharge and salinity control are

44 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT fortunately directly linked to current farm profitability. However, adoption is based on economics, not salinity. Soil conservation earthworks fall in the same category.

Should be adopted list

A comprehensive list of management strategies directly associated with salinity control is presented in Table 4. Although the list is not exhaustive it details many of the techniques currently available which are worthy of consideration for each major soil salinity problem in the region.

Farmers should consider each alternative on each soil-landform, and would probably chose several for each. A total of over 100 procedures could be adopted by any individual farmer to reduce a catchments salinity problem. In cases where individual farmers do not manage all of the catchment which influences their property, conservation groups can be formed to assist with cost sharing, research and implementation of a programme.

45 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

46

SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

Table 4. Catchment management recommendations and considerations for salt-affected soils in the central agricultural region

Catchment divide or hillside soils Midslope soils Lower Slope soils Valley soils Soils and landform units* Ulva Danberrin Booraan Acid Norpa Sandplain Collgar Merredin Belka Saline soil Saline (gravels (outcrop & (clayey sands (deep seeps (midslope (heavy (sandy (non saline soil & Soils) upslope (‘Wodgil’) sands) (saline duplex) clay valley groundwater) (complex) sands) soils) sands) soils) soils) < 10,000 ppm

Revegetation techniques Saltland agronomy x x x x x ! xxx!! Eucalyptus ! ! ! !!! ! !! ! ! strips(s) plantations(p) . s p s p s s s s s s p salt tolerant(st) st st Perrenial fodder trees !! x !! x xxxxx Perrenial fodder crops x ! xx! x x x x xx Agroforestry ! x !!!x xxx! x

Cropping rotations ** 1. BBB x x x x x x x ! x ! x 2. WWO !! x ! xx x xx x x 3. LWW x x x x ! x ! xx x x 4. WWW !! xx! x !!!xx 5. WPWP !!!xxx !!xx x 6. LWT(0) x x x !! xxxxxx 7. WWF x ! xxxx !!!xx 8. PPP x x ! xxx x ! xx x 9. LWP x x x x ! x ! xx x x

Engineering methods Pumping (for water supply) x ! xx!! ! xx ! x Pumping (for salt control) x ! xxxx xxx!! Flood structures (banks) x x xxxx !!!! !

48 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

Catchment divide or hillside soils Midslope soils Lower Slope soils Valley soils Soils and landform units* Ulva Danberrin Booraan Acid Norpa Sandplain Collgar Merredin Belka Saline soil Saline (gravels (outcrop & (clayey sands (deep seeps (midslope (heavy (sandy (non saline soil & Soils) upslope (‘Wodgil’) sands) (saline duplex) clay valley groundwater) (complex) sands) soils) sands) soils) soils) < 10,000 ppm

Tube drainage x x x x x !!xx x x Open drainage x x x x x !!!!!!

Banks/waterlogging control Large level(l)/goods(g) banks l x l x x x g x x g g Small contour(c) grade(g) banks x c c c c c g x x g g Small reverse banks x x x x x x ! xx !! Working lines ! ! ! !!! ! xx x x

Soil conservation practises Contour working ! ! ! !!! ! !!! ! Conservation fencing ! ! ! !!! ! !!! ! Soil ameliorants x x !!xx x !! xx Stubble management ! ! ! !!! ! !! xx Conservation tillage ! ! ! !!! ! !!! !

Key: x = not worth considering ! = worth considering or recommended * = landform units derived from Betteney et al., (1961-1964), nomenclature also relevant in Avon district via Mulcahy and other works ** = each rotation must include the best varieties, tillage and other agronomic practises possible to maximise profit and water use

Note: 1. The recommendations listed in this table are based on past and continuing research, and on farmers’ and Departmental staff observations. 2. Final advice, and strategies will depend on individuals position within the catchment, farmer group participation and local hydrogeologic and geomorphic characterists. 3. The landform units describe 11, of 14 major provinces recognised in the Merredin Soil Conservation Manual in preparation.

49 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

4.22 Great Southern Region

Current saline area

Census Area (ha) % of cleared land (‘79 figures) 1979 60,261 1.96 1984 62,532 2.03

Shires: Boddington, Brookton (1/2), Broomehill, Corrigin, Cranbrook, Cuballing, Dumbleyung, Gnowangerup, Katanning, Kojonup, Narrogin, Pingelly, Tambellup, Wagin, West Arthur, Wickepin, Williams, Woodanilling.

Note: Brookton figures were halved (Totals: ‘79 - 5078 ha; ‘84 - 4333 ha).

Cranbrook was included (Totals: ‘79 - 913 ha; ‘84 - 1274 ha).

Comments • Farmers usually underestimate saline areas. • From ‘quick’ roadside surveys of typical landscape types:

Kojonup district Balganip River catchment above Kojonup-Frankland Road. Slopes are about 5%. Valley floors are about 200 to 500 m wide.

Exposed rock - granitic and basaltic - is very common. Salinity occurs in drainage lines and as discrete hillside seeps.

Catchment area: 19,500 ha

Salt-affected area: ≅10% (i.e. 2000 ha)

Broomehill district Catchment north of Broomehill, flowing eastward.

Surveyed east of Great Southern Highway to Nymanip Pool. Slopes 1%. Valley floors from about 0.5 km to several kilometres wide. Dykes are common and some basement rock is exposed. Salinity mainly affects the broad valley floor. It only affects drainage lines higher up the catchment where dykes influence groundwater. Discrete hillside seeps occur.

Catchment area: 10,500 ha

Salt-affected area: > 1000 ha (> 9.5%)

Kwobrup Surveyed cleared area south of Kwobrup Swamp adjacent to the naturally saline, uncleared, broad, flat valley floor. Slope from catchment boundary to valley floor is 0.5%.

Cleared catchment area: 2650 ha

Salt-affected cleared area: 450 ha (17%)

50 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

Nvabing district Surveyed a catchment south of Nyabing flowing southwards to the Coblinine system. Slopes: valley sides 2 to 2.5%, valley floor ≅ 0.5%. Valley floor takes up 55% of catchment.

Dykes are very common. At present, salinity occurs along drainage lines and is only mild. The main drainage line at the base of this catchment is more severely affected.

Catchment area: 3900 ha

Salt-affected area: 375 ha (9.6%)

North Stirling Basin It is estimated that some 10% of the 50,000 ha basin area is presently salt-affected.

It appears that the present salt-affected area within the Great Southern District is higher than the 2% recorded in the 1979 and 1984 census, and is probably in the range 5 to 10%.

Potential saline area

Salinity is likely to spread out from drainage lines to the break of slope in valleys, up drainage lines on valley sides, and dyke and rock-bar seeps are likely to increase.

For the districts considered in the previous section: Approx Approx potential increase potential saline area (%) Konjonup 3 x 30% Broomehill 3 x 30% Kwobrup 3 x 50% Nyabing >5 x 55% N. Stirling 8 x 80%

For the Great Southern district, it is possible that between 30 and 50% of the cleared land could become salt-affected.

51 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

Time

With ‘average’ rainfall and current landuse, some 70% of the potential area could be affected within 20 years, and 95% of the potential area within 30 years.

Strategies

Being adopted • Fencing saltland (2%) • Surface drainage on saltland (1%) • Surface drainage around saltland (< 1%) • Tree planting on saltland for cover and groundwater water-use (1%) • Establishment of salt-tolerant grasses and forage shrubs (1%) • Deep drainage-open drains (farmer’s own design) (<< 1%) • Pumping groundwater from bores, open pits etc. (farmers’ own design) (<< 1%) • Wisalts banks • Treatment prescribed by consultants - pumping, relief wells, deep drainage, etc.

Should be adopted • Farmers concentrate too much on treating the saltland and not enough on the rest of the catchment (which is where the problem is caused). • Farmers should have three aims:

1. Decrease recharge.

2. Increase discharge.

3. Improve production from salt-affected land.

1. Decreasing recharge: • by increasing water-use throughout the landscape - crops, pastures, trees, ‘alternative’ agriculture. Generally, more research is required to define the most suitable and economic approach in specific areas. More extension is required where recommendations can already be made; • by improving surface drainage in areas prone to waterlogging; and • by disposing of excess surface water safely.

2. Increasing discharge: • by engineering means where feasible and economic. More work is required to identify economic methods; and • by biological means, i.e. trees, where feasible and economic.

52 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

3. Improving production of saltland: • by adequate fencing and drainage; and • by establishment of salt-tolerant shrubs and grasses. 4.23 South West Region

This region is covered by the Bunbury, Busselton, Manjimup and Harvey offices and includes the irrigated areas of the Swan Coastal Plain.

Current Status

Australian Bureau of Statistics survey in 1984 indicates that 3090 ha area salt- affected. However, this figure is considered to be a significant underestimate as it was estimated from a survey done in 1986 that about 35% or 6000 ha of the irrigation area was then salt-affected.

Potential Area

There are large areas of the Swan Coastal Plain that are considered to have the potential to become saline. Some 15-20% of the plain is at risk. This represents between 96,000 and 130,000 ha. However there is insufficient knowledge of the hydrology of the area to assess what proportion of this potential will be realized and when it will be realized.

Time to Development Potential

Current expansion of salinity in the area is rapid and a large proportion of the potential could be realized within 20 years.

Strategies

Current

Dryland areas: Surface drainage Trees

Irrigation areas: None with the exception of some limited grain feeding and adoption of laser levelling.

Preferred

Current methods of control involve intensifying surface drainage to reduce waterlogging and, along with fencing, encourage and manage pastures to provide ground cover principally in the late-spring, which is when capillary rise occurs. The aim is to manage the surface soil to encourage flushing of salts and minimize capillary rise by maintaining good ground cover. Over a number of years badly salinized land can be returned to productive pasture.

Trees can be successfully grown on saltland using mounding to improve surface

53 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT drainage and by placing trees on the mounds so that they are away from the main zones of salt accumulation (Angell, K., WADA pers. comm 1987). Puccinellia, a salt tolerant grass, is well suited to the area however this is not being extensively used.

Lack of knowledge of the hydrology of the salinity problem inhibits the formulation of further management options. Considerable hydrogeologic and other resource information are however available for the Swan Coastal Plain which is in urgent need of re-interpretation in relation to the occurrence and distribution of saline soils.

Irrigation Salinity

On-farm water use. Careful water management is needed to obtain the benefits of irrigation without the adverse effects of increased salinity and waterlogging. Good water control ensures that the required amount of water can be uniformly applied when it is needed, without large losses of water to’ the groundwater. For maximum grass production it is generally desirable to avoid water stress by maintaining low soil moisture deficits. Gravity irrigation systems offer less scope than sprinkler or trickle irrigation systems for close control of water applications. Gravity systems can however be modified to allow better water control through the use of laser controlled, precision land-levelling and automated water inlet gates. The move to laser levelling and re-layout of irrigation paddocks has progressed rapidly however automated water controls have not been adopted.

The full benefits of laser levelling are currently not being realized because very little local information exists on required bay dimensions and water application rates to achieve uniform water distribution with a minimum of water loss. Moreover there are no precise local experimental data that enable the determination of the optimum watering frequency or the amount of water required to “re-fill” the soil at each irrigation.

With gravity irrigation systems labour and operating costs are minimized by decreasing the irrigation frequency (resulting in higher application rates per irrigation) but yields and water use efficiency are in general increased by increasing irrigation frequency. There is thus a trade-off between production (frequency of irrigation) and profitability. At current levels of irrigated pasture production and quality it is doubtful that there is incentive to increase irrigation frequency. Only by improving the overall production of the farming system will farmers be able to make the necessary investments in water management systems that will improve water-use efficiency and reduce accessions to the groundwater.

Off-farm distribution system. A restraint to improved on-farm water use and reduced groundwater accessions is the irrigation water distribution system.

The current open channel distribution system was designed to supply water on a fixed rotation basis. A few years ago this was changed and farmers can now receive water on demand within three days of notification. Efficient on-farm water use requires that water be delivered on demand and if an effective water scheduling system causes a concentration of water demand there are some doubts about the capacity of current supply channels to deliver. Introducing greater flexibility into the water supply system inevitably reduces conveyance efficiency. Improved and better

54 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT maintained channel liners will reduce but not eliminate channel seepage. A pipe conveyance system, as installed in the Harvey Irrigation Area, virtually eliminates seepage losses and because the gravitational potential of the supply is harnessed it provides more options for distribution management, on-off controls and irrigation methods. Modernization of the distribution system to this degree, though very water efficient, is expensive. The Harvey scheme, completed in 1987 after nine years of construction, cost $9.2 m or $7500 per hectare serviced. A feasibility study prior to commencement of the project indicated that channel re-lining was more expensive.

Clearly, the injection of such levels of capital into the other irrigation areas can only be economically justified if it is applied to the best soils, allows transfer of water rights to these areas and results in more water efficient and productive farming systems. It is unlikely that this scenario could apply to irrigated grass production or that it would receive broad public acceptance.

Land drainage. To control root-zone salinity levels a sufficient downward flux of water is required to leach salts added in the irrigation water. Heavy winter rainfall assists this process. Beneath permanent pastures watertables need to be maintained between 1.0 to 1.2 m below the surface (Lyle 1984) to prevent salination of the surface over the summer. With cropping systems, where greater soil evaporation can occur, greater watertable depths are needed.

Where efficient water management cannot reduce groundwater accessions sufficiently, for example, where “foreign” water from channel seepage or groundwater discharge impinges on an area, groundwater drainage will be required. Tube drainage requires spacings of about 10-15 m (George, unpublished data) to be effective and is currently uneconomic.

Pumped drainage is also feasible and although initial tests in the Waterloo District were not encouraging, further testing is warranted. Pumped drainage in areas of fresh groundwater, offers the prospect of conjunctive use of groundwater and channel irrigation water. Pumping would involve the de-watering of the Leederville aquifer, a valuable groundwater resource, causing salinity management and groundwater resource management to be in conflict.

Transferable water entitlements. The establishment of an open market in irrigation water should, in theory, result in overall improved productivity of the irrigated areas by shifting water use to the more efficient managers and the more productive and less salt prone soils. Transferable water entitlements would lead to a greater concentration of irrigation on the better soils and possibly exacerbate salinity and waterlogging problems unless excellent water control can be achieved at the same time.

At present the over concentration of irrigation activity is prevented by the even geographic spread of water allocations throughout the irrigation areas and the restricting of irrigation ratings to one-third of the farm.

55 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

4.24 South Coast Region

This region is covered by the Albany, Jerramungup and Esperance offices and includes the Shires of Esperance, Dundas, Ravensthorpe, Albany, Denmark, Plantagenet and Jerramungup.

Current Status

Table 5 presents the data from the 1979 and 1984 Australian Bureau of Statistics saltland surveys.

Table 5. Areas of saltland in the South coast region Area (ha) Ratio 1984 area Shire 1979 1984 1979 area Esperance 2643 3773 1.43 Dundas 75 556 7.41 Ravensthorpe 736 923 1.25 Albany 42 136 3.24 Denmark 10 104 10.4 Plantagenet 1764 2933 1,66 Jerramungup 560* 792 1.41 Total 5830 9217 1.58

* Jerramungup Shire was included in Gnowangerup Shire in 1979. The estimate was made from the Gnowangerup Shire figure.

Potential Area

The A.B.S. figures (which must be treated with caution) indicate that salinity is expanding rapidly in the region. Overall for the region there was a 58% increase in the saline area between 1979 and 1984. The area with the largest potential for increase is considered to be the south coast sandplain. Data from borefields at Mt Beaumont, Cascades, Fitzgerald and North Stirlings. indicate that saline watertables are rising at between 0.3 m/year (Mt Beaumont) and 0.48 m/year (Cascades). The groundwaters in the region are saline to very saline and often with 5 to 10 m of the surface. When these waters get within 1.5 to 2 m of the surface salinity problems will emerge. There is some 1.1 million ha of low gradient land on the south coast and 10- 15% of this could become saline under current land use and climate i.e. 110,000 to 165,000 ha.

Time to Realize Potential

Linear extrapolation of the rates of watertable rise suggest that much of the potential will be realized within the next 30 years. A large area will become saline within the next 10 years - perhaps 75,000 ha.

56 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

Current Strategies

There has been some adoption of high water consumption land use strategies (e.g. lucerne) in the area. A number of farmers are planting trees, some have installed surface and deep drains; a few are planting salt tolerant pastures. However there is little co-ordination, on a catchment basis, although the local Soil Conservation Districts are making significant progress in this area.

Preferred Strategies

The appropriate land management strategy to prevent future salinization involves earthworks to control waterlogging, planting deep, well drained soils to perennial pastures, appropriate agronomic practices on cropping soils and strategic tree plantings on features such as lateritic or rocky ridges and upslope of intrusive dykes.

Methods are available for identifying the -landscape units and progress has been made in devising successful establishment methods of trees and perennial pastures.

Regional Summary Region Area 1984 Potential area Time to (ha) (ha) develop (years) Northern 86,400 600,000 20 Central 91,974 656,000 50-200 Great Southern 62,532 930,000 20 South West 3,090 96,000 20 South Coast 9,217 165,000 10-30

253,213 2,447,000

The potential for salinization is thus estimated to be about 10 times its current extent.

57 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

5. The Cost of Land Salinization

Measurement of the effect of secondary salinization on the land is difficult and estimates available in Western Australia are subjective, memory based assessments.

The latest survey, in 1984, estimated that there were about 255,000 ha of saltland in Western Australia which had been previously used for crops and pastures, representing 1.6 per cent of all cleared land.

Using the 1984 survey-as a base and accepting the lower expansion rate of 5.5 per cent per annum it is estimated that in 1988 there will be 314,575 ha of once productive land salt affected. The gross value of production lost due to land salinity is estimated at $44.2 million based on gross production figure of $140.5/ha/year.

Using the estimated rate of encroachment between 1984 and 1988 the annual loss of land will be 14,900 ha which at $140.5 gross value of production represents an annual decline in the value of production of $2.1 million.

The potential loss of land to salinity is estimated at 2,447,000 ha. (See section on regional assessment of potential for land salinization.) Using a gross value of production of $140.5 per ha/annum the potential production loss is $344 million (in 1988 dollars).

These figures are only for loss of agricultural production. Costs are also substantial in terms of loss of water supplies, loss of amenity and off-site costs such as enhanced rate of deterioration of machinery and appliances.

58 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

6. Salinity Research 1987/1988-

The Salinity & Hydrology Research Branch has responsibility for the majority of the salinity research conducted by the Department of Agriculture. The two relevant objectives of the Salinity & Hydrology Research Branch are: • To identify and quantify the causal agents of salinity and determine appropriate catchment management strategies to obtain production from the affected area, prevent spread of the affected area and reduce offsite effects of salinity. • To identify and quantify the cause and cost of waterlogging and determine appropriate catchment management strategies to obtain production from the affected areas.

Projects being done relevant to these objectives are listed below. More detail of these projects is available in the Division of Resource Management Research Summary 1986.

The research programme is broadly subdivided into five major areas: • Catchment hydrology • Land drainage • Saltland agronomy • Waterlogging • Agroforestry

However, because salinity is a landscape problem, the various facets cannot be clearly separated and thus there is considerable overlap between the sub-divisions of the research programme. 6.1 Catchment Hydrology

1. TITLE: Hillslope hydrology and water balance of areas containing level interceptor banks.

LOCATION: West of Narrogin.

OBJECTIVES:

To determine the water balance of the water held in the channel of level interceptor banks on different parts of a hillside. From this to infer the effect of the banks on waterlogging and salinity, in particular their effect on recharge to deep saline groundwaters.

To quantify where surface and shallow subsurface seepage waters are generated on a hillside and to relate these flows to soil and climatic conditions.

To geologically characterize the study area to help understand the spatial distribution of hydraulic properties and salt storages on the hillside.

59 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

2. TITLE: Surface drainage of clay flats.

LOCATION: North of Lake Toolibin.

OBJECTIVE:

To measure the effectiveness of shallow surface drains at different spacings in removing excess rainfall from heavy clay flats in the Western Australian wheatbelt.

3. TITLE: Salinity investigations of the Arthur River clay flats.

LOCATION: North of Lake Toolibin.

OBJECTIVES:

To understand the distribution of salt affected areas on the Arthur River clay flats north of Lake Toolibin. To determine whether the flats are at risk from salinity. To predict the effect any drainage or flood control works will have on the deep saline aquifer. 4. TITLE: Hydrologic investigations of valley systems in the Kellerberrin Soil Conservation District. LOCATION: Wallatin Creek and North Baandee catchments. OBJECTIVES: To understand the distribution of salt-affected areas in dissimilar valley systems in the Kellerberrin Soil Conservation District. To preduct the likely effect of any soil conservation and flood mitigation works in the valleys on surface water flows, and shallow and deep groundwater levels. To provide input to studies on the economics of alternative soil conservation strategies and on the value of remnant vegetation in wheatbelt areas. 5. TITLE: Seepage interceptor drains for waterlogging control in the ceral crop areas of Western Australia. LOCATION: Narrogin and Mount Barker. OBJECTIVES: To determine the effect of seepage interceptor drains upon the duration of waterlogging of duplex soil in south-western Australia.

To understand the mechanisms whereby seepage interceptor drains control waterlogging, so that the results may be extended to unstudied areas.

To determine the effect of interceptor drains on crop yields.

60 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

6. TITLE: Extend and significance of waterlogging in the Upper Great Southern.

LOCATION: Narrogin.

OBJECTIVE:

To determine the physical extent and economic significance of waterlogging in the Upper Great Southern.

7. TITLE: Quantification of catchment hydrological parameters.

LOCATION: East Perenjori.

OBJECTIVES:

To quantify the components of the hydrological cycle.

To determine methods for management of soil salinity and water logging

8. TITLE: The morphology and hydrological properties of red-brown and other natural hardpans.

LOCATION: Various catchments in the north eastern wheatbelt.

OBJECTIVES:

To describe and classify natural hardpans which occur in the north-eastern wheatbelt.

To identify the role of hardpans in waterlogging/salinity processes.

9. TITLE: Waterbalance of a deep sandy earth.

LOCATION: East Perenjori.

OBJECTIVES:

To measure the components of the waterbalance of a deep sandy earth under different land-uses.

To determine the effects of absorption banks on groundwater recharge.

To determine the interaction between the shallow perched and the deep regional groundwater systems.

10. TITLE: An investigation of the hydrologic processes responsible for the development of sandplain seeps and their effect on regional ground water systems.

LOCATION: Eastern wheatbelt.

61 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

OBJECTIVES:

To define the cause of sandplain seep development and assess their use as a potential stock water supply.

11. TITLE: Hydrology of salinization in the Mallee Road sump.

LOCATION: Fitzgerald.

OBJECTIVE:

To quantify the components of the hydrological cycle in the Mallee Road Sump.

12. TITLE: Crop water use in the Mallee Road sump.

LOCATION: Fitzgerald.

OBJECTIVES:

Establish a farmer size demonstration site to achieve maximum yields in a lupin crop and the following wheat crop, with the aim of encouraging further lupin sowings in the area to maximize landscape water use.

To establish a suitable rotation to maximize water use and yield. Measurements made were rainfall, dry matter, gravimetric soil moisture, silicon analysis, yield.

13. TITLE: Plant silicon content as an index of crop water use.

LOCATION: Fitzgerald.

OBJECTIVE:

To assess the accuracy of plant silicon content as an indicator of seasonal crop water use.

14. TITLE: The effect of lucerne pasture on the groundwater hydrology of a small catchment in the Esperance area.

LOCATION: Esperance.

OBJECTIVES:

To compare the groundwater hydrology and water balance under lucerne and subclover.

To determine the effect of land use on watertables and salinity control.

To collate data for use in water balance simulation models.

15. TITLE: Catchment hydrology - Perillup.

LOCATION: Perillup.

62 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

OBJECTIVES:

To quantify the components of the hydrological cycle.

To determine options available for treatment of the soil salinity in the catchment and the saline discharge into the Kent River.

16. TITLE: Geophysics in salinity research.

LOCATION: Cuballing, W. Narrogin, Frankland River, E. Wagin, Crossmans and Allandale.

OBJECTIVES:

To assess the use of various geophysical techniques in salinity studies.

17 TITLE: Identification and definition of recharge areas associated with secondary salinity in the Upper Great Southern.

LOCATION: Cuballing, W. Narrogin, Crossman, Merredin and Toolibin.

OBJECTIVE:

To establish criteria for identifying and defining relative rates of recharge on different landclasses. 6.2 Land Drainage

18. TITLE: Groundwater pumping to a reclaim a saline irrigation dam.

LOCATION: Frankland.

OBJECTIVE:

To determine the feasibility of groundwater pumping to reduce salt water inflow into a dam used for irrigation.

19. TITLE: Pasture response to improved surface drainage, Vasse Research Station

LOCATION: Vasse Research Station.

OBJECTIVES:

To quantify the response of annual pastures to improved surface drainage in the area represented by Vasse Research Station.

From the pasture response data determine the benefit/cost ratio of pasture improvement and laser levelling.

20. TITLE: Waterlogging control in cropland by drainage.

LOCATION: Mount Barker Research Station.

63 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

OBJECTIVE:

To assess and develop practical methods of drainage for waterlogging control on duplex soils in the high rainfall areas.

21. TITLE: Evaluation of sub-surface drains for reclaiming saltland.

LOCATION: Nugadong, Namban.

OBJECTIVES:

Assess cost and effectiveness of tube drains for reclaiming valley saltland in the wheatbelt.

Develop design and site assessment criteria for tuber drainage of wheatbelt soils. 6.3 Saltland Agronomy

22. TITLE: Effect of temperature and salinity on the germination of saltbushes.

LOCATION: South Perth.

OBJECTIVES:

This trial is part of a programme to screen Atrinlex species and ecotypes for improved forage production from salt affected land.

It aims to screen a number of saltbushes by characterizing the effect of temperature and salinity on their germination.

23. TITLE: Saltbush palatability and recovery from grazing by sheep.

LOCATION: Brookton.

OBJECTIVES:

This trial is part of a programme to screen Atriplex species and ecotypes for improved forage production from salt affected land.

Its aim is to establish if the saltbushes differed in ability to survive and recover from grazing by sheep. A secondary aim is to determine whether sheep have preferences for any of the saltbushes, inferring differences in palatability.

24. TITLE: Survival and growth of saltbushes in the field.

LOCATION: Tammin, Brookton, Katanning, Jerramungup, Busselton,Holleton, Walgoolan, Merkanooka, Bedford Harbour and Cranbrook.

OBJECTIVES:

64 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

These trials are part of a programme to screen Atriplex species and ecotypes for improved production from salt affected land. They aim to characterize and assess the survival and growth of a range of saltbushes planted as seedlings in the field.

25. TITLE: Productivity of saltbushes.

LOCATION: Tammin.

OBJECTIVES:

This trial is part of a programme to screen Atriplex species and ecotypes for improved forage production from salt affected land. It aims to assess the productivity of a number of saltbush species and to evaluate non-destructive methods for estimating biomass production.

26. TITLE: Comparative field establishment of saltbushes.

LOCATION: Tammin.

OBJECTIVES:

This trial is part of a programme to screen Atriplex species and ecotypes for improved production from salt affected land.

It aims to select saltbush species which establish easily by characterizing and assessing their field establishment from seed.

27. TITLE: Establishment of river saltbush selections.

LOCATION: Sturt Meadows Station, North of Leonora.

OBJECTIVES:

To compare six accessions of Atriplex amnicola for establishment on a saline scald in the pastoral zone.

28. TITLE: Comparison of Puccinellia selections.

LOCATIONS: 1. Pintharuka, 2. W. Pithara, 3. Tammin, 4. Merredin, 5. Walgoolan, 6. Cranbrook, 7. Jerramungup, 8. Fitzgerald, 9. Bedford Harbour, 10. Perillup.

OBJECTIVES:

To compare establishment growth and survival of Puccinellia selections on:

a. Low rainfall saline sites

b. Highly saline / waterlogged sites

c. High rainfall saline / waterlogged sites.

65 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

29. TITLE: Land reclamation - North Stirling Soil Conservation District.

LOCATION: North Stirling Soil Conservation District (NSSCD).

OBJECTIVES:

To define the hydrogeology of the NSSCD.

To develop drainage strategies for the district.

To develop land management practices which will halt secondary salinization, improve production and salt-affected land, reduce run-off, and prevent wind erosion.

30. TITLE: Salt lake water balance, North Stirling.

LOCATION: North Stirlings.

OBJECTIVES:

To define and quantify the hydrological systems operating on a lake in the North Stirling SCD.

31. TITLE: Varying niche height to prevent waterlogging affecting the establishment of three Atriplex species.

LOCATION: North Stirling SCD.

OBJECTIVES:

To determine whether increasing niche height improves establishment of Atriplex amincola, A. undulata and A. cinerea in waterlogged areas.

32. TITLE: The economics of saltland agronomy.

LOCATION: South Perth.

OBJECTIVES:

To illustrate how bioeconomic models can be applied to analyse soil conservation problems.

To estimate the potential economic benefits of growing saltbush on salt-affected land.

To identify how saltland agronomy can be integrated into the farm system.

33. TITLE: The effect of seedbed coating on the establishment of three Atriplex species.

LOCATION: North Stirling SCD.

66 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

OBJECTIVES:

To determine the effect of black latex paint coating treatment on the establishment of Atriplex amnicola, A. undulata and A. cinerea. 6.4 Waterlogging

34. TITLE: Waterlogging and growth of wheat in the field.

LOCATION: Muresk Institute of Agriculture.

OBJECTIVES:

To study effects of waterlogging on the growth of wheat under field conditions. Emphasis is being placed on assessing the effects of waterlogging on N- nutrition.

35. TITLE: Salt/waterlogging interactions in wheat.

LOCATION: South Perth.

OBJECTIVES:

To establish how salinity, waterlogging and the interaction of these factors affect the growth and ion relations of wheat. 6.5 Agroforestry

36. TITLE: Assessment of recharge reduction by managing trees and shrubs for oil and fodder production.

LOCATION: Wongan Hills Research Station.

OBJECTIVES:

To assess the ability of different tree species managed for oil and fodder production to use rainfall by interception and transpiration thereby affecting the recharge or deep drainage component of the water balance.

To assess the ol and fodder production of different tree species.

To use the results to make recommendations about planting of trees on recharge areas of catchments with a salinity or waterlogging problem.

37. TITLE: Hydrological effect of Tagasaste.

LOCATION: Bokerup.

OBJECTIVES:

To estimate the hydrological impact of Tagasaste on the landscape.

67 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

38. TITLE: Afforestation of a saline catchment.

LOCATION: East Brookton.

OBJECTIVES:

To determine whether a belt of trees will effectively intercept groundwater and thereby prevent further saline encroachment.

39. TITLE: Investigation of agricultural and agroforestry management systems to minimize salt encroachment in cropping and pasture land in the entral and western wheatbelt of Western Australia.

LOCATION: Boundain (25 km east of Narrogin).

OBJECTIVES:

To determine the effect of trees planted in an agroforestry design on a saline groundwater table.

40. TITLE: Tree density on pasture production.

LOCATION: Bowelling.

OBJECTIVES:

To evaluate Tagasaste as an alternative to replanting parts of the Wellington Dam Catchment back to eucalypts, thus maintaining the same agricultural productivity in the region.

To meet this objective a number of secondary objectives have to be realized:

(a) to evaluate Tagasaste as a fodder tree;

(b) to investigate the water use of Tagasaste;

(c) to assess the practicability of agroforestry farming Tagasaste;

(d) to determine the effect of tree density on pasture production.

41. TITLE: Agronomic manipulation in the Collie River Catchment.

LOCATION: Bowelling, 35 km east of Collie.

OBJECTIVES:

To evaluate the comparative annual transpiration rates of crop and pasture species suitable for areas of greater than 500 mm annual rainfall.

68

SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

Summary Of Expenditure By Department Of Agriculture On Salinity Research1980/81 - 1987/88

Saltland Hydrology, Research Total agronomy drainage and laboratory regional research

$$ $$

1980/81 -- -53,554*

1981/82 110,935 220,956 65,153 397,044

1982/83 125,805 303,580 86,668 516,053

1983/84 149,656 328,014 97,567 575,237

1984/85 179,151 414,719 113,263 707,733

1985/86 183,747 490,774 135,596 810,117

1986/87 214,045 459,990 148,958 822,933

1987/88 204,000 429,000 149,700 782,700**

* Salary is not included

** Estimated budget for 1987/88

70 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

7. Saltland Management, The Catchment Approach

One of the stated objectives of the Salinity and Hydrology Research Branch is “To identify and quantify the causal agents of salinity and determine appropriate catchment management strategies to obtain production from the affected area, prevent spread of the affected area and reduce offsite effects of salinity” (Annual Report of the Commissioner of Soil Conservation and Division of Resource Management, Department of Agriculture 1986/87).

This objective recognizes that salinity is a catchment problem and that any ameliorative measures must be catchment based. It is patent that there are no simple solutions to land salinity; the solutions lie in addressing the landscape water balance by reducing recharge and increasing discharge. This control of the landscape water balance must be achieved while maintaining the productivity of the land; be that productivity in terms of agricultural produce, water resources or public amenity.

The Department of Agriculture has adopted the catchment approach to saltland management. A catchment is considered to be a continum of management units within the natural watershed. With specific reference to salinity the catchment is broadly subdivided into two units - a discharge area where the vertical component of the hydraulic gradient is upwards and a recharge area where the vertical component of the hydraulic gradient is downwards. Nulsen (1984) in detailing the catchment approach to saltland management refers to the discharge area as “on-site” i.e. saline and the recharge area as “off-site”.

Management strategies have been developed by the Department for both discharge and recharge areas. The combination of strategies applicable to a particular catchment depends on the characteristics of the catchment. 7.1 Water is the Real Problem

When land is developed for agriculture a number of changes occur in the water balance of the landscape. The unseen change in the water balance after clearing is the decrease in plant water use and increase in the amount of water draining deep into the soil beyond the plant root zone. The extra quantity of water moving as deep drainage is small (20 to 80 mm/year) but it is this water that dissolves the salts stored in the landscape, causes a rise in the deep watertable and eventually causes the salinity problem. A more obvious change in the water balance after clearing is an increase in surface runoff. This is accompanied by an increase in shallow sub-surface seepage and the two processes can cause severe waterlogging problems in the valley floor.

Water flows in the landscape can be considered as two systems - a shallow system (surface runoff and shallow sub-surface seepage) and a deep system (deep drainage). The shallow system contains most of the water but is very low in salt; the deep system has relatively little water but has a high salt content.

Both systems must be managed to control the salinity problem. It is possible to manage both water systems and the management methods are not necessarily

71 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT complex or expensive. However, effective management requires an understanding of the processes occurring and an understanding of where in the landscape these processes operate. 7.2 Problem Definition

Before any management strategies can be effectively applied, the problem must be properly defined. Different strategies will be required if, for example, the problem is essentially a waterlogging problem than if it is caused by saline groundwater being forced towards the surface by a clay or rock bar. Problem definition requires an understanding of the waterflows in the landscape surrounding the saline area. Considerable investigation and observation is frequently necessary. 7.3 The Importance of Catchment Management

Appropriate management of saltland depends on the climate, hydrology, soils and economics pertinent to the specific piece of land. The management objective can either be to produce food, fuel or forage from the saltland, or to reclaim the saltland to allow production of non salt tolerant species. In most situations reclamation is a slow process and some form of production from the saline land should be an interim objective.

To obtain production from saltland it is necessary to improve both the physical and chemical conditions of the soil to permit plant growth. The improvements necessary can rarely be achieved simply by working on the salt affected area itself. It is often necessary to modify the land use on the catchment area above the saltland. Remember that the two water systems causing the problem originate some distance from the saltland. Thus the problem of management of salt affected land becomes one of catchment management, requiring manipulation of the environment of an area many times the size of the affected land. 7.4 Management of Recharge Areas

The objective of treatments on recharge areas is to reduce recharge. This can be achieved by increasing plant water use and by diverting excess water from the area so as to prevent ponding and ephemeral waterlogging. 7.5 Strategic Clearing

In areas not yet cleared strategic retention of native vegetation may be desirable if it is known that clearing certain areas will have a serious effect on salinity. Identification of areas which should not be cleared is difficult but recent advances in applying geophysics to salinity problems may provide an answer (Engel et al.1987). Certainly areas immediately upslope of intrusive dykes, which can be identified with a magnetometer, should not be cleared. Similarly areas high in the landscape with low bulk electrical conductivity, as identified by electro-magnetic induction techniques, should be considered for retention.

72 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

7.6 Replanting Trees and Shrubs

There is ample evidence in Western Australia that replanting recharge areas to trees and shrubs reduces recharge. Greenwood et al.(1985) found that at North Bannister the annual evaporation from trees (Eucalyptus cladocalyx, E. globulus and E. maculata) was some seven times the evaporation from grazed pasture.

A major replanting programme has been undertaken by the Water Authority in water supply catchments of the Darling Range. Watertables have been lowered under plantations in the Mundaring and Collie catchments.

Planting trees and shrubs on recharge areas of agricultural catchments is advocated by the Department of Agriculture. While it is not economic to indulge in large scale plantings, there are often areas in catchments which can be identified as “specific recharge areas” (Nulsen, 1984) which are small, make a major contribution to recharge and do not produce economic crops or pastures which should be planted to trees or shrubs. 7.7 High Water Use Crops and Pastures

Recharge can occur over a large proportion of a catchment. For example, Nulsen and Baxter (1982) identified 25% of a catchment east of Wongan Hills as being a significant recharge zone. Given that these areas cannot be economically planted -to trees or shrubs then it is essential that broad area strategies be adopted to reduce recharge.

Nulsen and Baxter (1982) outlined the potential of agronomic manipulation of the landscape water balance for controlling salinity. They showed that, for instance, a cereal lupin rotation contributed less water to recharge than a cereal-sub.clover pasture rotation. Farmers have adopted, for economic reasons, a cereal lupin rotation in much of the wheatbelt and there is evidence that saline seeps are drying up as a result (R. George, 1987, pers. comm.).

Perrenial pastures can be very effective in reducing recharge. Nulsen and Baxter (1987) reported that for the twelve month period from December 1984 to November 1985 at Gairdner River a rotationally grazed stand of lucerne cv.

Trifecta used 433 mm of water compared with the 231 mm used by the adjacent Osprey wheat crop. Rainfall for the period was 384 mm.

Lucerne has been used successfully in North America to dry saline seeps (Miller et al., 1981).

73 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

7.8 Tillage Practices to Maximize Crop Water use and Minimize Run-off Intensity of tillage has different effects with different soil types. On a deep loamy sand, Hamblin and Tennant (1981) found that differing tillage intensities caused differences in the water release curves on the top 0.1 m of the profile in the first year; these differences persisted through the three years of measurement. These differences in water release affect water use by plants. Hamblin et al.(1982) measured cumulative water use of wheat with three tillage practices, disc ploughing (DP) followed by a single pass with a scarifier and combine drill seeding, direct drilling with a combine seeder (CDD) after one spray of paraquat-diquat herbicide, and direct drilling with a triple disc drill (TDD) after spraying as above. After the first 60 days of growth, the DP treatment used significantly more water than either the CDD or TDD treatment. Total water use for the 130 day sampling period was 175 mm for the DP treatment, 160 mm for TDD and 164 mm for CDD. Thus for the conditions prevailing during this experiment, tillage treatments caused nearly 10% difference in water use. Since the experiment was done on well drained loamy sand, the lower water use associated with the TDD and CDD treatments translates to an increase in recharge. 7.9 Fertilizer Regimes to Maximize Crop Water Use It is well established that the level of nutrition influences plant growth. Nitrogen nutrition of cereals growing on well drained soils has a significant influence on production of leaf area and, since there is a relationship between leaf area and transpiration rate, an influence on water use. Halse et al. (1969) sowed wheat on a loamy sand at Wongan Hills, Western Australia, with three levels of nitrogen nutrition at sowing, 0, 56, 112 kg N ha-1 at sowing; the latter treatment had further N applications of 112 kg ha-1, 5 and 12 weeks after sowing. The maximum photosynthetic area index for the three treatments were 0.9, 2.6 and 5.8 respectively. Corresponding grain yields were 887, 1770 and 2980 kg ha-1. Using the approach of Tennant (1980) that 100 mm of rainfall is required for grain set and each additional mm produces 10 kg ha-1 of grain, the respective water requirements for the three treatments would have been 188, 277 and 398 mm. Because of diminishing returns per unit of fertilizer applied at high rates, luxury nutritional levels are not normally economic. However, if the management aim is to maximize water use on potential recharge areas, then the economic analysis might be different. 7.10 Management of Discharge Areas The aim of discharge area management is to obtain production from the area and, in conjunction with recharge area management, stabilize or reduce the area affected by salinity. Production from the discharge area can either be via salt tolerant shrubs or pasture or, with reclamation, via “normal’ agricultural species. Treatments applied on, or immediately around, discharge areas can either be engineering such as drains or banks or biological such as shrubs, grasses or trees. Usually a combination of both engineering and biological treatments is most effective.

74 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

7.11 Drainage In the wheat belt of Western Australia, drainage systems have been installed at a number of locations. The drains range from open channels 2.0 m deep to buried, slottled, plastic tube with a gravel envelope. All sites were subject to both waterlogging and salinity and it is not possible to apportion the results to amelioration of one or the other. For example, at Esperance Downs Research Station, sub-surface drains were installed in 5 ha of salt land at a depth of 1.5-1.7 m with a 40 m spacing (George and Lenane, 1982); in addition a single “W” drain was constructed through the drained area. During the winter of 1982, 354 mm of rain fell on the 5 ha drained area, equivalent to 17,700 m3. Only 1283 m3 (7%) discharged through the deep drains. The area produced a 1.8 t ha-1 barley crop which might be expected to transpire some 200 mm of water or 10,400 m3. Hence 6400 m3 of water falling on the 5 ha site is not accounted for; this presumably left the site as overland flow via the surface “W” drain. Thus 17% of the water leaving the site did so via the deep drains and the remainder (83%) via surface flow. While it has not been possible to assign benefits to one treatment or the other, the total treatment has been effective in returning the salt affected land to production. 7.12 Trees as Pumps Trees planted immediately on the margin of the saline areas have been shown to lower the watertable below the critical depth at some locations. The Water Authority has achieved acceptable results with lower landscape plantings in the eastern Collie catchment. At Boundain Engel (1987) pers. comm.) achieve a 2 m lowering of the watertable after five years with tree densitites as low as 83 stems per ha. Negus (1988 pers. comm.) obtained similar results to Engel at a site east of Brookton. Saline sandplain seeps in the eastern wheatbelt have been successfully dried up by planting a strip of trees immediately above them (R. George, 1987 pers. comm.). There is a definite role for trees in discharge areas to control groundwater depth. Some debate exists as to the longevity of trees in these situations and only time will resolve this debate. 7.13 Production from Halophytes Saltland in the agricultural areas of Western Australia can, if sown to suitable salt tolerant species, produce feed for stock on a regular basis which gives a positive economic return to the farmer (Salerian, 1987). The Department has devoted considerable resources over a number of years to select appropriate species and develop establishment techniques for revegetation of saltland. The current recommendations are summarized in a Farmnote by Malcolm 1986 some of which is extracted below: Factors to consider when deciding on a grazing plant for a particular type of saltland are the severity of salinization of the site and the degree to which waterlogging or flooding occurs.

75 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

7.14 Site Severity On most saltland the severity of “salting” is assessed by observing the species of “volunteer” plants present and the proportion of the area these plants cover. This plant cover may also be affected by seasonal conditions, cultivation and stock grazing intensity. It is convenient to divide Suitland into three categories: mild, moderate and severe. • On mildly affected saltland the usual plant is Mediterranean barley grass (Hordeum geniculatum), often called sea barley grass in Western Australia. Plant species sensitive to salt such as subterranean clover, barrel medic and capeweed are usually absent but annual ryegrass and woolly clover can be present. There may be some plants of sand spurry (Spergularia rubra), curly ryegrass (Pholiurus incurvus), ice plant (Mesembryanthemum nodiflorum), Plantago spp. and Cotula spp. On mildly salt affected soils, plants usually cover the whole area. • On moderately affected saltland the plants are usually Mediterranean barley grass, annual ryegrass and woolly clover amongst areas of bare ground. • On severely affected saltland the only plants present are sand spurry, curly ryegrass, iceplant, samphire, Plantago spp. and Cotula spp. After grazing by stock these areas are usually completely bare. If site severity cannot be assessed from the colunteer plant cover, the salt affected areas can be sown to an ‘indicator’ crop like barley or oats. • Mild areas may give a profitable return only is seasonal conditions are favourable, that is, a good opening rain for germination, no winter waterlogging and good finishing rains. • Moderate areas will not give a profitable crop even in favourable seasons. • Severe areas will not mature a crop at all. The site severity is usually related to the depth below the soil surface of saline groundwater (watertable). In a sandy soil the groundwater must be much closer to the surface than in a loamy soil to cause the same severity of ‘salting’. Typical depths to groundwater for the three classes of saltland severity are: Severity of saltland Depth* to saline groundwater Mild More than 1.6 m Moderate 0.8 to 1.8 m Severe 0 to 1.1 m

* This is only a guide as it varies with season and soil type

There is some overlap in the depth to saline groundwater between the classes of saltland severity. The depth to saline groundwater can vary between the seasons within the year. On some soil types, for example Morrel, severe salting may occur without any watertable.

76 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

7.15 Waterlogging and Flooding

Saltland sites may be permanently waterlogged due to seepage or seasonally waterlogged (usually in winter) due to shallow groundwater and excess water on the soil surface. Before planting species on saltland, minimize waterlogging by installing surface drains and contouring the catchment above’ the area.

The severity of waterlogging is best assessed by its duration. Salt tolerant forage plants are rarely killed by ‘flash’ floods, but when the soil surface is waterlogged for several weeks some species die. Few species survive when waterlogged for several months. 7.16 Salt Content and pH of Soil

It is necessary to confirm that salt is a problem by taking soil samples from 0 to 15 centimetres and from 15 to 30 centimetres below the soil surface from an area of bare soil during summer. Salinity is confirmed if at least one of the samples has above 0.2 per cent chloride or an electrical conductivity above 140 millisiemens per metre (mS/m) when measured in a 1:5 soil:water suspension. It is also necessary to check the pH of the samples - readings below 5.0 are associated with poor establishment of Puccinellia and poor survival and growth of shrubs.

Since the salt content of soil can vary greatly it is not useful as a guide to species selection. Volunteer or indicator plants serve as the best guide as these reflect the combined effects of soil salinity and other factors. 7.17 Salt Tolerant Plants for Grazing

• Barley (six-row) will tolerate mild salinity. Areas that no longer grow a profitable barley crop due to salinity may be planted to salt tolerant plants for grazing. • Paspalum (Paspalum dilatatum) is a perennial grass with mild waterlogging and salinity tolerance. • Strawberry clover (Trifolium fragiferum) will tolerate waterlogging and mild salinity. It will grow on the perimeter of relatively fresh seepage areas. • Tall wheat grass (Agropyron elongatum) is a perennial grass of moderate salt and waterlogging tolerance. It grows on the mildly and moderately affected pasts of saltland in areas receiving more than 375 mm annual “rainfall. It grows best in spring and summer on moisture from groundwater (not too saline) or rainfall. • Salt water couch (Paspalum vaginatum) is a summer growing grass, highly tolerant of salt and continuous waterlogging. It grows well in areas permanently wet by seepage but is not suited to salt lakes or samphire flats. It can prevent soil erosion in creeks and on hillside seepages. It may be used as a lawn grass. • Puccinellia (Puccinellia ciliata) is a winter growing perennial, tussock-forming grass highly tolerant of salt and waterlogging. It will grow on all salt affected soils in areas receiving more than 375 mm of annual rainfall. In drier areas its growth is less reliable.

77 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

• Bluebush (Maireana brevifolia) is a highly salt tolerant perennial shrub. It is sensitive to waterlogging and should not be planted if there is danger of being flooded for more than two to three days. • Wavy leaf saltbush (Atriplex undulata) is a highly salt tolerant perennial shrub. It is moderately tolerant to waterlogging. It will survive several weeks on a flooded site in winter. The branches can form roots where they rest on the ground thus aiding recovery from grazing and control of soil erosion. • River saltbush (Atriplex amnicola) is a highly salt tolerant perennial shrub. It is slightly more waterlogging tolerant than wavy leaf saltbush. The branches form roots readily and recovery from severe grazing is excellent. • Samphire (Halosarcia spp.) is represented by several species. All are highly tolerant of salt and waterlogging and will grow to the edges of salt lakes. The plant material has a high salt content but may be grazed by sheep provided other feed such as stubble or dry annual pasture is available.

Many farmers throughout the State are planting and using salt tolerant shrub and pasture species. Malcolm (1986) reported on a number of farms for which some grazing data were available. These were:

Mr O. Mott of Moulyinning has grazed sheep on about 800 ha of samphire regularly since the 1950’s. The samphire is grazed in conjunction with eight adjacent stubble paddocks in autumn and is a valuable feed reserve.

In autumn 1985, Mr P. York of Tammin put 2000 hoggets into a 24 ha paddock of morrel saltland growing bluebushes and saltbushes for several years. The bushes had been grazed in earlier years but because of a feed shortage in 1985 sheep were allowed to strip the bushes completely. The sheep went into the paddock in store condition, stayed one month, received no supplementary feed and were removed in store condition. This is equivalent to 2510 sheep grazing days per hectare, all at a time when other feed was extremely scarce. The bushes recovered well.

Mr K. Diamond of Maya has established 200 ha of wavy leaf saltbush over the past six years. The saltbush is grazed during crop seeding time to avoid the inconvenience of hand-feeding sheep at a busy time. As a result of having the saltbush his property can support an additional 800 sheep, (equivalent to 1460 sheep grazing days per hectare). Mr Diamond’s strategy allows him to defer grazing annual pastures early in the season, enabling them to grow and provide better grazing later.

Mr N. Jones of Ejanding has about 170 ha of bluebush. In 1984-85, 40 ewes grazed a 16 ha paddock of bluebush and another 70 ewes grazed a 28 ha paddock of bluebush. A stud ram was added to each paddock and the ewes and resulting lambs remained in the paddocks for eight months. Excellent lambs were produced.

Mr B. McGellin of Korbelka has about 150 ha of saltland growing bluebush and samphire. Each year in mid-March he puts 1500 pregnant ewes into this area for six weeks. The lambs are marked when the sheep are removed.

Mr D. Endersbee of Korbelka has about 240 ha of saltland carrying samphire, old man saltbush (A. nummularia) and bluebush. In November each year he puts 800 to

78 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

1000 young sheep into his saltland and removes them in good condition after five to six months. 7.18 Conclusion

Management strategies are available which will obtain production from the saline area, reclaim the saline area, minimize the rate of spread of the area or prevent areas becoming saline. These management strategies involve management of the landscape water balance and management of the saline area itself.

No adequate management strategy can be applied unless the factors causing the salinization are at least qualitatively understood; quantification of these factors will result in more efficient and more effective management. Once the problem has been defined, a combination of appropriate management strategies can be applied.

79 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

8. References Advisory Committee of Purity of Water (1977). ‘A study of catchments and recreation in Western Australia’ Compiled by the Working Group on Catchments and recreation. (See Darling Range Study Group, (1982).) Anderson, G.W. (1979). Research on agroforestry. In Proceedings of Agriculture and the Environment in Western Australia, pp. 67-68. (WAIT: Perth) Anderson, G.W. and Batini, F.E. (1980). Integrating agriculture and forestry. In ‘Land and Stream Salinity Seminar - Western Australia, November 1980’. (W.A. Government Printer) Annual Report of the Commissioner of Soil Conservation and Division of Resource Management (1986-87). W. Aust. Dept. Agric. Perth 1987. 132 p. Anon. (1982). An assessment of interceptor banks (Saline land management) Journal Agriculture. 23(4) P.134-135. Australian Bureau of Statistics (1979-1987). Consumer Price Index - Cat. No. 6401.6 Australian Printing Government Printing Service. Barrett-Lennard, E.G. (1984). Waterlogging in cereals in Western Australia. In: Climate and Wheat Yields. Proceedings of a symposium in Perth, February 17, 1984. Rural and Allied Industries Council, Perth, Western Australia, pp. 11-17. Barrett-Lennard, E.G. (1986). Effects of waterlogging on the growth and NaC1 uptake by vascular plants under saline conditions. Reclam. Reveg. Res., 5: 245-261. Barrett-Lennard, E.G., Leighton, P.D., McPharlin, I.R., Setter, T., and Greenway, H. (1986). Methods to experimentally control waterlogging and measure soil oxygen in field trials. Aust, J. Soil. Res., 24: 477-483. Barrett-Lennard, E.G., Malcolm, C.V., Stern, W.R.S., and Wilkins, S.M. (1986). “Forage and Fuel Production from Salt Affected Wasteland”. Proceedings of a Research for Development Seminar, 19-27 May 1984, at Cunderdin, Western Australia. Elsevier, Amsterdam, 459 pp. Barrett-Lennard, E.G., and Dracup, M. (1986). A porous agar medium for improving the growth of roots under sterile conditions. Plant Soil (in press). Barrett-Lennard, E.G. (1986). Waterlogging and wheat growth on saline soils. Agric. W. Aust, 27: 117-118. Bartle, J.R. (1982). Water use by trees and its application to salinity control. (Wind breaks; farm forestry). In: Proc. Trees in the Rural Landscape, Perth, W. Aust. Forest Dept., 1982, p. 156-170. Basco, A. and Fekete, J. (1968). Salt balances in irrigated meadow chernozems. Kiserl. Kozl., 61A 27-50. Batini, F.E., Selkirk, A.B. and Hatch, A.B. (1976). Salt content of soil profiles in the Helena Catchment, Western Australia. Forest Department of Western Australia, Research paper No. 23. Batini, F,E., Hatch, A,B. and Selkirk, A.B. (1977). Variations in level and salinity of perched and semi-confined groundwater tables, Hutt and Wellbucket

80 SALINITY IN WESTERN AUSTRALIA – A SITUATION STATEMENT

experimental catchments. Forest Department of Western Australia. Research Paper 33. Bennett, D., Thomas, J.F., Davies, H.L. and Downes, P.A. (1982). Model output and implications. Chapter IV. In ‘On Rational Grounds’ (Eds. D. Bennett and J.F. Thomas), pp. 68-116. (Elsevier: Amsterdam). Bennett, D., Thomas, J.F., Batini, F.E., Havel, J.J. and MacPherson, D.K. (1982). Background to the study. Chapter I. In ‘On Rational Grounds’. (Eds. ID. Bennett and J.F. Thomas), pp. 1-24. (Elsevier: Amsterdam). Bennett, ID., Havel, J.J., McArthur, W.M., Batini, F.E. and Murray, A.M. (1982). The Murray River catchment. Chapter II. In ‘On Rational Grounds’. (Eds. D. Bennett and J.F. Thomas), pp. 25-39. (Elsevier: Amsterdam).

Berryman, ID. and Frith, J.L. (1983). Reverse osmosis - a tool for improving water

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