Water Quality

This content is currently under review. Statistics date from 1990.

Water quality is highly variable, from place to place and from time to time, even within a particular river system. It is dependent on many factors, both natural and as a consequence of human activities. Rainwater is by no means pure, and when it reaches the earth its quality is further affected by the soils, rocks and vegetation over and through which it passes. Another major influence on river water quality is the rate of streamflow, in part due to the fact that at low flows, groundwater can make up a larger proportion of total flow to streams. Further, as is noted in the introduction to Water and Land Salinity, high salinities and turbidities, together with significant variations in flows, have always been natural features of rivers in the Basin, especially in the western parts.

Over much of the Basin, the natural quality of the water, that is, what it might have been like prior to European settlement, is not high. This is due to the biophysical nature of the Basin. Not only is it a naturally saline environment, turbidity levels are naturally high, and it would appear that most of the nutrients in the rivers are naturally occurring, originating in the rocks and soils of the catchment. The deterioration of water quality - the exacerbation of the above parameters and the addition of numerous other substances to the river systems as a result of human activities - is a totally different matter. It is a forceful reminder that water quality is critically dependent on the uses to which the land drained by a river is put. It is then that water quality can rightly be regarded as a measure of the health of the catchment.

What is involved in water quality?

As has been indicated, many factors are involved in water quality. Particularly important in the MDB are salinity, turbidity and nutrients. These are key indicators because of their importance to water users and their impacts on the aquatic environment (Bek & Robinson 1991). Salinity is discussed in Water and Land Salinity and turbidity and nutrients are discussed in more detail below. Other aspects of quality include temperature, dissolved gases, trace elements, pH, colour, silica, metals, pathogens, and the micro flora and fauna. The maps, diagrams and tables provide some illustrative data on major water quality parameters in the Murray-Darling Basin (Table 1 and Figure 1) (Bek & Robinson 1991; DWR 1993a). They are based on some of the considerable amount of water quality monitoring that is undertaken throughout the Basin.

Figure 1 Locations of selected water quality monitoring stations in the MDB: the numbers refer to the stations listed in Table 1

There is a general decline in water quality with distance downstream, though this is by no means a simple relationship. Critical to all parameters is stream flow (see Surface Water Resources and The Impacts of Water Regulation and Storage on the Basin's Rivers). Thus, for example, the "high variability in [Murray] River flow with time produces a correspondingly high variability in water quality ... in some stretches of the River, quality actually improves as the water moves downstream (Shafron et al. 1990). In any river, quite apart from variations over time, water quality can vary significantly over very short stretches. The high variability of stream flow not only directly affects water quality parameters, it also makes it extremely difficult to determine any overall changes in water quality (Mackay et al. 1988, vi).

Whilst water quality can be considered purely in terms of its chemistry and biology, its real significance is in terms of the uses to which water is put. Thus, water of a given quality will be suitable for some uses but not for others, the difference sometimes being only a minute quantity of one chemical constituent. For example, highly saline water can damage certain plants, while River Murray water that is used for steamraising in South Australia's Port Augusta power stations has first to be demineralised.

More often than not, however, water quality is considered in terms of pollution, the constituents that make water unsuitable for one or more uses. Some are of major and widespread concern in the Murray-Darling Basin and are considered in more detail below. Others are of less significance, in terms of their severity, frequency and extent, such as industrial effluent, bacteria, pesticide residues from intensive farming, and heavy metal residues from past gold and other mining (McKenzie-Smith 1990; Tiller 1990). Recently, evidence has emerged of the acidification of surface waters over time in the Goulburn and Broken rivers, no doubt as a result of increasing soil acidification (see Land Degradation). Other matters affect the waterways rather than the water itself, though they are no less significant, such alligator weed and water hyacinth.

The sources of pollution are many. As indicated above, there are the diffuse sources, in particular runoff from agricultural land. Not only does such runoff contain all kinds of substances, it is very difficult to control. Then there are the point sources, sometimes difficult to control, but much more readily identifiable. They include drainage from irrigation schemes, stormwater runoff from urban areas, effluent from urban sewage treatment works, and from industries and intensive agricultural operations such as feedlots (see Agriculture). There are now very few places along the main stream of the River Murray that discharge treated effluent directly into the River. However, in other parts of the Basin there is considerably more direct discharge, though increasing quantities of effluent are being diverted to on-land re-use (GHD 1992).

Turbidity and nutrients: critical water quality issues

Turbidity and nutrient load, like salinity, are critical water quality issues in the Murray-Darling Basin. They are also features of the natural biophysical environment, to which the native flora and fauna are partly adapted. They have become problems because of the uses to which the Basin has been put since European settlement and because their levels have been significantly increased.

Turbidity

Turbidity is a measure of water clarity and an indicator of the presence of suspended material such as silt and clay, and to a lesser extent, phytoplankton and zooplankton. The very fine clay particles that characterise the soils of much of the Basin are the main component. Turbidity is a natural phenomenon and has long been a feature of the Basin, but it has been exacerbated by the poor use and management of agricultural lands, especially from land and streambank erosion.

As with salinity, turbidity is strongly influenced by river flows and runoff from the land. For example, "Turbidities in the Darling River ... were around 25 NTU (Nephelometric Turbidity Units) in May 1983 during drought, but rose twenty-fold during flooding in June 1983" (Shrafron et al. 1990).* Also, in the River Murray, there is a marked downstream increase in overall turbidity levels (Figure 2). High turbidity levels are also found in the Broken Creek, Loddon and Edward rivers, as well as in the Darling and the Murray below its confluence with the Darling. The much higher turbidity levels in the Darling than the Murray are evident well down stream of the confluence of the two rivers.

Figure 2 Turbidity in the River Murray, median values 1978-1988 (source: Shafron et al. 1990)

Large suspended sediment loads in rivers have several effects. The sediment carries other pollutants, including nutrients. When river flows lose pace, as when they reach storages, the sediment settles to the bottom, among other things reducing storage capacity (an estimated 800,000 m³ of sediment settles in Lake Hume each year). High turbidity levels adversely affect aquatic organisms, often reducing visibility and at times causing their suffocation. High turbidity levels cause wear on equipment and water reticulation systems, and can block them. They also make water unsuitable for most uses, including drinking. High turbidity is a major reason for water treatment, even though it reduces the effectiveness of disinfection. It is a particular problem for the water supply systems in small towns in the western parts of the MDB. In the South Australian Lower Murray, "it is not unusual for the turbidity to exceed 100 Nephelometric Turbidity Units for periods of several months, hence the need for treatment. The World Health Organisation recommends a desirable maximum of 5 NTU for drinking water" (MDBMC 1987, 94).

In order to limit erosion and the movement of sediment to the rivers, it is important to maintain a vegetative cover on land and to keep livestock away from river banks.

* Nephelometric Turbidity Units are comparative measures of turbidity, the greater the turbidity the greater the number of units.

Nutrients, eutrophication and algal blooms

Eutrophication is the enrichment of waters with nutrients, in particular phosphorus and, to a lesser extent, nitrogen (Banens 1996). The major sources of these nutrients are:

- the rocks and soils of a catchment's natural environment;

- the sediments on the beds of rivers and lakes from which nutrients are released under certain physical and chemical conditions, as when the sediments are disturbed or oxygen is depleted;

- discharges from diffuse or non-point sources, especially in run-off from agricultural land and forests where soils are allowed to erode and where there is high fertiliser use; and

- discharges from point sources, such as effluent from sewage treatment works, industrial activities (especially food processing plants and abattoirs), feedlots and other intensive agricultural operations, fish farms, drainage from irrigation areas, and stormwater runoff from urban areas.

As Table 2 indicates, the contributions of the different sources vary between average, dry and wet years (GHD 1992). The point sources are of most significance in periods of drought and low river flows, as well as causing undesirable local effects. Overall, however, the diffuse sources are by far the most important (Donnelly 1995).

Nutrients attach themselves to soil particles. Soil erosion is therefore a significant factor in the movement of nutrients to waterways, while sediment transport is a major factor in the movement of nutrients within waterways. Thus turbid streams generally have high phosphorus concentrations and are often also high in nitrogen (MDBMC 1987, 94). For example, it has been estimated that some 600,000 tonnes of suspended sediment is carried past Wagga Wagga annually by the Murrumbidgee River, carrying at least 600 tonnes of phosphorus (Olive et al. 1994). Further, not only are bottom sediments of rivers and reservoirs an important current source of phosphorus, they contain enough to contribute to future problems for many years, even if further additions to the system could be prevented.

Total phosphorus concentrations are high throughout much of the Basin, certainly within New South Wales. They also show a steady increase downstream in the River Murray.

The results of high nutrients concentrations in waterways

High nutrient levels contribute to many problems in the Basin's waterways, including:

• algal and aesthetic scums;
• toxic blue-green algal outbreaks;
• detrimental impacts on other flora and fauna;
• taste and odour problems in domestic water supplies;
• algae blocking trickle irrigation systems and other equipment; and
• water plants taking over waterways and blocking water movement.

The most serious of the problems resulting from high nutrient levels is blue-green algae. Microscopic in size, and a natural part of the Basin's aquatic environment, the most common types are Anabeaena, Microcystis and Nodularia. Given favourable conditions, they reproduce at a very high rate to form blooms, explosions in growth that can dominate the local aquatic environment (MDBMC 1994, 5). In addition to nutrients, other major factors contributing to algal blooms are calm water conditions (as in lakes, reservoirs and rivers when reduced flows more or less eliminate movement and turbulence), low winds, sunlight (calm water results in lower turbidity, enabling light to penetrate well below the surface of the water), and warm water temperatures (usually associated with slow moving or stagnant water). However "The conditions interact with each other in a very complex way; consequently, it is not possible to blame algal blooms on any particular factor" (MDBMC 1994, 5). It must be noted that they have occurred when a number of these factors have not been present; and they have not occurred when all the factors have been present. Because of the generally high levels of turbidity in Australian rivers, higher concentrations of phosphorus can exist without resulting in excessive algal growth (compared with rivers overseas).

Algal blooms constitute a very complex problem (Schonfeldt 1993a and 1993b). In brief, they

occur because the natural checks and balances of a healthy river system have been changed. A healthy system generally has many types of plants and animals which make use of algae through a complex food ‘web’, which culminates in fish and fish-eating birds. As the environmental conditions and habitat of these organisms change, parts of the food web are removed and the balance of the system in disturbed. The disappearance of water plants from the main stem of rivers is an example of this disturbance. Introduced fish, such as carp, may also disturb the food web (MDBMC 1994, 6).

(See Fisheries and Wetlands.)

For many years, blue-green algae received little attention, except from a few concerned scientists. There was significant under-recording of algal blooms. This was in spite of many outbreaks, including some that caused livestock deaths, as in 1878 around Lake Alexandrina, others that gave rise to serious health problems, such as severe gastro-enteritis, as at Armidale in 1981 due to Microcystis aeruginosa, and a number of outbreaks in the South Australian Lower Murray and Lakes since the late 1970s. The situation changed dramatically in the summer of 1991-92, when "the largest river bloom of blue-green algae recorded anywhere in the world emerged along the Darling River" (MDBMC 1994, 3). This extended over 1,000 kilometres, while outbreaks occurred over the summer months at many other locations in the Basin, such as Lake Cargelligo, the Carcoar Reservoir, and Lake Mokoan (Table 3 and Figure 3). There is no conclusive evidence that the incidence of algal blooms has increased, especially since the 1970s; the increased reports may simply be the result of greater awareness.

Figure 3 Sites of recent algal blooms in the MDB (source: MDBMC 1994)

Problems created by algal blooms

Quite apart from their visual impact, algal blooms create a number of problems:

- toxins produced by some blue-green algae can cause liver damage, stomach upsets, and disorders of the nervous system in humans. Contact with high concentrations of algae can cause skin and eye irritations. Stock deaths have been widely reported, and there is evidence of poisoning of wildlife and domestic pets;

- they further affect water quality by causing undesirable tastes and odours, discolouration and unsightly scums. As the decaying algae die, they can reduce oxygen levels in the water, causing stress and even death to other aquatic organisms, especially fish;

- water supplies can be disrupted when filters and equipment are blocked and when toxins need to be removed. The impact of blue-green algal blooms on water supplies for urban centres within the Murray-Darling Basin can be significant. Many conventional water treatment works can remove algae, but they cannot usually remove the toxins produced by some blue-green algae: that requires a more complex and expensive treatment process; and

- recreation and tourism can also be adversely affected by algal blooms because many leisure activities, such as fishing and swimming, are based on water.

What can be done about nutrient pollution?

If natural sources account for the major share of nutrient loads, as continuing research is now indicating, then the improvement of land management practices to prevent erosion is of critical importance to the control of nutrient pollution. It also means that reducing nutrients from other sources will have only limited impact on the overall problem. However, every reduction will help, and there are other good resource and environmental reasons for reducing human-induced contributions, especially in terms of more localised environments. For example, due to its old sewage treatment works, Cooma, with a population of some 8,000 people, was putting more phosphorus into the Murrumbidgee than was Canberra. This contributed to algal blooms in the River and the consequent need for emergency water supplies for Cooma in mid-1994. However, the problem has been reduced by 96 per cent through the addition to the treatment process of ferrous chloride (a waste material produced by BHP in its steel-making process), which has been successfully used for a number of years in Canberra's Lower Molonglo Water Quality Control Centre. In the case of the Carcoar, a number of measures have been taken to reduce the quantities of nutrients entering the reservoir. A new sewage treatment works now serves Blayney, pollution control measures have been taken at the abattoir and associated feedlot, and an artificial wetland established where the Belubula River enters the reservoir.

If little impact can be made on the overall quantities of nutrients in the aquatic ecosystems, then the other factors contributing to algal blooms have to be examined. For example, a study of the Chaffey Reservoir and its catchment

has demonstrated that natural sources can dominate the delivery of phosphate to streams and water storages. In such instances reducing the delivery of sediment-associated phosphate to effectively limit algal growth is likely to be difficult. In Chaffey catchment for example, erosion is not rapid and sediment delivery is relatively low. It seems that reducing sediment delivery substantially could incur a significant economic penalty, and so reservoir management may be the best option (Caitcheon et al. 1995).

So, rather than trying to change only the management of the land components of a catchment, the focus of attention should be the overall management of the aquatic system, especially in terms of river flows (Donnelly 1995).

Clearly, then, another question has to be asked. Is the problem of blue-green algae due to increased discharges of nutrients to the rivers or is it due to the changes in the flow conditions? Studies are now indicating that the flow rate of rivers may well be the most critical factor. This is certainly supported by research undertaken at the Maude and Hay weir pools on the Murrumbidgee River (Figure 4) (Jones 1994). There have always been floods and droughts, but we are now seeing some of the consequences of the large program of river regulation that has primarily centred on the storage of water for off-stream use (see The Impacts of Water Regulation and Storage on the Basin’s Rivers).

Figure 4 Anabaena abundance compared with 14-day average flow in the Murrumbidgee River at the Maude Weir pool in the summer of 1993-94 (source: Jones 1994)

The issues have been addressed in various state-level documents (e.g. Government of Victoria 1995) and more particularly in The Algal Management Strategy for the Murray-Darling Basin (MDBMC 1994; NEMP 1996). A key factor is the adoption of a flow management policy to reduce the potential for low flows to combine with the other factors that contribute to algal blooms (see Conclusion).

Some other issues

Overall, toxic substances are not a serious concern in the Basin, though there have been occasions when such pollutants have had significant local and regional impacts. For example, the runoff from land in intensive production, including rice and other irrigated grain crops, can contain insecticides, pesticides, herbicides and fungicides. The newer chemicals are less persistent than ones previously used (which included, for example, organochlorins such as DDT and dieldrin) and do not accumulate in the fatty tissue of animals, but they are still toxic to fish and other biota, even at low concentrations (MDBMC 1987, 96). In the late 1980s-early 1990s, there were concerns over chemicals in a number of rivers in the central and north western regions of NSW, with high incidences being recorded of the insecticide endosulfan and the herbicide atrazine, both used in cotton growing (DWR 1993a). Though the levels were higher than desirable for aquatic ecosystems, they were below the levels acceptable under Australia's national drinking water guidelines. Most problems result from the incorrect use of chemicals and their run-off into streams. The aerial application of chemicals is the most difficult to accurately control and is still causing problems in some of the cotton growing areas. In the four years to 1995, there was a decline in pesticide levels, due to a reduction in their use (partly as a result of the drought), improved methods of use, and better farm management (Arthington 1995).

There have also been occasional industrial discharges, as well as accidents: for example, a number of accidents on the Hume Highway have resulted in petroleum products and other chemicals getting into the Yass River and its tributaries (it is a tributary of the Murrumbidgee and the town water supply for Yass). Pollution from boats and other users of waterways is a continuing problems, and includes garbage and litter, oil and chemicals, and toilets and waste tank effluents. There are now defined zones in the River Murray within which it is prohibited for vessels to discharge wastes to the river; boat operators must use pump-ashore stations located at various sites along the mid to lower Murray.

Microbiological and bacterial contamination is another continuing problem, particularly as a result of stormwater run-off from urban areas and pastures. This presents a health hazard from pathogenic micro-organisms where water supplies are not disinfected. For example, "The concentrations of E. coli bacteria occurring in the Murray are frequently in excess of limits recommended for both drinking water and recreation" (Mackay et al. 1988, vii). Even in the alpine areas of the Snowy Mountains, it is not safe to drink streamwater because of such organisms as Giardia spp.

Heavy metal contamination from mining operations has been a problem in some locations, especially older gold, copper, silver, lead and zinc mines (see Mining and Minerals Production).

As well as eutrophication, large water storages experience other problems. The main ones occur in the absence of any mixing of the waters, namely the development of thermal stratification and deoxygenation in the lower levels (DWR 1993b) (Table 4). In some storages, artificial destratification is used. Variable water offtake levels are also used in some reservoirs to reduce problems from the release of very cold waters downstream of large storages.

There have been a number of local outbreaks of exotic water plants that have the potential to do untold damage to the Basin's waterways and economy. Two are of particular concern. Water hyacinth (Eichhornia crassipes) is probably the world's worst aquatic weed. A native of South America, it is established in some Queensland coastal rivers. There have been occasional outbreaks on inland rivers, including some in the MDB. Potentially very serious was an infestation covering 7,000 ha in the Gingham Watercourse near Moree. This was brought under control but requires annual maintenance (Dyason 1987). Another native of South America is alligator weed (Alternanthera philoxeroides), which grows rapidly especially in stationary and slow moving water, and can soon choke waterways. It was limited to the Sydney and Newcastle areas, but in early 1994 was found in Barren Box Swamp near Griffith (Matthews 1994). Potentially, it is the most dangerous aquatic weed present in the Basin. Other water weeds include elodea (Elodea canadensis) and barnyard grass (Echinochloa crus-galli).

Groundwater quality and contamination

Many individuals, communities and industries depend on groundwater for their water supplies (see Groundwater Resources). For Australia as a whole, about 20 per cent of total water use is supplied by groundwater (see Water Use). As with surface waters, quality is determined by natural conditions and human activities. It is affected by the nature of the rainfall and surface waters before they enter the ground. Once below the surface, the water is affected by the nature of the soils and rocks through which it passes. Many naturally occurring substances, such as nitrate, can affect groundwater quality and determine its suitability or otherwise for different uses.

As well, groundwater quality is affected by pollutants of urban, industrial and agricultural origins. The same problems that affect surface waters also affect groundwaters, though they can take many years to become evident and are almost impossible to deal with. From agricultural activities, these include chemical pesticides and herbicides, and nutrients (especially nitrates) from fertilisers. Municipal and industrial waste dumps are a major cause of concern, with all kinds of substances being leached from them. Other sources of concern include organic pollutants, benzene from petrol (US studies have indicated that 25-35 per cent of underground petrol tanks leak), and cleaning fluids (from dry cleaning establishments).

The costs of water pollution

All of the water quality problems outlined above impose costs on water users within the Murray-Darling Basin and beyond. They also impose significant damage and costs on all components of the aquatic environments. Most of these costs, however, are difficult to quantify, especially in monetary terms.

Poor quality water can impact on crop production, especially when it is used for irrigation, affecting the health of plants and so reducing the quantity and quality of crops produced. This is particularly evident in terms of the impacts of saline water on many horticultural commodities (see Water and Land Salinity). Poor quality water also affects the health of farm livestock and, in extreme cases, as with some of the outbreaks of blue-green algae, can cause their deaths.

Domestic and industrial users are affected in various ways by water quality problems, depending on the nature of the problem and the users. As indicated above, turbidity is a concern for domestic water supplies. However,

Many small communities [are] faced with the option of poor quality water or, in some cases, prohibitive treatment costs. For many towns the situation might be summed up by one respondent to the Water 2000 urban water quality survey: "the water is poor but most residents are thankful for having water at all" (MDBMC 1987, 103).

The 1991-92 blue-green algae outbreak along the Darling River brought major costs. In NSW alone, there was an estimated $2.4 million loss of revenue to the tourist industry (though some tourists may well have visited other areas instead). Up to $2 million was spent on alternative water supplies and instigating the NSW Algal Contingency Plan. Supplying the 830 residents of Collarenebri, North Bourke and Louth cost $60,000. Earlier, the outbreak in March-May 1990 in Lake Alexandrina cost Strathalbyn $210,000 for alternative water supplies (NSW 1994, 32). At the same time, it should be noted that whilst they provide no benefits, "the costs of total elimination of [algal] blooms are likely to be unacceptably high relative to the likely benefits" (Young et al. 1993). The National Eutrophication Management Program has funded the preparation of a report on the costs of algal blooms (Atech 1999).

Recycling treated water

Increasingly, measures are being taken prevent pollutants getting into the natural environment and to treat waste water before it is returned to the hydrological system. Gradually, it is being realised that waste water is as much a resource as fresh water.

Treated or recycled water is being used to avoid returning it directly to waterways or where high quality or potable water is not required. Examples of water re-use off-river include the irrigation of wood lots (as at Loxton, Mildura and Wodonga), pastures (as at Mildura and Cobram), and golf courses (Myers et al. 1995). In some cases, effluent is used for irrigation without, or with only minimal, treatment. Waste water and sewage treatment plants are being constantly upgraded to improve the quality of their effluent. In addition, special waste water recycling plants are being established, such as the ACT's demonstration plant that is producing 300kl of clean water a day (to be increased to 1,000kl/day), which is used to irrigate playing fields. At Temora, treated effluent has been used for some years for watering playing fields and gardens as it is cheaper than using ‘new’ water. However, it has to be remembered that such treated effluent can only be used for irrigation when irrigation is required, and that is generally not the case through the winter months.

Combating the problems

Apart from the increased recycling of water, much is being done to tackle the Basin's water quality problems. As with Land Degradation, this is a major focus of the Natural Resources Management Strategy. Among the issues being addressed are groundwater quality in the MDB, in-stream management options for blue-green algae, water quality in the Border Rivers, and siltation in Lake Hume. The MDBC is also supporting flow management throughout the Basin in several ways. It is providing tools and information to assist environmental flow management by arranging independant audits of the implementing the Cap on diversions and the sustainability of rivers, and is coordinating the preparation of a flow management plan for the River Murray.

Complementing the work of the MDBC is the National River Health Program which has been developed to help provide the foundation for the enhanced protection of Australia's valuable water resources.  The Program consists of two major components, Environmental Flows Management and the National Assessment of River Health.  A major focus of the Environmental Flows component is the establishment of co-ordinated multi-disciplinary efforts in key catchments to identify flow requirements necessary to ensure the health and viability of rivers and aquatic ecosystems.  The Assessment of River Health is utilising biological, physical and chemical assessment techniques to produce the first nation-wide assessment of river health.

In addition, at the community level, the national-level Waterwatch program, which complements the work of Landcare, is responsible for considerable water quality monitoring, standardised across the country, activities that complement work done by various state government agencies. However, there is still a lack of co-ordination of the work that is being done (Nagy et al. 1995).

Conclusion

"Looking back, that giant algal bloom may have been a blessing in disguise! It put pressure on all of us to get the rivers cleaned up" (Mike Hayes on Blooming Algae).

There is a long history of water quality problems in the Murray-Darling Basin, but the 1991-92 outbreaks of blue-green algae brought them to public notice in a way that had never occurred before. Many proposals have been put forward to improve water quality, especially in the Murray and in terms of salinity. For example, in 1970, Gutteridge Haskins and Davey (GHD 1970), proposed constructing a canal paralleling the River Murray to carry 'fresh' water, with the River becoming a 'drain'. Unfortunately, the problems are continuing, as a recent report on the Murrumbidgee River has indicated (DLWC 1995). In the words of the responsible NSW Government Minister, it is also a "disturbing report, presenting a picture of reduced flows and declining water quality".

The National Water Quality Management Strategy has a difficult objective, yet its achievement is essential to the long-term well-being of the Murray-Darling Basin:

to achieve the sustainable use of the nation's water resources by protecting and enhancing their quality while maintaining economic and social development (ANZECC 1994, 6).

The Murray-Darling Basin Ministerial Council's policy on water quality is a guiding principle for policy decisions and on-ground action across the Basin:

to maintain and, where necessary, improve existing water quality in the rivers of the Murray-Darling Basin for all beneficial uses - agricultural, environmental, urban, industrial and recreational

• in the case of those parameters such as salinity and nutrients which are already recognised as causing problems, the policy is to improve existing water quality

• in the case of other parameters which may at the moment be well below recognised limits, the policy is to endeavour to ensure that existing quality is not allowed to deteriorate.

Adopted by the Murray-Darling Basin Ministerial Council at Meeting No 9, 31 August 1990

Flow Policy for the Murray-Darling Basin

To maintain and where necessary improve existing flow regimes in the waterways of the Murray-Darling Basin to protect and enhance the riverine environment.

Adopted by the Murray-Darling Basin Ministerial Council at Meeting No 14, 29 June 1994

The main water quality problems in the Basin's rivers are excess amounts of substances that occur naturally in the Basin, in particular salt, suspended clay particles (turbidity), and nutrients. They have all been exacerbated by human activities. They cannot be separated from the land and its use. They are also a consequence of reduced river flows. Much greater attention needs to be given to flow management to provide flushing flows, to reduce pollution levels, and endeavouring to provide flows that are closer to the natural situation. Hence the critical importance of total or integrated catchment management.

If there is to be any improvement in the quality of water and the health of the rivers, there will have to be increased flows in most of the Basin's rivers (MDBMC 1995). Because of the high levels of water abstraction, many of the rivers are experiencing drought conditions virtually every six years out of ten. However, change is dependent on greater water availability, which can only come from reduced consumption.

References

ANZECC (1994): National Water Quality Management Strategy: policies and principles: a reference document. Agriculture and Resource Management Council of Australia and New Zealand / Australia and New Zealand Environment and Conservation Council, Canberra.

Arthington, A. (1995): State of the Rivers in Cotton Growing Areas of Northern New South Wales and the Border Rivers with Queensland. Occasional Paper Series No.2. Land and Water Resources Research and Development Corporation, Canberra.

Atech Group (1999) Cost of Algal Blooms LWRRDC Occasional paper, In preparation

Banens, B. (1996): "Eutrophication". Australian Science, 17(2), 29-32.

Bek, P. & Robinson, G. (1991): Sweet Water or Bitter Legacy: state of the rivers - water quality New South Wales. Department of Water Resources, Sydney.

Caitcheon, G. et al. (1995): "Nutrient and sediment sources in Chaffey Reservoir catchment". Australian Journal of Soil and Water Conservation, 8(2), 41-49.

Cottingham, P. et al. (1995): Algal Bloom and Nutrient Status of Victorian Inland Waters. Department of Conservation and Natural Resources, Melbourne.

DLWC (1995): State of the Rivers Report: Murrumbidgee Catchment 1994-1995. Volume 1. Department of Land and Water Conservation, Sydney.

Donnelly, T.H. (Editor)(1995): Review and Scoping Study of Catchment Phosphorus Sources. Consultancy Report No. 94-26. Division of Water Resources, CSIRO, Canberra.

DWR (1993a): Central and North Western Regions Water Quality Program: report for water users and the community '91-'92. NSW Department of Water Resources, Sydney.

DWR (1993b): Water Quality in NSW. NSW Department of Water Resources, Sydney.

Dyason, R. (1987): Water Hyacinth. Agfact P7.6.43. New South Wales Department of Agriculture, Sydney.

GHD (1970): River Murray Salinity Investigations. Report by Gutteridge Haskins & Davey for the River Murray Commission, Canberra.

GHD (1992): An Investigation of Nutrient Pollution in the Murray-Darling River System. Gutteridge Haskins & Davey for the Murray-Darling Basin Commission, Canberra.

Government of Victoria (1995): Nutrient Management Strategy for Victorian Inland Waters. Government of Victoria, Melbourne.

Jones, G. (1994): River flow and blue-green algal blooms. Seeking Solutions No.21. Division of Water Resources, CSIRO, Canberra.

Mackay, N. et al. (1988): Water Quality of the River Murray: review of monitoring 1978-1986. Murray-Darling Basin Commission, Canberra.

Matthews, P. (1994): Alligator Weed: a threat to the irrigation industry and wetland habitats. NSW Agriculture, Orange.

McKenzie-Smith, F.J. (1990): Biocide Contamination in the aquatic Environment: a study of the Ovens and King Rivers region. Scientific Series Report 90/004. Environmental Protection Authority of Victoria, Melbourne.

MDBMC (1987): Murray-Darling Basin Environmental Resources Study. Murray-Darling Basin Ministerial Council, Canberra.

MDBMC (1994): The Algal Management Strategy for the Murray-Darling Basin: a component of the natural resources management strategy. Murray-Darling Basin Ministerial Council, Canberra.

MDBMC (1995): An Audit of Water Use in the Murray-Darling Basin. Murray-Darling Basin Ministerial Council, Canberra.

Myers, B. et al. (1995): Effluent Irrigated Plantations: design and management. Technical Paper No. 2. CSIRO Division of Forestry, Canberra.

Nagy, L. et al. (1995): Water Quality Monitoring in Australia. Report to Environment Protection Agency. Aquatech, Canberra.

NEMP (1996): National Eutrophication Management Program: 1995-2000 Program Plan. Land and Water Resources Research and Development Corporation, Canberra.

NSW (1994): Our Water: a review of the water resources of New South Wales and the key issues relevant to their future development. Second edition. Department of Water Resources, Sydney.

Olive, L.J. et al. (1994): "Phosphorus and sediment dynamics in the Murray-Darling Basin". Land and Water Management - making it happen: conference proceedings, April 1994, Albury. Soil and Water Conservation Association of Australia, New South Wales Branch, Sydney.

Schonfeldt, C. (Editor)(1993a): Algal Management Strategy: technical advisory group report. Murray-Darling Basin Commission, Canberra.

Schonfeldt, C. (Editor)(1993b): Algal Management Strategy: background papers. Murray-Darling Basin Commission, Canberra.

Shafron, M. et al. (1990): "Water quality". pp. 147-165 in The Murray, edited by N. McKay & D.Eastburn. Murray-Darling Basin Commission, Canberra.

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Table 1 Water quality data for the Murray-Darling Basin, 1994-95

1 - Monitoring stations located on Figure 1 by numbers.

Source: Murray-Darling Basin Commission.

Table 2 Total point and diffuse source nutrient inputs to streams in the Murray-Darling Basin

 Source: GHD 1992, S-8.

 Table 3 Algal blooms in Lake Mokoan, 1979-1994 

Source: Cottingham et al. 1995, 38.

 Table 4 Water quality problems in large reservoirs in the New South Wales portion of the Murray-Darling Basin

x Problem occurs in storage

A Artificial destratification of the storage

Source: DWR 1993b, 8