Water 229

Chapter 6

WATER

Most human population centres around the world have developed where:

• there are permanent supplies of water;• the water is of adequate quality.The term, adequate quality, means the water:• does not contain excessive amounts of suspended muddy material;• does not contain harmful dissolved salts or other chemicals;• does not have any objectionable odour or taste.

Water is one of the most important resources on Earth. It is essential to maintainall forms of life - human, animal and plant. Water is not only needed by everyindividual for drinking and washing, it is also required for gardening, farming anda wide variety of industrial activities. But, like any other mineral resource, wateris unevenly distributed over the Earth's surface. Some areas have large, readilyaccessible supplies - elsewhere water is scarce or absent. Most city dwellers inAustralia probably take it for granted that they always will have a supply of freshwater available at the turn of a tap. Vet water is not a limitless resource. Australiais one of the world's driest lands, where water is a resource that must be managed,i.e. collected, handled and used efficientlY.

~.

).60.2

96.2

100.0

Storage Total water S!:ore Available freshwatercomponent

volume ~. volume(kmJxIO') (km1xIOJ)

oceans I 458000 97.2 not available

icecaps and glaciers )2 250 2.15 not available

underground watergroundwater 9 )oo 0.62 9300soil moisture 7: 0.OO5 nOl available

surface waterlakes )45 0.02) )45streams 15 0.001 15

atmospheric water 15 O.OOI not availableI 5OO 000 100.0 9660

Saline water inoceans: 97.2070

• Ice capsand glaciers: 2.15070

" Groundwater: 0,625070• Surface Water: 0.0240':'0.. Atmospheric

Waler: 0.001 %

Figure 6-1Rehabilitation of a town watersupply bore at Wyatt Street,Portland, 1988.This bore was drilled in the late19505 to supply part of the waterused in the town of Portland.After several decades, the supplydeclined because the iron pipesdown the hole had rusted. TheDepartment of Industry DrillingUnit rehabilitated the bore byremoving the old casing andscreens and replacing them withnew stainless steel equipment. Alarge rotary drill was used to raiseand lower tools in the hole.Usually these machines are used todrill to depths of up to 1500metres. With this machine, drillingmud (bentonite) was passed downthe hole throughout the operation.The mud served various purposes.In particular it stopped the flow ofhot artesian water I while work wasin progress, by filling the pores ofthe surrounding rocks. In thephotograph, rehabilitation hasbeen completed. Hot water andsteam were allowed to gush fromthe hole until the mud was cleanedout. (Photograph courtesy ofDepartment of Industry).Figure 6-2 (right below)Distribution of water around theworld.The total volume of water in theworld is about 1500 million cubickilometres. Most of this water istoo salty for human consumption.Only a small amount is readilyavailable freshwater and over 96%of this occurs underground.

230 Chapter 6

Hydrology

Water cycle

Unfortunately people cannot readily use the largest accumulations of water onour planet. The vast oceans are too salty for most uses and, so far, it is too expensiveto purify sea water because of the high energy costs involved. The polar ice capsare also large storages of pure water, because they are formed from snow and hail.However, no practical method has been found to transfer this water to the populatedarid pans of the world where it is needed.

Apart from its uses as a mineral commodity, water also plays a major rolein many natural physical and chemical processes. Some of these processes haveadver e effects on mankind and wherever possible, efforts are made to controlthem. For example, the power of flowing water over land can lead to destructivesoil erosion, flooding rivers can cause widespread damage to land and property,and the seas are constantly attacking many coastlines. Because flowing water cancarry large loads of sediment, silt may eventually fill reservoirs, lakes, channels andharbours. The quality of water can be degraded because water can readily dissolveand transport harmful salts and other polluting chemicals.

The science of water is called hydrology. It concerns the occurrence, distribution,movement and properties of water in its three physical forms - solid, liquid andgas - on and below the Earth's surface and in the atmosphere.

Just as some economic geologists specialise in the search for new deposits ofmetallic ores or fuel minerals, there are others whose interest is chiefly water. Suchspecialists are called hydrogeologists or simply hydrologists. Their main tasks areto identify where suitable water supplies occur and to ensure that water supplieswill remain available in the future. Hydrologists are also concerned withenvironmental problems that involve water.

In this chapter, discussion is concentrated on the two categories of water thatare of most value to people for their domestic, farming and industrial uses. These are:• water collected at the surface of the land in natural and man-made storages;• water extracted from natural reservoirs beneath the surface of the land. This is

termed groundwater.

Some of the environmental issues relating to water are also considered. Theseinclude pollution and the loss of fertility in agricultural land due to waterloggingand the build-up of harmful salts in soils.

The water cycle (also known as the hydrologic cycle) is a concept used to show thatall water is involved in an endless cyclical movement. As illustrated in simple termsin Figure 6-3, all water that falls on the Earth's surface, whether as rain, hail ornow, eventually returns to the Earth's atmosphere as water vapour. The energy

for this circulation is provided by two major forces:I. Force of gravity - this causes water to fall through the atmosphere and to move

downwards over and under the Earth's surface.2. Heat radiated by the Sun - this causes water to evaporate from the land and

ocean, and water vapour to rise in the atmosphere.

The water cycle has no beginning nor end, but it is convenient to describe itby starting with the oceans, which contain most of the world's water. Waterevaporates from the surface of the oceans. The amount for a given area is greatestnear the equator where the Sun's heat is most intense. Water vapour is nearly pureas it contains only small amounts of salts.

Warm air currents lift the moist air masses through the atmosphere. Eventuallyat higher levels, these masses become cooler causing the water vapour to condenseas rain, snow or hail. These three forms are collectively called precipitation.

Precipitation may return water directly to the oceans or it may fall over land.Not all precipitation reaches the Earth's surface. Some evaporates as it falls throughwarmer air. Part of it is intercepted close to the surface of the land by either man­made structures, e.g. buildings, or by living things, e.g. plants. Some of this wateralso returns to the atmosphere by evaporation.

Precipitation that reaches the ground surface becomes part of the so-ealled landphase of the water cycle. It is this phase that is of most interest to the human race.Some of the water on land does not travel far. It may be temporarily retained inpools and puddles on clayey soils, in hollows and crevices in rocks, or in the upperlayers of soils. This water is largely lost by evaporation.

Most of the water falling on land, however, moves downwards under theinfluence of gravity. Part moves across the land, where it is termed overlandflow.The remainder penetrates the ground by a process called infiltration.

Water 231

ocean evaporation

preClpltalIOn(snow fall)

evapotranSpiration

evaporation from land.lakes. and waler courses

evaporatIOn ofram droplels

preCipitation(rainfall)

,

--"6/~_ solarrad,allon

;;::;{/ , ,

Iatmosphere

Figure 6-3The water cycle.There is a continuous interchangeof water between the land, theocean and the atmosphere.

Overland flow consists of rainwater and, in some places, water derived frommelting snow or glaciers. Most of this water drains into streams and eventuallyreaches lakes, swamps, dams or oceans. Some water is lost from flowing streams,however, by evaporation or by percolation into the beds of the streams.

If rainwater does not evaporate from the ground or run into streams, it seepsdownwards into the ground. Infiltration is most likely to occur where there are nofast-flowing streams, the land is fairly flat and the surface soils are porous. Somewater clings to soil particles and may be drawn into the roots of plants: this is calledsoil moisture. After the plants use the water, it evaporates back into the atmosphere,mainly through the leaves, by a process known as transpiration.

The remaining moisture continues to move downwards through successive layersof soil, weathered rock and fresh rock. This movement is possible because thereare spaces provided by fractures, joints and the pores between the various mineralgrains. At some depth, known as the water table, all the openings in rocks and soilsare saturated with water. Below the water table, the movement of water changesfrom a vertical downward movement to a predominantly sideways motion downa very gentle gradient. It slowly moves laterally through interconnected passagesuntil it discharges as springs or seepages into streams, lakes, swamps or oceans.

Although water is constantly moving and changing its state in the water cycle,the movements are erratic, both in time and place. The relatively fast flow rate ofmany surface streams contrasts with that of groundwater, which may take manythousands of years to reach the sea.

The water cycle may be modified by human activities in various ways. Landclearing for agricultural or other purposes results in decreased interception andtranspiration by natural vegetation. The accelerated run-off of rainwater may causesoil erosion. Alternatively there may be greater infiltration leading to increasedstorage of water underground. The passage of water from the land to lakes andseas can be interrupted by the construction of dams, stormwater drainage schemesand irrigation channels, and by the sinking of bores and wells. Most water usedby people, however, eventually returns to the oceans to perpetuate the hydrologiccycle.

Surface water People may obtain water directly from streams and lakes, or they may collect itfirst in dams built across stream valleys. Water flowing along a stream is a mixtureof water running off the land into the stream and former groundwater, that hasemerged as springs or seepages in the banks of the stream. Groundwater dischargesmay provide the only water feeding a stream during dry periods.

232 Chapter 6

Figure 6-4The dam wall of Lake Eildon nearthe township of Eildon.This is a large earth and rockfilldam that impounds the waters ofthe Goulburn, Delatite and otherrivers draining the East VictorianUplands. The first dam was builtin 1927 and it was enlarged in1955 to become the second largestreservoir in Victoria. The hill atthe end of the wall is theSugarloaf formed by south-westdipping, thick-bedded sandstonesand siitslOnes. The dam wasconstructed mainly (0 supply waterto the Goulburn valley irrigationarea but it is also a popularrecreational area for boating andfishing.

After precipitation falls on the ground, it may either evaporate, run off intostreams or percolate down into underlying soils or rocks. The main factors, whichdetermine what proportion of the water follows each of these three routes, areclimate, topography, geology and vegetation.

Climate: The total amount of rain and snow falling in an area each year is importantand also the frequency, intensity and duration of the falls and the time of yearwhen they occur. Most heavy rain from thunderstorms is likely to run off intostreams, whereas gentle rain over a long period usually penetrates the surface.

Temperature is also important, as higher temperatures lead to greaterevaporation of surfaoe water. Temperature also determines when and how quicklysnow melts.

Topography: Generally there is considerable run-off from steep terrains, whereason gentle slopes most water infiltrates into underground storages. The altitudeand orientation of water drainage basins (or watersheds) are also importantindirectly, because of their influences on temperature and precipitation.Temperature usually falls with increasing altitude and this leads to greater fallsof rain or even snow in the uplands. Evaporation, however, decreases inmountainous areas. Because the Sun is always to the north of Victoria,evaporation is greater on the northern than on the southern mountain slopes.

Geology: This is mainly important because of its effect on present-day topography.The type of rocks in an area, their structures and the nature of the overlyingsoils also control the amount of water that passes below the surface. The moreporous rocks and soils are, the easier it is for water to infiltrate them.

Vegetation: Trees, plants and grass absorb a lot of water through their roots. Theyalso retard run-off after rain so that greater quantities of water percolate intothe ground. Vegetation also reduces soil erosion on steep slopes so that waterflowing through forested country is usually clear.

SELECTION OF SITES FOR STORAGE DAMSIn Australia, many communities are provided with permanent water supplies. Theseare obtained either from storage dams constructed across watercourses or, in a fewplaces, from lakes. Holding river water in dams also helps to reduce potential flooddamage that may occur after heavy rains. In some places the force of falling waterreleased from dams can be used to generate hydro-electricity.

Engineering, economic and social factors must be considered when the site fora new water storage dam is being selected. Research is carried OUt to establish thewater requirements of the communities the dam will serve and to ensure that anyadverse effects on the natural environment will be minimised. [t is also desirablethat no valuable agricultural land should be 10 t beneath the water and that peopledownstream from the dam should not lose their customary supplies.

Groundwater

Water 233

Geographic factors tend to control the selection of the site for a dam. The wallshould be built preferably where the valley is deep, so that adequate water isimpounded by the structure, The valley should also be narrow to minimiseconstruction costs and to ensure that the surface area exposed to evaporation iskept to a minimum.

However, geological factors often determine where the fmal site will be. Detailedgeological mapping is carried out to identify any zones of porous or fractured rocksthat would allow water to leak away from the dam. The geological work carriedout to assist dam selection is discussed further in Chapter 7.

As explained in the earlier discussions about the water cycle, part of the water thatfalls on land infiltrates below the surface. Some of this water is used by plants,but most of it penetrates deeper under the force of gravity. On its downward paththe subsurface water encounters either unconsolidated earth materials, (soils andlayers of loose sands, gravels and clays) or consolidated earth materials, (hard rocksof different ages and types).

There are two zones of water underground, an upper unsaturated zone anda lower saturated zone, called the groundwater zone. In Victoria, the unsaturatedzone is rarely more than 50 metres thick and in some places it is very thin. However,elsewhere in Australia the thickness can range up to several hundred metres,particularly in some arid regions. The uppermost pan of the unsaturated zone iscalled the soil water zone. It is commonly less than 2 metres thick and is importantbecause it supports the growth of plants.

In the saturated zone, all interconnected openings between the minerals formingthe rocks or sediments are filled completely with water. This zone may be up to2000 metres thick. At still greater depths rocks are usually toO compact to containany significant water. The upper surface of the zone of saturation is called the watertable.

Supplies of groundwater are obtained by excavating wells or drilling bores intothe saturated rocks below the water table. Water can be extracted from shallowwells and bores by pumps driven by windmills, whereas mechanically-or electrically­driven pumps are connected to deeper boreholes.

Before considering the behaviour of groundwater in detail, it is neees ary tounderstand the significance of two terms which are commonly used in groundwaterstudies. These are porosity and permeability.

POROSITYPorosity is the property of rocks that explains their ability to store water. Porosityis supplied by spaces between mineral grains that form rocks and soils. The e spacescan be filled with water. Where the spaces are interconnected, they serve aschannelways along which groundwater moves.

FSecondary porosityby fraetunng and JO n: ngas In granite

Figure 6-STypes of rock porosity.Examples of different kinds ofspaces in rocks where water can bestored.A-D primary porosity .

• spaces present when therock is formed.

E-F secondary porosity.• spaces appeared afrer the

rock formed.Well-sorted sedimentarydeposit having highpflmary PCHOSlty.

DBasalt honeycombed by veSicles(small gas caVities) which, ifInterconnected, prOVide hlghpermeability and lair porosIty

POOrly-sorted sedImentary depoSilhaVIng low primary porosity

ESecondary poroslryIncreased by solutIOn, asin limestones

Well·sorted sed,mentary dePOSjIWI!l, poroSity diminished by thedepoSlllon of minerai matter In theIntersQCt!s, e.g. dunng consolida:on

234 Chapter 6

Porosity may be either primary or secondary (Figure 6-5). Primary porosity,(also known as intergranular porosity), was produced by the original geologicalprocesses that formed a rock or soil. Unconsolidated sediments, such as sands andgravels, have good primary porosity because there is a lot of space between theparticles. They are therefore capable of holding large amounts of water.

On the other hand, consolidated rocks usually have low primary porosities.Many igneous rocks, such as granites, are completely crystalline and contain fewpores. The same applies to many sedimentary rocks where the spaces between mineralgrains are usually filled with cementing materials, such as quartz or limonite.

Secondary porosity, (sometimes known as fracture porosity), only occurs inconsolidated rocks. The spaces were developed after the rocks were formed. Theycan consist of fractures, joints and fault zones in all kinds of massive rocks andalso solution features, such as caves, in limestones.

PERMEABILITY

Earth materials are said to be permeable if water passes through or can be pumpedfrom them easily. The permeability of a rock is controlled by the sizes of the spaceswithin it and by the extent to which they are interconnected.

It is important to note that rocks with the same porosity need not have thesame permeability. For example a gravel and a silt may have the same porosity,because the total space between the gravel grains may be the same as that betweenthe much finer particles of silt. Thus equal volumes of gravel and silt can store equalquantities of water. However, gravel can release more of its water and release itat a faster rate when pumped, because it is much more permeable than silt. It isdifficult to pump water from silt or clay because the water is more strongly heldwithin the tiny pore spaces by molecular and capillary forces.

AQUIFERS

The groundwater zone may be imagined as a huge natural reservoir in rocks. Itsstorage capacity is equal to the total volume of pores or openings that are filledwith water. At anyone location, groundwater may be found either in one continuousbody or in several distinct rock layers. Porous water-bearing rocks, which can yielduseful supplies of water, are called aquifers. Less permeable rocks, that restrict themovement of groundwater into or out of adjacent aquifers, are termed aquitardsor simply confining beds (Figure 6-8).

In any area, where an aquifer is present, the nature of the rocks and thegeological structures control:

• the amount of water that can be stored in the aquifer;• the rate of movement of groundwater through the aquifer;• the yield of water that can be pumped from the aquifer.

Even in areas of high rainfall, if the geological conditions are unsuitable, groundwatersupplies are limited. For example, the East Victorian Uplands is a high rainfall region,where Palaeozoic sedimentary rocks outcrop exten ively. These rocks contain goodquality groundwater but, because they have low permeability, bore yields are small.Conversely, with favourable geological conditions, substantial supplies of goodquality groundwater may be obtained even in areas of low rainfall. For example,the town water supply for Alice Springs is obtained from the alluvium of the ToddRiver and the deep Mereenie Sandstone of the Amadeus Basin, both permeableformations.

Aquifers perform two functions:

• they serve as natural storage reservoirs;• they distribute water from place to place.

They are lOrage reservoirs because they contain water that can be tapped bybores or wells. They are also distribution systems, because water enters aquiferswhere they outcrop, travels through underground openings and eventually dischargesat springs, rivers, lakes or the oceans. The outcrops of an aquifer are called its intakeor recharge areas (Figure 6-6). Aquifers can carry water from intake areas in distanthigh rainfall areas to arid regions, where surface flows rarely occur. Mostgroundwater nows very slowly through the ground - u ually at a rate of only afew centimetres to several metres per day.

Aquifer are commonly classified as either unconfined or confined (Figures 6-7and 6-8).

Water 235

Figure 6-6An aquifer recharge ares nearMurrindal in East Gippsland.The cleared country is on LowerDevonian limestone. There are nopermanent streams in this area.Most water percolates into theground through fractures in thelimestone. Two large opensinkholes (dolines) can be seen.The limestone provides an aquiferwith good quality water, and it iscovered to the south by moreclayey rocks of the TaravaleFormation. In the background, theforesled hills are on west-dippingignimbrites of the Snowy RiverVolcanics. These rocks are'tighter'. that is groundwatercannot penetrate them as readilyas it does the limestones. Surfacestreams are commoner in thiscountry. (pholograph byN.J. Rosengren).

Figure 6-7Occurrence of groundwater in anunconfined aquifer.Groundwater occurs in gravels andsands of Tertiary age that weredeposited in a valley cuI by a riverthrough folded Palaeozoicsedimentary rocks, e.g. AvocaDeep Lead al Avoca, Burnt CreekDeep Lead, south-east of Dunolly.Water enters the aquifer Ihroughthe surface sands and particularlythrough Ihe bed of the river.Figure th'l (below)Occurrence of groundwater in aconfined aquifer.Groundwater occurs underpressure in a gently dipping sandyformation of Tertiary age, whichis largely overlain by an aquitardof clays and silts of lowpermeability. The Palaeozoicbasement rocks are alsoimpermeable. Waler tapped bybores will rise to the level of thepotentiometric surface.

I Unconhncd aquilor ----.-1I---e.g. Tcnmry Deep Lead

1-.4- recharge area for unconlmcd aqlJllcr~

\l'

Producing boreinto aouifer

-l"\8DP?"",= JI_-<:::i';.:i;~"-"""UNSATU"ATED

~~~r~~;~~~:~:I~cr V-''-_Lt.::':::'::::.:'':.'W':!1iiEijti~~JS/i: ZONE

SATURATEDZONE

_.... Conlincd Aquifer

e.g. Margin 01 Tertiary BasinRecharge

~~;~f~;r ~~ Ory boret t t t t (Too shallow)

.. UNSATURATED / Non·flowing bore". ZONE / (Sub·artesianI

~~~~..,...AJI:~'~;., Flowing bore...... ~~...... h: (artesian)

::~...~~~~, ~ ';~~~....~ ~""::.. ~ ~~r- ~ - -_

S..q ~ ~'::'.. .~":...~ ,: :. ":... -""::....... Potentiomeuic surface""Ut"J "'.:.. ........ ...:."' -: ~· ...cOI'J"';~ ....~":....... (Ievelmdlcates pressure of"-4 '>- ,,'" ~ qq.........., 1

I~o "" ....""::..":....... ~... (Io* ''10'''':...'':...'':............ water ,n conlined aqUifer)....""::.. /)Sr. Or!l)q....":... --: ."':"-S:-::--=-__

,"'-";.. ":... ::'9iJ6 110,., I..~'":.."":..--__-"':..- _• ' '::'.. ""::.. '11t!y)~ :.. l-__"":..__"':..__":.. --:..-

...-:,. -:.. ""::.."1 t-----:..------:..-"":..":..--:..--...... ~ ~~.... :-.... "":.._-:.._"":.._'":......"":..'?>..,..__S:::::E:.:A..:L:::E;;V..:E:::L'---_:~..,..... "'" ~...."i :..'":.. --:.. "":.. --:..__...."":.. '":..__....--___

----~~'\---/) ---------Low permeability basement rocks __;::::f:~~_+permeablesandstone

e.g. folded Palaeozoic shales - aquifer containing water__________..:l.. .L:.-l__...L:::::,._=-_~~__L_..Junder pressure

236 Chapter 6

Unconfined aquiferAn unconfined aquifer is a permeable geological formation that extends from theland surface down to an impermeable base. It is generally only partly filled withwater. The water is at atmospheric pressure at the water table. This means that ifa bore penetrates below the water table in an unconfined aquifer, the water willnot rise up the hole. An unconfined aquifer can be recharged by infiltration of wateranywhere over the area in which it occurs. The Tertiary sands, that occur inMelbourne's south-eastern suburbs, are an example of an unconfined aquifer.

Confined aquifersA confined aquifer is a permeable geological formation, which is largely overlainby less permeable confming beds. The latter act as a seal preventing the groundwaterfrom escaping upwards. A confined aquifer is fully saturated except in the intakearea where it outcrops. Groundwater in confined aquifers is under the pressure ofthe atmosphere at the intake area plus that of a head of water from the intake area.Therefore, when a confined aquifer is penetrated by a bore, water rises above thetop of the aquifer. The level to which the water rises is called the potentiometricsurface and it reflects the pressure in the aquifer at that locality. If the pressureis su fficient the water will rise above ground level to produce an artesian or flowingbore. In sub-artesian bores, the water rises but does not reach the surface. Confinedaquifers occur in all the major Tertiary sedimentary basins in Victoria.

AQUIFER MATERIALS

For simplicity, groundwater can be considered to occur either in porous rock aquifersor fractured rock aquifers. The groundwater in both of these types can be eitherunconfined or confined.

Porous rock aquifersIn Victoria, the most important aquifers are more-or-less horizontal beds ofunconsolidated sands, gravels and shell fragments, which have good primaryporosity. These occur mainly in Tertiary sedimentary basins, where they are mostlyinterbedded with finer-grained confining beds. There are also good aquifers oversmaller areas in sand dunes and in alluvial deposits along the courses of ancientburied streams. Some 10 - 30070 of these rocks is occupied by space and they canyield large supplies of water when tapped by bores. Some Mesozoic sandstones andPalaeozoic sandstones and limestones, especially those that are not greatly folded,also have sufficient pore space for them to act as moderately good aquifers. Somevesicular basalts hold large quantitie of water.

Fractured rock aquifersIgneous and metamorphic rocks, and completely cemented sedimentary rocks canform aquifers where they are strongly fractured. Outcrops of fractured rocks invalleys generally provide favourable groundwater conditions as the fractures in theseareas tend to be wider.

In Victoria, some Palaeowic sedimentary rocks in the uplands and the extensiveNewer Volcanic basalt plains of western Victoria form fracrured rock aquifers.

SELECTION OF SITES FOR GROUNDWATER BORESIf a borehole is drilled at any locality in the State, it will eventually at some depthreach the water table and below that will pass into rocks saturated with water.However, the chances of finding useful quantities of good quality water at sufficientlyshallow depths to justify the costs of boring and installation of a pump vary greatlybetween different districts. It is necessary to have a knowledge of the local geologyto be able to predict whether a groundwater aquifer is likely to be found at anyparticular site.

Con ider a landowner, who wants to sink a bore in a district where there arealready scattered successful bores. It may be possible to anticipate the yield, salinityand depth to the water table on the property by considering the results from theother bores, provided the geology is similar. This is possible because thecharacteristics of aquifers only vary gradually from place to place. For example,the salt content increases slowly from the intake area to the final discharge zone.

On the other hand, if local information is not available or if nearby boreholeshave yielded varying results, the landowner would be advised to seek geologicaladvice. Over the years, variou Government authorities have built up records aboutthe State's water re ources. This infonnation is a"ailable to landowners at theMelbourne office of the Rural Water Commission. Geological ad"ice is particularlydesirable, where there are different types of rocks below the surface of a property.

Figure 6-9Use of water in houses in Victoria.

Water qualityand use

Figure 6-10Quality standards for drinkingwaterThe World Health Organisationhas recommended that waterconsumed by humans should meetthe standards given in the tablebelow. In some areas somesubstances may be present inhigher concentrations than thoserecommended without any illeffects resulting, e.g. bore watercontaining up to 2000 pans permillion total soluble salts isdrinkable.

Water 237

No discussion on the search for groundwater would be complete withoutmention of water diviners. These people claim to be able to detect the presence ofunderground water with the aid of a divining rod. Some also claim to be able topredict the depth at which water will be found and even its salinity. Diviners workon the assumption that groundwater flows in underground streams and that theycan detect the locations of these streams. This is a fallacy, for underground wateris normally distributed over a wide area in a particular rock formation. Its ooeurrencedoes not resemble a surface stream, but a vast buried lake. There is thus rarely onespecific site on a property that is more favourable for the discovery of undergroundwater than all other possible sites. It is true that many bores drilled on the adviceof diviners are successful. However, this is generally in areas where supplies areplentiful and a bore at any site would intersect an aquifer.

There are some situations, where the best water supplies are restricted to certainnarrow zones. This happens where particular geological units are more porous orfractured than the surrounding rocks. Examples are gravels at the base of deep leadsediments along old valleys, shattered rocks along fault zones and wide, fracturedquartz reefs. Geological skills may be particularly helpful in tracing these featuresbelow the ground.

People using water naturally hope it will cause no harmful effects. For instancethey do not wish to become ill through drinking water, they do not want laundrywater to soil clothes, they do not want irrigated crops to wilt nor stock to die. Whenwater is used in industry, it must not corrode the machinery.

The quality of water is the net result of various chemical, biological and physicalfactors, which affect it as it passes through the water cycle. When water evaporatesinto the atmosphere from the Earth's surface, it is pure, consisting solely of watermolecules. By the time it returns to the ground as precipitation it will probably havecollected some impurities, such as dust or dissolved salt. The latter is most likelyto be present in coastal areas, where salt spray is blown into the air from the sea.

Continuing through the water cycle, water either passes over or under the surfaceof the land. In doing so, it dissolves salts and organic substances from the soilsand rocks it encounters. Water usually becomes progressively more saline as it travelsaway from its source. Surface water usually contains living organisms and suspendedmuddy material derived from the erosion of soils. It can also become discolouredby dissolving iron salts or organic matter. Harmful impurities al 0 may be introducedby human activities giving polluted water.

For every process in which water is used - be it domestic, agricultural orindustrial - there is a limit to the amount of contamination that can be tolerated.

1. Domestic drinking water standards are described by upper limits for a largenumber of bacterial, physical and chemical con tituents. Domestic drinking watershould contain less than 1500 mg/L of dissolved salts. Some metal ions are highlytoxic and their maximum allowable concentrations are very low in drinking water.Nitrates, which may be derived from human or animal wastes, are also veryharmful. Water should also be colourless and free of any cloudiness caused bysuspended sediment.

One property of water, that can be undesirable although not necessarilyharmful, is hardness. Water is said to be hard, if it will not lather when soapis introduced. Hardness is caused by calcium and magnesium ions in solution.Hardness is temporary, if it can be removed by boiling. This is the case if calciumis present in solution as calcium bicarbonate. Boiling causes the calcium toprecipitate as calcium carbonate. However, if other anions such as sulfate arepresent, the hardness is permanent: this can only be removed by water softeners.Hard water is common in limestone country, as in the Warrnambool - MountGambier region.

2. Agricultural standards for water are based upon the effects of the chemicalconstituents on animals, soils and plants. There are different upper limits ofsalinity for different crops and animals. Generally plant are more sensitive tosalts than animals (Figure 6-11).

3. Industrial standards vary with the panicular indu try. As example, sail contentsup to only 100 mg/L and 150 mg/L are allowed in the rayon and papermanufacturing industries respectively, whereas up to 850 mg/L may be used incarbonated drinks.

J 500450065007000

11000IS 000

so1000I 500I 500250080006000I 700

238 Chapter 6

Figure &-11Salt tolerances in waler used forfarm animals and crops.

In the United States of America, ithas been estimated that an averageperson requires about I gallon(U.S.) (3.8 litres) of water eachday to survive. But the tOlal usageworks out at aboul J800times this amount per person,when the waler used for alldomestic, farm and industrialpurposes is taken intoconsideration. Water use inAustralia is probably similar.

Groundwaterversussurface waterfor majordevelopment

-----:-:--------------7.::":::-;-::=.--Usage Upper Umit of Salinity

TDS (mg/L)

Irrigationtobaccocitrus lretS, garden plantslegumes (e.g. sltawbcrry clover)vines, grasses, cabbageslucerne, cOltonbarleywhealmaize

Farm animalspoultrypigshorsesmilking cows and ewes in lambbeef cattleother shttp

Fishgold fish 8 800rainbow trout 9 300brown trout 3 700

ote: the saJt tolerances for crops and animals are guidelines only. Actual results depend on many factors, suchas the: proportions of individual salts. the composition of pastures, etc.

TREATMENT OF DOMESTIC WATER SUPPLIESThe suitability of natural water for human consumption is only poor to fairthroughout most of Vicloria. Consequently the water held in surface andunderground storages must be treated in various ways before it is distributed throughhousehold supply systems. The following are the common treatments applied inVictoria:

I. Chlorination: Diseases can be transmitted by bacteria and viruses in water; hencewater supplies must be disinfected. Chlorine gas or sodium hypochlorite solutionis added to kill harmful micro-organisms. The total chloride ion content mustnot exceed 600 mg/L however.

2. Filtration: Surface water is often cloudy due to the presence of clay, silt or organicmatter in suspension. Although these substances may not be harmful, theirpresence is a frequent cause for consumer complaints. They may also interferewith the disinfecting process. Coarser suspended panicles can be removed byfiltering the water through sand; it is also often neces ary to add a chemical suchas alum (aluminium sulfate). The suspended particles combine with the alum toform a denser mass, which then settles out - the process is known as nocculation.Sometimes calcium hydrate (Ca(OH),) or soda ash ( a,CO,) is also added topromote effective settling and to correct the acidity of the water. Finally the wateris filtered through layers of sand and gravel to remove the nocculent.

3. Decolouration: Iron compounds can cause problems, especially in groundwatersupplies. Although they are not harmful to humans, they can discolour waterand cause brown staining of clothes and porcelain ware. They can also causean unpleasant taste sometimes. Iron is removed by aeration, filtration or theaddition of lime. The latter increases the pH of water, causing iron oxides toprecipitate.

4. Fluoridation: In recent years, sodium nuoride has been added to many watersupplies to reduce dental decay.

5. Some groundwaters contain sufficient hydrogen sulfide to produce an obnoxiousodour. This can be removed by spraying the water into the air to release the gas.

6. In a few supply schemes using groundwater, the water is either cooled or thehardness is reduced.

In the past, it was usual for public authorities to think in terms of damming riversas new water supplies were needed. However, in many areas alternative permanentsupplies are available underground in aquifers. There are advantages anddisadvantages associated with developing groundwaler as opposed to surface water.

ADVANTAGES OF USING GROUNDWATERVast water storages are usually available in aquifers and these are not affected greatlyby annual variations in rainfall. Groundwater storages are highly efficient because

Water inAustralia

Figure 6-12Average rainfalls of the continentsand the proportions that arerelained as run-off and lost byevaporation and transpiration.

Wate, 239

there are no losses due to evaporation or leakage and there is no silting up as timepasses. The machinery required to tap groundwater is compact and the number ofbores can be increased gradually as demand increases. Aquifers may be availableimmediately below the district to be supplied and so costly pipelines from distantreservoirs are not required. Overall, groundwater supply schemes involve lessenvironmental disruption than do surface schemes.

DISADVANTAGES OF USING GROUNDWATERIt is more difficult to evaluate the storage and pumping capacities of aquifers.Groundwater usually contains higher concentrations of dissolved salts and is morelikely to be hard. The costs of operating groundwater schemes can be higher thanthose from surface reservoirs, especially if water is pumped from considerable depths.There are no side benefits from underground storages, as they cannot be used forrecreation activities or hydro-electricity generation.

JOINT USE OF SURFACE WATER AND GROUNDWATERFrom the discussions so far, it is apparent that surface water and groundwater aretwo related resources. To make the best use of both sources of water, it is desirableto prevent losses of good quality water to the ocean. To do this, joint surface andunderground supply systems should be developed wherever possible. There areof course some areas where useful supplies of only one kind of water are available.Over much of Victoria, however, yields could be substantially increased by employingjoint schemes.

Surface water should be stored to meet most requirements in years of averageto high rainfall, whereas groundwater should be retained primarily for use in yearsof low rainfall. Such usage depletes groundwater storage when natural recharge islowest. The drawdown in the water level creates storage space that can be replenishedlater, either by natural recharge in years of more plentiful rainfall or by artificialrecharge. Aquifers can be recharged artificially by pumping water into their intakeareas from surface dams. Water can also be injected under pressure into confinedaquifers.Australia is overall the driest inhabited continent. This explains why it is also theleast populated continent and likely to remain that way. Not only are its waterresources scanty but they are also very unevenly distributed over its area. Rain fallsupplies, the main source of surface and groundwater, vary considerably from placeto place, from season to season and from year to year. Although the average annualrainfall is 420 millimetres, one-third of Australia receives on average less than 250millimetres of rain each year. The limited extent of Australia's surface water re ourcescompared with those of other continents is shown in Figure 6-12. Australia not onlyhas the lowest average rainfall, but it also has the greatest rainfall losses bytranspiration and (mainly) evaporation.

COnlinent

Africa. America

S. AmericaAsiaEuropeAustralia

Area(km')

302100002A 260 0001779000044 030 00097100007690 000

Average annualrainfall (mm)

660660

13l{)610580420

Average annual run-off(rom) (~o rainfall)

158 24264 40486 36220 36232 40

55 13

EvapoIranspiral ion

(mm) (~o rainfall)

502 76396 60864 64390 64348 60365 87

terresourcesof Victoria

Although many people believe that Melbourne has a very cold, wet climate, thisis not the case. Figure 6-13 shows that of all the Australian capital cities, onlyAdelaide, Hobart and Canberra have lower rainfalls than Melbourne.

Victoria is certainly better endowed with water than South Australia and mostof the inland of the continent. However, its water resources are appreciably lowerthan those of the eastern half of ew South Wales, much of Queensland andNorthern Australia and the western pan of Tasmania. At regular intervals alongthe eastern coast of Australia, major rivers carry large volumes of water to the PacificOcean from high rainfall areas in the Eastern Highlands. Most of this water is notused. These rivers contrast with the smaller Victorian streams which enter Bass Strait.

Most of the water used in Victoria is derived from rain, snow and hail, whichfalls within the borders of this small State. Consequently, the climatic patterns overdifferent parts of Victoria determine how much water is available to the population.The only exceptions are the Murray River, which receives part of its water fromtributary streams flowing from southern New South Wales, and the Snowy River,which flows southward across the State border into East Gippsland.

THE CLIMATE OF VICTORIATo understand the distribution of water in Victoria, it is useful to consider the State's

240 Chapter 6

o 25 SO 15 100

~-J.......Albury

WodOt'IQa

_400_ fsohyst With 1Jvef;J9f1 annualr8mlan In millime/res

MELBOURNE

Gee1otl!t

Swan H,I

iiIiiiiiiiiii

-(

climate, particularly its precipitation. Victoria's weather is largely determined bycells or wnes of atmosphere at relatively high pressure (called highs) that move fromwest to east across the southern part of Australia. Between these highs there aretroughs of lower pressure, called lows. Separating these air masses of differentcharacteristics, there is usually afront. The fronts are often moisture-bearing systems.The highest rainfalls occur where moist air masses coming from the west and south­west are forced to rise over mountainous country. The rising air is cooled and socannot carry as much moisture. This results in falls of rain or snow.

In summer, Victoria can also experience the after-effects of tropical storm cloudsdriven down from northern Australia. East Gippsland is less affected by the westto east moving pressure systems. Most of its rain comes from large pressure cellsthat form off the south-east coast.

Figure 6-13Average annual rainfall forAustralian capitalcities.

Figure 6-14Distribution of rainfall in Victoria.[sohyels are lines connectinglocalities with equal averageannual rainfalls measured inmillimetres. The interval berweenthe isohyets is increased to 300millimetres in the higher rainfallareas of the Uplands to avoidhaving closely-spaced isohyets.There are also fewer recordingstations there.

Average annual precipitation over Victoria ranges from less than 250 millimetresover parts of the Mallee plains to more than 2500 millimetres in parts of the uplandsof north-eastern Victoria (Figure 6-14). The rainfall map shows a pattern of isohyetsthat is similar to that of the contours on a topographical map of the State.

The main land feature influencing precipitation is the Central Victorian Uplands.Moist air masses, moving inland from the Southern Ocean in an easterly to north­easterly direction, quickly rise to cross the Divide. This causes them to drop a largepart of their moisture. Precipitation is therefore higher and more reliable on thesouthern and western slopes. Local rainfall highs also occur in other elevated areassuch as the Otway Range, Wilsons Promontory, The Grampians, the StrzeleckiRanges and the far south-eastern part of Gippsland. There is a rapid fall inprecipitation going north from the Divide.

Because most rain falls on the western sides of mountains and high ridges, thereare many areas of comparatively low rainfall (rain shadows) on the downwind oreastern slopes. Rainfall shadows occur in many valleys and basins in the uplandsas well as in broad low-lying areas protected in the west by ranges. For example,the Werribee Plain between Melbourne and Geelong is a drier area shadowed bythe Otway Range to the south-west. The northern part of the Snowy River valleyin Victoria is also in a rain shadow.

Victoria's annual precipitation varies quite markedly from year to year. Longperiods of low precipitation occur from time to time leading to a drought everyfive to eight years. Droughts occur most frequently in the north-west of the State.They are least common in coastal areas.

WATER BALANCE FOR VICTORIAFigure 6-15 shows what happens to the precipitation that falls in Victoria. Mostof it returns directly to the atmosphere through evaporation and transpiration. Onlya small proportion infiltrates to aquifers. About 15"7. runs into streams and of thisabout one fifth is diverted to reservoirs. The remaining four fifths eventually reachesthe Southern Ocean, partly via coastal lakes. The rates of evaporation anatranspiration in Victoria are much higher than the averages for most countries ofEurope and North America.

Figure 6-15Water balance for Victoria.

Average annual volume of precipitation in VictoriaAverage annual flow in Victorian riversAnnual recharge to groundwater systemsEvaporation and transpiration

Water 241

150000000 ML22500 000 ML

I 500 000 ML126 000 000 ML

Figure 6-16Streamflow in the major Victorianrivers.

A megalitre (ML) is one million litres or 1000 cubic metres (approximately the volumeof water in an Olympic size swimming pool). It is a convenient measure in hydrologyas one ML of water covers one square kilometre to a depth of one millimetre.SURFACE WATER RESOURCESIn Victoria there are 3820 named watercourses with a combined length of 56 000kilometres. The amounts of water flowing in Victorian streams are recorded at morethan 500 stream gauging stations. The measured streamflow characteristics of somemajor Victorian rivers are given in Figure 6-16.

River length Average Maximwn annual Minimwn annual Streamflow Recordingsannual Slreamnow discharge recorded started

streamflow(km) (ML) (ML) (Year) (ML) (Year) At (Year)

Goulburn 563 I 680 000 5 930 (XX) 1974 228000 1972 McCoy's Bridge 1965Glenelg 454 637 000 I 630000 1956 38800 1967 Danmoor 1948Loddon 392 186000 461 000 1974 36200 1967 Kerang 1953Mt.Emu Creek 305 61 100 232 000 1923 1240 1967 Skiplon 1921Wimmera 290 136000 570000 1956 Nil 1902 Horsham 1889Hopkins 280 294 000 953 000 1960 15 SOO 1967 Hopkins Falls 1955Avoca 269 47600 129000 1973 3480 1982 QuamblUook 1963Mitchell 250 936000 2420 000 1974 209 000 1982 GlenaladaJe 1937Lalrobe 250 860 000 I 800 000 1956 276000 1982 Rosedale 1937Campaspe 245 203000 886 000 1974 2830 1902 Rochester 1886Yarnl. 245 722 000 I 440 000 1924 128 (XX) 1982 Warrnndyte 1891Wannon 233 235000 528 000 1983 8690 1982 Henly 1967O\'eRS 227 I 110000 2 880 000 1956 195 000 1982 Wangarall3 1886Broken Creek 245 70 SOO 107 000 1978 39600 1967 Rices Weir 1965Milia Mitta 219 I 230000 3 860 000 1956 354 000 1979 Thllandoon 1934Thomson 208 305 000 738 000 1970 48 900 1982 Wandocka 1969Macalister 201 460 000 I SOO 000 1952 48100 1982 Glenmaggic 1919Thmbo 198 324 000 I 190 000 1974 43800 1982 Ramrod Creek 1965Broken 192 236000 I 130000 1917 4610 1943 Goorambal 1916Barwon 187 236000 663 000 1978 17 100 1982 Pollocksford 1906Kiewa 184 665000 I 4SO 000 1974 193 000 1967 Bandiana 1965Maribyrnong 182 1I10CK) 342 OXI 1916 5860 1982 Keilor 1908Snowy in Victoria 162 I 740 000 5930000 1950 159000 19~2 Jarrahmond 1922(tolal length 432)Murray (NSW) 2530 Average annual now inlO South Australia S 793 712 ML(Source Rural Waler Commission)

The pattern of run-off, and therefore streamflow, closely follows the patternof rainfall distribution, as might be expected. The only rivers with high flows arethose rising in The Grampians, the Otway Range and the East Victorian Uplands.The large, mainly mountainous, region east and north-east of Melbourne contains80010 of the State's total surface water re;ources. Of this, aboUl equal quantities flowouth to the ocean and north to the Murray River. There is a low percentage of

run-off in the north-western sector because the terrain is mostly flat and the rainfallis under 500 millimetres per year (Figure 6-17).

Figure 6-17Contrasting streamnows in threesectors of Victoria. ,",-,'-~MIdura

Ii'; "I',,In';111I111'11

& Are.,.1S a percentage 01 me total 01 V.etOfr.l

25 50 :S 100, ,t

~'iOI'I"t"f5

242 Chapter 6

Figure 6-18Groundwater provinces ofVictoria with directions ofgroundwater flows. The letters A­AI, 8_81, etc. refer to thegeological cross~sections shown inFigures 6-25 to 6-27 inclusive.

Streamflows vary considerably throughout the year and from year to year. Theyare usually greatest between July and October, especially in the western half of theState. In general, streams in eastern Victoria have th.,e most reliable flows.

The quality of water in Victorian streams is measured periodically, mostly atthe stream gauging stations. The results show that there are large variations in qualityacross the State, although in general, the quality is better in the east than in thewest. However, in western Victoria, low salinity streamwater is available in theOtway, Grampians and Macedon ranges. Water quality generally deterioratesdownstream due to the combined effects of natural and human influences.

Streams within the Central Victorian Uplands, in East Gippsland and in south­western Victoria are generally clear and contain low amounts of mud. On the Gtherhand, streams in the north-western part of the State and those draining farmlandsand major urban centres are generally muddy. This is because much of the nativevegetation has been removed in these areas and so the soil is easily eroded.

GROUNDWATER PROVINCES OF VICTORIAVictoria's groundwater resources come mainly from Cainozoic aquifers in theMurray, Otway, Western Port, Port Phillip and Gippsland basins and Palaeozoicfractured rock aquifers in the uplands (Figure 6-18). The generalised hydrogeologyof the main groundwater provinces in Victoria is given in Figures 6-19 to 6-24 andillustrated in Figures 6-25 to 6-27.

The volume of groundwater in Victoria is estimated to be between 400 and1000 million megalitres (400 to 1000 cubic kilometres), enough to cover an area thesize of the State to a depth of between two and four metres. Unfortunately thegroundwater is not evenly distributed; there are considerable variations in the depths,yields and salinities of the different aquifers.

Groundwater Province E~~mated recharge Authorized groundwater

Murray Basin

Olway Basin

Port Phillip Basin

Western Port Basin

Tarwin Basin

Gippsland Basin

Uplands

(MUyr)

105000

425000

45000

25000

20000

435000

445 000

15000000

extraction. 1987-88 (MUyr)

2648'0

66 j2'

1960'

59350

77 576

30828

538486•Actual 8lt.1raCIIOn is estlmale<! tobe about 25% 011 at au:holised

2,5 50 is 100, I ,

Kilomelres

S!>~ :7 8 t;;" e: ~. 5- ~ S' ~ a ~ 0 :!1- 8. I'.,) -.0 CIl en ." Cl n Q. n A.1.., OQ'< VI c:: c ::; 0 0: =r :r o' b '< 3 '0 C

" " ~ 3 :;.; cr 3 ~ .0 0 ~ ::J. a ~ a ~'< n ::J" C " ..... c __. £l,l 0 _. 0. ell

" ~ - < 0 0 _.o Q. (") ~o_. _. if eo !:;. o' ~o" 0 '"-, tI) :::::I ::s _.- ""i en T-<~OQ ::1.0 :::::I Q. .:< Cl 0 :r § _. a ~_. gas 0 n' &).. 3 -.~ 0.::1 C ...!l 5- - n ... -'!!:l '0 ~~.5o _. ~ ~ 0Q n~ ':"'18.5-<:5''2'0:::::1 no e?.:: :r-C('Zi' a c:;- g _. n :l ~;. A.1 3 0 3 (=j' '< N. ge.::I::SO'Oll>a- .De o:T;......J

- 0. 9- g 15'< !l S; "·~·14 '!!l " ~~ gg Cl osA.1 o.Q ~n'O 000:::::1_."C -DO 15" ~ g .. " " gn < 0 _.... ..,...... 0 :J. ::::I _ 0'"!.~~::::fIg g-.., 0 n C 3 I.ti 0.0 Cl

n :J':r - !'" g' 60 an 0 ~ <!S. c~g~c 0" -~Q,2.VI ell a g. O":a. Q -

~

Geological Wlil "1ain occurrence Depth to aquifer Aquifer thickness Rock types Aquh'er type and ronn Common salinity Range of bert Groundwater usesfonning aquifer rangt (roglL TDS) yields (LIsee)

Shepparton Formation extensive occurrence oUlcroppina or formal:ion 25 10 125 m sand and gravel indivijual sand and gravel highly variable genera II y less irrigation. stock and domesticin me Riverine Plain, subcroppinS· thick. individual sand interspersed in a aquiftrs range from isolated than 5 usage; groundwater is also pumpedalso along the margins and gravel beds arc: clay and silt ribbon-like oodies to semi· from aquifers shallower than 2.5 mof the Western Uplands less than .5 m thick matrix cOnlinuous sheets. ShallCM' to lower the water table toin the 5t Arnaud- aquifers arc: unconfined, control salinity.Dimboola·Horsham deeper aquifers art oonfined.".

Parilla Sand widespread occurrence; generally covered by 40 to 1.50 m but sand and silt with uneonfined sheet-like sand 1000 to 40 000 2 to 5 ground....'llter mostly too saline formain development is about 1.5-20 m of generally between 60 inlerbedded htavy aquifer mostly greater than use, Clapt along the southernto north·west of line QU3lemary sediments, to 80 m thick mineral bands up to 5000 margins of the basin where it isthrough Echuca and outcrops near Kerang one metre thick used for stock watering and toHorsham and in southern part supply the towns of Goroke and

of basin Pine Hills.

Cali viI Formalion similar distribution 25 to 130 m 20 to 50 m sand and gravel unconfined in the south but less than .soo up to up to 12.5 used around basin margins forto that of Shepparton confined to lhe north by 40000 irrigation and S10ck watering,Formation the overlying Shepparton and for town supplies for Elmore.

Formation. Aquifer consists Katunga, Strathmcrton. andof separated alluvial Chillern.valleys close to theUplands. Further norlh thesevalleys coalesce to form asheet-like formation

Duddo Li mc:stone Malice and Wimmera 50 to 190 m 50 to 130 m limestone confined sheet-like 1000 to 3.500 up to 1.5 some 5lock ....'lltering and tOYlnregions (mostly weSt limestone aquifer, porosity (becomes progressi~1 supplies for Murrayville.,of north-south line inerea~ by development of more saline to Cowangie., Lillimur, Kani\'ll,joining Robinva.le and solution cavities the t'3st) Miram, Nhill.Murtoa)

Warina Sand basal Tertiary 1.50 to 420 m up to 200 m thick in sand and gravel confined sheet-like aquifer I(XX) to 12 000 up to .so generally not used because of theaquifer oocurs the Mildura area but depth of the aquifer and itsthroughout most of is considerably marginal to poor water quality.the basin thinner under the

Riverine P1ain

·Subcropping t leans the formation is present below a shallow cover of soil.

Figure 6-19Generalised hydrogeology of themain Cainozoic aquifers in theMurray Basin.

~~

~

Figure 6-20Generalised hydrogeology of themain Cainozoic aquife~ in theOtway Basin.

Geologkal unit Main occurrence Depth to aquifer Aquifer thickness Rock types Aquifer type and fann Common salinity Range of bore Ground""luer usesfanning aquifer range (mg/ L TDS) yields (LIsee)

Bridgewater Formation dWlCS of the Mowu outcropping up to 45 m, bUI mostly dune limcstone. unconfined aquifer with 600 to 1600 less than 2 gock walering, minor domCSticGambier coastal IS to 25 III calcarenite. primary porosity usageplains. western 0, W"J.y calcareous an dBasin siliceous sand

Newer Volcanics basalt plains of outcropping up 10 120 m. mostly basah. scoria. unconfined frnctured rock 100 to 8000. mostly up to 60 bUI stock watering, irrigation.SQulh-western Victoria Icso; than 70 m luff aquifer greater lhan 2OCX) mostly less lila domestic use including townextend across Otway I.S supplies for Penhursl, Dunkeld,Basin from Geelong 10 Caramut, Morllake, Lismore.the Harnillon·I>Ortland Strtatham and Stockyard Hillarea

Pon Campbell extend across thc outcropping or 100 to 250 m limestone, Alarly unconfined where Ol.ucrops SOO to 7000 up to 2S stock and irrigation supplies,Limestooe southern Otway Ilasin overlain by Nl""er limestone, marl to partly confined beneath typically around domestic and waler supply for

from Curdies Ri~r Volcanic basalts basalt lSOO Koroh, Caslenon and Sandfordin the east to theSouth AustralianBordcr

Gellibrand Marl occurs throughout outcrops a10llg up to 4SO m marl, calcareous .....eathcred top of outcropping SOO 10 2SOO, mostly 0.1 100.S windmill supplies for stockmosl of Otway Basin western flanks of clay, silt Gellibrand Marl fonns minor greater than 1.500 walering from weathered ponion

Otway Range (wt:':>t of unconfined aquifer of oUlcropCurdies River),c1st.where at depthsup to 300 III

Mepunga r'Ormation occurs th roughoul mostly subsurface til up 10 160 Ill, Illostly quam. sand and confined sand aquifer, .500 to 1000 10 to SO not used except in Ihe Barwonmost of the Otway depths up 10 600 III less than 40 m calcareous S'l.nd sheet·like fonn Downs area where it forms part ofBasin the supply for Geelong

Dilwyn r'Qrmat;on cxtensivc occurrence outcrops in the SO to 150 III eastern quam'. sand, clayey unconlined aquifer in SOO to 1500 except up to liS aquifer mainly used for townthroughout the Otway Gcllibrand River Otway llasin, over sand, sill outcrop areas, elsCVtlhere in Warrnambool area supplies only because of depth;B~in vaJlt:y along the 1000 m in l::tortland confined where salinities towns include Por11and, Pon

western flants of the area ~ ewer S<XXl Fairy, Heywood, Peterborough,Otway Range and in Pon Campbell Timboon and tolhe Merino area; augment supply to the GedongeL~cwherc O\'Crlain by systemup 10 HXXl III ofyounger rocks

Pebblc l::tomt I'onnmion throughOut Otway Il::J.sin mostly subsurface mostly less Ihan 100 Tn quarlz sand and confined aquifer 300 to 1000 I to 20 generally 100 deep for Ulilisaliononly; underlies gr:wcl, sill and eu:q,t in Barwon DCMln5 area whereDilwyn I'i>nllation clay it fonns part of the supply for

O«long

'l1,.()or~~

'"

"GeologIcal unit /l,lain occurrence J)cplh 10 aquifer Aquifer thickness Rod. types Aquifer type and form Common salinity Range of bort Grdundv,'31er uses(onumg <lqUlft:r range (mgll TDS) yields (Lisee)

dune dct>O'll' small OCl;urrcnl;"C" in OUlcR>!>ping thin. l11Cl1lly less So'md. medium to unconfined sand aquifer. less than 1000 up 10 2.5 stock and domestic supplythe Cr.lllbournc and than 6 III coar\C quartz sheet-like formL:Ulg 1....1ng arca:.

,,11m ial deposit.. Longwarry to Dalmorc outcropping less than 7 III clay. sand and unconfined ~d and gra\'el highly variable up 10 10 stock and domestic supplygm\'cl aquifers of shoe·ming 500 10 SOXl

form inlerbedded in clay

Western POrl Group occurs throughout the outcropping 10 sub· 20 10 17S rn sand. gm\'cl. combined aquifer system of 300 to 3000 101040 mainly used for irrigation(Ilaxlcr. Shcr\\ood mId WC\lcrn I\>n Basin outcropping Q\'(.'r most limcstone, clay, sheet-like form, which is parlicularly in the Dalmon: -Yallock fonnations) of the e:lstcrn IX1rt sill WId lignite generally wlconfined OI:ctpt Cora Lynn area; elsewhere used

of the basin; c()\'ercd whert CNcriain by clayey for ~ock and domestic supplies;by up 10 75 III of soils this aquifer system suppliesday in the western more than SO'1t of the groundwaterhalf used in the Western Pon Basin

Older Volcanics \\idespread ()(."Curren(."(.' OUicropS in IOto75m basalt. basuhk fraCiured basalt aquifer less than 2000 in 2 to 25 irrigation of market gardens inthroughoul basin Cr:mbournc area and cl.'ly confined by basaltic clay western half of the Cranbourne • Oyde area. and

along Heat h II ill and O\ocrlying sediments basin; 1000 10 ~ock supplies in area north-westFaull. covered by up 2(XX) in eastern of Cora Lynn10 250 III III l:cnlr:tl half

"-part of basin

(hilder\ "unnation main occurrcn(."(.' is in SO to 250 III 51050 III "-'lnd and gr.tvcl confined sand and growe! 500 to 2000 2.5 to 25 generally not utilised c:xccpt toYal1ock-'t~nnathan- (underlie-. Older with lignite and aquifer provide ....mer for Lang Lang lown

~Lang Lang area Volcanic..) clay beds supply

Figure 6-21Generalised hydrogeology of themain Cainozoic aquifers in theWestern Port Basin.

~'"...'"

Figure 6-22Generalised hydrogeology of Ihemain Cainozoic aquifers in thePort Phillip Basin.

Geological unil Main occurrence Depth to aquifer Aquifer thicknc" Rock type)" Aquifer type and form Common salinit)' R.1ngc of bore GroLlnd",mcr us~

forming aquifer mnge (mg/ L TDS) yields (Lisee)

Wcrribce Delta soulh of Wcrrilx:c outcropping up 10 30 111 ~ih. 'land, gravel. unconfined sand and gravel 500 to 6C()() S to IS mainly used for irrigation ofclay; silty sand aquifers of shoe-SIring market gardens. washing dairiesin lower part of ronn. interbedded with clay and stock wateringdeposits; minorgmvcl and sandof IevC'Cs

dune deposits soulh-castcrn ~uburb!l outcropping thin. I~ lhan 6 m sand unconfined sand aquifer. less Ihan 1000 less than 0.2 garden \I\'alcring csptCiaJly duringof Melbourne between limited areal extent periods of ....-alcr restrictionsMordialioc andFrank'iton and inBC3umari~ area

Bridgewater Formation Ncpean I\:nimula outcropping 200 m sand, sandy unconlined sand aquifer, 300 to 1200 up to 25, mOSt domestic use, garden watering.we-t of Selwyn hult calcarenite, sheet-like form recorded ytc-Ids irrigation in Banco area. stock

shelly sand. mud, are less than wateringclay 1·2

Newer Volc'.lIli!.:\ Werribec Plain\ west outcropping generally betY"CCll basalt. scoria, multi-layer fractured rock up to 40 but 100 to less than stock water and minor irrigationof Melbournc SO and 150 m pyroclastics aquifer system with sheet- gencrally less than 6000 of salt tolerant crops in rural

like basalt aquifers )·2 mostly greater areas, low grade industrial usesseparated by clay layers; than 2SOO in western suburbs of MelbourneuppermOSt aquifer isunconfined, lower aquifersare confined

Moorabool Viaduct ....'C:.\I of Melbourne. cit her outcropping or Ics~ than 30 rn sand, elayey sand, unconfined aquifer in greater than 3000 mostly less thar small utilisation only; some stockForm3lion Grelong area and underlying Newer ~lldy clay, gravel, outcrop areas but confined 1.6 watering. watering of foreshore

llellarinc l':nin'iula Volcan ic ba<ialt ... quanlite, sandy where covered by basalt; reserve on the Bellarinelimestone sheet-like form Peninsula. salt production at Lara

Fyan\ford Format ion . ea.\tern and \Out h- outcropping 201080m sand, gmvd, silt, unconlincd to conlincd sand, 100 to 6800 up to 18. household garden wateringIlrighton Groop - ea\lern \uburb\ of clay, shelly 'lands, gravel and limestone average about 1500 typically less especially during periods of waterBaxter Sand\tOIIC Mclbourne, and inland calcarenite, aquifers - coarser sediments than 2.6 restrictions, irrigation and stock

to the Dandenong- limestone lend to be: lemicular watering in rural areas, minorCranbournc area although the deposits as a industrial and commercial usage.

who~ arc: sheet-like dairy washing, golf coursewalering

OkJcr Volcanic_\ \Outh--ea~ or OUlcrop\ in IOto40m basal! fractured rock aquifer. 300 to 8000. up to IS. stock supplies and irrigation ofMelbourne from Cranbournc aea: up unconlined in Cranbourne average about 2000 typicall)' less markel gardens and pastures in theCranbournc 10 Pon 1090 III d\."Cp low:lrd\ area, elsewhere confined than 5 Lyndhurst-Cranbourne area. golfPhillip Hay I'on Phillip Hay beneath younger sediments course watering at Cranbourne

Werribcc Formation we-lor Melbourne rrQIll oUierop... in IlaCdlU\ greater thWl 150 m sand. gravel. clay. unconfined to confined 2000 to SOOO west up to SO some industrial usage in westernBal:chu\ Mar.h to Mal'\h area only - up Bacchus Marsh area; lignite aquifer of sand and gravel, of Melbourne and suburbs of Melbourne, used 10Altona: Melbourne to 400 III dl.'Cp under 20 to 80 m under sheet-like form Nepean Feninsula; top-up Cherry Lakes at Altona.\uburbs between Wcrribcc Pluins: 40 Werribcc Plains; 10 10 ISOO to 3000 irrigation of salt-tolerant cropsMentone and Fmnk\ton: to 90 III on Morninglol 40 III south--east of sout h-east of in the Bacchus Marsh area,Nerx--an I\'nilhula we...t I\'nin~ula: SOO 10 Melbourne; 250 III Melbourne watering of golf courses in theof Selwyn r-ault 900 In 011 Ncpcan NCpc'dJl I':ninsula south-eastern suburbs of Melbourne

I\'nimula

'l10>

()

'"-@:

~0>

Geolog)ca) unit Main occurrence Depth 10 aquirer Aquirer thickness Rock types Aquirer type and ronn Common salinity Range or bore Groundwater usesronning aquirer range (mglL TDS) yields (Lisee)

Quaternary alluvium covtrs most of the outcropping S to IS m s.1nd, gravel, sill sand and gravel beds are gencrally less than highly \'ariable, irrigation (particularly along theand Haunled Hill basin and clay unconfined aquifers 1000 generally ~ss Mitchell River) and stockGravel than S watering

Boisdale furmlUion occurs throughout .5 to IS m 50 (0 ISO m sand, silt. clay, sand aquifer oonfincd generally less than S to 20 mainly ror irrigation in the Salebasin to the east of minor gmvel and beneath days in upper pan SOO area and lown supplies ror Sale.Traralgon coal or ronnation or in O\-'Crlying Wurruk. Boisdale and Briagolong

alluvium

Gippsland Umestone occurrence restriaed 150 to 250 m 100 to .soo m limestone, marl confined limestone aquirer. 1000 to 2500 up to 10 but not utilised because: it isto south~astem pan sheet-like form generally Ies.s overlain by more producth'Cof basin beyond a line than 2 aquifers rontaining better qualityjoining 'farram-Sale- groundwaterBairnsdale-Qrbost

Balook rormlUion narrow belt cxtending 100 to ISO m 250 to 480 m sand confined sand aquirer less Ihan 1000 unknown stock y.'lUer, possible irrigation;north-south across (up to 20?) not greatly lIilised because: ofbasin in Rosedale area relatively small extent

Latrobe Y.1l1cy Group occurs throughout ncar surface (Icss 100 to at least no m sand, gravel. sill sand and gravel aquifers or less than 900 up to ISO groundy.'3tCT from Morwell rormation(Yallourn, Morwell and basin [han .so m) in eastcrn and clay with major lens-like form art confined used for 1l'afalgar lown supply;Traralgon formations) part or basin but brown coal seams by interbtdded coal and day rurther casl in the Latrobe Y.1l1cy

d~per (betwttn 600 Depression the groundwater is usedand 900 m) towards for irrigation; more than n 000the coast MUyr are pumped from sanck below

the brown coal open cut mines atMOf\l,'ell and Loy Yang to reduct theupward pressure of groundwater tomaintain stability in the coalfaces and SlOp heaving of pitDoor

Thorpdale \bkanics western part or basin. up to .so m uptoOOm basalt. basaltic confined fraaured basalt less than 1000 highly variable probably minor Slock watering andmain occurrence is in clay, turf (inter- aquifers, valley-like rorms but generally irrigation at Thorpdalethe small Moe Swamp bedded with either less than 4Basin in the Moe- Traralgon orDarnum-Willow Morwell r'OrmationGrove area sedimcnts)

Childers furmlUion similar distribution IS to 20 m in .5 to 40 m sand. gravel. silt confined sand aquirer or less than 1000 kss than S some Slock watering and irrigationto Thorpdale Vokanics northern part or Moe and clay sheet-like fonn in the Moe Swamp Basin

Swamp Basin; up to250 m in theY.lrragon:rra falgararca

Figure 6-23Generalised hydrogeology of themain Cainowic aquifers in theGippsland Basin.

i~

Figure 6-24Generalised hydrogeology of lheUplands Province aquifers.

Region Geological unit Main occurrence Depth to aquifer Aquifer thickness Rock tyJ)CS Aquifer type and fann Comlllon salinity Range of bore Ground........ler usesfanning aquifer (salur.ltcd range (mgl L TDS) yields (Lisee)

Ihkkness)

Southern Uplands Older Vok:anics Strzelecki Ranges outcropping 101060 III basalt. 00s.11tic unconfined fractured basah mostly less than up 10 S irrigation principaJly for• Otway and only, mainly between clay aquifer 1000 potatoes and some paStures, slock

Strzelecki ranges leongm lin ,Uld wateringThorpdalc and in theWarmgul area

Lower Cretaceous main rock lUlits in outcropping 200-300 Ill? sandSlOIlC, unconfined fractured rock 1000 10 3000 0.1 10 1.3 not greally utilised; minor Slock(Olway and Strzelecki the Otway and (c:x.ccpt where siltstone. aquifer groundwater in ""'31eringgroups) Strzelecki ranges oo.'trlain by mudstone., the Strzelecki

Okler Volcanics) conglomenue, Group tends tothin black coal be at the higher"",m, end of the range

East Viaorian alluvial deposits extensh'e occurrenetS outcropping or sand. gravel. silt unconfined (outcrop areas) 100 to 1000 as high as 125 used mainly for stock ....'3leringUplands in the UplWld tracts in part covered and clay to confined (buried areas) and irrigation particularly in the

of the Murray, by )'Ounger rocks, sand aquifers of valley-like O~ns River v.allcyMilia Mina. Kiewa. mainly Newer formOvens and Goulburn \blcanic basaltRivers

Older Volcanics and Silvan-Wandin area outcropping basalt, 10 to SO m; basalt and basaltic unconfined fracturtd basalt 100 to 1300 up to IS. stock and domestic use, irrigationsub-basaltic sand sub-basaltic sand clay O\~rlying aquifer hydraulically generally less of market gardens. non-citrus

uplo20m sand. gravel. silt connected with Wlderlying than 5 orchards. pastures and fodderand clay sand aquifer crops

Palaeozoic sedimollary main rocks of the mClStly 200-300 m? sandstone. unconfined fractured rock SOO to 3000 0.1 to 15. mainly used for stock andand igneous rocks East Viaorian outcropping sillStone, aquifer gcnerally kss than mostly less oomCStic supplies exccpt in the

Upl::ll1ds mudstone, shale; 1000 in the higher than 3 Kinglake and Monbulk areas wheregranite. rainfall areas ground....'31er is used c:xtensivtlygranodiorite for irrigation

West Victorian NtY.'er Volcanics extensive in the outcropping 10 m to 100 m basaJt. unconfined fractured rock SOO to 3500 more man 10 stock and domestic use, irrigationUpb.nds Woodend-Kilmore and mostly around basaltic clay aquifer where highly particularly in the Ballarat-

BaJlarat-Daylesford- SO m fractured but Daylesford area; town water supplyMaryborough areas generally less for Lanctfield, Woodend,

than 2 Trentham, Gordon, Mt Egerton.Learmonth. Waubra and Avoca

alluvial deposits most significant are O'o'trlain by S<'ll1d. gravel. silt confined beneath Newer 500 to 1500 5 to 15 stock, domestic and irrigation!..oddon River Newer Volcanic and clay Volcanic basaltdeposils basalt

Silurian· IX\'Onian The GrampiwlS outcropping 2OQ.300 m? sandstone. unconfined sand (scrtt) SOO to 2000; 1()Y.<er up to 10 largely unusW otcept for somesillStone. and fractured rock aquifer salinity groundwater stock watering and as town ....'3termudstone. system in scree on slopes supplies for Willaura, lake Bolac,conglomerate of The Grampians MoysIon, Glenthompson. Wickcliffe;

aquifer also provides back-upsupoly for Hamilton

Palaeozoic sedimentary main rocks of the most 200-300 m? sandstone. unconfined to confined mostly 1000 to generally less mainly used for stock watering andand igneous rocks West Viaoriall outcropping siltStone. fractured rock aquifcrs 3000; includes than 2 minor irrigation; where

Uplands except where mudstone. shaJe. mineral waters of mineralised as in the Hepburncovered by

granite.central Victoria Springs-Daylesford area, the

alluvial deposits groundwater is bottled and soldand/or basalt granodiorite

commercially

'l1ex>

(")=r~~en

Waler 249

Figure 6-25Murray Basin: cross-sectionsshowing the geological formationsthat are aquifers and confiningbeds.

The locations of the cross-sections in Figures 6-25 to 6-27 inclusive are hownon Figure 6-18.

~ Duddo Limestone

§ Bookpurnong Beds

~ Pre-Tertmry tk,sement

AqUIfer

Confmmg beds

Conflnmg beds

AqUifer

Mmoraquder(Groundwater

basemonf)

Name of Borehole1

o Panlle. Sand

.1--_.1 Olney Formallon

A

I >.

"f- e:0;-ct: -0_° .#200 Z.f CO

~0 'l'

0

Vl .200~a;::;;

400

.600

B e:f- "rfJ >,w ~

200 :i: °0

Vl

~

~200

.400

Figure 6-26Otway Basin: cross-sectionsshowing the geological formationsthat are aquifers and confiningbeds.

C'

K.IOnlNr.,\1{,'r/:."'11I1 •...;..·,,'.·

C

AQuoicr

COnlifl"'{} bf'ds

~Pon Campbe/lllfflCSlone

E----laelM)I',lIldA.l.lfl{(. 01 N;ItI;lw.lIUlt. Mar/

G'ouno'.\J!~r b.lSCm('nts

jcon/.) fIS scme "'.<TICI iIfJ4J ~e,sl

DOtiwyn FormatIOn

DPemoer M!J(/f;IOrJ;J

o

1':,1,,""\......11,,,,:..,,/,,/ !Vfllr

250 Chapter 6

Figure 6-27Gippsland Basin: cross-sectionsshowing lhe geological formationsthat are aquifers and confiningheds.

"li " E' ....~ lfl

" <a: Co~ C " '"0 .li "

j ~;. c i ~

;.; ~. f=~ '"~ ~ 0 0 . '"g " g

~~ ~ 0

;;' " ~ " oS r- :c.'" '" -'

F

~ 11)()()..J

11!i()-,

If,{)()

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II(jr,~nl(/I.CX:(Ilc

e 0

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(£GlppSlafld L.mc5/0fl('

DLatrooe V"Ucy Coal MC,ISUI('S

1::::::16it/ooll Form..l/lOn

IIl/li,"-'

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COIII.Il"",,/:1t::t~",)."1 ···.·'I~.~I.

" III .1qU",'fS ",,/11,11.1;, t.

1If/U,lcr

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1<,OIl/.JIII<: .<:a"~' UNit" ,Ktrlll",;:J

Water usein Victoria

Victoria occupies only 3"70 of Australia's land area but it contains over 25010 of thenational population, making it the most densely populated State. There is thus amore concentrated demand for water in Victoria than anywhere else in the continent.Most Victorians live in Melbourne and districts close to Port Phillip Bay. However,they use water mainly for domestic and industrial purposes and so account for only20"70 of the State's water consumption. By contrast, 78"70 of the total is used forirrigated agriculture north of the Central Victorian Uplands.

SURFACE WATER SUPPLY SYSTEMSA dam provides a means of collecting surface water from rivers, so the water canbe transferred later to areas where it can be used. II' the annual streamOow of ariver is reliable, sufficient water can be stored during the cooler, weller months tocope with demand in the hotter, drier periods of the year. In most parts of Victoria,however, this method does not provide an assured water supply, even allowing forrestrictions on use in drought years. The generally high annual variability of rainfallover the State has made it necessary to build reservoirs with large storage capacitiesrelative to annual streamOows and average water usages. Many of Victoria's largedams therefore have been designed to provide 'over-year' storages, that are sufficientto fulfil needs over periods equal to the longest sequences of dry years ever recorded.Unfortunately large storages are costly to build and they suffer high evaporationlosses. Most Victoria's storages, however, also play an important role in controllingstreamOows, so reducing potential Oood damage.

The first major water storage in Victoria was Van Yean Reservoir. It wasconstructed in 1857 to supply the rapidly expanding Melbourne metropolitan area.Other works began soon afterwards to provide water to provincial towns and laterto irrigation areas. Since then many urban water supply systems have been developed.This is because there has always been a public demand to have so much water storedthat rationing can be avoided, even in times of drought. This popular desire hasnever been fully realised and probably never will be. The total capacity of Victoria'smajor storages exceeds 15 000 000 megalitres, which is equivalent to 1110re thall 7()0f0or Ihe mean annual discharge or all Viclorian rivers (Figures 6-28).

o 25 50 75 100! ! , ! •

Kllomelfes

17

Figure 6-28Major surface water storages inVictoria and the rivers on whichthey are buill.

• Midura

.Swan HIli

Rural Supplies1 Toobndo 12 Warang32 RocJdands 13 Ellden3 Bellfield 14 NlllahCoolie4 West Barwon 15 Mckoan5 Lal Lal 16 Wilham Hoven6 Melton 17 Butlalo7 Memmu 18 Hume8 Pykes Creek 19 Oarlrnoulh9 Tullaroop 20 Glenmagg~

10 Cairn Curran 21 Blue Rock11 EppaloCk 22 Tarago

Albury. '.~ WodongaVo-9 ~ '\.

1. .,~~

" 19

Water 251

Melbgllfne's SIJQply23 Thomson24 L:pper Varia2S O'Shannassy26 Maroondah27 Sugalloal28 van Yean29 Greenvale30 Silvan31 Card,n'3

Map Storage Construction Stream Full storage Main usesreference completed capacity of waler+

(enlarged) (megalitres)

I Toolondo 1953 off-stream 106 000 I, D& S2 Rocklands 1953 Glenelg 348000 I, D& S3 BeUfield 1966 Fyans 78500 I, D& S4 West Barwon 1965 West Barwon 22000 T5 Lal Lal 1972 West Moorabool 59 500 T6 Melton 1916 Werribee 17000 I7 Merrimu 1969 Pyriles 19000 T, I8 Pykes Creek 1911 Pykes 24000 T9 Tullaroop 1959 Tullaroop 74000 I10 Cairn Curran 1956 loddon 148000 I EII EppaJock 1962 Campaspe 31200012 Waranga 1910 (1926) off-stream 411 00013 Eildon 1927 (1955) Goulburn 3 390 000 E14 Nillahcootie 1968 Broken 40 00015 Mokoan 1971 off-stream 365 00016 William Hovell 1971 King 13 50017 Buffalo 1965 Buffalo 2400018 Hum. 1936 Murray 3038 000 E19 Darlmoulh 1978 Mitta Mitta 4000000 .E20 Glenmaggie 1929 Macalister 190 000 D&S21 Blue Rock 1983 Tanjil 200 000 C, T, 122 Tango 1969 Tarago 37500 T23 Thomson 1983 Thomson 1 110000 T, I24 Upper Yarra 1957 Yarra 200 000 T25 O'Shannassy 1928 O'Shannassy 4000 T26 Maroondah 1927 Watts 22000 T27 Sugarloaf 1980 off·stream 95000 T28 Van Yean 1857 Plenty 30000 T29 Greenvale 1971 off-stream 27000 T30 Silvan 1932 off-stream 40 000 T31 Cardinia 1973 off-stream 287 000 T

+ ~HS: I irrigation; T tOwn supply; D & S domestic and slock; E electricity generation; C cooling water for powerstallon

Two very large integrated systems dominate the State's water supply. The largestin volume is the Goulburn-Murray Irrigation District of northern Victoria. It drawson a number of major headwater storages and is operated as one interconnectedsupply system. The largest in economic terms is the Melbourne metropolitan systemin south-central Victoria, which supplies water to about 70"70 of all Victorians. Smallersystems provide dome5tic or farm water in other pans of the State (Figure 6-29).

252 Chapter 6

Figure 6·29Major public water supply syslemsin Victoria.

I....... r-~r.1Id ..·a

"I\IiIiIiIIiI

~Port'and

ImgattOn DlstrlClS13 Gol.llburn Campaspe

" ..-.2 Mlmay VaRcy3 Torrumb.auy4a Nyah4b Robonvalc4C Red Chlls. Mdduill. MCfbelll, Yella

5 Macahslcr6 Wcmbee1 B3lXhuS MaishB Colban9 !iorsh3m MllrlOa

Urban Supply Districts10 Otway11 Geclong BClla"ne Pcnmsulil12 Barl.:!lat13 Melbourne14 Momongton Peninsula 3 0.51"C\IS Latrobe Valley

Domestic & Stock Supply16 WIITl1nc'aMaJIae

25 50 75 100, ' , ,

Kllomelres

A complex network of channels and pipelines is used both to transfer waterfrom storages to areas where it is needed and to release water down natural riversystems. Many pipelines within each system are interlinked, so that water arrivingat one location can be from more than one storage or from different storages atdifferent times.

Pipelines in Melbourne and other urban areas are mostly underground. On theother hand, in the country most distribution systems for public irrigation and stockand domestic supplies are open channels. There are about 21 ()()() kilometres of waterpipelines in Victoria, over half of which supply the Melbourne metropolitan area.There are also 23 ()()() kilometres of open channels in rural supply systems, including4000 kilometres required for drainage and flood protection.

Most water storages provide scenic, recreational areas. Boating and fishing arepermitted on some. A few such as Reedy Lake, north of Nagambie, are managedprimarily to assist the breeding of water birds.

GROUNDWATER SUPPLYThere are more than 69 000 bores and wells extracting groundwater in Victoria.Without them, primary industry and some other rural developments would not bepossible over those parts of the State that are not linked to surface supply schemes.AboUI 250 ()()() megalitres of groundwater are extracted annually in Victoria. In theearly days, groundwater was mainly used for watering farm animals. Nowadays,150000 megalitres obtained from 6000 high·yielding bores are used for irrigatingvarious fodder crops and market gardens. [n addition, 40 ()()() megalitres are usedfor town supplies.

An important use of groundwater is to supplemenl surface water supplies duringdroughts. For example, in the Melbourne suburbs many private water bores areused for watering gardens during periods of water restrictions. This kind ofgroundwater use has increased greatly since higher excess water rates were introducedin 1987.

URBAN AND INDUSTRIAL USE OF WATERReliculated water systems upplyabout four million people around melbourne andin 345 country towns. Most water comes from surface storages, but 34 towns,including Portland, Sale and Nhill, are dependant on groundwater aquifers (Figure6·30). A further 28 lowns, including Geelong, add groundwater to their surfacewater supplies. [n addition, 29 towns have emergency supply bores.

Water 253

Figure 6-30Victorian towns with publicgroundwater boresand reticulated supply systems.

',' oC~'a

.0

e1')II· -'-"--.:l_;~

1:1· '''oco.,_ ~

"

31::: .! c •:13- -

-.:J2

.~

\J

10·

SW2.I\H

-.

iI. _2

iIIi:l 0 •... 6i -\

. 7"-I-.RJ

ill.'" .,I •

GroundW31er Bore num~r Supply source Aquiftr tapped To~ os supplied Suppl)province on map LocalilY Ty~

Murray Basin I Murra)'\iIIe I bore Duddo Limestone Murra)'\lille full2 Co"ang~ I bore Duddo Limestone CO'o'angie full3 Lillimm 1 bore Duddo Limestone Lillimur full4 Kaniva 2 bores Duddo Limestone Kani'3 fullS t\·liram 1 bore Duddo Limestone Miram full6 Nhill 6 bores Duddo limestone hill full1 Goroke 2 bores PariUa Sand Goroke full8 Apsky I bore Duddo Limeslone Apsley full9 Pine Hills I bore Parilla Sand Harra" full

10 Elmore 2 bores Cali\'il Formation Elmore full

" Kalunga I bore CaliviI Formalion Katunga full12 Strathmerton I borc Cali\'il Formation Strathmcrton full13 hiltern 3 bore Cali\'il Formation Chillern full

Otway Basin 14 Healhfield 1 bore Port Campbell Limestone Castenon. SanMord panIS Heywood 2 bores Dilwyn Fonnmion Hey\\ood full16 Portland 4 bores Dilwyn Formation Portland full11 Pon Fairy 3 bores Oil"" yo Formation Port Fairy fun18 Koroit 3 bores Port Campbell Limestone Koroil fuJI19 Pcnhurst I bore & spring C'\\Cf Vokanics Pcnhur:,t full20 Dunkeld I bore C\lICf Volcanics OunL.e1d part21 CaramUi I bore & spring C\lI~ Vok:anics Caramut full22 Monlake I borc spring Ncv.Cf Volcanics ~lonlaL.e part23 Curdie Vale- I bore Dil"")11 Formation \\'arrnambool24 Petcrborough I bore Dil"" yn Formation Pe(erborough full2S Port Campbell I borc Oil .... ),o Formation Pon Campbell. Timboon full26 aar.... on Do.... ns .. bores Oil"")T1 Formation Gedong. Angl~.Torqua~. pan

83f\\on Heads. Q.:ean GfO\e. Dr:osdale.Porlarlington. Queensdiff. Lropold. PointLonsdale. Win....hel~. Indented Head

21 Lismore spring C\\c.T Volcanics Lismore part28 Slre3lham 1 bores C\\Cf \'okank-s Slre3tham full29 Sl(xl yard Hill spring C\\Cf Volcanil.."S SL.ipton full

We;aem Port Basin JO Lang Lang I bore Childers Formal ion Lang Lang full

Gippsland Basin 31 Trafalgar I bore Morwcl1 Formalion Trafalgar panJ2 Sal, 5 bart'S lloisdalc Fonnalion Sale. WurruL. full33 l30isdalc I bore Hoisdale r"Ormation BoiMJale full34 Briagolong 2 borcs l30isdale Formation Uriagolong full

Up(;lllds 35 Barnawartha 2 bol\."'S bascmelll l3:trna\\aftha full36 La.n..·cfiekl I bore l..'\\I..'f Volcani..·s 1..1.I1 ....... licld pari31 Mount Mal..'Cdoll 3 bores dacite and b.1.scnwnt Woodcnd part38 li'cntham 1 bores twer Vok:ank's TrClllham p..1.rt39 Goldon I bore C\\ cr Volcank's Gonlon. Mount Egl..'flon full.0 Learmonlh 2 bo= Nl'\\ef Vok:anks u.--annOlllh full41 Waubra , bore C\\Cf Vok:anil,."S \\aubra full42 Dung Dong I bore basement AH)o.';I panH ~lO)~on West 2 bo= basement \\ iIIaura. I aL.t· Bol1.c. parI

M~'IOll., (ilelllhomp".ln. \\ id.....htk.4 Heath Point 2 bo= ~mCIII \krino lull

• Borcfll'k1 10 il'k.TCasr .....:llcr 1;\1('1('11)' for \\'arrnambool Ixll\~ "..,,,-d in 199(); ""OIl\p&cllon of "hcm~ pro(XhI.."t.I fur II:N~.

254 Chapter 6

Most Water used in urban areas is for domestic purposes. There are also somewater-intensive industrial activities, such as fruit canning in north-eastern Victoria,power generation and brown coal mining in the Latrobe Valley, metal refining nearGeelong and textile production in the Geelong, Ballarat and Warrnambool areas.

The Geelong district and Portland urban supply systems have groundwatercomponents that are of special interest. At Portland, four bores extract groundwaterfrom the confined Dilwyn Formation aquifer at depths of between 1100 and 1300metres below the surface (Figure 6-1). They supply a population of over 10000persons with domestic and industrial water. The groundwater has a temperatureabout 60°C. To make use of this heat, groundwater from the newest bore, drilledin 1983, is passed through heat exchangers. These extract heat energy before thewater enters the reticulation system. The energy is used for heating a number oflarge municipal buildings and the local swimming pool. The existing water supplysystem has a potential heat output of 1600 kilowatts, of which only 600 kilowattsare currently used.

In years of average to high rainfall, water for Geelong and the BellarinePeninsula comes from dams in the catchments of the Barwon and Moorabool rivers.The supply system also includes four bores at Barwon Downs, some 50 kilometreswest of Geelong, near the headwaters of the Barwon River. No suitable groundwateris available closer to Geelong. The aquifer tapped by this borefield has a large volumeof groundwater in storage but its annual recharge is fairly small. Consequentlygroundwater from the aquifer is only used during times of drought. The groundwaterstorage is allowed to recover in non-drought years. Measures to replenish the aquiferstorage artificially are being tested.

IRRIGATIONIrrigation is by far the largest user of water in Victoria. Nearly all of it comes fromsurface storages (Figure 6-31). The total annual consumption of about 3 550 000megalitres by irrigation would be enough to supply the Melbourne metropolitanarea for about eight years. The combined full capacity of the three largest irrigationstorages, Dartmouth, Eildon and Hume, is nearly six times the volume of waterheld in Melbourne's nine storages. Unfortunately there are substantial losses byevaporation and seepages from open channels and farm dams.

SUb'IOlal

Sub-Iotal

TOlal all ..aurr.:t:'o

Privale grouflIJwatcr divcr\iom oo

Volume applied A \'(.Tagc usage1981/88 1977-86(ML) (MLlyr)

1 147 705 974000415 381 JOI 500412 7]1 328 500579 492 505 500

2 555 J09 2 109 500

, J06 , 50018984 20100

120894 138000147 184 165 600

190 581 140 00011 lJl) 120005 562 , 300

15 189 1250020 217 IS 000

204 569 IS' 000227 466 153 00025000 15000

.1 402 990 2 K19 "XlO

150 000 J10 000

3 552 990 2 IJ291)()()

I 1002300

1600019400

IIlO 0008500059000

114000438000

581 100

40 000

621 100

32 (XX)

3 100I 5003 2002 <)()()

41 000)4 (0)

6000

r\pprox. areaunder

irrigation (ha)

Irrigation Area

Goulburn-Murray Irrigmion District:Ia Goulburn·CampaspcIb Loddon2 Murray Valley] Torrumbarry

Dircct pumping from Murray River:4a Nyah4b Robinvalcole Merbein·Rcd C1irr..

O. onFigure6·29

5 Mar.:aliSlcr6 Wcrribee7 l3ar.:chus Mar\h8 Coliban9 Hor..ham-Murloa

DirC\:1 pumping from Milia, OVCI1\, KiewaPrivate \urfal'C water divcr-.ionPumping from priv.Ui.' off·\lrcam dam\o

Total \Urfal'c watt:r

Figure 6-31Irrigation in Victoria.In many areas there was asignificant increase through theJ980s in the amount of water usedto irrigate farmlands.

• - C'>lirnalctl 3.\ IDOl. of volumc frolll on·"rr.:;UTl \loragc....00 _ r.:\tilll;tll-U a... JOOlo of aulhori'>(,'t! cxlra..:lion volullIe.

Most irrigated land is located north of the Celllral Victorian Uplands and issupplied by water from the Goulburn and Murray River systems. The largestirrigation district south of the Central Victorian Uplands is thc Macalister systemin Gippsland. Two small irrigation districts at Bacchus Marsh and Werribee in centralVictoria use water from the Werribee River and its tributaries. Areas supplied bygovcrnment-controlled public irrigation systems are shown on Figure 6-29. Thercare also some private irrigated areas scattered throughout the State. These divertwater directly from nearby rivers and creeks.

Figure <>-32Spray irrigation of citrus treesfrom a private channel in theSwan Hill district.It is more efficient to irrigate bysprays than by sheet flooding. Lesswater is needed and there is lessdanger of salting developing.Large losses of water occur due toevaporation along the open supplychannels, especially during thelong, hot, summer months.(Photograph courtesy of RuralWater Commis ion.

Figure <>-33Spral' irrigation of pastures atLake Boga.(Photograph courtesy of RuralWater Commission).

Water 255

Irrigated farmland covers only 4"70 of the total area devoted to farming inVictoria, but it produces about one·quarter of the State's agricultural production.About four·fifths of aU irrigation water is used on pastures, that feed meat anddairy animals. Only 10% is used for intensive cropping, but these products havea high value. The main crops produced are fre h canning and jam frUits, vegetables,tobacco, table and wine grapes, hops and citru fruit . Higher levels of productivityare achieved on irrigated farms than would be pos ible if the farms relied on rainfallonly.

The average value of production per hectare per megalitre from Victoria'sirrigation areas is fairly low compared \oilh'that from most other irrigation areaswithin Australia and overseas. This i because most of the water is used for low.value pastures grown on red·brown soil of northern Victoria. These soils cannotbe used for intensive cropping under irrigation because:• the clay subsoils retard drainage and become waterlogged after over·irrigation

or wet weather;• after several years of cultivation the soils set hard, making it difficult for irrigation

water to infiltrate, for roots to grow and for seedlings to emerge.

STOCK AND FARM DOMESTIC USEOutside the irrigation areas, there are some public water supply works, which catermainly for domestic usage and the watering of tock on rural holdings. These aremainly in the north·western part of the State, where the rainfall is low, there areno permanent urface water supplies and usable groundwater supplies are limited.In this region, water is di;tributed from dams in The Grampians and, to some extent,directly from the Murray River (Figure 6·29).

The system of channels in the Wimmera and MaUee region is one of the largestof its kind in the world, extending over some 28 500 square kilometres with a totallength of more than 10000 kilometres of mostly open channel. Large farm damsand town storages are filled from these channels once a year, usually in winter.

256 Chapter 6

Figure 6-34An irrigation channel lock andfootbridge across a channel in theMildura district.lrrigation water is obtaineddirectly from the Murray Riverand distributed along openchannels. Gates are opened in thelocks to regulate the ilow of waterdown the channels. (photographcourtesy of Rural WalerCommission).

In the Millewa system, which is supplied by pumping from the Murray Riverto Lake Cullulleraine, open channels were replaced by pipelines in the early 1970s.This eliminated losses by seepage and evaporation and so greatly reduced the quantityof water pumped through the system.

ELECTRICITY GENERATIONWater plays an important role in the generation of Victoria's electricity suppliesin two ways. Large volumes of water from the Hazelwood Pondage, near Morwell,and Blue Rock Reservoir, on the Tanjil River, are used for cooling purposes at thelarge coal-fired power stations in the Latrobe Valley. At Morwell open cut,groundwater is pumped from a sand aquifer below the coal and used for powerstation cooling and fire prevention.

In north-eastern Victoria, there is minor production of hydro-electricity. Thisis generated when the force of falling water turns turbines. The Rocky ValleyReservoir on the Bogong High Plains is the main storage for the Kiewa hydro-electricscheme. In addition, power stations at four other dams, including the HumeReservoir, generate electricity intermittently when water is being released forirrigation. 0 water is lost when hydro-electricity is generated.

MINERAL WATERMineral water wa defined in the Victorian Groundwater (Mineral Water) Act 1980as ... "groundwater which in its natural state contains carbon dioxide and othersoluble matter in sufficient concentration to cause effervescence and impart adistinctive taste". Natural (unbottled) mineral water also has a slight odour. Whenit is left in a bottle for orne days, a brown deposit of iron oxide usually appears.This is the product of a reaction between dissolved iron salts and the water whenit is exposed to air.

There are about 120 known mineral springs, mostly clustered in the Daylesforddistrict of central Victoria. About half the springs are on public land. The policyof the State Government is to protect thi resource for the people of Victoria. Theyhave free access to springs on public land and free use of mineral water there.Commercial companies have also unk bores on private land to obtain large suppliesof natural mineral water. This is treated to remove any objectionable odour or tasteand to stop the precipitation of iron oxides. It is then bottled and sold as commercialmineral water.

Springs and bore yielding mineral water are located in folded and fracturedOrdovician sedimentary rocks, especially andstone. Some are also found in youngersediments and ba alts. Mineral springs occur where the water table intersects theland urface, usually along creeks. Boreholes for mineral water are often sunk intoaquifer near natural springs.

Mineral water contains from 1000 to 10 000 mg/L total dissolved solids withan average of about 2500 mg/L. It differs from most Victorian groundwater in thatit has higher bicarbonate and lower chloride concentrations, and abundant carbondioxide is present.

Mineral springs were di covered during the gold rushes in the Midlands region.For a long while, there was controversy among geologists about their origin. It wasthought the water might be of volcanic origin, because there are many valley flowsof Newer Basalt in the ranges. However, it is now generally accepted that mineral

Environmentalproblemsassociatedwith waterin Victoria

Water 257

water is normal groundwater recharged by rainfaU and stream infiltration. The saltspresent are either contained in rain or they are dissolved from rocks through whichthe groundwater passes. Explanations differ as to the origin of the carbon dioxide.It is most likely formed by the oxidation of carbonaceous matter in Ordovician rocks.The slight odour and taste present in most mineral water is caused by hydrogensulfide, which may be formed by the oxidation of pyrite (FeS,) in the rocks. Somepyrite may be converted to soluble iron salts. However, there are still some peoplewho think the carbon dioxide might be derived from deep-seated magmatic activity.

Through storms and floods, water can often have an adverse affect on the naturalenvironment. Problems with water can also arise due to careless human actions.Two major environmental issues are discussed below.

POLLUTION OF WATER SUPPLIESAs water passes over or through the ground, it may dissolve or carry contaminatingsubstances, which can threaten life systems using the water. Pollution may be ofbiological or chemical origin.

Biological pollution may occur where bacteria and viruses, derived from humanand animal excreta, are introduced into water by inadequate waste disposal systems.This form of pollution is minimised in the extensive Melbourne and MetropolitanBoard of Works supply systems by excluding people and stock animals from thecatchment areas.

Fortunately biological pollution is usually very low in groundwater, becausemicro-organisms are killed rapidly as water passes through rocks and soils.Nevertheless serious local contamination can occur where a herd of farm animalscongregates on porous ground that forms the intake to a shallow aquifer. Thereis a greater risk of groundwater pollution occurring in limestone country. Pollutedsurface water can pass down quickly through various holes and fractures to anaquifer. There it can flow through caves to other parts of the aquifer without anyfiltration occurring.

A wide range of chemicals may cause pollution of either surface or undergroundwaters under various circumstances. For example, pesticides and fertilisers canbecome dangerous substances if they are dissolved by watcr percolating into streamsor down to the water table. Dangerous heavy metal ions can enter water systemsfrom such things as old cars dumped in gullies. Liquid effluents from certain factoriesmust not be dispo ed of in streams or stormwater drains. Care must always be takenin siting and designing rubbish dumps to avoid the possibility that percolating waterwill dissolve contaminating substances and carry them into shallow aquifers (seealso Chapter 7).

THE SALINITY PROBLEMIn recent years a major environmental problem has gradually been recognised inVictoria and adjacent States. Dissolved salts (especially sodium chloride) in soilsand water are killing natural vegetation and reducing agricultural productivity. Theproblem has arisen because of two reasons:

I. The water levels in shallow aquifers in many districts have risen close to or abovethe land surface (Figure 6-39).

2. The concentrations of salts in both surface and underground waters have increasedabove the levels which can be tolerated by many plants.

Most crops, pastures and natural species of plants become stunted or even diewhen their roots absorb saline water. As a result, there are many rural areas wheretrees have died off and farming has become unprofitable due to low yields fromcrops. The areas affected by the salinity problem are shown in Figure 6-35.

There are other Ie s common problems a sociated with saline waters. Forinstance, during summer some dams in western Victoria become so salty that theycannot be used by stock. In northern and western Victoria, household equipmenthas been damaged by salty water supplies. Saline waters in streams and wetlandsmay adversely affect fish, water plants and wildlife.

258 Chapter 6

Figure 6-35Areas in Vicloria affecled byexcessive salts in soih andgroundwaters.

................

.....-....."'-.. ......

o 2p 5' is 100

Krlo:net~es

Bairnsdale •

Sall-affecled land.. In northern Irrigalion regions, 70%ollhe Kerang and 20% ollhe Shepparton regions aresalt prone. In dryland areas, numerous outbreaks ofsalinity occur Ihroughoullhe zones shown on this figure.Many isolated occurrences are In areas where there is

considerable polenliallor salinity to spread.

Iff/galion regions

Irngation salting

Dryland salling

Isolaled drylandsaltmg occurrences

• Shepparton

..

.. .... .. ..MELBOUR E

........

ooo

Bendigoe

Kerang.

Figure 6-36Land near Kerang severelyaffecled by salinity problems.The water table has risen close tothe surface in this district and thesalt content of the water hasincreased. The salt has killed aforest of red river gum trees, aspecies that usually thrives onriver nats. (Photograph byP.G. Dahlhau ).

Figure 6-37Low succulent vegetation on a saltpan near Kerang.A high concentration of saltsoccurs in the soils on the noors oflakes and depressions in northernVictoria. The salt occurs wheregroundwater leaks to the surfaceand evaporates. The nature of thevegetation depends on theconcentration of salts. Thesucculent shrubs in the photographhave no value for feeding stock.(Photograph courtesy of RuralWater Commission).

Figure 6-38Interlocking sodium chloride(common salt, halite) crystalsdeveloped in a soil at Lake Boga.The crystals were left after theevaporation of saline groundwater.(PhOlograph courtesy of RuralWater Commission).

Water 259

The causes of the salinity problem

Natu ral salinityThroughout recent geological time, there have been salt marshes, salt pans, salt lakes.salt-affected soils and saline streams and aquifer in some pan of Victoria. Theyare especially common in the nonhern and western regions. The highestconcentrations of salt occur in the Mallee, because the rainfall is low and Cainozoicmarine sediments of the Murray Basin inherently contain a lot of salt. Howewr,overall natural saline features only cover a small area and have not seriously limitedthe extent of land available for farming.

Induced salinityAfter the early gold rushes of lhe 1850s. increasing numbers or Eurl'I"'an selliersbegan clearing the country for farming. It appeared that most of thc Slatc ,)ntsidethe Central Victorian Uplands wa suitable for either agriculture lH' animal ~razing.

This was so, because soils were arable, water supplies were adequate and the landwas flat to rolling.

The basic causes of the modern salinity problem commenced in the middle ofthe nineteenth century. Opening up the country for farming led to the clearing oflarge areas of forests. Trees, particularly eucalypts, lake in and later transpire muchmore water than do grasses and crops. As a result, in cleared areas, a higherpercentage of the rainfall infiltrated to the water table than happened where foresttrees absorbed the water. The result was that water was added to the groundwaterzones in the agricultural areas faster than it was discharged illlO streams throughsprings. Consequently the levels of many water lables gradually rose. In many areas,lh~ waler table has IlOW rCi:ll."hcd the grollnd sllrrac~. forming swamps and boggyareas. These did not exist before European sell1cmcnl began (Fi~nrc 6-39).

260 Chapter 6

HI Typica11940s Land P,'ofilc

lr:ln-.pir;uilltl h,' dl'I1:-('\T;":I'I;lliull t'l'<!Ute·,.

inlillrallUn 10 \\:lll't' lahl..,

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Figure 6-39The effects of land use changeson lhe level of the waler table.There is a greater danger thatsalinity problems will occur whenthe water table rises close to thesurface. The clearing of nativeforests in groundwater rechargeareas to provide farmland hasreduced the amount of waterremoved as transpiration andincreased the amount of waterpercolating down to the watertable. This has caused the watertable to rise, thus increasing thedanger that a salinity problem willdevelop in the irrigation area.

(;ruun<!\\':llCr dis<:harg<.' Will' Gnlllndwall'" 1'1'Chnrgl' ZOlle

iITig:::liull ;It'l.·;l~:

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to l'lrl';UIl

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It·,..,; tran"plr;llillll

dnbnd ;It"\'<l!•.;

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III 1,11111,,111'[';11'\'

(;rllun<!\\,llt'l'i'olIIH'

b) Typical 1980s L:Uld Pl'Ofilc

Much of the groundwater close to the surface in Victoria is saline, particularlyin western Victoria. There are two reasons for this. Groundwaters usually containmore salts than surface waters, because they are in the ground for longer periodsand in contact with greater quantities of soils and rocks. In addition, the heat ofthe Sun evaporates water from soils down to a depth of about two metres. Thewater that remains therefore becomes increasingly salty. Even where there was goodquality groundwater originally, prolonged evaporation can lead to a build-up ofsalts in the soils.

Many native Australian trees (e.g. eucalypts) can withstand moderately saltygroundwater. However, as the water table rises to the surface, the groundwaterbecomes permanently waterlogged. Under these circumstances, trees gradually die.Grasses and crops are even less tolerant of salts, so they also die when the watertable reaches the surface. The spread of saline waters has therefore caused a lossof farmland and a fall in the yields on some remaining farms. In addition, thereare dwindling numbers of birds and other wildlife in the salt-affected areas.

Irrigation has increased the spread of salinity in some areas, because mOre wateris being added to the land than would be from rainfall alone. Saline groundwaterhas seeped into many streams, thus extending the problem downstream.

About 2400 square kilometres in Victoria are affected by salinity problems atpresent, an area equal to the combined surfaces of Port Phillip Bay and WesternPort. It has been estimated that this area will double by the year 2000. The valueof agricultural products lost each year increases by more than $50 million. Lossesof farm revenue inevitably lead to financiallosse by other sections of the community.

Control of salinity problemsThere are no easy or cheap ways of reducing the concentrations of salts that haveaccumulated in soils and waters over a long period. Considerable research is beingcarried out by Federal and State organisations to identify the extent and causes ofthe problems and to produce solutions. It appears that attention will have to begiven both to removing existing saline waters and to reducing the quantities of waterentering the shallow aquifers. Some of the control measures, which will have tobe undertaken at either regional or local farm levels, are indicated below.

Regional control schemes1. The water table is being lowered in some areas by pumping groundwater into

lakes, where evaporation takes place. There are over 80 evaporative ponds closeto the Murray River.

The futureof waterin Victoria

Water 261

2. A grander scheme is being investigated, which would aim to transfer excess waterin a system of pipelines from affected farmlands in New South Wales, Victoriaand South Australia to a discharge locality in the ocean near the mouth of theMurray River.

3. Extensive revegetation is being carried out in some areas where there is an intakeof water to aquifers. This is especially applicable to land outside the irrigated areas.

Farm-based controlsI. Improved drainage of low-lying areas and land grading, so that excess water flows

off the land instead of soaking in and raising the water table.2. The sealing of irrigation channels to reduce leakage of water into the ground.3. Pumping and reuse of irrigation water before it dissolves more salts or evaporates.4. Change from flood irrigation to more economical watering techniques, e.g. trickier

systems.5. Planting of salt-tolerant trees (e.g. Swamp Yate, Albacutya Red Gum) around

farm boundaries, near water channels and dams, and on salt-affected land. Thisis more appropriate to dry land farmers.

6. Planting salt-tolerant pastures and deep-rooted species such as lucerne.7. Fencing off severely-salted areas to prevent stock killing the remaining plants,

which bind the soil and help prevent erosion.8. Modifying cropping practices to minimise the amount of fallowed land. More

water infiltrates bare land than that covered in grass or stubble ..9. Revegetation of groundwater intake areas, especially those on south-facing slopes,

where there is less evaporation.

Throughout lhe past century, the volume of water slored in Viclorian reservoirshas doubled with each generation. The growth rate of water consumption is greaternow than it has ever been in the past. Some measures to conserve water have beenintroduced. For example, it is now compulsory to install dual-flush toilets in newhomes in the Melbourne metropolitan area. In some rural areas, waste water is beingsuccessfully reused to grow crops. However, even with water conservation, Victoriawill need more water to satisfy future demands. In the long term, the extent to whichthe State's population can go on expanding will be limited by the availability of water.

SURFACE WATER POTENTIALIt has been estimated that only 43070 of the total flow in all Victoria' streams couldbe diverted for major water supplies. Just over half of this has already beendeveloped. The remaining water is unsuitable for use either because of its poor qua1Jtyor the high costs needed to develop it. This applies particularly to the lower reachesof streams, where the land is generally flat and unsuitable for dam construction.

The rivers with the most potential for fUlure damming are those draining theuplands of central and eastern Gippsland, and the Otway and Strzelecki ranges.The surface water resources of north-eastern Victoria are already extensivelydeveloped and in north-western Victoria there are no significant rivers. In the south­west, the stream waters are generally of unsuitable quality.

The future cost of collecting water from streams will be much greater than itwas in the past. Most untapped resources are located a long way from cities wherewater is likely to be needed. The development of untapped resources will requiresubstantial capital investment for transporting water over long distances. The presentdistribution is largely achieved by gravitation. However, in the future, expensivetunnelling or pumping or both will be needed to transport water between differentriver basins. It is also probable that the major supply systems will be interconnected.This will increase management flexibility and capacity utilisation, improve reliabililYand reduce costs.

Apart from the problems of cost, there will also be environmental issues toconsider. Areas such as the East Victorian Uplands and the Otway Range (e.g. AireRiver) have the greatest potential for new storages. However, they are also regardedas conservation and recreation areas. The planning of Victoria's most recent storages,Thomson and Blue Rock dams, included provisions for maintaining certain minimumflows downstream of the storages. All future developments will probably beaccompanied by similar rigorous environmental flow requirements. This will reducethe yield of the storages for other purposes and further supplies will be needed ateven greater costs.

GROUNDWATER POTENTIALGroundwater now accounts for only a small part of the water used each year inVictoria. Since surface water is heavily committed, it is certain that use of

262 Chapter 6

Figure 6-40Torrumbarry Weir on the MurrayRiver, east of Gunbower.River water is retained behind theweir and distributed throughirrigation channels to properties onthe Riverine Plain. (photographcourtesy of Rural WaterCommission).

groundwater will increase in the future, especially from basins that offer large yieldsof low-salinity water.

Care must be taken to ensure that problems of over-development and pollutiondo not occur in Victoria, as they have in some overseas countries. Schemes to developmore groundwater must recognise that the resource is replenished by the infiltrationof only a small portion of the State's annual rainfall. The average recharge rateis about I 500 000 megaHtres/year, although the total amount of water storedunderground is certainly hundreds and possibly thousands of times greater than this.

The maximum volume of groundwater that could be used each year is theamount available when long term inputs by recharge equal the outputs by naturaldischarge and groundwater extraction. In some places, it may become possible touse artificial recharges to increase the rate of replenishment, thereby increasing thesustainable yield. The estimated annual extraction of groundwater at present is250000 megalitres, which is only about 17070 of the estimated recharge. There is clearlyconsiderable scope for further development of Victoria's groundwater resources.However, not all the State's groundwater could be extracted economically nor isit all of good quality.

The largest undeveloped groundwater resources are in the Gippsland and Otwaybasins and in the north-east of the State. By contrast the useful groundwaters inthe northern and north-western regions, the Western Port Basin, the Werribee Deltaand the Ballarat and Silvan-Wandin areas are already heavily committed. Inparticular, excessive use in the Cora Lynn-Dalmore area of the Western Port Basinhas depleted the groundwater store, creating a risk of intrusion of sea water fromWestern Port. In 1971, this basin was declared a Groundwater Conservation Areato enable extraction to be controlled and so halt the intrusion of sea water.

Environmental issues are also becoming increasingly more important indesigning major groundwater extraction systems. For example, at the Batwon Downsborefield, local streamflow, discharge from springs and the elevation of the landsurface (to indicate any land subsidence) are all monitored to detect any adverseeffects of pumping on the environment.

Figure 641Buffalo Dam on the Buffalo River in north·eastern Victoria.

This small dam was built in I%5, mainly to conserve water for irrigatedfarming. Excess water can be released down the spillway in the middle ofthe dam. Coarse pieces of rock on the outside of the dam wall protect theinner materials from erosion by waves.

The highest range in the background is composed of granite (A). Thelowest hills are Ordovician sedimentary rocks (C). Between A and C, thelower range consists of contact metamorphosed Ordovician rocks (8) in anaureole adjacent to the granite. (Photograph by courtesy of the RuralWater Commission).

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Figure 6-42Lake Tyrrell, a salt lake near Sea Lake in north-western Victoria.

In this area. the water table is near the surface. Highly saline groundwater discharges from the banks of the lake on to the normally dry bed.Evaporation of this water leaves a thick crust of salt that can beharvested. (Photograph by P.G. Dahlhaus).

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