Baden WilliamsScience, Technology, Environment and Resources Group

15 June 1995

ParliamentaryResearch Service

Research Paper No. 301994/95Murray-Darling Basin: Ecologically

Sustainable Irrigation?

CONTENTS

Major Issues , 1

Glossary of Terms 3

Introduction _ 5

The Water Resource _ 6Surface Water 10Groundwater 10

Principles of Irrigation 11Reducing Groundwater Recharge 14Irrigation Waste Water Disposal IS

Irrigation Water Use 20

Managing the Water Resource 22Managing Water Supply 23Managing Water Quality 23Managing the River Environment 24

The Irrigation Industry Dilemma 25

The Government Dilemma 26Government Initiatives 27Detemlining Irrigation Policy 29

The Present Approach 29Possible Future Approaches 30

References 33

Murray-Darling Basin: Ecologically Sustainable Irrigation?

Major Issues

The Murray-Darling Basin (MOB) is a major contributor to Australian agricultural production,with an annual output of $10-12 billion annually. Of this, the irrigation industry contributesabout $4.5 billion.

About one third of the 1.6 million ha irrigated land has groundwater tables within 2m of the soilsurface and 150.000 ha is salinised. These figures could well double within the next 30 to 40years unless effective solutions are implemented immediately.

Off-site effects of the irrigation industry include saline groundwater discharge into adjacentlowlands and surface streams with the result that a number of terrestrial and aquatic systems arebeing damaged or destroyed. Waste water containing agricultural chemicals, such as nitrogenand phosphorus, are contributing to algal blooms in waterways and pesticide and herbicidedamage may also be implicated in the future. Groundwater discharge will, in the future, affectpractically all irrigation areas in the MDB because. unlike coastal catchments, groundwatercannot drain freely to the sea.

The dilemma for the irrigation industry is that it is virtually impossible not to use more waterthan is actually required by the crops. The excess water adds to. or recharges. the underlyinggroundwater systems which then mobilise and transport soluble salts back into the surfaceenvironment. It is unlikely that improved management practices will be sufficient to overcomea continuing problem of groundwater recharge and subsequent discharge.

The dilemma for the Commonwealth and State governments is that. having embraced theprinciples of Ecologically Sustainable Development (ESD), they are now committed to puttingthose principles into practice. To date the approach with respect to the irrigation industry hasbeen:

• to provide information and training in better land management practices; and

• to devise economic incentives to encourage a more efficient use of water.

The information and training exercise is proving to be of limited success as not all farmers canafford the suggested measures. The economic measures have yet to be fully implemented andare mainly based on the premise that users should pay a realistic price for water and that theyshould pay for any pollution generated. The only 'carrot' offered has been the introduction oftradeable water licences. but even this measure is only likely to shift the problems to new areas.

The tulcertainty generated by a new environmental awareness on the pan of governments is nothelping to produce a sensible solution. Irrigators are denying evidence of their involvement inenvironmental damage and are in no mood to negotiate on increased water charges. Governmentdepartments are conveniently forgetting that they have in the past encouraged and contributed topractices resulting in irretrievable environmental changes in the major rivers of the basin, and tocontinuing groundwater! salinity problems. Policy makers seem :0 be committed solely toeconomic instruments. and they persist in expressing their views in a language that is unJikely toresult in any effective communication with irrigators.

2 Murray.Darling Basm.- Ecologically Sustamable IrrigatIOn"

One possible solution is relatively simple. although it may be cos[Jy in the first instance. TheStates and State governments have. through the MDB Agreement, already demonstrated that theheat can be taken out of an argument simply by agreeing to forget the past and to get on with thefuture. The future in this instance is to admit that no amount of research and development isgoing to result in universal implementation of 'best practices'. Even if the 'best practices' werelargely successful, governments would then be faced with a problem of similar magnituderesulting from dryland fanning.

A realistic approach is to provide a comprehensive drainage and wastewater disposal system toservice both irrigated and dryland groundwater recharge problems. At an initial cost of $6billion and an annual service charge of $66 million this does not seem to be outside the realmsof reality - particularly when the annual servicing would cost less than I per cent of annualagricultural production.

In addition there is a large wban population that also has a stake in having access to a healthyrural and riverine environment for recreational purposes. It would be reasonable to expect thatpan of their tax money should be used towards establishing a pennanent system of environmentprotection.

There would, of course, also need to be a contractual agreement with irrigators concerning waterusage and cost and with dryland larmers concerning practices resulting in excessivegroundwater recharge. The development of such contracts would simply mirror the processalready established between the Conunonwealth and States

Until governments and fanners sit down together and discuss realistic solutions more and moreproductive land will be lost and more and more ecological systems will be destroyed.

Murray-Darling Basin: Ecologically Sustainable Irrigation? 3

Glossary of Terms

aquifer Any part of the soil profile or underlying rock material that will allow water to drainwhen opened to the atmosphere. For example, if a hole is drilled into the soil and waterdrains into the hole then an aquifer has been penetrated. There are many types of aquifer,depending on their position and structural characteristics.

capillary water In some ways the water that is held in soil pores behaves in the same way asif it were held in a bundle of glass tubes of very small diameter. Water moves upwards fromthe saturated zone by capillary forces alone in the same manner as water rises up through apiece of blotting paper dipped in a glass of water. The finer the pore size the greater thecapillary rise.

EC units The electrical conductivity (EC) of water provides a measure of the amount of saltdissolved in the water. The International Unit for electrical conductivity is deci-Siemens permetre (dS/m) but frequently in the literature we find the use ofmilli-Siemens per centimetre(mS/cm) or micro-Siemens per centimeter (uS/em).

1000 pS/cm = 1 mS/cm = I dS/m

To avoid completely confusing the farming community it has become the practice to refer to

pS/cm as 'Ee units'.

free water evaporation At meteorological stations the daily evaporation of water ismeasured from a standard sized pan of water. It is reported as Pan Evaporation in rrun/day.Evaporation from open bodies of water (lakes, rivers) is taken as about 0.7 x Pan Evaporationand is referred to as the potential free water evaporation.

Gigolitre (Gl or GL) 1,000 megalitres.

groundwater Water contained within the pore space of soil and rock materials.

groundwater discharge Groundwater that escapes into a stream bed, lake or ocean, orthrough the land surface. Sometimes it is referred to as return flow.

groundwater mound A groundwater table is usually more-or-Iess parallel with the soilsurface. In sites where groundwater recharge rates are high, a mound may develop in thegroundwater table. When recharge is reduced or stopped the mound slowly disperses back tothe same level as the surrounding groundwater table.

groundwater recharge Water that has drained below the root zone of any local vegetationand which is then able to drain downwards to add to the underlying layer of saturated soil. Inan irrigation system this water may be referred to as the leaching fraction.

groundwater table Refers to the upper surface of a layer of soil or rock material that issaturated with water.

4 Murray-Darling Btwn: EcologIcally Sustamoble IrrlgolJon?

levee bank When streams overflow they dump suspended soil panicles on the surroundingflood plains. The largest particles drop out of suspension first so it is quite common for astream to have sandy banks. If the stream then changes course the old sandy levee banks areleft stranded in the landscape in the fonn of low dune-like structures.

light textured soil Soils are described as light textured if they contain a large proportion ofsand particles. Heavy textured soils, on the other hand, contain a high proportion of clay.

Megalitre (MI or ML) ] million litre•.

pore space Soil is a porous material made up of solids, water and air. The pore space in aclay is often about half of the total soil volume. i.e., 50 cubic centimetre (cc) pore space rer100 cc soil. Usually about 45 cc of that pore space would be pennanently filled with water,with the remaining 5 cc occupied by air. Thus the capacity for the clay to absorb more wateris 5cc per 100cc soil. This is referred to as the effective or available porosity.

riparian zone The land immediately next to a creek or river. For soil conservation purposesthe width of the riparian zone is usually taken as 20m on each side of the creek and thenatural vegetation in the zone is protected by law.

salinisation The process of accumulating soluble salts at or near the soil surface. Thisusually occurs by evaporation ofgroundwater that discharges through the soil surface.

salt scald When salt concentrates at the soil surface it kills the vegetation, thus leaving thesoil surface exposed to erosion by wind and water. The bare soil surface is referred to as a'salt scald'.

Murray-Darlmg Basin: Ecologically Sustainable Irrigation? 5

Introduction

Water is a relatively scarce resource in the 1.06 million square kilometre Murray-Darling Basin(MOB). Annual rainfall across the basin varies frem less than 300mm per year in the west to amaximum of about 3.000mm per year in the eastern ranges. This is offset to some degree by anannual potential free water evaporation rate of 3,000 mm in the west to 1,200 mm in the east.Only two to three per cent of the annual input of 466.000 Gigalitres of rainfall actually entersthe stream system (I Gigalitre (GI) = 1000 million litres).

The geographic range of the MDB also means that frequently one or more parts of it can beexperiencing drought conditions whilst the remainder is having nonnal rainfall. For example, inrecent times the Darling River ceased to flow in 1991 and again in 1994 due to drought insouthern Queensland and northern New South Wales.

Historically the Murray and Darling Rivers have had, and still do have, an important influenceon the development of agriculture in this country. Annual agricultural production from the basinis in the range of$1 0 to 12 billion and it contains 75% of Australia's irrigated lands.

The role of the Murray has changed markedly since early European settlement. Initially, it was amajor transport link between the coast and inland grazing areas but, because of its erratic flowpatterns, action was taken to regulate the flow with a series of locks and weirs. Only 16 of the35 planned structures were ever completed because railways took over as the preferred fonn oftransport. However sufficient regulation was achieved to ensure that the Murray would never bethe same again in tenns of what is now called its 'natw"al environment'.

Added to river regulation there has been a series of land settlement schemes instituted bygovernments with a vision of converting the MOB into one of the major food bowls of theworld. Unfortunately the knowledge of how to manage a diverse environment was almostcompletely lacking. Hence tbe bydrological regime of tbe MDB bas been irreversiblyaltered and witb it many biological systems have been modified or destroyed.

Less than 15 years ago government depanrnents were still very reluctant to admit that theirwater management policies and actions were responsible for high groundwater tables, soil andstream salinisation, dying redgum forests and the disappearance of many bird. animal, andaquatic species. The 1980s saw a massive turnaround in the environmental consciousness ofgovernments and they are now attempting to persuade landholders to help reverse the damage ofpast actions. The new objective of governments is 'Ecologically Sustainable Development'(ESD). This derives from the World Commission on Environment and Development (WCED,1987) definition of sustainable development, viz., a policy that 'meets the needs of the presentwithout compromising the ability of future generations to meet their own needs.' Morespecifically. the Commonwealth Government (1990) enunciated the following principles ofESO:

6 Murray-Darling Basin: Ecologically Sustainable Irrigatlan?

• improvement in material and non-material well-being;

• intergenerational equity;

• maintenance of ecological systems and protection of biodiversity;

• global ramifications, including international spillovers. international trade andinternational cooperation; and

• dealing cautiously with risk. uncertainty and irreversibility.

In spite of the legalistic type language used, there would be few that disagree with the notion ofESD since it appeals to the environmental conscience. However it remains to be seen howsuccessful such an appeal will be since, unlike governments, landholders still have to make aliving from their land. They may not be able to respond rapidly enough to prevent degradationof the soil, water and biological resources of the MOB from continuing well into the future. Thereal questions that need to be answered are whether governments:

• can define realistic objectives within ESO principles; and

• what incentives will be required to achieve those objectives.

At the moment government objectives appear to be generic rather than specific. Forexample, it is easy to fonnulate a policy saying that salinity and nutrient levels in the riversystem need to be lowered but real progress will not be made until specific objectives andspecific incentives/disincentives are agreed to with individual landholders.

Since the irrigation industry is by far the largest user of water diverted from the Murray-Darlingriver system, this paper examines the question of whether irrigation is an ecologicallysustainable fonn of land use within the MOB.

The Water Resource

The greatest proportion of irrigation water in the MDB is obtained from surface streams andreservoirs. with only about 3 per cent being extracted from groundwater. Swface water supplies,although of good quality, are subject to the vagaries of climate whilst groundwater use isrestricted to areas having high yielding aquifers with low salinity water. The basin is comprisedof 26 sub-catchments which provide discrete geographical units for management purposes(Figure I). The Murray·Darling Basin Commission is responsible for managing water flow inthe River Murray and as far north as Menindee Lakes in the Darling River. This will bediscussed in more detail in a later section.

Murray-DariinK Basill." Ecologically Sustainable Irrigation? 7

Figur~ I:

Sub·Uasins and Calchmenls of1he J\1urra.y-D:uling Basin

MUIIII""- OAllllNG O'V'S'ON

.UllOO· ....NC ... NN..' OIV'SION

//,

/

" "_.-.0 c h "'_

" A "n c Cv " .••••n , K._Ie _ •.. - -... ,- ...........-

._.

..-

'"

"

''-'10_l_"'_--_....--_.--10...__

__... 11....K_. ""-------~---..._.--.. --

..--_._--_ __.<•••,,_.._----.. .-..... ...

••,•••,••..".,"......"..

......._--_._ ......__.-

\1DB~lC (1987)~Iurra~ -Darling Ba~in

EI1\ ITonment31 Re~ouTces Study

8 '\//lrrt~I·-Dar/il1g Basi,,: EcologIcally S/lsflImahle IrTl~a'lO" "

Figure 2

Salinity and Flow alMorgan, Soulh Australia

Data supplied by ~1D13C. 1995.

.\Iurruy-Durlillg Bosin: Ecologically Sll.flainable Irrigotion? 9

Figure 3

Gronllt in Stale l>i\'Cl'"sions from rhe ~lu ......a)'

"00,- ----,

__ H,. So"IIo W"leS In" 0' , ...",n./___ V,cIOt'" In., 01 "'I",ns}

•-. - So,,'" A"SI',,'"+ ~l" no' '~'QOIe'" Ref",ns"Of ,~""OII

"'00

''''''

...

...

IRl'I........~ ."1.. _"ea lOul_1uH'Cl 'Of ".og.tl_.nd I>'lUeG bK_10 1!'Ie ...e<\

,II I, Ii ((, I, J I I'\ II , I I" 1\' I II\I"I~A I

A I \,1 Y \1,\1\ JI If' I+ I r J II

", I ", I, ", ,

I I 1\ I,

\ I ", , I,,r

,I1 '1,

,,i ~, ":!. I~' II I

'" 1/1 III' Jii,'II

III

I,I ,, II ,, I,,I,

ij, ... \, I I, • .j

"

TIIC \IUlT<I~· \IDBC (19Q()1

JO "'lurray-Dar/mg Basm: EcoloJ.!,If;ul(l' Suslamable Irrlgalion.?

Surface Water

Stream flow results from two sources:

• surface runoff during and after rainfall. This flow is usually of quite short duration(hours). and

• groundwater returning to the surface in situations where creek and river beds are inciseddeeply enough to intercept the groundwater system. Return flow of groundwater maycontinue unabated for weeks to many months. It also carries with it various amounts ofsoluble salts which are discharged into the stream system.

About 60 per cent of water flow in the Murray River originates from the wetter south-easterncatchments. The Darling and Mwrumbidgee catchments contribute about 12% and 11 % to totalflow. respectively.

The average discharge of water at the mouth of the Murray is now about 4,500 Gigalitres/annum as compared with the 12,600 GI that would be expected if there were no upstreamdiversions of river water. In extreme drought years the Murray barely manages a surfacedischarge into the sea because of the high evaporation losses that occur in Lake Alexandria. Infact about halfof the water delivered to South Australia each year is lost in this way.

The highly variable climatic conditions experienced in the MOB arc reflected in the very erraticstream flow record shown in Figure 2. Also shown in FigW'e 2 is the salt concentration of theMurray River water at Morgan (South Australia) over the same time period. Since flow and saltconcentration are more or less inversely related, salinity has b«ome an important indicatorof both the quality of the natural resource and management of the flow regime.

Diversions from all of the rivers in the MOB. for human purposes, now account for 10.000 to11.000 GI year (Close. 1990). or more than twice the amount that flows out of the Rivert\.1urray into the sea. Diversions have continued to increase over time (Figure 3) and. even withan increased concern alx>ut water usage by governments, the upward trend shows Iinle sign ofabating.

Groundwater

Very large volumes of groundwater are present in the MDB but the quality and ease with whichit can be pumped is very variable. TIle most useful supplies, for irrigation purposes. aregenerally obtained from relatively shallow sand and gravel beds in the vicinity of existingstreams. The proximity of these aquifers to surface streams also improves their rechargecharacteristics due to downward and lateral leakage from the surface water.

In 1984/85 8.320 GI of water \vas used \\ithin the Murray-Darling Basin for irrigation purposes(MDBMC. 1987). Of this 163 Gl. or approximately 3 per cent of the total. was groundwater.The ratio and quantities for the remainder of the MDB may be somewhat different and changesmay have occurred in the intervening decade but detailed. up-to-date statistics are not in areadily available form.

Murray-Darling Basin: Ecologically Sustainable Irrigation? II

Principles of Irrigation

It is a basic premise of any irrigation system that an excess of water, above plant requirements,must be applied to the crop. This excess water is called the leaching fraction and as a rule ofthumb should not exceed about 10 per cent of the applied irrigation and rain water.

A leaching fraction is necessary because plants, when taking up and transpiring water from thesoil, leave soluble salts behind. Taken to the extreme, plants could acrually kill themselves byconcentrating salt in the root zone. Hence it is necessary to have either an excess of irrigation orrain water to flush the soluble salts below the depth of the root zone.

The excess water (and salts) continue to drain downwards and evenrually add to the underlyinggroundwater table (Figure 4a). If the additions exceed the capacity of the groundwater system todrain out into a stream, or the sea.. a groundwater mound will develop beneath the irrigationarea. If the mound rises to within 1 to 2m of the soil surface then groundwater can evaporatedirectly to the aunosphere by moving upwards through the soil pores in much the same way aswater rises up through a piece ofbloning paper when it is suspended in a glass of water. As thecapillary water evaporates at the soil surface. salts are concentrated in and around the root zone.

Discharge of groundwater at the soil surface creates either waterlogging and/or salt scalds(Figure 4b), depending on the rate of discharge. Even good quality groundwater contains somesoluble salt and if it discharges slowly at the soil surface, salt concentrations in the root zonewill gradually increase, simply due to evaporation.

It is not always appreciated by irrigators that quite small amounts of water escaping below theroot zone can result in a relatively large rise in the water table (Figw-e 5). Although 40 per centor more of the subsoil volume consists of pore space, it is never completely dry. Hence the'effective porosity' may be as low as I to 5 per cent of the total soil volume. Thus the drainageof lmm of water below the root zone can result in an increase in the height of the saturated soilzone of20 to 100mm. That is, the height of the groundwater table increases by 20 to lOOmrn bythe addition of Imm of water. Increases in watertable heights, beneath irrigated areas. arefrequently in the order of 200 to 500mml year. For example in the Berriquin Irrigation Area(NSW) groundwater tables were 20m or more below the surface in 1950 but rose to within 2mof the surface in about 30 years of irrigation.

The mound is not only a hazard to the irrigated area but, because it creates a pressure onsurrounding groundwater systems, it has offsite effects as well. These effects may be manifestedas increased flow of saline water into neighbouring streams or as discharge through the soilsurface oflowlying neighbouring areas. Given that there is about 1.6 million ha of irrigated landin the MDB then groundwater mounds, due to irrigation, have the potential to influence aconsiderable area within the basin.

Unless the problems of groundwater recharge associated with irrigation practices can besolved on a basin-wide basis, the irrigation industry cannot possibly be regarded as beingecologically sustainable.

I ~ ,\ II/rray-Darling Basin: Ecologically SI/s/ainable I,rigotillil 0'

Figure -kl

Irrigation and Rain \Vater

Figure 4b

r" infall

Evaporation & Salt Concentration

irrigation

e'"3porath"e concentrationor salt

r" infall

\ I"n·,,,"·' )arl/lll! flul"Il1 T:cologicallr Sustainable Irrigation? 13

Figurl.:5

Groundwater Rechargl" due to nislill~ ~Hil moisture :It depth,groundwater recharge eneeds irrig:ltinll or rainfall input.

--. ---v~

;< 3 3c 3 3~

~~

" ~ 00- n n

~ or0~ ~ ~

'< ~ ~

0 0 ",~ 0., ~ "~r;

~

- ~~

~c.,

~ 5 0 ~" " '"~

~

'"~ c

"c

r; or <l ~

~ ~

" 0- :E 0- r; "~ 0 ;:; ~ 0-

"~ ~ ."

'"'" r; OT ~~~ 0 0

~~ ~ ~ ~ '";;; ~

~0

0 ~

0- ~~

".

14 Murray.Darling Basin: EcologicaJ/y Sw;IQlIfoble Irrigalion?

Reducing Groundwater Recharge

Reference to Figure 4a shows that reduction in groundwater recharge is related to a number offactors:

• The physical characteristics of the SOil are a major determinant factor. Excessivelypermeable soils allow rainfall and irrigation water to drain below the root zone before thecrop has a chance to use it. Given the spatial variability of many soils of alluvial origin thisfrequently presents a problem in the physical layout of irrigation bays.

• The water use characteristics of the cmi' grown can influence the amount of groundwaterrecharge. Such factors as the depth of the rooting system, the duration of the crop. theamount of leaf area produced, and physiological factors related to the arnoWlt of waterused per unit of dry matter production all affect the water use efficiency of the crop.

• Irrj~atjon practices that need to be considered include the method of applying water (flood,furrow, sprinkler, trickle), the speed with which excess surface water can be drained (thisalso involves paddock design and land surface levelling), the frequency of irrigation, andwhether any soil moisture monitoring techniques are employed.

The longer water is ponded on the soil surface the more opportunity there is for drainagedown through the prolile and for groundwater tables to rise. Thus tbe rice industry, whichdepends on maintaining a flooded soil surface for periods of 100 days or more,represents a major bazard witb respect to groundwater recbarge. On the other hand, witha deep-rooted fodder crop such as lucerne, it is technically possible to achieve quite lowleaching fractions.

Electromagnetic induction methods are now available for mapping soils in terms of whetherthey will be 'leaky' or not when subjected to irrigation (Beecher, 1994). However Statedepartments have been reluctant to apply the techniques on an industry-wide basis. Variousinfiltration tests or evaluations based on the thickness of underlying clay layers, as used in thepast, have simply not been good enough for determining the suitability of riverine plains soilsfor irrigation purposes.

All of these factors are under the direct control of the irrigator. Some options may be relativelyexpensive but they are not imJX>ssible to achieve. The decision to implement one or otherpractice is usually made on financial grounds but undoubtedly tbe availability of cheapirrigation water has not encouraged tbe adoption of environmentally responsiblepractices.

Murray-Darling Basin: Ecologically Sustainable Irrigation? 15

Irrigation Waste Water Disposal

Groundwater discharge will, in the future, affect practically all irrigation areas in theMDB because, unlike coastal catchments, groundwater cannot drain freely to tbe sea. TheMurray Basin is a saucer-shaped structure filled with largely water-saturated sediments. Thedeepest part of the basin (approximately 600m) is in the Renmark - Wentworth area andgroundwaters naturally gravitate in that direction. The River Murray also flows in that directionand has cut an outlet to the sea through the south-western rim of the basin. For any groundwaterto escape it must pass through this relatively narrow. sediment-filled gorge or discharge into theriver itself The restriction to flow means that watertables are close to the surface throughoutthe basin and that rainfall and irrigation water entering the land surface can only escape bybeing transpired by vegetation or by discharging through the soil surface. Unfortunately tbetype and distribution of vegetation systems that have been established since Europeansettlement canDot handle the rainfall inputs, let alone irrigation inputs.

Even with the management tools described above it is likely that a large proportion of irrigatedfarms will continue to contribute excessive amOlUlts of water to the underlying groundwatersystems. In parts of northern Victoria and in the Munumbidgee Irrigation Area, waterloggingand salinisation have reached such dimensions that some land is simply being written off as'sacrificial discharge areas'. Acceptance of sacrificial areas really means an admission offailure to manage irrigation systems in an environmentally responsible manner.

A part of that failure is due to past and present land managers, but inappropriate waterdistribution systems designed by departmental irrigation engineers have also contributed toleakage into groundwater systems over many decades. For example in Victoria water supplychannels to the Wimmera District are now having to be replaced with a pipeline due to theexcessive channel leakage. Also in the Jemalong-Wyldes Plains Irrigation Areas of NSW amain supply channel was built on top of an old levee bank of the Lachlan River simply becausethe levee was the highest part of the landscape and so facilitated water distribution to farms.However the light textured levee bank. soils allow considerable leakage into a local groundwatermound.

It is possible that a vegetation strategy could be devised that would restore the water balance toa state where groundwater discharge did not represent a threat to the environment. Howeverthis is only being approached in a piecemeal way at the moment through such Landcare-typeprojects as tree planting (Williams, 1995). In order to buy time whilst an effective biologicalsolution is implemented, the most sensible approach would be to install a comprehensivedrainage system and dispose of the waste water in an environmentally acceptable manner.

Extraction of groundwater can be achieved by installing horizontal drains below the depth ofthe crop root zone or by pumping water (vertical drain) from the groundwater zone. The cost­effectiveness of either depends on the hydraulic properties of the soil. For example, in somesituations one pump (tube well) may draw down the water table over an area of one to a fewsquare kilometres whilst in less permeable soils pumping may not be an option at all. In theJaner case horizontal drains are used and these drain into a common sump from which the wastewater is then pumped.

16 Murray-Darlmg Basin_· EcologlCOJJy Suxtainable IrrIgation?

Depending on the salt concentration of the waste 'Water. it i~ sometimes possible to mix it withexcess irrigation water that has been drained from the soil surface and then add it to goodquality supply water for the next irrigation (Figure 6). There is of course a limit to how manytimes such water can be recycled as the salt concentration increases with each cycle.

A large proportion of drainage water is not re·used at all. In the past it was often dischargedinto a natural drainway (and eventually into the Murray River system). Now it is commonlypumped to an evaJX>ration basin. Evaporation basins may be self-enclosed systems (in whichcase they have a finite life) or the concentrated brine may be pumped back into the river at timesof high river flow. The evaporation basin/dilution flow technique is presently the favouredoption although the longtenn environmental consequence of creating a pool of concentrated saltbrine beneath an evaJX>ration basin is still poorly understood. If thaI brine should unexpectedlybe mobilised into surrounding groundwater systems then there would be a potential forconsiderable environmental damage.

About 2 million tonnes of salt is discharged into the sea from the Murray River each year.Figure 7 shows that on average. salinity in the River Murray increases from <100 EC units atthe headwaters to about 800 EC units at Lake Alexandrina. Major increases in concentrationoccur at the junction of Barr Creek with the Murray and again downstream from Lock 5. Thelatter input is due to groundwater discharge directly into the Murray. as it comes under theinfluence of the bottleneck to subsurface flow. described earlier.

The health of land within the Murray basin depends to a great extent on the ease with whichgroundwaters can drain naturally, or be pumped. into that drain. In other words we are tryingto manage the Murray both as a supply line of good quality water and as a drain forhighly saline ground and evaporation basin water. It is not a happy combination. Othercountries faced with similar problems have separated the supply and waste disJX>sal problemsby constructing dedicated drainways.

For example Pakistan is building a canal stretching more than a thousand kilometres through theIndus Valley to carry waste groundwaler to the sea. In California., where irrigatiun salinityproblems commenced in the I880s, there are nwnerous concrete-lined drains leading intowetlands. Agro-politics and environmental concerns are still holding up the construction of amain disposal drain to the sea - 20 years after its first proposal. Egypt also faces a massivedrainage problem now that the Aswam Dam has prevented a regular flushing of salt out of theNile floodplain.

Murray-Darling Basin: Ecologically Sustainable Irrigation? 11

Figure 6

Evaporation Basin

Irrigation Water

REUSE

Surface Drain--------------------------------~

Horizontal Drain

-----------------------~

VerticalDrain

.. "

GroundwaterMound·

18 l/llrra)'-Darli"K Basi,,: £cQlogicully Sustainable Irrigalion?

Figure 7

River Murray Salinity Profile

~;',)J

I,~ Y.l

"<oJJ

"~00 ~

~'"~,,u::,XlOt••" 0~

i:.:J ,;-••'00 ::-=i~••:.

""i>i

II,.--

___ I..""""....

__ 1.'eChan

//

----

The Murray: MDBC (1990)

,

i:=:'~/lt:f .4.IL~/rdj" I

·Hurray-Darling Basin: Ecologically Sustainable Irrigatio,,? 19

Figure 8

Irrigation Development in the Murray-Darling Basin

• Stale sponsored irrigation

Major privale off-riverirrigation schemes

Major areas of irrigationby privale river pumping

ABARE (1991)

20 Murray-Dadmg Basin: £Cologlcally Sustainable Irrigation?

Irrigation Water Use

The irrigation areas of the MDB are shown in Figure 8. and surface and groundwater irrigationusage for 1984/85 is provided in Table 1. It will be noted that groundwater extraction byirrigators was highest in the Condamine-Culgoa (Qld), Namoi and Munumbidgee (NSW),Broken R..iver (VIC). and Lower Murray (SA) catchments. Diversions for irrigation increased by33 per cent between 1984/85 and 1992/93 (Table I) with an extraordinarily large increase inthe Upper MurraylKiewa/Ovens region of Victoria. There is, however, some doubt concerningsome of the comparisons as the MDBC has now changed its stream flow accounting system.Such changes make it difficult to extract valid trends for particular irrigation areas.

Some 75 per cent of Australia's irrigation occurs in the MDB and it presently produces anannual gross income of about $4.5 billion from the production of livestock, fodder crops, rice,cotton. fruit and vines.

The total area irrigated mmually is approximately 1.6 million ha (Table 2). One difficulty inobtaining accurate figures for irrigated areas is due to the nature of the agricultural enterprise.For example data for irrigated grain and hay crops is relatively straightforward, but wherefanners simply apply water once or twice a year to grazed pasture land, they do not necessarilykeep accurate records oCthe area irrigated. An 'autumn flush', to stimulate pre-winter groy.,1h ofsemi-improved pastures is a common practice in many irrigation districts. Whether thisqualifies the land as being 'irrigated' is a moot point.

Water application rates are commonly in the range of 5 to 15 Mllha, i.e., the equivalent of anextra 500-1500rnm of rainfall per year. High water use crops such as rice may have applicationrates well in excess of20MI!ha, depending on the soil characteristics.

Water is supplied under licence either by State diversions from the rivers, private diversions orprivate groundwater pwnping. The cost of supplied water varies from state to state but rangesfrom as low as $2.78/M1 in the Namoi Valley in NSW to S62/M1 in the Wimmera District inVictoria. The large price variation is due almost entirely to the cost of distributing water. TheNamoi irrigators provide their own distribution system whereas in the Wimmera District waterhas to be piped to the area.

Various fonnulae for water use are applied by the State water authorities to cover basic andexcess aJlocations and many historical anomalies still persist. For example, until recently in thelemalong-Wyldes Plains Irrigation Districts, water used in excess of the entitlement costconsiderably less per unit that for the entitlement itself Similarly. some areas are charged fortheir full allocation whether they use it or not. Such pricing structures encourage wasteful useof the water resource.

Murray-Darlinf? Ba.~in: Ecologically Sustainable Irrigation? 21

Table!

Irrigation Water Use in the Murray-Darling Basingigalitres (GI)

1988/89 1984/85'Averageto 1992/93"

No. Catchment Groundwater Surface Water Surface Water

I Upper Murray 0.1 3.22 Kiewa River 0.1 5.1 15673 Ovens River 2.5 11.24 Broken River 25.9 352.65 Goulburn River 66 1304.3 17107 Loddon River 9.0 1210.2

6 Campaspe River 9.0 136.3 1018 Avoca River 0.2 19.19 Murray-Riverina 5.1 1637.1 205310 Murrumbidgee 21.2 1898.6 2443

II Lake George 0.1

12 Lachlan 7.5 110.8 249·"13 Benanee 1.7

14 MaBee 6.2 488.026 Lower Murray River 43.7 220.0 86015 Wimmera - Avon 0.3 \9.316 Border Rivers 2.0 67.7 7817 Moonie not23 Warrego 0.2 applicable24 Paroo18 Gurydir 1.8 155.0 30019 Namoi 38.6 98.0 24820 Castlereigh 2.1 0821 Macquarie-Bogan 4.8 198.3 46522 Condamine-Culgoa 76.6 53.0 132

Upper Darling 188Lower Darling 66.3 335

TOTAL 263.4 8056.8 10729

, MDBMC (1987)" MDBC (1995. unpublished)... NSW Water Resources Council (1991)

22 Murray-Darling Basin: Ecologically Sustainable Irrigation?

Table 2

Area of Irrigated Crops and Pastures in the Murray-Darling Basin1991193 a.(hedares)

Qld NSW -Vic SA MDB1991 121157 859656 470400 110000 15612131992 118214 895475 452000 104000 15696891993 128014 864388 478500 117000 1587902

a. Estimated by summing dala from the following ASS Slatistical Divisions:Qld: Darling Downs, South West, Fitzroy, Central WestNSW: Northern, North Western, Central West. Murrumbidgee, Murray, WestVic: Wimmera, Mallee, Loddon-Campaspe, Goulbum, Ovens-MurraySA: Total State

Managing the Water Resource

Management of River Murray flow is the responsibility of the Murray-Darling BasinCommission (MDBC) which is the executive ann of the Murray-Darling Basin MinisterialCOWlcil (MDBMC), representing Queensland, New South Wales, Victoria, South Australia andthe Commonwealth. It is the primary responsibility of the MDSC to regulate river flow onbehalf of the member States. In effect this means that South Australia, which contributesvirtually nothing to swi'ace flow, receives at least 1850 GI each year. New South Wales andVictoria share flow above Albury and retain control of their respective tributaries below Albury.

The initial River Murray Waters Agreement 1914 between the Commonwealth, New SouthWales. Victoria and South Australia concerned water flow only. In 1976. on therecommendation of the four governments, the River Murray Commission (RMC) commencedmonitoring water quality and a nwnber of environmental parameters in the Murray Basin.

A new River Murray Waters Agreement 1982 became a Schedule of the River Murray WatersAct. 1983. The laner was amended in 1987 to become the Murray-Darling Basin Act 1983 andformally established a Murray-Darling Basin Ministerial COWlcil (MDBMC) and the Murray­Darling Basin Commission (MDBC). Queensland joined the Murray-Darling Basin Agreementin 1992 and now participates in the Commission's Natural Resource Management Strategies(NRMS). The Murray-Darling Basin Act 1983 was repealed to become the Murray-DarlingBasin Act 1993. and included the new Murray-Darling Basin Agreement 1992. Schedule C ofthat Agreement contains the details of a Salinity and Drainage Strategy. It is expected that otherStrategies (Algal Management. Irrigation Management and Natural Resource Management) willbe wTinen into the Agreement as they become finalised.

Murray-Darling Basin: Ecologically Sustainable Irrigation? 23

Managing Water Supply

Traditionally State water resources departments have been responsible for the supply anddistribution of irrigation water. However, in NSW, Victoria and South Australia, there is a movetowards privately run distribution systems. This has been brought about largely by the irrigationindustry's long proclaimed conviction that it could handle the task more efficiently than the'government'. Also, it appears that governments are not showing too much reluctance at passingon the responsibility of managing a resource that is both costly to operate and which has majoradverse impacts on the environment.

The Irrigation Corporation Act 1994 of the NSW Parliament formalised this arrangement forColeambally, Jemalong-Wyldes Plains, Lower Murray, Mwrny and Murrumbidgee areas. TheAct made specific reference to the environment and to the efficient use of water as matters thatshould be considered before granting a licence to an irrigation corporation. It also mentions'land and water management plans' on a number of occasions but nowhere does it define justwhat they might be.

Regardless of these proviSIOns Irrigation Management Boards, conslstmg of communitymembers, are already assuming responsibility for water deliveries whilst Land and WaterManagement Plans are still being developed. It remains to be seen whether the Boards (orCorporations) pay any more than lip service to removing the groundwater problems that havedeveloped under decades of government department control.

Managing Water Quality

A number of resources management strategies, including a 'Salinity ancj Drainage Strategy',have been developed (MDBMC, 1989). For the first time past argwnents about who was toblame for polluting the river system were put aside and the States, together with theCommonwealth, agreed on a course of action to restore water quality and other naturalresources within the Murray-Darling Basin.

Under the Murray-Darling Basin Agreement 1992 each State makes a financial contributiontowards the management of the river and remedial works designed to reduce the inflow of saltinto the Murray River (Table 3).

24 Murray-Darling Basin: £CologtcallySustainable Irrigation?

Table 3

Contributions under the Murray-Darling Basin Agreement(S'OOO)

91/92 92/93 93/94Commonwealth 6203 5864 5962

I New South Wales 9264 9973 9836Victoria 9264 9979 9842South Australia 9264 9880 9758Queensland 0 347 199

33995 36043 35597

The States then receive salt credits that allow them to dispose of some of their own salinetirainage water back into the river. Only drainage actions approved by the MDBMC can beimplemented. The net result should be:

• a steady decrease in average salinity at Morgan (SA) which, because it is downstreamfrom the major irrigation areas, is the reference site with respect to monitoring riversalinity.

• triumph for a commonsense approach to solving a natural resource problem.

The perfonnance of any salt interception scheme designed to reduce inflow of sait into the rivercan be assessed quite accurately at the extraction point in terms of tonnes of salt removed.However the variable nature of water and salt flows (Figure I) means that little credence can begiven to their statistical trend lines (Close, 1990). Thus the eITect on river water quality dueto landuse changes, such as more efficient irrigation techniques or reafforestation, cannotbe assessed qu?ntitati,'ely at this stage. Given the large temporal variability in river salinityit is curious that the Alurray-Darling Basin Agreement 1992 defines a 'significant effect' as onethat alters the average salinity at Morgan by the extraordinarily small amount of 0.1 EC unit. i.e.,about 60 milligrams salt per 1000 litres.

Managing the River Environment

Salinity is not the only aspect of water quality in need of attention. Pollution of the riversystems with urban and agricultural wastes has seen a marked increase in the occurrence oftoxic algal blooms. particularly during periods of low river flow. Hence considerable effort isnow being directed towards protecting the river system from being used as a waste disposalunit. and for the reuse of waste water for other productive purposes. On average, irrigationdrainage contributes about 10% of the phosphorus and nitrogen loads measured in theMurray-Darling river system each year. (GHD. 1992)

Murray·Darling Basin: EcologicallySwlainable Irrigalion? 25

Urban and sewerage waters account for greater than 30% of phosphorus and nitrogen loads inthe river system in an average year. Treatment and use of this water for irrigation of tree lotshas been trialled successfully in a number of places and this may well become the norm formany growth centres along the MDB waterways. Similarly, revegetation of the riparian zonemay soon be seen as the most effective means for preventing diffuse sources of surfacepollutants from entering waterways.

The MDBMC is now reserving water for flushing rivers at times of very low flow as a means ofpreventing algal blooms. Such 'environmental' water use does. of course, create some conflictwith irrigators, particularly dwing periods of drought. Another 'environmental' watermanagement initiative in 1994 was the agreement by the MDBMC to allocate an average of I()(}GlIyr towards the periodic flooding of the Barmah-Millewa redgum forest area. Regulation ofriver flow over many decades had seen a marked deterioration of this forest due to lack ofregular flooding. In a similar vein New South Wales reserves water in the Lachlan andMacquarie valleys for wetland and waterbird habitat management.

It seems that at last we are recognising that the surface water resources of the MDB are not justfor agriculture and human consumption, but are also a very necessary part of the widerbiological environment.

The Irrigation Industry Dilemma

The dilemma facing the irrigation industry in the MDB is that. on one hand, it is regarded asbeing highly efficient and productive; on the other hand. it is clearly responsible for aconsiderable amount of environmental damage. The MDBMC (1989 background papers)estimated that there are more than 500,000 ha of irrigated land with a water table at less than 2mfrom the soil surface. Of that area, ahout 150,000 ha has surface soil salinity problems. Ifattempts to reverse this process are not successful then over the next 30-40 years the area withshallow watertables is likely to double and the proJX>rtion with salinised surface soils willincrease markedly.

Surrounding dryland agricultural areas are also suffering from rising groundwater tables andsecondary salinisation of surface soils caused by excessive clearing of deep-rooted, pennanentvegetation. The cause is the same as in irrigated areas, viz, recharge of groundwater systems byrainwater infiltrating below the rooting depth of existing crops and pastures. Although the rateof groundwater rise is probably only one fifth to one tenth of that in irrigated areas. it never-the­less is responsible for more than 1 million ha of salinised land in :he MDB.

The problem is not just one of degrading irrigated land as adjacent dryland areas are alsoaffected. However the fact that some of the dryland problems originate from their own landusepractices makes it difficult to apJXlrtion blame. Tbis situation is botb a challenge to tbeenvironmental conscience of irrigators and an escape from accepting responsibility.

26 Murray.Darling Basm: Ecologically Sustainable Irrigation?

The Government Dilemma

There has been a massive increase in infonnation provided to irrigators and dryland farmersthrough the National Landcare Program (Williams, 1995) but tbere is still a strong sense ofdenial, or at least a considerable amount of selective acceptance of scientific information,in the irrigation industry. This is well demonstrated by Graham Blight (1992), (then)President of the National Farmers' Federation and himself a rice farmer, who in presenting apaper on 'Sustainable water use: an agricultural perspective'. said:

In the Murray-Darling Basin, salinisation is largely due to the slow change over the last500,000 years to a more arid climate. and not solely due to the impact of settlement. Theregion's salt problem is more a result of the geological structure which acts as a salt trapthan of the impact of fanning practices.

Of course it is not only the irrigation community that has difficulty in coming to tenns withenvironmental realities. For example. Ashley Cooper. Vice-President of the QueenslandCattlemen's Union, speaking about clearing trees in areas close to the Dividing Range, wasrecently quoted (AAP, 31-3-95) as saying,

It is a fact of life that land degradation in those areas is the result of too many trees that donot allow grass to grow.

Both landusers reflect a very common attitude amongst irrigation and dryland fanners, viz.,accepting information supportive of their own industry and rejecting less favourable evidence.

However one might well be inclined to sympathise with both landholders when faced withacademic jargon from governments and emotive statements by some environmentalists. Forexample, the following erudite statement on salinity would not be likely to arouse any feelingsofenvironmental responsibility amongst irrigators ( Powell, 1994):

The grim spectacle of salinisation could be interpreted as a warning of primeval naturalpurifications. a violent purging of presumptuous intruders.

Whilst these statements may cause wry comment, or righteous indignation in some areas. theyare really symptomatic of a major problem facing govenunents committed to implementingecologically sustainable development policies. Environmental advisors aDd governments, forwbatever reason, are simply not creating a sense of urgency amongst irrigation farmen tort'view tbeir options before large amounts of land are irretrievably damaged. .

Water diversions. presumably dominated by irrigation demand, continue to rise regardless ofenvironmental considerations (Figure 2). Much of that increase, at least since the early 1980s isdue to a fuller utilisation of the original water entitlements and to trading in licences. rather thanto govenunents issuing new licences. Nevertheless it indicates scant regard for the very landresources upon which the industry depends for its survival.

Murray-Darling Basin: Ecologica/Jy Sustainable Irrigalion? 27

The irrigation industry would probably argue that it actively supports research through variousgovernment Corporations and participates in the development of Land and Water ManagementPlans. However most of the research is directed towards maximising production rather thandevising sustainable systems. It is possible that the regional Land and Water ManagementPlans, now nearing completion in a number of irrigation areas, will provide a vehicle foraddressing this problem in the future.

Of all the irrigation practices contributing to environmental damage, using permeable soil is themost intractable. From the author's personal experience there is still considerable resistancewithin the industry to any thought of retiring land from irrigation, even when that land isdemonstrably unsuitable with respect to ground water recharge. It really should be the fintpoint of negotiation between irrigaton and governments but to date little effort has beendirected towards tbis problem by either party.

Government Initiatives

Much has been written about government involvement in developing irrigation areas, the supplyof water storage and distribution systems, irrigation agronomy research, and research into thesubsequent environmental problems associated with irrigation. It is not the pwpose of this paperto review a topic that has been, and still is being, reviewed regularly. The overriding fact to befaced is that practically all irrigation areas in the MDB are creating environmentalproblems.

There is now to to 15 years experience of government programs designed to assist intechnology transfer in areas suffering from water logging and salinity. There is also therealisation that although information transfer schemes are generally regarded by the farmingcommunity as a 'good thing', there is still a major blockage in the system with respect to theadoption of ecologically sustainable fanning techniques.

Even in the longer running Victorian experience the process is painfully slow. For example,Stephen Coats (1994) in recounting his experience with irrigators in the Shepparton area, 'MUte:

Denial is the first reaction, followed by frustration and perhaps anger and thenrationalisation and discussion. This eventually leads to acceptance and then action.Perhaps the Goulbum Valley is up to the rationalisation and discussion phase...

That is a description of an area that has been subjected to intense community education andtraining for more than a decade!

It is difficult to believe that a majority of irrigators has not heard of groundwater problemseither through Landcare groups or via various agricultural media outlets. If they are aware andare choosing to ignore the messages then there will need to be a radical rethink of the approachthat should be adopted by governments. A clue to this situation may lie in a statement by Capeet a1 (1994):

Most people will not change unless the pain of change is perceived to be less than the painof staying the same.

28 Murray-Darling Sa.rln. £c:oJof{lca/~,' Sustainable 1r"?,atlOn"'

This could be interpreted as saying:

• change will not take place until the landholder is on Ihe verge of going broke. or

• change will not take place unless governments impose compelling financial incentives.

In the first case the process of 'going broke' would almost cenainly entail considerableenvironmental damage to the particular irrigation farm and also to offsite areas. Hence it is notsensible for governments to sit back and wait for the inevitable to take place.

In the second case considerable thought has already been given 10 the measures governmentsmight employ. Recommendations (ESD Working Groups: Agriculture, 1991; Council ofAustralian Governments, 1995) seem to favour:

• encouraging use of water in more profitable enterprises by making irrigation licences atradeable item;

• increasing the cost of irrigation water to achieve complete cost recovery;

• removal of cross-subsidies used to reduce water costs; and

• imposing a tax on waste products. i.e .. the polluter pays.

Simmons et al (1991) point out that subsidisation costs are in the order ofS)OO million/year forthe basin and that efficiency gains of about $40 million/year could be achieved through thetransfer of water entitlements.

Undoubtedly this 'carrot and stick' approach would have some benelicial effects but like manystrictly economic approaches there could well be some unintended consequences.

One obvious consequence is that the sale of irrigation quotas simply shifts the groundwaterrecharge problem to another area, where the degradation process commences all over again. Asecond difficulty would be in devising and administering a sensible monitoring system onindividual properties to assess a pollution tax.

TIle then Commonwealth Minister for Primary Industries and Energy, Simon Crean (1992),expressed the opinion:

You are not going to address. in my view. the solulion by saying you go out and chargefanners more for water. because that marginalises the issues in a way that polarises thedebate. I think the real problem with the ESD debate is that it has been polarised.

Murray·Darling Basin: Ecologica//y Sustainable Irrigation? 29

Determining Irrigation Policy

The Present Approach

The Australian and New Zealand Environment and Conservation Council (ANZECC) and theAgricultural and Resource Management Council of Australia and New Zealand (ARMCANZ)(1994) released an outline of policies directed at a National Water Quality ManagementStrategy (NWQMS) as part of the National Strategy for Ecologically Sustainable Development(1992). The stated policy objective of the NWQMS is:

to achieve sustainable use of the nation's water resources by protecting and enhancing theirquality while maintaining economic and social development.

This all-embracing objective is a clear statement of where the nation wants to go but. if takenliterally, it might well be regarded as impractical and idealistic. Even if irrigation in the MDBceased today it could still take decades before groundwater mounds dispe=d and damaged landcould be rehabilitated. Also groundwater recharge in dryland agricultural areas would have tobe controlled before there was any chance of preventing discharge of highly saline groundwaterback into the River Murray.

The objective, enunciated above, requires some clarification. In the 'Policies and Principles - AReference Docwnent' (ANZECCIARMCANZ, 1994b) the statement on objectives commenceswith the words 'to pursue sustainable use .. .' rather than 'to achieve sustainable use .. .' Howeverin the main text it reverts to 'achieve'. The irrigation industry, for the reasons describedpreviously, would find it virtually impossible to fulfil the first objective but might well beprepared to 'pursue' sustainable water use.

The 'Policies and Principles' document is directed principally at water quality in relation to pointand diffuse sources of pollution. However in assessing irrigation, or indeed agriculture ingeneral, an over-riding factor is water quantity. Excess water (rainfall or irrigation) is itself awaste product of those industries because it mobilises soluble salt and frequently discharges thatsalt into distant parts of the environment. The absence of an easily monitored cause-and-effectlinkage appears to have been recognised by ANZECCIARMCANZ since it included a 'bestmanagement practice' philosophy for diffuse source pollution management. But this begs thequestion of whether the authors simply chose the soft option or whether they were implying thatit really falls into the 'too hard' hasket.

Waste management options were clearly defined in a series ofactions of decreasing desirability:

• waste avoidance

• recycling or waste reclamation

• waste re-use

• waste treatment to reduce potential degrading impacts

• waste disposal

30 Murray-Darling Basin: EcologIcally SWlamable Irrigation?

In applying these options to the irrigation industry it is clear that there are a nwnber of landmanagement options designed to avoid the wastage of water. Recycling and re-use of drainagewater have been discussed and their limitations recognised. There is no economically viablepotential for treating drainage water to remove soluble salts and the presently preferredevaporation basin/dilution flow disposal system has been described in less than enthusiasticterms. Together they add up to 'best management practices' and together they are unlikely tosolve the problem of groundwater recharge to a sufficient degree to prevent continuingenvironmental damage in large parts of the Murray-Darling Basin.

Hence discussion of 'regulatory' and 'market' approaches are more academic in nature thanrealistic at this stage. In effect the micro-econo.nic reform approach, adopled by the Council ofAustralian Governments. says 'we will keep on increasing the cost of irrigation until either theinefficient users drop oul or the problem goes away'. Of course this approach is tempered withstatements concerning social equity. conservation of biodiversity, dealing cautiously with risk.economic diversity/resilience and global issues. However these issues have barely surfacedwith respect to the irrigation industry. It would seem that econocrats, endoned by the majorpolitical parties, have little appreciation of the biological system with which they aredealing.

It also seems surprising that government technical advisers are apparently unaware that thegroundwater problem simply wiJI not go away in tbe foreseeable future by more efficientwater use alone. As explained earlier. the necessity of a leaching fraction and the spatialvariability of soils will almost certainly ensure that the process of excessive groundwaterrecharge will continue, even under so-called 'best management practices'.

Possible Future Approaches

Clearly, the first policy statement governments need to make with respect to a system ofirrigated agriculture in the MOB, is one that lets irrigators know whether they have a long termfuture in that industry. So far this does not appear to have happened since the only statementsreleased to irrigators concern options for increased future controls. If govenunents. in theknowledge of certain continuing environmental damage, do support the notion of a $4.5billion/year industry then they must:

• state the level of environmental damage that society is prepared to condone; or

• be prepared to install a groundwater disposal system to protect the environment.

The first option would mean providing very specific. area by area, definitions of the amoWlt ofgroundwater recharge that would be permissible. and providing monitoring systems to ensurecompliance. The second would mean a comprehensive drainage system with disposal ofwaste water external to the basin. Surface and subsurface drainage schemes already exist inmost irrigation areas. For example in the Murray Basin aoom 700.000 hectares are serviced bysurface drains and I 15.000 hectares by subsurface drains (MDSC. 1990). However a further900.000 ha and 350.000 ha \,,·ould benefit by surface and subsurface drainage. respectively.Moreover it is questionable whether the existing disposal systems can be regarded as beingenvironmentally sound.

Murray-Darling Basin: Ecologically Sustainable Irrigation? 31

It is technically feasible to install a drainage system that would remove all waste groundwaterfrom irrigated areas and dispose of it in an environmentally acceptable manner. A 1990 reviewof the 'pipeline to the sea' proposal (MDBC, 1990) showed that full watertable control wouldcost about $6 billion. with an annual operations and maintenance cost of $66 million. The lanerrepresents less than I per cent of the annual $ I0-12 billion of agriculnue production from theMDB. All options considered showed a negative present value. However such a calculationtakes no account of the value that the community in general places on being able to visit anenvironmentally healthy countryside or river system. Neither does it take into account the factthat past governments have actively supported land use systems that have created the presentproblems and that there may be a moral obligation to rectify that situation.

Two major advantages of installing an effective drainage system would be:

• for a moderate extra cost it would service not only irrigated lands but dryland farmingareas as well. In fact, as mentioned previously, there is little point in remedying irrigationrecharge in isolation because dryland recharge is of at least the same magnitude and is afar more intractable problem to solve.

• it would enable the implementation of a drainage tax on individual irrigated holdings andhence act as an incentive for more efficient water use. Drainage volumes per unit areawould provide a very good monitoring test for assessing compliance and performance.

One argwnent against the provision of a comprehensive drainage system is that it couldencourage the continued wasteful use of irrigation water. However, as suggested above. itwould be quite feasible, in consultation with the irrigation industry, to arrive at 'reasonable'water application rates for particular soils and for particular crops. The technology exists formapping the relative risk of different soil types (Beecher, 1994) and the technology also existsfor monitoring and mapping shallow groundwater systems. The fact that these tools have notreceived widespread use in the past is probably more a reflection on the willingness ofdepartments involved in the irrigation industry to produce this type of infonnation rather than alack of resources. In fact one Land and Water Management Plan, at Berti in South Australia,has implemented a system based on perfonnance. If a property is unable to meet an agreed setof water-use conditions the water entitlement is bought back by the water authority and the fannis converted to a dryland system (Conroy, 1995).

Although not specifically advocating a drainage system. a more radical funding system has beensuggested by Meyer (In Conroy, 1995). He supports an 'environmental levy' on all foodconswned to ensure that food-producing resources are protected. Such a proposal for the S10billion/year food industry is certainly consistent with present government policy in other areas;e.g., funding road infrastructure through a multi-billion dollar per year fuel tax.

Regardless of the final agreed fonnula.. it is essential that me irrigation industry be consulted ina meaningful way as a 'bunker' reaction has developed in response to being singled out forcriticism. It is relatively easy for the community to blame irrigation farming systems forenvironmental damage and to ignore other landuse practices. Likewise. State Departments areequally sensitive to the issue of blat, Ie.

32 Murray-Darling Basin: Ecologically Sustainable Irrigation?

The Commonwealth and States Agreement on the management of the Murray-Darling riversystem provides a good example of what can be achieved in such a divisive and threateningsituation. The governments simply agreed to wipe the slate clean, as far as past managementpractices were concerned, and to start again with an agreed set of rules. All partners to theagreement contribute financially and receive trade-offs in return.

There is no reason why similar contractuaJ agreements could not be worked out with irrigatorsand dryland fanners. The trade-off between providing an effective drainage system, and henceincreased productivity, would be the rationalisation of the inigation water system to meet themicro-economic objectives of COAG. Also there wouJd need to be trade-offs concerningirrigation practices and environmental perfonnance with realistic compensation mechanisms forconvening to an approved dryland system.

It is unlikely that anyone formula would apply to all irrigation areas due to their widegeographic spread and their relative impact on the surrounding environment. However it shouldnot be beyond the wit of irrigators and governments to come to a mutually profitable approach.

Murray-Darling Basin: Ecologically Sustainable Irrigation? 33

References

Australian and New Zealand Environment and Conservation Council (ANZECC) andAgriculture and Resource Management Council of Australia and New Zealand (ARMCANZ)(1994a) Water quality management - an outline ofpolicies.

Australian and New Zealand Environment and Conservation Council (ANZECC) andAgriculture and Resource Management Council of Australia and New Zealand (ARMCANZ)(1994b) Policies and principles for water quality management - a reference document.

Australian Water Resources Council (AWRC) (1992) Water quality management in the ruralenvironment: A reference docwnent. AWRC, Australia.

Beecher, H. G. (1994) Identifying groundwater recharge sites in irrigated landscapes using EMinduction techniques. NSW Remote Sensing Newsletter, 5., No.2.

Blight, G. (1992) Sustainable water use: an agricultural perspective. in, Proceedings NationalConference on 'Water quality management and ecologically sustainable development:Delivering opportunities. AWRC & ANZECC, Adelaide.

Close, A. (1990) The impact oJman on the naturolf/ow regime. in, The Murray (eds N. Mackay& D. Eastburn). Murray Datling Basin Commission, Canberra.

Cape, 1., Chatnala, S. and Syme, G. (1994) National Program Jar Irrigation R&D: Technologytransfer and adoption in irrigation. Land & Water Resources Research & DevelopmentCorporation (LWRRDC), Canberra.

Coats, S.(1994) Keys to successful industry development. in, National Program for lnigationR&D: Technology transfer and adoption in inigation (LWRRDC), Canberra.

Commonwealth of Australia (1990) Ecologically sustainable development. A Commonwealthdiscussion paper. Dept Prime Minister & Cabinet, Canberra.

Conroy, F., (1995) Sustainability: irrigation in the balance. Rural Research, No 166, 15-17.

Council of Australian Govemments (COAG) (1995) Repart oj the expert group on assetvaluation methods and cost-recovery definitions for the Australian water industry. Feb. 1995

Crean, S. (1992) Water quality management and ecologically sustainable development. in,Proceedings National Conference on 'Water quality management and ecologically sustainabledevelopment: Delivering opportunities. AWRC & ANZECC, Adelaide.

Ecologically Sustainable Development Working Groups (1991) Final Report. AGPS. Canberra.

34 Murray-Darlmg Basm: £cologlctJ/~~' Sustainable IrT/gation?

Fleming. P. F. (1982) IrriKation and drainaKe in the Murray-Darling Basin. In Murray-DarlingBasin Project Development Study: Working Papers. CSIRO. Division of Water and LandResources. Canberra.

Guneridge. Haskins & Davey (GHD) (1992) An im·e.uigation of nwrient pollution in theMurray-Darling River Jystem. Report to MDBC. Canberra.

Murray-Darling Basin Ministerial Council (MDBMC). (1987) Murray-Darling Basinenvironmental resources study. MDBMC. Canberra.

Murray-Darling Basin Ministerial Council (MDBMC). (1989) Murray-Darling Basin naturalresources management strategy: backgroundpapers. MDBMC, Canberra.

Murray-Darling Basin Ministerial Council (MDBMC). (1989) Salinity and Drainage Strategy.MDBMC, Canberra.

Murray-Darling Basin Commission (MDBC) (1990) A pipeline to the sea. Report prepared byGutteridge, Haskins & Davey; ACIL Australia; Australian Groundwater Consultants.

Murray-Darling Basin Commission (MDBC) (1990). Report to the Murray-Darling BasinMinisterial Council on a Drainage Program for the Murray-Darling Basin.

Murray-Darling Basin Commission (MDBC) (1993) Algal Management Strategy for theMurray-Darling Basin. Draft. MDBC. Canberra.

New South Wales Government (1994) Irrigation Corporations Act 1994 No.4!. New SouthWales.

New South Wales Water Resources Council (1991) Water Facts.

Powell. 1. M. (1994) Environmental degradation. '.mstainability' and the Murray-DarlingBasin. People and Place. 2.- 6-13.

Simmons. P.. Poulter. D.. and Hall. N.H.. 1991 Management a/irrigation water in the Murray­Darling Basin. ABARE Discussion Paper 91.6. Commonwealth GoV!. Printer, Canberra.

Williams. B.G. (1995) LancJcare and the Mythical Money Tree. Parliamentary ResearchService. Research paper No. 22. Dept Parliamentary Library, Canberra.

World Commission on Environment and Development (WCED) (1987) Our Common Future,(the Brundtland Report). Oxford University Press. Oxford.