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5. Perception of increasing salinity associated with the irrigation of the murray valley in south Australia

Michael Butler

Introduction

Along the River Murray Valley in South Australia (Fig. 5.1), irrigation activities have resulted in several types of environmental disruption which, while not directly life threatening, have caused reduced livelihood levels and/or change in the livelihood of farmers through deterioration of soil quality. In addition, because of the steadily increasing salinity gradient downstream, irrigators in the lower reaches of the river have been forced to use water of undesirably high salinity. There has been considerable damage to crops and orchards in irrigated areas during periods of high salinity. Highly saline water piped from Mannum to Adelaide (the capital city of South Australia) for domestic consumption has caused serious problems for industry and has affected domestic gardens. In the sense of the definition above, salinization can certainly be seen as contributing to the process of desertification in South Australia.

This paper is concerned with the human dimensions of the salinization problem in South Australia. The perception of the problem and of the range of alternatives available for the management of the problem is investigated by questionnaire survey of irrigation farmers along the Murray in South Australia, of Adelaide residents, and also of relevant government officials. The study highlights human perception as a critical variable in the desertification process. It also suggests that success in the battle against desertification can only be gained by altering perception through effective education.

The Murray Valley in South Australia

South Australia is the driest state in Australia and Australia is the driest continent in the world. Only 3 per cent of the state receives an annual rainfall over 500 mm (20 inches) while 83 per cent gets less than 250 mm (10 inches). The River Murray in South Australia is 700 km long but is the state's only major river, and a large part of South Australia relies on it wholly or partly for its water supply. Metropolitan Adelaide, the Mid-North, upper Yorke Peninsula, the industrial cities at the head of Spencer's Gulf, the upper South-East, and domestic and stock users along the river are all supplied wholly or partly from the Murray. Irrigators along the Murray Valley are totally dependent upon the river for irrigation water used on vines, trees, pastures, and vegetables. In all, the river supplies about 66 per cent of the state's consumption in an average season, but this can rise to approximately 83 per cent in a dry season (Engineering and Water Supply Department 1977a).

The River Murray in South Australia is 700 km long (Fig. 5.1). The Murray Basin in South Australia is underlain by a considerable thickness of Tertiary marine limestone, which in turn is capped by fresh-water riverine and lacustrine deposits which may reach 60 metres in thickness. The surface characteristics of the basin are strongly related to a series of Pleistocene and Recent aeolian deposits laid down as a series of east-west sand dunes. These sand dunes represent the rearrangement by prevailing westerly winds of littoral deposits left by the retreating sea in Tertiary times (Sprigg 1952). This sand dune country on both sides of the river valley from the Victorian border to Murray Bridge is known as the Murray Mallee and takes its name from the eucalypt vegetation known as mallee . Much of this mallee vegetation has been cleared for agricultural purposes (see chapter 4), but remnants of it remain along roadsides and on some of the larger dunes.

Along much of its course in South Australia, the River Murray is incised into the underlying Tertiary limestone, producing vertical cliffs. The area available for intensive agricultural development is restricted to relatively narrow alluvial flats on the insides of meander bends or in the loops of abandoned meanders. The other alternative is to irrigate the sandy mallee soils at the top of the cliffs. Of the 35,000 ha of irrigation along the River Murray in South Australia, 10,000 ha are within the valley itself, and the remaining 25,000 ha are on the highland soils adjacent to the river valley (Cole 1977).

Cole (1977) divides the Murray Valley Proper in South Australia into three tracts (Fig. 5.1). Tract 1 consists of the swamps, once permanently flooded, which occupy the first 90 km of the river valley upstream from the mouth. Tract 2 is defined as the predominantly low terrace soils of the narrow river valley upstream from the swamps to Overland Corner. Tract 3 is composed of the high and low terrace soils of the river valley from Overland Corner to the Victorian border.

FIG. 5.1. Study Area in South Australia

The heavy clay soils of the reclaimed swamps of Tract 1 are high in organic matter, and while the level of irrigation management is low, they have remained productive through 80 years of irrigation. The low terrace soils of Tract 2 are saline gray clays with poor physical properties and are subject to flooding. Consequently, agricultural use is limited. In Tract 3 about 15 per cent of the area is high terrace, having clay soils with sand layers at depth and at the surface. The horticultural areas of Renmark, Cobdogla, and Berri are established here.

The higher mallee soils at the top of the cliffs are characterized by some variability as both salt and clay have been redistributed during wetter climatic periods. There was a movement of salt and clay particles out of the higher parts of the ridges and a corresponding accumulation in the lower troughs (Gutteridge, Haskins, and Davey 1970, 14). The general pattern for these higher ridges, then, is for sandy, well-drained ridges alternating with saline, clayey depressions.

The groundwaters are generally highly saline in the area through which the River Murray passes in South Australia. Salinities are often higher than the salinity of seawater. The regional groundwater trend is towards the river through aquifers of medium transmissibility, notably the Loxton Parilla-Diapur sands and the Morgan and Mannum limestones, and the deep incision of the river allows considerable inflow.

The Settlement Process

Aboriginal people lived along the River Murray for over 30,000 years. They lived in harmony with their environment and did not put any undue pressure on the hydrologic system.

Over the last 150 years western man has made increasing demands on the river and has considerably altered both the hydrological and ecological systems.

At first, in the absence of alternative modes of transport, the River Murray was seen as an important avenue of trade, and from 1850 to 1905 the river was plied by paddle steamers transporting supplies to settlers and bringing wool and other products to the ports. With the advent of competing railways, navigation rapidly declined so that by the beginning of the twentieth century, navigation was all but over.

After the very severe droughts of 1880 caused the abandonment of large areas which had unwisely been taken up in the north of the state, South Australians began to look for land which was associated with a guaranteed water supply IWilliams 1974, 147). This was at a time when irrigation was being actively talked about, and this seemed to provide the answer. None of the rivers and streams originating in South Australia were suitable for large-scale irrigation projects, and so irrigation developments have been concentrated along the River Murray.

In 1881 Governor Jervois reclaimed 3,300 acres (1,335 ha) of swampland along the Murray near Wellington. This was followed by a further reclamation of 650 acres 1263 ha) at Woods Point in 1882. Five years later an agreement was entered into between the government of South Australia and the Chaffey brothers from America for the establishment of private irrigation works near Renmark.

During unemployment troubles in 1893, the government authorized the formation of a number of village settlements, run on community lines, and 11 of these were established in the Upper Murray district (Tract 3 in Fig. 5.1). For a variety of reasons most of these settlements failed. Lyrup settlement is the only one remaining and is at present run on a cooperative system of water supply with individual settlers having independent holdings on perpetual lease. After 1896, most of the other settlements were dissolved, or reorganized by the government. From then until very recently almost all irrigation developments were government sponsored. In 1908 a new settlement was established at Berri, and first allotments were made in 1911, followed by Cobdogla in 1918. In 1912, 2 of the village settlements, Waikerie and Ramco, were incorporated as a Government Irrigation Area, and some years later Holder was included.

The government reclaimed and subdivided more swamps along the lower reaches of the Murray in 1904. Work commenced with the Burdett and Mobilong areas and extended into other areas, so that by 1929 most of the suitable swamplands between Mannum and Wellington had been reclaimed and settled (Engineering and Water Supply Department 1970, 2).

After World War I, Soldier Settlement areas were developed in the Cobdogla, Waikerie, and Berri areas and in new areas at Cadell, Chaffey, and Block "E" of Renmark. No further government areas were developed for horticultural purposes until after World War I I, when Loxton Irrigation Area and the Cooltong Division of the Chaffey Area were developed as War Service Land Settlement schemes.

In 1923, about 12 years after irrigation had been commenced in the Berri and Moorook areas, it was found necessary to introduce drainage schemes because of problems with waterlogging and salinity. In the 1920s the whole Cadell Area was drained, and in the 1930s and 1940s comprehensive drainage schemes were installed in most areas. Many government irrigation areas are now supplied with drainage, including Chaffey, Loxton, Berri, Cobdogla, Moorook, and Cadell. Drainage schemes are also being installed in the Renmark Irrigation Trust Area and the Lyrup Village District.

Irrigation Methods

Irrigation is confined to two main types, one involving high lift pumping (Tracts 2 and 3 in Fig. 5.1), and the other gravity flood irrigation in the reclaimed swamp areas in the lower reaches. Due to the high valley sides it is not possible to command large areas for irrigation by means of gravity channels utilizing the natural fall of the river.

At a typical high lift irrigation settlement there is a main pumping station, operated by electricity, on the bank of the river. The water is lifted from the river to heights of 30 metres or more and is run into the main channel, which may be 3 or 6 metres wide. From the main channel, subsidiary of "block down" channels are given off.

The settlers' holdings in the older settlements usually include 10 to 20 acres (4 to 8 ha) of water ratable land, but in the newer settlements at Loxton, Cooltong, and Loveday they vary from 20 to 30 acres (8 to 12 ha) with a few over 30 acres. There is no limit to the area of land or the number of sections which may be held, but that area of ratable land which one person may hold is limited to 50 acres (20.2 ha).

The reticulation of the settlement is so arranged that a main channel or pipeline is adjacent to each settler's holding, and at irrigation periods each settler is given water by the opening of appropriate channel gates, or valves, leading to the block down channels for the stated number of hours allotted to him by the irrigation authority. The usual watering period is four hours per acre (ten hours per ha) based upon a flow of 2 feet (0.06 m3) per second, which provides a 6 inch (15 cm) irrigation (Engineering and Water Supply Department 1970, 2). The water irrigates the fruit trees or vines by flowing along furrows prepared prior to each irrigation. In some of the new settlements, the reticulation in the settler's block is by pipes and the irrigation is by overhead sprays, movable or fixed, with a tendency at present to convert to under-tree sprinklers. Another recent development is a move towards providing water on order rather than at fixed times.

In the reclaimed swamp areas (Tract 1 in Fig. 5.1) the approach is different. Embankments keep the river from the "swamps," and, when irrigation is required, sluice gates in the embankments are opened to allow water to enter the channels and gravitate throughout the area, each lessee flood-irrigating his holding as water becomes available to him in roster order.

The Salinity Problem

The process of salt accumulation in rivers of arid regions from natural solutions of minerals and from irrigation processes is the age-old nemesis of those peoples whose livelihood depends upon irrigation in the arid zone. Man's ability to control salinization of irrigated lands and to control salt concentration downstream from irrigated areas has been tested from the beginning of recorded history. There have been some successes and many failures, and these are well documented by Eckholm (1975) and Teclaff and Teclaff (1973). Irrigation in an arid region involves a drastic change in hydrology, and, from the Tigris, Euphrates, and Indus to the Rio Grande and Colorado, it has led to increasing soil and river salinity. The situation with the River Murray is no different.

The South Australian Engineering and Water Supply Department recognizes the importance of the salinity problem:

Unquestionably, in terms of economic, environmental and social cost, the major immediate threat to the River Murray is dissolved salts, commonly referred to as salinity. [Engineering and Water Supply Department 1977b, 3]

The recent River Murray Working Party Report (1975) also highlights the salinity problem: "The Committee recognizes that salinity is the major water pollution problem in the River Murray."

The Size of the Problem

Generally the amount of salt passing through the river at any time is constant at around 3,000 tonnes per day. Consequently, during periods of high flow, the concentration of salinity is less, and during periods of low flow the concentration is more. So periods of low flow are the periods of most concern.

The World Health Organization accepts 830 EC units as the maximum desirable for drinking water. It is also the level at which overhead irrigated citrus suffers a 10 per cent loss of yield (Engineering and Water Supply Department 1977b,3). At the level of 1,250 EC units furrow and under tree irrigated citrus suffers a 10 per cent loss, and overhead irrigated citrus suffers permanent damage. For almost 20 per cent of the time since 1962 the salinity of the River Murray at Morgan has exceeded 850 EC units, and on several occasions has exceeded 1,250 EC units. The Engineering and Water Supply Department has admitted that if agricultural losses are to be reduced, and if acceptable domestic and industrial water is to be supplied, salinity in the Murray must be reduced (Engineering and Water Supply Department 1977b, 4).

FIG. 5.3. Effect of River Structures on Salinity Downstream

The Origin of the Problem

As the sea retreated from the Murray Basin in Tertiary times, seawater was trapped in the underground sands and limestones. From these vast underground reservoirs of salt, salinity finds its way into the River Murray by three means: These are (1 ) natural inflow; (2) river structures; and (3) irrigation drainage.

1. NATURAL INFLOW

Considerable salinity finds its way into the river by natural drainage. This has been going on for thousands of years, and the process is illustrated in Fig. 5.2. According to the Engineering and Water Supply Department (1977b, 5). these inflows are of particular concern in the lower reaches of the Murray and particularly in South Australia because they are generally at a greater rate and of higher concentration than upstream. Because the underground salt reservoirs are enormous, this process will continue for thousands of years to come.

2. RIVER STRUCTURES

Salinity is also increased by the locks and weirs along the Murray. These structures were completed between 1922 and 1935 at the insistence of the South Australian government, which was determined to maintain the navigability of the river despite the fact that the river trade had virtually disappeared by the turn of the century. The locks and weirs increase river levels by several metres. This causes increased pressure on underground saline groundwater, forcing the salinity into the river downstream as shown in Fig. 5.3.

3. IRRIGATION DRAINAGE

When land is irrigated it is normal for a proportion of the water applied to drain through the soil and then find its way into groundwater storages or nearby rivers. In the Murray Basin, irrigation drainage seeps through the underground saline strata, becomes increasingly saline, and then finds its way back into the river. In the past, this problem has been partly tackled by intercepting irrigation drainage in underground tile drains, and then pumping it to evaporation basins on the river flats. Unfortunately, seepage from these basins causes a return of high salinity flows to the river. In addition, the capacity of the basins is insufficient and occasional releases of saline water are necessary. This again returns saline water to the river. Irrigation drainage which is not intercepted and diverted to evaporation basins eventually reaches the watertable. This builds up what is called a "groundwater mound." This again causes increased seepage of saline water to the river (Fig. 5.4).

FIG. 5.4. Effects of Irrigation on River Salinity

FIG. 5.5. Salinity to Impact Relationship

The South Australian Contribution

Of the 1.1 million tonnes of salt which pass through the Murray Mouth every year, 64 per cent derives from Victoria and New South Wales (Engineering and Water Supply Department 1977b, 6). South Australia has no direct control over this. Nevertheless, 400,000 tonnes of salt do enter the river in South Australia. According to the estimates of the Engineering and Water Supply Department (1977b, 6) this total comprises the following:

1. Natural inflow: 130,000 tonnes per annum
2. River structures: 100,000 tonnes per annum
3. Irrigation drainage: 170,000 tonnes per annum

Solutions

The Engineering and Water Supply Department has made it clear (1977b, 6) that whatever solutions are adopted, there can be only relatively small reductions in River Murray salinity. This is because a substantial proportion of inflow is simply not controllable. For example, considerable natural inflow will continue whatever action is taken. However, the negative impacts of salinity can be significantly reduced by a small improvement in present salinity levels. The salinity-to-impact relationship is as shown in Fig. 5.5.

The Engineering and Water Supply Department is currently investigating a range of options, which are discussed below.

POLITICAL ACTION

South Australia has no direct control over the actions of the upstream states. The only way in which South Australia can exercise any voice in matters such as upstream pollution is through its representation on the River Murray Commission. However, despite a recommendation of the River Murray Working Party (1975) that the commission be given effective power over the management of the quality of River Murray water, it remains responsible only for quantity, and the states are continuing to argue over the issue. The difficulties faced by South Australia are highlighted by a statement by the New South Wales government representative to the River Murray Working Party: "Water pollution control in South Australia is regarded as a matter for that state alone" (River Murray Working Party 1975, 9/11). The South Australian Engineering and Water Supply Department (1977b, 8) considers that all states should aim at significant reductions in their salinity contributions to the river system.

UPGRADE EXISTING EVAPORATION BASINS

This proposal involves holding the drainage in basins when river salinity is high, and then discharging the saline water during high river flows. This proposal would have virtually no effect on the mean annual river salinity, and
would be environmentally unacceptable because of the effects of these basins on the flood-plain ecology. Cost is estimated at $1.7 million (Engineering and Water Supply Department 1977c, 9).

DIRECT DISCHARGE TO THE RIVER

The suggestion here is to abandon all basins and remove them from the floodplain. All drainage would then be discharged directly into the river. The net effect of this would be an increase in salinity and greater economic cost to the community. There would, however, be environmental benefits at basin sites through vegetation recovery. Cost is estimated at $1 million (Engineering and Water Supply Department 1977c, 9).

SEGREGATED DISPOSAL

This proposal involves the use of basins only for high salinity drainage. Low salinity drainage would be discharged directly into the river. This would produce an overall reduction in salinity of 5 per cent. Environmental conditions at evaporation basins would improve, although they would still remain on the floodplain. Cost is estimated at $2.7 million (Engineering and Water Supply Department 1977c, 10).

NOORA BASIN

This proposal involves the establishment of a new basin at Noora (20 km east of Loxton) to serve Renmark, Berri Barmera, and Cobdogla. It is estimated that this would result in an overall reduction of 15 per cent in average river salinities. The cost would be between $16 million and $20 million (Engineering and Water Supply Department 1977c, 11).

OCEAN DISPOSAL

This proposal involves the collection of all excess drainage from the Upper Murray district and the pumping of the waste to the ocean near the Murray mouth. This would result in an overall reduction in mean river salinity of 16 per cent, but it would cost approximately $90 million (Engineering and Water Supply Department 1977c, 11).

NEW RIVER MURRAY WATERS AGREEMENT

This proposal involves building new River Murray Commission storages and renegotiating the River Murray Waters Agreement to increase dilution flows to South Australia. This would be an effective solution, but it would involve the construction of a major dam at a cost of approximately $120million.

SEPARATE SUPPLY

A supply channel or pipeline would be taken from Lake Victoria so that the River Murray downstream from Lock 7 would then serve as a drainage carrier. This would enable unrestricted discharge of South Australian irrigation areas to the river, and good-quality water would be received by the majority of downstream users. There would, however, be severe environmental damage associated with high salinities downstream from Lake Victoria. The cost would be at least $200 million (Engineering and Water Supply Department 1977c, 14).

WATER ON ORDER

In government irrigation areas, the roster system is being replaced by the "water-on-order" method of supplying irrigation water. Current investigations suggest that the reduction in drainage run-off could be as high as 20 per cent (Engineering and Water Supply Department 1977c, 14). This could decrease saline seepage to the river in the long term, and minimize the rate of growth of ground water mounds. Costs are regarded as minimal.

IMPROVED IRRIGATION PRACTICES

This proposal involves the conversion of irrigation from furrow to sprinklers, micro-jet, or drip. It is estimated that conversion of 45 per cent of furrow in the Riverland (Tract 3 in Fig. 5.1) could result in an overall reduction of 4 per cent in average river salinities (Engineering and Water Supply Department 1977c, 14). Application rates would be lower and there would be less seepage to the river. There would also be less effluent reaching the evaporation basins. The average yield of some irrigated crops would increase by 20 per cent to 30 per cent. There is a need for the availability of low-interest loans to encourage farmers to convert. Cost is estimated at approximately $10 million.

LAND USE REDISTRIBUTION

One way of reducing drainage quantities is to reduce the amount of irrigation in the Riverland. This could be achieved by (a) property consolidation, (b) changing the types of crops grown, (c) changing to dry-land farming, or (d) returning the land to other uses. This could involve moving irrigated areas farther from the river and the cessation altogether of irrigation in some areas. The Industries Assistance Commission in its 1976 Report on the Riverland concluded that about 17 per cent of Riverland farmers are economically non-viable. The commission recommended assistance be given to cease irrigation in these instances, and to find alternative occupations for these farmers. This would result in a reduction of drainage effluent by 17 percent, and a reduction of river salinity on average by 3 per cent. In addition, economic benefits would accrue to the remaining irrigators. The cost of buying out and relocating 17 per cent of Riverland irrigators would be around $20 million and would have to be implemented over a long period of time-say 20 years (Engineering and Water Supply Department 1977c, 16).

The Perception of Salinity

Throughout the world, the successes in controlling the salinization of irrigated lands have come about through scientific and technological advances. The failures have generally resulted from man's inability to apply the knowledge and processes available to him. Most scientific experts agree that salinization need not get out of control in irrigated lands if available management techniques are applied. This, however, implies substantial capital investment, as well as the ability of farmers and other decision-makers to accurately perceive both the problem and the range of alternative solutions available to them.

A great deal of work has been done on people's perception of life- or income-threatening environmental hazards, particularly if of a catastrophic nature. Less attention has been directed at topics relating to damage caused to man's activities by changes in the environment occurring over an extended time span. Studies which have been made of slowly occurring environmental disruptions indicate not only a general lack of awareness of the hazardous nature of these long-term effects, but ignorance of their present existence (Rountree 1974). Environmental pollution falls into this category, and salinity is certainly one form of pollution.

A major finding from environmental cognition studies is the sketchy and distorted information that most people have about the cause and content of environmental pollution (David 1971; Aulicems et a/. 1972; Wall 1973). Another important finding is that there is a significant difference between the perception of the lay public and that of technical managers in the area of water resources management (Mitchell 1971, 139). Mitcheil's research suggests that there are significant differences between the perceptions of technical managers and the public, but not between the perceptions of sub-groups of the public. It follows from this that the opinion of the public should be consulted in resource management situations. Another conclusion arrived at by Mitchell (1971, 152) is that is is possible to generalize about the public on cognitive, affective, and behavioural variables.

There has been very little research into the perception of salinity specifically. Gindler and Holberts (1969, 389) have suggested that, with the early appearance of salinity in the Colorado River, it was not believed likely to increase. It was commonly believed that silt would somehow blanket the salinity and even reduce it. Dregne (1975, 49) has shown that attitudes towards salinity control measures on the Colorado River fluctuate with the amount of irrigation water available. When the flow of the river is above normal, excess water is available for leaching salts, and the salinity problem recedes. In dry years, the opposite is true and pressures are generated to reduce irrigation water salinity. Jackson (1977) administered a questionnaire to farmers and non-farmers in Utah Valley, Utah, in order to determine the level of awareness of environmental damage associated with irrigation. The results of the survey revealed that farmers seemed to be more concerned about the damages from irrigation as determined by their voluntary responses to open-ended questions about irrigation damage. One fourth of the farmers indicated that they perceived some damage from irrigation, but only 10 per cent of the non-farmers so responded. When asked whether they were aware of specific damages, however, three times as many non-farmers as farmers indicated awareness of such damage as erosion, alkalinity, waterlogging, and so forth. Farmer perception of damage increased only slightly when asked about specific types. Both groups displayed a level of awareness lower than anticipated. Livermore (1968) surveyed 60 citrus growers in Renmark, Berri, Loxton, and Waikerie in South Australia's Riverland district. He found that growers who were well-off tended to admit that salinity had affected them, while those who were obviously struggling tended to discount the effects, and to refuse to admit that salinity was a serious problem.

This research suggests one major and two minor hypotheses for investigation in the South Australian situation:

Major Hypothesis 1: Because salinity is such a complex and slowly developing phenomenon, both farmers and the general public will have a very sketchy and distorted idea of the nature of the problem and of the range of solutions available.

Minor Hypothesis 2: There will be a significant difference in perception of the salinity problem among the farmers, the general public, and the technical managers.

Minor Hypothesis 3: In accordance with the general findings of a wide range of research into the perception of hazards, farmers will be found to adopt a rationalizing stance in the face of the threat from salinity, will discount the bad side effects of any ameliorative measures tried, and will tend to rely on the government for solutions.

The Investigation

The above hypotheses provide the framework for this investigation. The study is aimed at gaining some insight into the salinity problem as perceived by those most directly affected by it. It is largely a study in environmental perception.

Methodology

The investigation was conducted by questionnaire surveys of farmers from the Loxton Irrigation Area, Renmark Irrigation Area, and the Murray Bridge/Mypolonga district (see Appendix 5.1). A second questionnaire survey was administered to randomly selected residents of Adelaide (see Appendix 5.2). Finally, open-ended interviews were conducted with official resource managers both in the local districts and also in Adelaide.

COMPOSITION OF THE SAMPLE

In the Murray Bridge/Mypolonga district 27 farmers were selected by the use of block numbers and a table of random numbers. This sample represents more than 50 per cent of farmers in the district (Table 5.1).

TABLE 5.1. Murray Bridge/Mypolonga Sample Characteristics

In the Loxton district 37 irrigation farmers were selected by the use of block numbers and a table of random numbers. This sample represents more than 10 per cent of blockers in the district (Table 5.2).

TABLE 5.2. Loxton Sample Characteristics

In the Renmark district 64 irrigation farmers were selected by the use of block numbers and a table of random numbers. This sample represents more than 15 per cent of blockers in the district (Table 5.3).

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