Peter Hekmeijer, Warrick Dawes - CSIRO · Peter Hekmeijer, Warrick Dawes. Assessment of salinity management options for Axe Creek, Victoria: ... AXE CREEK CASE STUDY, FEBRUARY 2002

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Assessment of salinitymanagement options forAxe Creek, Victoria:DATA ANALYSIS AND GROUNDWATER MODELLING

Peter Hekmeijer, Warrick Dawes

Assessment of salinitymanagement options forAxe Creek, Victoria:DATA ANALYSIS AND GROUNDWATER MODELLING

Peter Hekmeijer, Warrick Dawes

Authors: Peter Hekmeijer1, Warrick Dawes2

1. Centre for Land Protection Research, NRE Bendigo.2. CSIRO Land and Water, Canberra.

CSIRO Land and Water Technical Report 22/03MDBC Publication 08/03

Published by: Murray-Darling Basin Commission

Level 5, 15 Moore Street

Canberra ACT 2600

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Internet: http://www.mdbc.gov.au

ISBN: 1 876 830 49 2

Cover photo: Arthur Mostead Margin photo: Mal Brown

© 2003, Murray-Darling Basin Commission and CSIRO

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To the extent permitted by law, the copyright holders (including its employees and consultants) exclude all liability to any person for any

consequences, including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from

using this report (in part or in whole) and any information or material contained in it.

The contents of this publication do not purport to represent the position of Murray-Darling Basin Commission or CSIRO in any way and are presented

for the purpose of informing and stimulating discussion for improved management of Basin's natural resources.

This work was made possible through the concerted efforts over many years of local andregional hydrogeologists who first developed and populated the concept of CatchmentCharacterisation from a dryland salinity perspective. Many of these are mentioned in Coram(1998) and Coram et al. (2000), and have contributed to various aspects of this and other workover a number of years.

This report was funded under the Murray-Darling Basin Commission funded StrategicInvestigations and Education projects (SI&E) Grant Number D9004: ‘Catchment characterisationand hydrogeological modelling to assess salinisation risk and effectiveness of managementoptions’. Special thanks to the members of the Project Steering Committee for advice andfeedback.

The authors would like to thank Phil Dyson of Phil Dyson & Associates, Bendigo, for his expertopinion for this study and for reviewing the final report. David Heislers and Wayne Harvey, of theVictorian Department of Natural Resources and Environment and the Centre for Land ProtectionResearch are thanked for providing informed input and reviews. Editorial support was providedby Pauline English (CSIRO Division of Land & Water, Canberra).

Acknowledgements

C A T C H M E N T C L A S S I F I C A T I O N : A X E C R E E K C A S E S T U D Y , F E B R U A R Y 2 0 0 2

i

Executive summary

C A T C H M E N T C L A S S I F I C A T I O N : A X E C R E E K C A S E S T U D Y , F E B R U A R Y 2 0 0 2ii

Introduction

The Axe Creek catchment in north-centralVictoria is an intermediate-scale fracturedrock aquifer system in the Murray-DarlingBasin. Groundwater dynamics and salinityprocesses are significantly influenced bygeologic structures within the catchment.The Axe Creek case study was undertaken to:

1. outline the hydrogeological features ofthis geologically distinctive catchment

2. conceptualise the groundwater flowprocesses for recharge and dischargeto enable modelling of this part ofCampaspe River system

3. model the historical and present-dayhydraulic head trends in thecatchment and relate these to surfacedischarge features

4. simulate the lowering of groundwaterheads by broad-scale rechargereduction.

Site Description

The Axe Creek catchment lies within theCampaspe River catchment in north-centralVictoria. The 33 km2 study area is locatedimmediately south-east of Bendigo, withdrainage towards the northeast, to theCampaspe River. The mean annual rainfall forthe study area is 550 mm, with winter andspring rainfall slightly dominant. Nativevegetation was initially cleared in the 1850sduring gold mining times and, subsequently,through the 1900s with agricultural activities.Land use today includes small-scale livestockgrazing and agriculture. Native vegetation stillcovers 20% of the area, and there is someproduction forestry.

Groundwater system

The Axe Creek aquifer is an IntermediateFlow System in a fractured rock aquifer(fractured Palaeozoic bedrock; Coram et al.(2000). Hydraulic gradients for groundwaterflow follow the topographic gradient from BigHill Range in the south-west to theCampaspe River in the east. A majorcomplication however, is that the mainfractures in the aquifer run north-northwestand not in the direction we would expectflow to occur in.

The defining feature of the catchment is theWhitelaw Fault that cuts the catchment intotwo distinct areas. Upslope of the fault thecountry is steep with incised streams,shallow soils and a reasonable amount ofnative tree cover. Fractures mainly run in thedominant north-northwest direction withweak connection in the direction of thesurface topography. Downslope thelandscape is much flatter with gently rollingterrain and extensive agriculturaldevelopment. Many more fractures arepresent to connect groundwater flows in thedirection of head gradient. The Whitelaw faultcuts across the major streams of Axe Creek,

Location of Intermediate Groundwater Flow Systemsin fractured rock in the Murray-Darling Basin.


iii

and of the adjoining catchments to the northand south. The role of the Whitelaw Fault isnot fully resolved, but it is theorized that itinterrupts groundwater flow and redirects ittoward the creeks where it is discharged. It isnot known if groundwater flow from adjacentcatchments is transferred in to, or out of, theAxe Creek catchment.

Fracture zones in the bedrock enablegroundwater movement from the ranges to thealluvial terraces and plains. The major fracturezones strike north-northwest, followingbedding planes and fold axes. The WhitelawFault is the most substantial of these structuresand is defined by an elongate high relieflandform that transects the catchment.Secondary fractures perpendicular to the mainstructural trend transmit groundwater north-eastward between the major fractures,although parts of the Whitelaw Fault presentsan obstruction and redirects somegroundwater flow north-westward.

Recharge is mainly thought to occur in thehigh relief upslope areas of Axe Creek. Thinsoils with direct connection to fracturedbedrock and higher annual rainfall provide anideal conduit for recharge to the groundwatersystem. Rates as high as 100 mm/year areestimated, although the average over thewhole of Axe Creek is only 15 to 20mm/year. Surface soil salinisation of primeagricultural land in the lowland valley floorsbecame apparent in the 1940s. On bothsides of the Whitelaw Fault, salinegroundwater discharge is controlled by theabrupt break of slope. In particular, salinedischarge is concentrated in small valleysimmediately downslope from where theycross-cut the Whitelaw Fault. Althoughsurface discharge areas appear to havestabilised, shallow water levels and streamsalinity are compounding problems in thecatchment.

Groundwater modelling

The FLOWTUBE model, a simplegroundwater model based on Darcy’s Law,was used to simulate the effect of variation ingroundwater recharge on the groundwaterflow system. Historical and present-dayhydraulic head trends in the catchment weremodelled to represent the rise in water levelsof the last 100 years.

The simulated heads show substantialgroundwater level rises in the upslope partsof the catchment. The differences betweenpast and present water levels are lesspronounced approaching the Whitelaw Faultand are negligible further downslope.Simulated changes in surface flux during thelast 60 years show substantial spikes at theWhitelaw Fault zone. Comparison of fluxesand the capacity of the aquifer to transmitthese fluxes suggest that, even prior to landclearing and consequent recharge increases,some shallow water levels may have beentypical for the catchment.

FLOWTUBE modelling of recharge reductionsof 50% and 80% of the present rechargerates, to represent assumed pre-clearinglevels, indicates that only the upper part ofthe catchment responds with appreciabledrops in water levels. These reductionswould be achieved in the first 20 to 50 yearsof recharge reduction, with little changethereafter. No change in water level at theWhitelaw Fault nor through the catchmentdownslope, is indicated for the modelled 100 years. Only the area upstream from theWhitelaw Fault would benefit from rechargereduction, whilst the flatter eastern lowlandswould remain largely unchanged.

Portability of conceptualmodel, tools and results

The hydrogeology of the Axe Creekcatchment is complex, reflecting thedistinctive geology and structural influencesthat characterise the area. Variability ingroundwater behaviour across the catchmentis further expressed in bore hydrographs. The parameters of the Axe Creek aquiferused in modelling are poorly constrained andhighly variable, and modelling necessarilyincorporates some assumptions. Coram et al. (2000) suggests that fractured rockaquifers may manifest only a small area ofsurface salinity but result in a highly salinestream that exports a disproportionateamount of salt to the main rivers.Observations in Axe Creek support this.

In fractured rock environments generally,engineering solutions to control drylandsalinity, primarily by pumping, are often difficultand impractical due to uncertainty of theinterconnection and extent of the fracture


iv

networks. In situations such as Axe Creek,where saline discharge areas may havestabilised, suitable management of croppingand grazing rotations to minimise recharge isappropriate, along with living with manifestsalinity. Because of the unique and complexcharacter of Axe Creek catchment, thefindings of the hydrogeological investigationsand modelling are not readily transferable toother areas. The results of the present studycan only be applied to other fractured rockaquifers within the context of local conditions.

Conclusions

• The Axe Creek catchment is verycomplex, and is completelycontrolled by the structures in thefractured rock aquifer, principally theWhitelaw Fault.

• Modelling indicates that someshallow water levels, and evenseasonal discharge to streams, mayhave been present even under pre-clearing conditions.

• Much of the recharge occurs in thesteep uplands of the catchment andthis is where any biological rechargemanagement must be applied.

• In any reasonable timeframe of lessthan a century, no appreciabledeclines in groundwater levels weresimulated downslope of theWhitelaw Fault with up to 80%recharge reduction.

Recommendations

• Management of cropping andgrazing systems is required tominimise recharge on the lowerslopes, and living with the currentstable saline areas are appropriateoptions.

• Monitoring of creeks for flow and salinity upstream anddownstream of the Whitelaw Fault in Axe Creek and adjacentcatchments may help clarify its rolein the greater area.

• Monitoring of the saline areas will determine whether they have stabilised, but flow and salinity data for the main creek must be gathered to check for any trends or changes.

• Collection of data from otherfractured rock catchments inVictoria and New South Wales will provide a better understandingof key processes in these highlyvariable aquifers.

Acknowledgements i

Executive summary ii

1. Introduction 1

2. Physical setting 22.1 Site description 22.2 Climate 22.3 Geology 22.4 Hydrogeology 6

2.4.1 Groundwater trends 62.4.2 Groundwater salinity 9

2.5 Soil types 102.6 Land use 112.7 Salinity extent 13

3. Conceptual model 153.1 Hydrogeology 153.2 Recharge 15

4. Groundwater modelling using FLOWTUBE 164.1 Numerical model 164.2 Special considerations 164.3 Model parameters 164.4 Historical simulation 174.5 Future scenarios 20

5. Discussion and Conclusions 235.1 Summary 235.2 Future directions 235.3 Conclusions 24

References 25

Appendix 1: Aquifer parameters 27

Table of contents


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Dryland salinity is a major issue in Australia,and we urgently need clear information toguide appropriate investment in catchmentstoward management of the problem.Understanding the catchment-scaleprocesses is crucial for identifyingmanagement options, but in most Australiancatchments our existing understanding anddata collection is too limited to provide this.

The physical factors governing drylandsalinity vary across Australia, according tovariations in geology, landscapedevelopment, the amount of salt stored inthe landscape, and climatic characteristics.Likewise, the viable options for managingdryland salinity, and the timescale ofgroundwater and salinity response, vary fromregion to region. The variation ofgroundwater-driven dryland salinity,according to these first-order factors, hasbeen described for the whole of Australiathrough the National Land and WaterResources Audit (NLWRA) project ‘AustralianGroundwater Flow Systems InfluencingDryland Salinity’ (Coram et al. 2000).

Within the NLWRA Program 2, four case studyreports have been published. Each describesthe conceptual understanding of a flowsystem, models the prior and current situationin terms of land use and groundwaterrecharge, and examines possible futureoptions for biological recharge reduction andgroundwater pumping (Stauffacher et al.2000, Baker et al. 2001, Hekmeijer et al.2001, Short et al. 2000). In the CatchmentCharacterisation project another threecatchments are studied—the South LoddonPlains and Axe Creek in Victoria, andKyeamba Creek in New South Wales. The ultimate aim of an extensive investment in producing such reports is to cover all thedifferent flow systems identified in Coramet al. (2000).

The Axe Creek catchment in north-centralVictoria is an intermediate-scale fractured rockaquifer system (in weathered Palaeozoicbedrock). The geology of the area is complex,characterised by major bedrock structures and

fracture systems that play an important role ingroundwater dynamics and salinisationprocesses. The north-northwest strikingWhitelaw Fault transects the catchment and, in part, presents an obstruction to groundwaterflow and, elsewhere, conducts groundwaterout of the catchment. Saline groundwateroutcrops on both sides of the topographicallyelevated Whitelaw Fault zone, particularlydown-gradient, in valleys below the fault scarp.In the lowest part of the catchment, near theconfluence of Axe Creek and the CampaspeRiver, salinity is related to the influence of theMt. Sugarloaf Range bedrock high.

The Axe Creek case study was undertaken to:

1. outline the hydrogeological features ofthis geologically distinctive catchment

2. conceptualise the groundwater flowprocesses for recharge and dischargeto enable modelling of this part ofCampaspe River system

3. model the historical and present-dayhydraulic head trends in thecatchment and relate these to surfacedischarge features.

1

1. Introduction


2

2.1 Site description

The Axe Creek study area lies within thecatchment of the Campaspe River, in northcentral Victoria. It is located immediatelysouth-east of the city of Greater Bendigo(Figure 1) and comprises 32,800 hectares orapproximately seven per cent of theCampaspe Catchment.

The Axe Creek sub-catchment is bounded tothe south-west by the Big Hill Ranges andenclosed to the north-east by the Mt.Sugarloaf Range. Axe Creek rises on thenorthern slopes of Mt Alexander (742 mAHD), and flows northward joining theCampaspe River near Axedale (140 m AHD).

2.2 Climate

Rainfall data has been obtained for the city of Bendigo, 20 km north-west of the studysite. The average annual rainfall at Bendigo is 550 mm. A rainfall trend analysis has beencalculated for the Bendigo rainfall station(Figure 2). The bar graph indicates thedeviation from the mean annual rainfall. The accompanying line graph shows thecumulative deviation.

Rainfall and evaporation data were obtainedfrom the Lake Eppalock weather station(Figure 3), 10 km east of the Axe Creekcatchment. Winter and spring rainfallaverages slightly exceed 50 mm/month, with fairly equitable monthly averages, <50 mm/month, during other seasons. Mean annual evaporation for the station is 1460 mm while mean annual rainfall is 540 mm.

2.3 Geology

A granodiorite intrusion and associatedmetamorphic rocks (Mt Alexander and theBig Hill Ranges) form the southern margins ofthe catchment. Known as the HarcourtBatholith, it is Upper Devonian in age andconsists of coarse-grained, grey granodioritethat becomes finer-grained and slightlyporphyritic towards the margins. The

granodioritic terrain, the southern extremity ofthe catchment, makes up approximately25% of the catchment. The geomorphologyof this terrain ranges from gently undulatingfoothills (<5 degrees) to the steeper slopes ofMount Alexander (>30 degrees). Outcropsand boulders are common on the steeperslopes whilst the lower slopes often comprisesandy colluvium.

The granodiorite intrudes sedimentary rocksof Ordovician age and has produced anarrow zone of contact metamorphism.Hornfels, slates and quartzites are thedominant rocks in the metamorphic zone,and are more resistant to weathering thaneither the Harcourt Granodiorite or thesedimentary rocks further north. Differentialerosion in the region subsequently led to thedevelopment of a metamorphic aureole thatis morphologically expressed as the Big HillRange. The aureole has steep upper slopes,up to 30 degrees, with gentler slopingcolluvial fans on the lower slopes.

Further north, beyond the Big Hill Rangesthe terrain comprises steep to hilly landsformed on highly folded and fracturedsedimentary rocks of marine origin. Theserocks strike north-south and are fracturedalong bedding planes and joints. Theselow-grade metasedimentary rocks areestimated to be at least 10,000 m thickcomprising alternating layers of inter-bedded slates, shales, siltstones andsandstones.

A prominent feature of the catchment isthe north-south trending line of hills thatmark the boundary between the steepercatchment headwaters and the gentlermid-catchment terrain. This lineartopographic feature represents the erodedscarp of the Whitelaw Fault. The Fault liesparallel to the strike of the folded marinesediments, and vertically displaces theserocks by at least 1,500 m. The WhitelawFault is the most prominent of a series offaults associated with the deformation ofthe Ordovician rocks during MiddleDevonian times (Gray 1988).

2. Physical setting


3

Figure 1. Location of Axe Creek catchment study area.

Figure 3. Mean annual climate data for the Lake Eppalock weather station.


4

Figure 2. Bendigo rainfall 1970–1999; average annual rainfall is 550 mm.


5

Whitelaw

Fault

0 5 km

N

Ordovician metasediments

Newer Volcanics

Coonambidgal Formation

Shepparton Formation

Tertiary Gravels

Harcourt Granodiorite

Colluvium

Marine: sandstone, siltstone, shale, chert; Castlemainian supergroup

Extrusive: tholeiitic to alkaline basalts, minor scoria and ash

Fluvial, lacustrine: clay, sand, sandy clay

Fluvial: silt, sand, minor gravel

Fluvial: gravel, sand, silt

Intrusive: adamellite, granite, granodiorite, medium grained, pale grey

Fluvial: “gully” alluvium, colluvium: gravel, sand, silt

Figure 4. Geology of the Axe Creek sub-catchment (after King and Wilkinson 1975).


6

2.4 Hydrogeology

Groundwater movement occurs throughfractures and joints in the bedrock. The most significant flow occurs through the metasediments rather than through thegranodiorite (Dyson 1983). The fractureslargely comprise small bedding plane faultsand joints and fracture permeability isgreatest within the upper 30 to 50 metres.Groundwater flow rapidly decrease beyondthese depths (Dyson pers. comm.) and openfractures seldom extend to depths greaterthan 100 m.

The Axe Creek catchment is classed as anintermediate groundwater flow system.Groundwater flow is northward, some 20-30 km from the headwaters of thecatchment. The hydraulic gradient is steep in the metamorphic ridges in the southernheadwaters and becomes gentler in thesedimentary hills, reflecting the broadtopographic gradient. Local groundwaterdischarge occurs in some instances at thebase of the metamorphic ridges, while morewidespread discharge occurs where thesteeper sedimentary hills of the headwatersgive way to the gentler rolling hills of the midto lower catchment. The piezometric surfaceshows little response to local topographicvariations, except in the steeper terrain wherelocal break of slope salinity sometimesoccurs. Most groundwater discharge andsalinity issues occur within the valleysimmediately beyond the scarp of theWhitelaw Fault.

The Whitelaw Fault is the major controllinginfluence on groundwater flow and salinedischarge (Dyson pers. comm.). It dissectsthe catchment into south-western and north-eastern sectors and directs groundwater flowalong its axis to adjacent catchments furtherto north-west.

Groundwater flows north-eastward in theheadwaters of the catchment following thetopographic gradient until it encounters theWhitelaw Fault. The high permeability faultzone distributes groundwater to dischargezones both within and adjacent to the AxeCreek sub-catchment. Groundwater exitingthe fault zone continues to flow northward ina direction that is broadly coincident withstream flow. In the lower catchment, near

Axedale, flow appears to be interrupted bythe Mt. Sugarloaf Range, evidently promotingdryland salinity in the vicinity of the junctionof Axe Creek with the Campaspe River.

2.4.1 Groundwater trends

Groundwater monitoring has beenconducted within the catchment for at least20 years. Figure 6 shows the location ofobservation bores. Some 25 deep boreswere drilled in the early 1980s, and severalshallow piezometers were established in boththe late 1970s and the mid 1990s. Table 1provides a summary of groundwaterobservation bores currently being monitored.

Hydrograph trends throughout the catchmentvary according to the location of the bores inthe landscape. Figure 5 depicts a longitudinaltransect illustrating variations in groundwaterbehaviour from the upper to lower catchment.Bore 19 is from Axe Creek headwatersimmediately above the Whitelaw Fault andshows an overall increasing trend. Bore 20 islocated on the slopes of the Big Hill Rangeand exhibits both seasonal and episodicfluctuations with an overall trend that isneither rising nor falling. Bore 23 is on thedown-thrown side of the fault; and thewatertable trend indicates a rise of 3 cm/year.Bores 15 and 16 are located further down-slope from the fault, Bore 15 being thefurthest from the fault. Bore 15 exhibits aslightly falling trend that reflects the lower thanaverage rainfall of the past five years. Bore16, positioned near a discharging drainageline, also shows a slight falling trend.


7

Figure 5. Selected bore hydrographs within the Axe Creek catchment.


8

SKM boresNRE boresAxe Creek catchment

0 5 km

N

4685046849

4684646845

4684846851

46843

46844

682860011 15

680268036801

6808 68062568106809

681168126813

68146815

2422 23

291617

14 12136818

68196817

681668226821

6820

286807

60010111096805

6804

60012 1918

21 6823

69496944

20

60009

68246825

46847

68276826

Figure 6. Monitoring bore distribution within the Axe Creek catchment.


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TABLE 1. Bore monitoring data within the Axe Creek Sub-catchment

Bore Bore Water Water *Trend EC Position Lengthnumber depth depth depth description of

Spring Current record1993

(m) (m bgl) (m bgl) (cm/yr) (µS/cm)

9 30 19.3 20.7 flat 8,300 19

10 30 14.3 15.8 flat 14,000 19

11 30 8.8 10.57 flat 5,800 19

12 47.5 29.9 29.78 3.6 2,600 19

13 41 25.29 25.12 2 4,000 19

14 27 14.38 15.73 flat 6,400 19

15 49 8.2 8.9 -3.7 13,000 17

16 50 1.88 2.91 -2 15,000 17

17 50 -0.27 0.37 -2 16,000 15

20 50 8.78 10.01 flat 3,000 mid ridge 17

21 100 9.9 12.32 -7.3 8,730 15

22 100 0.56 1.87 -3.7 3,550 discharge 15

23 200 2.75 2.33 2.7 3,900 stream bank 15

24 102 13.1 13.25 7.3 6,500 14

25 42 8.07 9.26 flat 12,650 17

26 39 5.72 7.42 3.6 9,900 17

27 48 9.33 11.25 2 8,700 17

28 10 22.9 25.86 -3.6 3,600 17

29 50 -0.42 0.69 -7.3 13,000 15

30 45 7.6 9.48 flat 2,160 17

31 78 13.8 15.37 -7 3,000 17

32 50 1.48 2.79 flat 5,800 17

33 72 9.04 10.37 -2 2,020 19

6816 11.6 0.67 0.88 n/a 8,060 2

6817 4.9 0.73 1.04 n/a 10,080 2

6949 15 0.59 2.2 -43.8 8,260 4

60009 8.5 0.9 1.35 n/a 2,400 -1

60010 9 1.19 1.91 n/a n/a -1

60011 8 1.03 1.92 n/a 14,500 2

60012 17 4.98 5.84 -32.8 n/a 2

2.4.2 Groundwater Salinity

Groundwater salinity generally increasesnorthward, with variations relating tolandscape position. Table 1 of availablegroundwater data shows the range ofsalinities within the catchment.

Groundwater salinity within the granodiorite is in the range of 400 to 750 µS/cm. Mid-catchment, the range is 5,000 to 12,000µS/cm and in the lower catchment the rangeis 7,000 to 21,000 µS/cm.

* Negative numbers indicate a falling trend.

2.5 Soil Types

Soil distribution is shown on Figure 7.Infiltration data for the two most common soiltypes is shown in Table 2. Comparison ofthe infiltration rate of the red and yellow

duplex soils and the stony red soils isindicative of recharge potential. In general,the thin stony red gradational soils havemuch greater potential to recharge thegroundwater system (Jenkin and Dyson 1983).


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TABLE 2. Saturated infiltration of Axe Creek Soils (after Duff et al. 1985).

Type of soil developed on Saturated infiltration rateOrdovician sediments

Range Mean (mm/day)(mm/day)

Duplex: red (Dr) or yellow (Dy) – top of B1 horizon 3 – 7 5

Gradational: stony red (Gn) 5 – 200+ 200+

�

Figure 7. General soil distribution across the Axe Creek catchment (Rowan 1990).


2.6 Land use

Land use within the catchment issummarised in Table 3 and illustrated inFigure 8. Approximately 20% of thecatchment is covered by native vegetation,although selective logging (over the last 150years) has altered much of this. Since the1970s there has been a shift in allotment sizefrom broad-scale agriculture to hobby farmscale—the effect of this land use change isyet to be realised. Small channels were dugin the late 1800s—the Coliban System—tosupport a substantial wine industry prior tothe phylloxera epidemic. The Coliban Systemof drains is still utilised although the highwater prices have restricted its use torelatively limited flood irrigation.

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TABLE 3. Land use proportions within the Axe Creek catchment.

Land use Area (ha)

Agricultural land 894.3

Cropping 124.1

Horticulture 0.9

Improved pastures 398.8

Livestock grazing 526.5

Managed reserve protection 205.9

Nature conservation 160.1

Plantation forestry 1.3

Production forestry 260.3

Other non–productive use 83.1


12

0� 5 km�

Axe Creek boundary�Agricultural land�Cropping�Grazing�Managed resource & native veget�ation�Other non-production use�Forestry�

Figure 8. Land use within the Axe Creek catchment.


2.7 Salinity extent

Surface soil salinisation first becameapparent in the mid to late 1940s (Duff1985). Prime grazing land on the main valleyfloors deteriorated rapidly after the 1940s.Native vegetation clearing was initiatedthrough gold mining activities in the 1850sand continued unrestricted through to the1900s when agricultural land uses prevailed.Saline groundwater discharge is confined tovalley floors (Figure 9). On the eastern sideof the Whitelaw Fault salinity is controlled bythe topographic break of slope. On thewestern side of the fault the process is morecomplex, although break of slope processesare involved particularly where the influenceof the fault is dominant.

Salinity occurrence below the Whitelaw Faultis controlled by groundwater flow within thefault zone. Where valleys intersect the fault,groundwater is released. The discharge siteat the lower end of the catchment, nearAxedale, appears to be a consequence ofrestricted surface and sub-surface drainagecaused by the presence of the Mt. SugarloafRange.

Landholders believe the discharge sites havestabilised in extent. The total affected area isapproximately 276 ha. This is largelytopographically controlled so it is unlikely thatdischarge areas will increase because nearlyall the drainage lines down gradient of thefault are already salt affected. Salt loadsexiting the Axe Creek catchment range from5,000 to 15,000 tonnes per year (Dysonpers. comm. 2001), with recent recordsaveraging around 7,000 tonnes annually(Jolly et al. 1997).

13


14

Bendigo�

Surface topography�Mapped saline area� 0� 5 km�

Figure 9. Dryland salinity and surface topography within the Axe Creek catchment.

3. Conceptual model


3.1 Hydrogeology

Groundwater flow is essentially towards thenorth-east, following the topographic gradient.Fractured zones within the Ordovician bedrockfacilitate groundwater movement from theranges to the alluvial terraces and plains. Themost significant fracture zones are along thebedding planes and fold axis. These strikenorth-northwest, parallel to the Whitelaw Fault.A series of secondary fractures (A-C joints)exist perpendicular to the main fracture suiteand these transmit groundwater between theprimary fractures. Groundwater flowprogresses north-eastward down thecatchment as a consequence of theseinterconnected fracture zones. Figure 10illustrates the general groundwater flowpatterns in the vicinity of the Whitelaw Fault.

The Whitelaw Fault interrupts the generaldown-gradient flow of groundwater from theheadwaters of the Axe Creek. Extensivefracturing within the fault zone provides achannel along which groundwater is able tomigrate towards the north-west. Salinegroundwater discharge occurs within smallvalleys draining the fault scarp immediatelydown-slope from the fault. Groundwater hasbeen recorded in the vicinity of the fault todepths as great as 72 m. It is plausible thatgroundwater flows may occur to depths asgreat as 200 m but flows deeper than 100 mare minimal and uncommon.

Hydraulic conductivity of the fractured rockranges from 1-2 m/day in the upper 50 metres(Hodgson and Finlayson 1990). Dyson (pers.comm. 2001) suggests a transmissivity ofapproximately 5 m2/day with values as high as20-30 m2/day possible. Specific yield rangesfrom 0.05-0.03 (Dimos et al. 1994)

3.2 Recharge

Recharge is not evenly distributed throughoutthe catchment, and is controlled by fractureand soil development (Dyson 1983). In theupper catchment, recharge to the Ordovicianmetasediments occurs where soil cover is minimal.

15

Whitelaw Fault

5 km

Groundwater flow

Fractured Rock basement

Groundwater discharge

Direction of fault throw

Figure 10. Schematic 3D diagram of groundwaterflow in the Axe Creek catchment.

On the upper alluvial plains recharge iscontrolled by soil type. As previouslyindicated, infiltration rates vary markedlybetween the duplex soils and the gradationalstony soils. Dyson (1983) estimates upperrecharge rates in the Axe Creek catchment ofthe order of 60–100 mm/year. The highrecharge area applies to approximately 30%of the landscape.


16

4.1 Numerical model

FLOWTUBE (Dawes et al. 1997; Dawes et al.2000, Dawes et al. 2001) is a simplenumerical one-dimensional groundwater flowmodel. It is a mass-balance model that solvesfor a change in hydraulic head induced byrecharge and discharge fluxes, and net lateraltransfers in the direction of flow. The results ofFLOWTUBE are considered to be a hydraulichead transect along a groundwater flow path.

The model considers a one or two-layersystem. In the case of a single layer the aquiferis assumed to be unconfined and havingvariable transmissivity dependent on thesaturated thickness of aquifer. In the case of atwo-layer system, the lower layer is assumedto contain any lateral transmission of waterwhile the upper layer contributes storagecapacity only. In this case the lower layer isusually confined or semi-confined, and howthis is conceptualised controls the simulatedmechanism for groundwater discharge.

4.2 Special considerations

FLOWTUBE is ideally suited to homogenousuniform isotropic media, such as sand andgravel aquifers, and massive clay depositswithout preferred pathways or barriers. TheAxe Creek aquifer comprises an extensivefractured rock structure, which is geologicallycomplex with major faulting and preferred flowdirections. Theoretically this is the least suitableaquifer configuration for FLOWTUBE, and theparameterisation of the aquifer will be a criticalissue for both fitting of current heads andconfidence in simulated future scenarios. Infractured rock environments, it is also difficultto estimate the extent of aquifers. In manycases they are simply assumed to becoincident with topography, however, theinfluence of fractured rock aquifers can extendbeyond the topographic divides of a catchment.

The two main aquifer parameters inFLOWTUBE are hydraulic conductivity andspecific yield, both of which are difficult to

measure or estimate directly in fractured rockenvironments (Freeze and Cherry 1979,Lapsevic et al. 1999, Love and Cook 1999).A further confounding problem in fracturedrock aquifers is the anisotropic nature of flow,i.e. water tends to flow preferentially in thedirection of the fractures, rather than in adirection indicated by hydraulic headgradients. Pump tests in the Axe Creekcatchment (Dyson pers. comm. 2001) haveresulted in strongly elliptical drawdown conesrather than classical circular patterns. Itremains within the parameterisation of theaquifer to select representative volumes largeenough to make Darcian flow estimationvalid. If measured conductivity values are notavailable, the fitted values will berepresentative only at the scale of theFLOWTUBE segments.

The final factor to consider in the numericalimplementation and conceptual model is therole of the massive Whitelaw Fault that cutsacross the centre of the catchment. There isvery compelling evidence that the fault acts asa net conductor of groundwater and that thegroundwater therein originates from within AxeCreek catchment. It is noteworthy that creeksalinity is observed where Axe Creek crossesthe fault line. Water conducted by the faultescapes through fractures at these crossings,therefore affecting local heads and creek flows(Dyson pers. comm. 2001). The distribution ofsaline groundwater discharge sites both alongand coincident with the fault zone is clear.However, the fault scarp also no doubtfunctions as a potential groundwater barrier inplaces. Apart from where Axe Creek cutsthrough, the fault scarp is a high relief landformthat almost certainly restricts northwardgroundwater flow (Dyson pers. comm. 2001).

4.3 Model parameters

The robust modelling of Axe Creek withFLOWTUBE requires that the precedingcaveats be acknowledged in both describingthe aquifer and placing the conclusions in

4. Groundwater modelling using FLOWTUBE


context. To begin this exercise, we start withFreeze and Cherry (1979) who state:

‘As with granular porous media, thecontinuum approach involves thereplacement of the fractured media by a representative continuum in which the spatially defined values of hydraulicconductivity, porosity and compressibilitycan be assigned. This approach is validas long as the fracture spacing issufficiently dense that the fractured rockmedia acts in a hydraulically similarfashion to granular porous media. Theconceptualisation is the same, althoughthe representative elementary volume isconsiderably larger for fractured mediathan granular media. … Snow (1968,1969) has shown that many fractured-flow problems can be solved usingstandard porous-media techniquesutilizing Darcy’s Law and an anisotropicconductivity tensor.’

To best draw out the effects of the fracturedrock aquifer and the Whitelaw Fault in the AxeCreek catchment, the FLOWTUBE segmentswere constructed in the direction of surfacewater fluxes, which are orthogonal to the mainfracture strike direction and that of the fault.The role of the fractures is to maintainrelatively uniform and stable water levelsacross a FLOWTUBE segment. This justifiesthe implicit assumption within FLOWTUBE,and groundwater flow models in general, thata single water level value is representative.

To satisfy the constraint that ‘in fracturedmedia the representative volume needs to bemuch larger [than porous media],’ the 12FLOWTUBE segments are two kilometreslong, normal to the direction of flow, andcover the width of the catchment, whichranges from four to 20 km. On this last point,we have assumed, for convenience, that thegroundwater and topographic catchmentboundaries are the same. While this is almostcertainly not the case, there is insufficientdata to otherwise delineate the boundaries ofthe larger system that Axe Creek lies within.

Conductivity and porosity estimates wereobtained from expert opinion and review(Dyson pers. comm., Petheram pers. comm.)effective conductivity values are likely to beless than 1 m/day, and that porosity is lessthan five per cent. Observation bores have

been drilled that intercept groundwaterbetween 50 and 100 m below the surface in the vicinity of the Whitelaw Fault, so amaximum thickness of 100 m for the aquiferupslope of the fault was imposed.Downslope, the thickness was decreased to50 m, comparable to values estimated andused in local fractured rock systems obtainedfrom drilling below the fault (Dyson pers.comm.). In recognition that the fractured rockaquifer in a very steep section at the westernedge of the catchment is unconfined orweakly confined, the aquifer is assumed tobe double the usual thickness there.

The fracture density was assumed to increasedownslope toward the fault, with more smallfractures present to connect the dominantconduits. Transmissivity is greatest in the faultzone through much more extensive fracturingboth along the main fault and oblique to it(Dyson pers. comm.). To accommodate thisobservation, the hydraulic conductivity wasincreased linearly downslope from a minimumvalue of 0.1 m/d to 1.0 m/d and held constantthereafter. Using a dye technique, Hodgsonand Finlayson (1990) estimated hydraulicconductivity within the fractures to be between0.7 and 6.5 m/d. The porosity of the aquiferwas argued to behave similarly to conductivity,increasing fracture density leading to increasedavailable pore space. The porosity thereforefollows the same pattern as conductivity, using a range of one to ten per cent. A full list of theparameters is in Appendix 1.

4.4 Historical Simulation

Dyson (1983) suggests that current averageannual recharge to Axe Creek catchment isbetween ten and 40 mm/year, but is morelikely to be near the lower end of this range,around 15 to 20 mm. Up to 83% of this totalrecharge was assumed to be derivedupslope of the fault, where soils are thin andskeletal and recharge through surface crackswill be most rapid (qv. §1.5). Using thisinformation, recharge in FLOWTUBE wasdistributed across the area upslope of theWhitelaw Fault increasing in a geometricpattern, doubling each segment furtherupslope. For the pre-cleared case, rechargevalues of 20, 10, 5, 2 and 1 mm/year wereapplied down the catchment with zerorecharge downslope from the fault, resultingin a catchment average rate of 3 mm/year.

17

For current recharge estimates, all valueswere multiplied by a factor of five, increasingthe catchment average rate to 15 mm/year.This average recharge rate accommodateshigh rates 50-100 mm/yr in the uplands.

In the following simulations an evaporationextinction depth of 2 m was assumed with amaximum extraction rate of 110 mm/year, andno special consideration of the role or effect ofthe Whitelaw Fault was incorporated.

Figure 11 shows the result of using 3 mm/yearrecharge distribution to attain a pre-clearingequilibrium condition (indicated by the Year1900 line), and then simulating for 100 yearsusing the 15 mm/year distribution. Thesimulated heads show distinct rises in theupslope area of Axe Creek with slowtransfers laterally to the fault zone and below.After 50 years the heads have come close to the surface everywhere, over most of thecatchment, coincident with the empiricalevidence that grazing land deteriorated in the1940s (qv. §1.7), resulting in various rates of discharge and stabilising heads for theremainder of the simulation. Soil salinity hasbeen mapped along creeks and low-lying

areas of topography from high up near thewestern divide down to the catchment outlet,except for a 6 km reach of stream betweenStrathfieldsaye and Axedale, approximatelybetween 14 and 20 km on Figure 11.

To better fit this behaviour, the conductivitynear the catchment outlet was doubled. Thenew head map is shown in Figure 12, butsince flow is now less restricted, the headtransect for 1940 rather than 1950 is shown.The root mean square difference betweenheads in 1940 and 2000 is 1.38 m, and from1950 to 2000 is 0.07 m. The position of theWhitelaw Fault is indicated on the graphs,and is very prominent in Figure 13 whichshows the flux rates along the catchmenttransect. This area is the first to deviatesubstantially from a purely rechargingsystem, and remains a spike on thesimulated graph to the present day. There isdischarge through the entire central sectionnow covering all areas mapped with salinesoils except close to the confluence of AxeCreek and the Campaspe River. As noted,salinity in this particular area appears to bederived locally by the damming effect of theMt. Sugarloaf Range (qv. §1.7).


18

Figure 11. Simulated rise in water levels in Axe Creek catchment over the course of 100 years. The root meansquare difference of heads from 1950 to 2000 is less than 12 cm.

Figure 13. Simulated changes in surface flux in Axe Creek catchment over 100 years. Pre-clearing recharge valueindicated by the black line amounts to 3 mm/year, while the ‘current’ recharge rate expressed by the red line is 15 mm/year.


19

�

Figure 12. Simulated rise in water levels in Axe Creek catchment over the course of 100 years. The root meansquare difference from 1940 to 2000 is 1.38 m.


20

Another way to interpret groundwaterdischarge is to compare fluxes to thecapacity of the aquifer to transmit them. InFLOWTUBE, Darcy’s Law is used to estimatelateral flux rates. This empirical equationstates that flux is the product of aquifer widthand thickness, slope of the local water table,and hydraulic conductivity of the aquifer. Wecan use the down-catchment land surfacegradient as the maximum possible watertable gradient to estimate the aquifercapacity along the FLOWTUBE transect.

Figure 14 shows the aquifer capacity incatchment average mm/year with the landsurface, along with the assumed pre andpost-clearing recharge rates. It can be seenfrom this graph that the pre-clearing rate isonly barely accommodated by the inferredaquifer parameters, so FLOWTUBE suggeststhat some shallow water levels may haveexisted before recharge was ever increased.With the low slope of the aquifer capacitycurve from 10 to 20 km downslope, a smallincrease in recharge from 3 to 5 mm, forexample, could cause shallow water levels todevelop across this entire area. Conversely,due to the rapid change in capacity around 4 km downslope fluxes between 10 and 20 mm/year would make very little differenceto the area of land affected, but the differencewould be discharged to the surface.

4.5 Future Scenarios

In fractured rock environments engineeringsolutions to control dryland salinity, primarilyby pumping, are often difficult due to theuncertainty in tapping and pumping fromfractures that will effect the areas of interest(Love and Cook 1999, Hekmeijer et al.2001). Due to this constraint, the classicparadigm of recharge reduction at the near-surface through vegetation manipulationdominates (Reid et al. 1997, Hatton andNulsen 1999). Given that there is (i)substantial uncertainty in fitting the waterlevels within Axe Creek, (ii) only expertopinion supporting the physical parametersof the aquifer, and (iii) considerable variabilityin level and trend in groundwaterhydrographs in Axe Creek, a simulationmodel like FLOWTUBE is most appropriatelyused to look at the medium and long termtrends in heads.

FLOWTUBE will be used to examine theresult of reducing surface recharge by 50%,and by 80% to approach pre-clearing levels.Figures 15 and 16 show the simulatedeffects over 100 years on water levels andsurface discharge by reducing present-dayrecharge by 50%. There are apparentlymodest gains in terms of groundwater levelsin the steepest parts of the catchment,

Figure 14. Aquifer capacity with land slope as driving gradient, compared with assumed pre and post-clearingrecharge levels.


although much of the drop occurs within the first 20 to 50 years. The state in 2100 is readily appreciated by inspection of Figure 14, where an annual recharge rate of 7.5 mm plots only 4 km further downslopethan the current recharge rate.

The surface discharge graph in Figure 16indicates that the simulated recharge areaprogresses downslope closer to the WhitelawFault, but that all parts in the much flatter

eastern area remain unchanged. All thesimulated change in discharge occurs at thefault itself, which may indicate a reduction indischarge to the streams that cut across thefault. The implication of this rechargereduction simulation is that only the streamsin the eastern uplands, and associated areasof dryland salinity, would benefit directly froma reduction in recharge. Further, thereappears to be no benefit for any areadownslope of the Whitelaw Fault.

21

Figure 16. Simulated reduction in surface discharge over the next 100 years assuming a 50% reduction in surfacerecharge rates over the entire catchment.

Figure 15. Simulated reduction in water levels over the next 100 years assuming a 50% reduction in surfacerecharge rates over the entire catchment.


22

Figure 17. Simulated reduction in surface discharge over the next 100 years assuming a 50% reduction in surfacerecharge rates over the entire catchment.

The other simulation for future scenariosinvolves a return to assumed pre-clearingconditions with a five-fold decrease inrecharge relative to the current day. Figure 17shows the simulated reduction in water levelsalong the catchment transect over 1,000years. The first century again has the greatestgains in terms of water levels, but a reductionin simulated water levels around the Whitelaw

Fault itself takes considerably longer.Progression of heads for the next millennium isslow after 2100, with the simulated dischargeat the Whitelaw Fault not ceasing for another400 years after this. At the year 3000,discharge is confined to the pre-clearing areasused as initial conditions for the simulations,and the discharge rate is less than five per centabove pre-clearing rates.


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5. Discussion and Conclusions

5.1 Summary

The Axe Creek catchment in central Victoriais complex in terms of geology andhydrogeology. The aquifer of interest is anextensive highly fractured aquifer with thedirection of strike, and therefore the preferredflow direction, perpendicular to the surfacetopographic gradient and main drainagetrends. While the area of salinised dryland isnot large, there are substantial areas withshallow water levels, and stream salinity is acompounding problem for the catchment.The impact of downstream salt loads in theCampaspe River is the major issue.

Simulations of historical conditions suggestthat the Axe Creek aquifer could have filledwithin the 40 to 50 year timeframe,compatible with local anecdotal evidence.Simulations of nominal future rechargescenarios suggest that it would take muchlonger for the system to return to pre-clearinglevels than it has taken to fill up, possibly bya factor of up to ten. No consideration wasgiven to possible engineering measures inthe main fractured rock aquifer. Thesimulations presented here are the firstapplication of a transient groundwater modelto the Axe Creek catchment. Even with theknown difficulties simulating flow processesin a fractured rock environment, the simpleFLOWTUBE model appears to perform well,and presents plausible results. Thesignificance of the Whitelaw Fault is evidentfrom the simulated head distribution andsurface discharge figures, without any specialmodelling of the feature per se.

5.2 Future Directions

Perceived future directions derive from thenature of the aquifer and the limitations of themodelling approach. Obviously, ourunderstanding of the hydrogeology of thefractured rock system in Axe Creekcatchment is not comprehensive. As with allstudies aimed at modelling scenarios, moredata is usually desirable to fully describe theaquifer of interest, the flow processes, spatialand temporal distribution of sources and

sinks of water, and the extent of each layer of material. A further problem lies with theprocesses that we have used to model theAxe Creek catchment rather than with thehydrogeology. There is a great deal ofspecific information—some of which comesfrom Axe Creek, and some from other moreintensely studied fractured rock terrain—thathas not been taken into account in the AxeCreek study. Furthermore, from agroundwater perspective, the Axe Creekhydrogeology is not excessively complex.The movement of groundwater throughoutthe catchment can be readily constrainedfrom the distribution of groundwater heads,the distribution of current discharge sites, a sense of the distribution of the fracturezones and the yields from drilling ofobservation bores, along with informationfrom the published literature. Moreover,drilling additional bores or carrying outadditional hydrogeological investigations isprobably not going to add to the story inhand. The difficulty in modelling lies in thefact that we are attempting to apply a‘numerical’ model to a system that cannot bedefined in strict numerical terms because ofthe inherent variability of the inhomogeneousand isotropic conditions.

Future model applications to Axe Creek willneed to examine more closely the role of theWhitelaw Fault. Utilisation of measuredparameters for Palaeozoic rocks fromelsewhere in the Lachlan Fold Belt may alsobe appropriate. Modifications that would berequired to the FLOWTUBE model, forexample, include: (i) bifurcating flowlines, (ii) head based lateral transfers betweenadjacent flow tubes, and (iii) a treatment oflinear pressurised pipes as an analogy formajor faults. Some of these appear to berelatively simple but as the complicationincreased, there would be a shift away tocomplex models that are already in use, such as MODFLOW, rather than continualmodification of existing code. The limitationswith treating a fractured rock environmentwith continuous porous media techniques willremain until better models of large fracturedsystems are developed.

5.3 Conclusions

The cautions and caveats in §4.3 do notallow strong conclusions to be drawn on theapplications of FLOWTUBE to the Axe Creekcatchment. The model appears to deliver aplausible result with minimal parameter fitting,although this might also be due to the natureof the system and strong break-of-slopebehaviour. If the Whitelaw Fault and thetopographic patterns were not so intimatelylinked it may have been possible to estimatethe contributions of both.

The conclusion from the final scenario that itwould require pre-clearing recharge rates andfive centuries to minimise or eliminate theeffect of the fault on streams that cut it mustbe taken in context. The caveats in §4.3mean that while the apparent flow within theAxe Creek system may have been controlled,recharge from an adjacent catchment orregion may be flowing in and eliminating anygains, or the fault may transport water out ofthe Axe Creek catchment and significantlyspeed up the result.

The inherent complexities within fracturedrock environments make ready extension ofthis work difficult. These factors includeestimating both specific and bulk hydraulicproperties of the media, the spatial andtemporal distribution of both recharge anddischarge fluxes, and the physicalboundaries of the aquifer. However, giventhat up to 40% of the Australian continent isunderlain by fractured rock aquifers (Loveand Cook 1999) and much of the expressionof dryland salinity is within these regions, it remains an important system to understandand remedy.


24

References

Baker, P, Dawes, W, Bond, W, Stauffacher, M, Gilfedder, M, Probert, M, Huth, N, Gaydon, D, Keating, B, Moore, A,Simpson, R, Salmon, L, Stefanski, A 2001, Assessment of Salinity Management Options for BillabongCreek Catchment, NSW: Groundwater and Crop Water Balance Modelling. CSIRO Land and Water,Canberra.

Dawes, WR, Stauffacher, M & Walker, GR, 2000, Calibration and modelling of groundwater processes in theLiverpool Plains. Technical Report 5/00, CSIRO Land and Water, Canberra.

Dawes, WR, Walker, GR & Stauffacher, M, 1997. Model building: Process and practicality. In Proceedings ofMODSIM97, A McDonald & M McAleer (eds.), Modelling & Simulation Society of Australia, Canberra,pp.317-322.

Dawes, WR, Walker, GR & Stauffacher, M, 2001, Practical modelling for management in data-limited catchments.Mathematical and Computer Modelling, 33, 625-633.

Dimos, A, Chaplin, H, Potts, I, Reid, M & Barnewall, K, 1994, Bendigo Hydrogeological Map (1:250 000 scale)Murray Basin Hydrogeological Map Series. Australian Geological Survey Organisation, Canberra.

Duff, JS, Jenkin, JJ & David, GA 1985, The Axe Creek Salinity Study Part A: Catchment Characterisation for SalinityControl, Axe Creek. Victoria Soil Conservation Authority, Bendigo.

Dyson, PR, 1983, Dryland salting and groundwater discharge in the Victorian uplands. Proceedings of the RoyalSociety of Victoria, 95, 113-116.

Freeze, Ram & Cherry, JA 1979, Groundwater. Prentice-Hall, Englewood Cliffs.

Gray, DR 1988, Structure and tectonics. In Geology of Victoria, JG Douglas & JA Ferguson (eds.), GeologicalSociety of Australia—Victorian Division, Melbourne, pp.1-29.

Hatton, TJ & Nulsen, RA 1999, Towards achieving functional mimicry with respect to water cycling in southernAustralian agriculture. Agroforestry Systems, 45 (3), 203-214.

Hekmeijer, P, Dawes, W, Bond, W, Gilfedder, M, Stauffacher, M, Probert, M, Huth, N, Gaydon, D, Keating, B, Moore,A, Simpson, R, Salmon, L & Stefanski, A 2001, Assessment of Salinity Management Options forKamarooka, Victoria: Groundwater and Crop Water Balance Modelling. National Land and Water ResourcesAudit, Canberra.

Hodgson, L & Finlayson, B 1990, Single well dilution: its use in groundwater investigations for salinity management.Australian Journal of Soil and Water Conservation, 3, 37-43.

Jenkin & Dyson 1983, Hydrological Properties of Soils Relevant to Dryland Salinity in Central Victoria: Groundwaterand soil salinisation near Bendigo, Victoria. In Collected Case Studies in Engineering Geology, Hydrogeologyand Environmental Geology, MJ Knight and RB Smith (eds.), Special Publication 11, Geological Society ofAustralia, Sydney, pp.229-257.

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King, RL & Wilkinson, HE 1975, Bendigo 1:250,000 Geological Map 1st Edition. Geological Survey of Victoria,Melbourne.

Lapsevic, PA, Novakowski, KS & Sudicky, EA 1999, Groundwater flow and solute transport in fractured media. InThe Handbook of Groundwater Engineering, JW Delleur, (ed.), CRC Press, New York.

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Reid, M., Clifton, C & Heislers, D 1997, Dryland salinity management in the Victorian uplands. In Proceedings ofMDBC Groundwater Workshop 97, Toowoomba, Murray-Darling Basin Commission, Canberra, pp.66-71.

Rowan, J 1990, Land Systems of Victoria. Department of Conservation and Natural Resources, Victoria, Melbourne.

Short, R, Salama, R, Pollock, D, Hatton, T, Bond, W, Paydar, Z, Cresswell, H, Gilfedder, M, Moore, A, Simpson, R,Salmon, L, Stefanski, A, Probert, M, Huth, N, Gaydon, D, Keating, B, Coram, J & Please P 2001,Assessment of Salinity Management Options for Lake Warden Catchments, Esperance, WA: Groundwaterand Crop Water Balance Modelling, Technical Report 20/00, CSIRO Land and Water, Canberra.

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VandenBerg, AHM & Wilkinson, HE 1982, Victoria. In Late Proterozoic to Devonian sequences of the south easternAustralia, Antarctica and New Zealand and their correlation. Special Publication 9, Geological Society ofAustralia, Sydney, 36-47.

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Appendix 1


Aquifer parameters

This appendix shows the modelled aquifer parameters (as a FLOWTUBE input file), for thisstudy.

# axe creek catchment, fractured rock aquifer, 165 km^2

# fractures strike approx sse-nnw, segments aligned with

# whitelaw fault

#

# chead(m) cdist(m)

130 1000 -1 -1

#

# roff->aq disch->land max disch(m/yr)

1 0 0.0001 -1

#

# extinc depth disch rate (m/d)

2 0.0003

#

# gw surf wid thk bas K len por idc

269.46 500 18000 250 250 0.1 2000 0.01 2

247.35 310 19800 100 210 0.2 2000 0.02 3

229.36 270 17500 100 170 0.3 2000 0.03 4

217.11 240 16900 100 140 0.4 2000 0.04 5

208.92 220 18300 100 120 0.5 2000 0.05 6

202.20 210 17700 90 120 0.6 2000 0.06 7

195.00 200 14200 80 120 0.7 2000 0.07 8

185.00 190 12600 70 120 0.8 2000 0.08 9

175.00 180 10400 60 120 0.9 2000 0.09 10

165.00 170 10400 50 120 1.0 2000 0.10 11

155.00 160 8600 50 110 1.0 2000 0.10 12

145.00 150 8100 50 100 1.0 2000 0.10 13

135.00 140 4200 50 90 1.0 2000 0.10 -1

27


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Integrated catchment management in the Murray-Darling BasinA process through which people can develop a vision, agree on shared values and behaviours, make informeddecisions and act together to manage the natural resources of their catchment: their decisions on the use of land,water and other environmental resources are made by considering the effect of that use on all those resources and onall people within the catchment.

Our valuesWe agree to work together, and ensure that our behaviour reflects that following values.

Courage

• We will take a visionary approach, provide leadershipand be prepared to make difficult decisions.

Inclusiveness

• We will build relationships based on trust andsharing, considering the needs of futuregenerations, and working together in a truepartnership.

• We will engage all partners, including Indigenouscommunities, and ensure that partners have thecapacity to be fully engaged.

Commitment

• We will act with passion and decisiveness, takingthe long-term view and aiming for stability indecision-making.

• We will take a Basin perspective and a non-partisan approach to Basin management.

Respect and honesty

• We will respect different views, respect each otherand acknowledge the reality of each other’s situation.

• We will act with integrity, openness and honesty, be fairand credible and share knowledge and information.

• We will use resources equitably and respect theenvironment.

Flexibility

• We will accept reform where it is needed, be willingto change, and continuously improve our actionsthrough a learning approach.

Practicability

• We will choose practicable, long-term outcomesand select viable solutions to achieve theseoutcomes.

Mutual obligation

• We will share responsibility and accountability, andact responsibly, with fairness and justice.

• We will support each other through the necessarychange.

Our principlesWe agree, in a spirit of partnership, to use the followingprinciples to guide our actions.

Integration

• We will manage catchments holistically; that is,decisions on the use of land, water and otherenvironmental resources are made by consideringthe effect of that use on all those resources and onall people within the catchment.

Accountability

• We will assign responsibilities and accountabilities.

• We will manage resources wisely, beingaccountable and reporting to our partners.

Transparency

• We will clarify the outcomes sought.

• We will be open about how to achieve outcomesand what is expected from each partner.

Effectiveness

• We will act to achieve agreed outcomes.

• We will learn from our successes and failures andcontinuously improve our actions.

Efficiency

• We will maximise the benefits and minimise thecost of actions.

Full accounting

• We will take account of the full range of costs andbenefits, including economic, environmental, socialand off-site costs and benefits.

Informed decision-making

• We will make decisions at the most appropriate scale.

• We will make decisions on the best availableinformation, and continuously improve knowledge.

• We will support the involvement of Indigenouspeople in decision-making, understanding the valueof this involvement and respecting the livingknowledge of Indigenous people.

Learning approach

• We will learn from our failures and successes.

• We will learn from each other.

Documents

Peter Hekmeijer, Warrick Dawes - CSIRO · Peter Hekmeijer, Warrick Dawes. Assessment of salinity management options for Axe Creek, Victoria: ... AXE CREEK CASE STUDY, FEBRUARY 2002