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Looking after all our water needs

Water resource allocationand planning report seriesReport no 48September 2013

Ord

surface water allocation plan


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Department of Water168 St Georges TerracePerth Western Australia 6000Telephone +61 8 6364 7600Facsimile +61 8 6364 7601National Relay Service 13 36 77

www.water.wa.gov.au

© Government of Western Australia

September 2013

This work is copyright. You may download, display, print and reproduce this materialin unaltered form only (retaining this notice) for your personal, non-commercialuse or use within your organisation. Apart from any use as permitted under theCopyright Act 1968 , all other rights are reserved. Requests and inquiries concerningreproduction and rights should be addressed to the Department of Water.

ISSN 1327-8428 (print)ISSN 1834-2620 (online)

ISBN 978-1-922124-79-1 (print)ISBN 978-1-922124-80-7 (online)

Acknowledgements

This plan was developed over many years and involved many people. In particular,the Department of Water acknowledges Ian Loh for his hard work, dedication andexpertise.

The following people also contributed to this plan:

Project team – Mike Braimbridge, Guy Chandler, Robert Cossart, Emily Harrington,Robyn Loomes, Simone McCallum, Clare Meredith, Kathryn Smith, JacintaThompson, Karis Tingey and Jessica Seares.

Project board – John Connolly, Ben Drew, Patrick Seares, Dave Munday, Chris Gunbyand Susan Worley.

For more information about this report, contact:

Kununurra Regional OfficeKimberley Region, Department of Water

27 Victoria HighwayKununurra Western Australia 6743Telephone 08 9166 4116

Disclaimer

This document has been published by the Department of Water. Any representation,statement, opinion or advice expressed or implied in this publication is made ingood faith and on the basis that the Department of Water and its employees arenot liable for any damage or loss whatsoever which may occur as a result of actiontaken or not taken, as the case may be in respect of any representation, statement,opinion or advice referred to herein. Professional advice should be obtained before

applying the information contained in this document to particular circumstances.

This publication is available at our website or for those with

special needs it can be made available in alternative formats such as audio, large

print, or Braille.


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Ord


Department of Water

Water resource allocation

and planning report seriesReport no 48

September 2013


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Message from the Minister

Ord surface water allocation plan

The Ord River is one of the most significant waterways inWestern Australia. It provides for an iconic agricultural

project, supports local tourism and sustains the unique

Kimberley environment.

Under the State’s Royalties for Regions program we are

seeing the largest development of irrigated land in the

Ord River area since the 1960s. The Ord Irrigation

Expansion Project is focused on the development of the Goomig farmlands,

some 7400 hectares to the north of Kununurra.

This is the first stage in a longer term plan to maximise the irrigation potential of the

region. Further stages of development include 5000 hectares on the Knox Plain and

1000 hectares of irrigable land in the Ord West Bank.

This Ord surface water allocation plan supports, first and foremost, water for irrigation.

It outlines how the Department of Water will provide reliable water for irrigation as

development continues, while ensuring there is enough water in the lower Ord River

to sustain the natural environment.

The plan also provides a blueprint for new water release rules for the Ord River dam

power station and defines how licences will be adjusted over time.

The plan builds on many decades of water management by the Department of

Water, the Water Corporation and Ord irrigators and sets a new benchmark for

water allocation and licensing in the area.

As a strategic document, this plan will ensure the relationship between all water

users – agriculture, power generation and the environment – is managed equitably

and for the wellbeing of all Western Australians.

Hon Terry Redman, MLA

Minister for Water

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Contents

Message from the Minister iii

Summary ix

1 Plan context and scope 1

1.1 Purpose of the plan 1

1.2 Plan area 2

1.3 Water resources covered 2

1.4 How we developed the plan 5

1.5 Main stakeholder interests 5

1.6 Plan timeframe 7

2 What the plan will achieve 8

2.1 Outcomes 8

2.2 Resource objectives 9

2.3 Strategies 9

2.4 Measuring the success of the plan 9

3 Current and projected water demands 10

3.1 How water is distributed in the Ord 10

3.2 Irrigation demands 13

3.3 Water demands for power 17

3.4 Environmental, social and cultural water demands 20

3.5 Balancing the demands for water 22

4 Water allocation 24

4.1 Water allocation limits 24

4.2 Allocation approach 25

4.3 Environmental water provision 28

5 Water licensing 32

5.1 Legislative requirements 33

5.2 Licensing large-scale irrigation 34

5.3 Licence conditions for hydroelectricity 36

5.4 Licence conditions for environmental water 42

5.5 Licensing small-scale irrigation and other self-supply users 45

5.6 Integrating water management 45

5.7 Licensing policies 47

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Ordsurface water allocation plan

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Contents

6 Monitoring for the Ord River 52

6.1 Evaluating resource objectives 52

6.2 Trigger and response mechanisms 53

6.3 Environmental monitoring 54

6.4 Monitoring for future planning needs 57

7 Implementing and evaluating the plan 58

7.1 Implementing the plan 58

7.2 Evaluating the plan 59

Appendices 61

Appendix A — Restrictions and water release rules 62

Appendix B — Annual Ord River stakeholder meeting 67

Appendix C — Operations software 68

Appendix D — Future 10 MW power station on the Kununurra Diversion Dam 69

Appendix E — Trigger levels for ecological monitoring parameters 71

Appendix F — Monitoring sites on rivers in the Ord River plan area 73

Appendix G — Map information and disclaimer 75

Shortened forms 76

Glossary 77

References 79


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Contents

Figures

Figure 1 Plan area, proclaimed areas and irrigation areas (stage areas) 3

Figure 2 Subarea boundaries 4

Figure 3 How water is distributed from the Ord River and Kununurra Diversion dams 11

Figure 4 Current (Stage 1) and proposed irrigation development

areas in the plan area 14

Figure 5 Recorded and projected demands on the East Kimberley electricity grid 19

Figure 6 An example of the expected flow regime (environmental water provision)

for the lower Ord from Lake Kununurra to Tarrara Bar 29

Figure 7 Irrigation restriction trigger levels for current and full allocation 36

Figure 8 Current hydropower restrictions for 350 GL/yr of irrigation (as at July 2013) 37

Figure 9 Enhanced rules approach for hydropower restrictions for 350 GL/yr

of irrigation 40

Figure 10 Comparison of electricity generated under current and enhanced

rules with increasing water supply 41

Figure 11 Environmental water restrictions for current and full allocation 44

Figure 12 Streamflow monitoring sites and ecological monitoring reaches

in the lower Ord River 56

Tables

Table 1 Stakeholders of the Ord plan 6

Table 2 Water demand for irrigation developments in the Main Ord subarea 17

Table 3 Allocation limits for the Ord surface water allocation plan area 25

Table 4 Baseflow requirements to be measured at Tarrara Bar gauging station 30

Table 5 Wet season peak flow requirements to be measured atTarrara Bar gauging station 31

Table 6 Infrequent wet season flood events to be measured at

Tarrara Bar gauging station 31

Table 7 Limits on Pacific Hydro’s electricity generation 38

Table 8 Local licensing policy specific to the Ord plan area 48

Table 9 Monitoring in the plan area 53

Table 10 Trigger and responses in the plan area 53

Table 11 Management responses required by Department of Water,

Water Corporation and Ord Irrigation Cooperative 55

Table 12 Actions to implement the Ord surface water allocation plan 58

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Contents

Figures in Appendices

Figure A1 Irrigation water supply and reliability as currently licensed –

current irrigation (350 GL/yr), high power demand

and current release rules 63

Figure A2 Irrigation water supply and reliability with full entitlements

and the enhanced rules – irrigation licensed to limits (750 GL/yr),

high power demand 64

Figure F1 Rainfall and river monitoring sites in the Ord River plan area 74

Tables in Appendices

Table A1 Restriction policies – as currently licensed (as at July 2013) 65

Table A2 Restriction policies – Current irrigation, high power demand,

enhanced release rules scenario 66

Table D1 Electricity generated with and without a 10 MW hydropower station

at the Kununurra Diversion Dam – (a) 350 GL/yr of irrigation with

current release rules, and (b) 750 GL/yr of irrigation with the

enhanced rules approach. 70

Table E1 Trigger values for macroinvertebrates, fish and vegetation 71

Table E2 Nutrient and physico-chemical trigger values 72

Table F1 River level monitoring sites 73

Table F2 Rainfall monitoring sites 73


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SummaryOrd surface water allocation plan

Purpose of the plan

The Department of Water is responsiblefor managing and licensing the state’swater resources under the Rights in Waterand Irrigation Act 1914 (WA). This waterallocation plan sets out how we willallocate and license surface water fromexisting infrastructure in the Ord River areato manage the competing demands ofirrigation, hydroelectricity generation andthe lower Ord environment, while also

recognising the river’s social and culturalvalues. The plan will guide water licensingin the transition to full allocation from theexisting infrastructure.

Our approach for managing surface waterallocation and licensing in the Ord:

• secures 865 GL/yr from the existinginfrastructure at a very high reliabilityfor current and future irrigationdemand

• defines water release rules forthe Ord River Dam power stationto meet downstream irrigationand environmental commitmentswhile maximising hydroelectricitygeneration

• shows when water restrictions forhydropower, irrigation and theenvironment will apply to managecompetition for water in dry periods

• establishes how we will licensewater use and adjust water licencesas irrigation and hydroelectricitydemands change over time.

Water availability in the Ord surface water area

The department will grant water entitlementsup to 905 GL/yr (see table) from the existinginfrastructure in the Ord surface water area.Of these, 865 GL/yr will be from the Main Ordand Carlton-Mantinea subareas downstreamof Lake Argyle. As these entitlements canonly be granted because of Lake Argyle’sstorage, they are designed to be fullysupplied in 95 per cent of years.

The 750 GL/yr at a very high reliabilityfrom the Main Ord subarea is particularlyimportant to agricultural development. Asof January 2013, 335 GL/yr of this has beenlicensed to the Ord Irrigation Cooperative(OIC) to supply its members in the Ord Stage1 area. Most of the extra water for irrigationexpansion will be diverted from the Ord Riverwithin the Main Ord subarea. This includeswater to supply the Goomig, Knox Plain andWest Bank areas in Western Australia, and

the Keep River Plain in the Northern Territory.Small amounts of water will also be requiredto supply minor infilling of the Stage 1 areaand new self-supply pumpers who divertfrom the river.

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x

Summary

Subareas Allocation limit

(GL of water entitlements

per year)

Annual reliability (per year)

Water available forgeneral licensing

Upper Ord 15 Variable Yes

Main Ord 750 95% Yes

Tarrara-Carlton 0 – No

Carlton-Mantinea 115 95% Yes

Dunham River 25 Variable Yes

Total 905

Most of the 115 GL/yr of waterentitlements available from the Carlton-Mantinea subarea (starting 56 kmdownstream of the Kununurra DiversionDam) is expected to be granted for newirrigated agriculture proposals on eitherside of the lower Ord River, near HouseRoof Hill.

The allocation limits for the Main Ordand Carlton-Mantinea subareas wereset so that sufficient water would beleft in the lower Ord River to maintain ahealthy environment. In most situationsthe environmental flow regime will alsosupport community values.

In most years, the requiredenvironmental flows will be met byreleases for hydropower and inflow

from the catchment downstream of theKununurra Diversion Dam (particularlyfrom the Dunham River). Releases forenvironmental flows will be restricted tothe minimum required flows during dryyears to balance competing demandsfor water. As more water entitlementsare granted, the dry season flows willbe lower than they are now.

The department is assessing andadvising government on supply options

should additional water be needed forirrigation expansion.

If major infrastructure or supplysystem changes are agreed, thenwe will update water managementarrangements accordingly.

Licensing approach for theOrd area

This plan defines the current rules andrestriction policies that govern therelease of water at the Ord River andKununurra Diversion dams and theapproach we will use to update theseas irrigation and electricity demandschange. It also defines trigger levels inLake Argyle for hydropower, irrigationand environmental water restrictions indry years.

Power station water release rules

Water release rules apply to waterreleased through the hydropower stationat the Ord River Dam. The current setof rules is a condition of the waterlicence for operation of the Ord Riverand Kununurra Diversion dams. A setof enhanced rules to optimise watersharing benefits will replace currentwater release rules when the presentpower supply agreement is modified.The water release rules are linked withLake Argyle’s water level and powergeneration is restricted when storagelevels in the lake are below average.


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Summary


The enhanced water release rulesallow for:

• 750 GL/yr of water from the MainOrd subarea to be available in95 per cent of years

• an average of between 238.1 and248.6 GWh/yr to be generated

• a minimum of 89.4 GWh/yr to begenerated

• environmental water to be at orabove requirements 93 per centof the time.

Managing in dry periods

Based on the long-term data record, weexpect irrigation supply to be restrictedon average in five out of every100 years, when water levels in LakeArgyle are low. To manage waterscarcity in these dry years, this plan setsthe trigger levels in Lake Argyle at whichrestrictions will apply to hydroelectricityproduction, irrigation and other licensedwater use, as well as releases for theenvironment.

To make it clear when restrictions willapply, trigger levels have been set forboth the current and enhanced rules.

Adjusting licences over time

We will adjust water entitlementsto match water use (as far as ispractical) to maximise the amountof water available for irrigation andhydroelectricity production at eachstage of irrigation development. Toachieve this, we will review and adjustexisting licences (Water Corporation andOIC) when applications for more than

30 GL/yr of new entitlements are madeand/or as electricity demands change.

This will ensure that future irrigationexpansions can access secure, reliablewater while maximising hydroelectricityproduction while irrigation expands.

How the department developedthis plan

We developed the plan using new

ecological studies, hydrologicalmodelling and water demandprojections completed in the Ord areasince the 2006 plan. This work:

• updated our knowledge of theOrd River catchment’s hydrology

• defined water availability fromLake Argyle under a range offuture demand scenarios

• refined the environmental waterneeds of the lower Ord River (theenvironmental water provision).

We have used this information to confirmthe water resource objectives andallocation limits of the 2006 plan andset new water release rules for this plan.We based this work assuming a futureclimate in the Kimberley similar to thatexperienced in the region from 1906–07to 2003–04, given global circulationmodels do not indicate a clear wettingor drying trend for the Kimberley area.

We involved stakeholders throughoutthe plan’s development, including themain licensees (Water Corporationand OIC), as well as other water users,state and federal agencies and localgovernment. In mid 2011 we met withall interested parties to discuss aspectsof the plan relevant to them and in2012 we released the Ord surface water

allocation plan: for public comment(DoW 2012a). We used the publicsubmissions to clarify, improve andfinalise the plan and responded topublic submissions in a statement ofresponse (DoW 2013).

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Chapter OnePlan context and scope


The Ord River expansion project is

now underway, with state governmentfunding committed under the Royaltiesfor Regions program. In 2014, the firstwater is expected to be deliveredto the first 7340 ha of new farmlandin the Goomig area, with demandgrowing rapidly over the next fiveyears. Other stages of agriculturalexpansion are expected to occur ina similar timeframe, although theseare still subject to regulatory approvalprocesses.

1.1 Purpose of the plan

Working alongside our stakeholders,the Department of Water developed thisplan in response to:

• state and federal governmentinvestment in the Ord Riverexpansion project and the needto provide absolute clarity onthe water available for irrigationdevelopment from existinginfrastructure

• the need to balance newirrigation demand withthe growing demand forhydroelectricity and the needs ofthe downstream environment

• recommendations from theEnvironmental Protection

Authority (EPA) to maintain thepost-dam environment of theRamsar-listed Ord River floodplainand wetlands

• new hydrological and ecological

work we have completed sincethe 2006 plan.

To address these circumstances andsupport the transition to full allocationfrom existing infrastructure, this plan:

• sets out how much water isavailable for consumptive use,especially for irrigation expansion

• explains how we will manage

water through consistent andcomplementary licensing, licenceconditions and water releaserules that meet the water requiredfor irrigation, hydropower and theenvironment as often as possibleas irrigation developmentsproceed

• refines environmental waterprovisions.

The allocation limits and releases from

lakes Kununurra and Argyle in this planare based on current dam infrastructure,existing commitments to hydroelectricitygeneration and maintaining thedownstream environment. Separateand complementary to the plan, we areassessing and advising on water supplyoptions should more water be requiredfor irrigation expansion.


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Plan context and scope

1.2 Plan area

The Ord surface water allocation planarea is in the north-eastern Kimberley.The plan area covers the WesternAustralian part of the Ord Rivercatchment. It extends from the WesternAustralian border to west of Halls Creekand north to the Joseph Bonaparte

Gulf and includes lakes Argyle andKununurra and the town of Kununurra(Figure 1).

The plan specifically applies to the OrdRiver and Tributaries surface water areaand the Ord River Irrigation District(Figure 1) proclaimed under Part III ofthe Rights in Water and Irrigation Act1914. This means that any water divertedfrom the Ord River and its tributariesin Western Australia will be licensed

according to this plan. However, theplan sets aside water for potentialirrigation use in the Northern Territory.While water diverted from the Ord Riverin Western Australia would be managedin line with this plan (chapters 4 and 5),water use in the Northern Territory wouldrequire some administrative and minorlegislative changes to manage cross-

jurisdictional arrangements.

1.3 Water resourcescovered

This plan covers the surface waterresources of the Ord River catchment toits tidal limit (Figure 1), including runoffthat contributes to Lake Argyle from theNorthern Territory.

To best administer water allocation andlicensing, we have divided the planarea into five subareas (Figure 2) basedon infrastructure and changes in riverchannel morphology. The five subareasare the:

• Upper Ord – the catchmentupstream of the Ord River Dam,including Lake Argyle

• Main Ord – the catchment

between the Ord River Dam andTarrara Bar gauging station,including Lake Kununurra

• Tarrara-Carlton – the catchmentbetween Tarrara Bar gaugingstation and House Roof Hill

• Carlton-Mantinea – thecatchment between House RoofHill and the tidal l imit

• Dunham River – the Dunham River

catchment.

We used these boundaries to setenvironmental flow provisions andallocation limits. For further information,see Section 2.5 of the supportingmethods report (DoW 2012b).


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Figure 1Plan area, proclaimed a reas and ir r igat ion areas (stage areas)Ord surface water allocation plan

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Ord plan area

Proclaimed areas

Irrigation District

Surface water area

Government of Western AustraliaDepartment of Water

Map reference: C2114/0004

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1

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Figure 2Subarea boundariesOrd surface water allocation plan

4

1 Plan context and scope


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1Plan context and scope

Ord



The 99-calendar-year sequence(1906–2004) of streamflow used includesvery dry conditions (e.g. the 1930s)and very wet years (the past 10 yearsof records). The allocation limits andrelease rules have been set to sharewater effectively under the full range ofthese conditions.

We have revised the environmental

water provision in response torecommendations from the EPA tomaintain the post-dam environment ofthe Ramsar-listed Ord River floodplainand wetlands (EPA 1999). The EPAmade these recommendations basedon the requirements of the Council ofAustralian Governments’ Water ReformFramework of 1994.

We established the plan’s current and

future licensing approach by workingwith the Water Corporation, PacificHydro, Ord Irrigation Cooperative (OIC),Department of Regional Developmentand Lands and Department ofAgriculture and Food (DAFWA).

For more information about waterallocation planning, see Waterallocation planning in WesternAustralia: a guide to our process (DoW 2011c). For more details of the

information and process we usedto develop the allocation limits andlicensing approach, see Ord surfacewater allocation plan methods report(DoW 2012b).

1.5 Main stakeholderinterests

Engaging and consulting withstakeholders was a major part ofdeveloping the Ord surface waterallocation plan. In the Ord area, anumber of groups are interested inwater allocation (Table 1).

1.4 How we developedthe plan

We developed this plan using newecological studies and hydrologicalmodelling undertaken since 2006.This work:

• used extra rainfall and flow data

to update our understandingof the Ord River catchment’shydrology

• defined water availability fromLake Argyle under a range offuture demand scenarios, basedon a past sequence of dam inflow(1906–07 to 2003–04)

• defined how much water needsto remain in the lower Ord River to

meet environmental needs (theenvironmental water provision).

Working with water users and othergovernment agencies involved inthe area, we used this new work toconfirm the water resource objectivesand allocation limits and set thewater release rules in this plan. Theplan’s objectives closely align with thegovernment’s commitment to expandirrigated agriculture in the Ord area,while providing enough water forhydroelectricity generation and theriverine environment downstream ofLake Kununurra.

In setting the allocation limits andrelease rules we assumed thefuture climate will be similar to thatexperienced in the Kimberley between1906 and 2004. Our use of past climaterecords is appropriate given the globalcirculation models used to project future

climate in the region do not indicate aclear wetting or drying trend to 2030.


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1

Ord



Table 1Stakeholders of the Ord plan

Interest group Stakeholders

Agriculture and irr igation Ord Irr igation Cooperative (and SunWater1), self-supply irrigators,

Department of Agriculture and Food and Department of Regional

Development and Lands

Public water supply Water Corporation (the bulk water supplier)

Individuals Commercial businesses, boat operators and riparian water users

Indigenous Native title holders, Miriuwung Gajerrong Corporation, Indigenous

interest groups

Industry Pacific Hydro, Rio Tinto

Local government Shire of Wyndham – East Kimberley

Other state agencies Department of Envi ronment and Conservation and Off ice of the

Environmental Protection Authority

Federal agencies Department of Sustainabi lity, Envi ronment, Water, Population and

Communities, National Water Commission

In mid 2011 we updated stakeholders onthe progress of the Ord plan for publiccomment and met with all interestedparties in Perth and Kununurra to discussaspects of the plan that involved them.In 2012 we released the Ord surfacewater allocation plan: for publiccomment (DoW 2012a) for a 15-weekpublic comment period (May 25 toSeptember 14, 2012).

The main interests raised by stakeholdersthrough consultation and submissionson the plan for public commentincluded:

• whether adequate water wasbeing allocated for irrigationexpansion and how the planrelated to the Royalties forRegions Ord-East Kimberleyexpansion project and the OrdFinal Agreement

• what the water availability was,both overall and per hectare fornew farm lots, as well as reliabilityof supply (95 per cent of years)

• priority of water allocation whenLake Argyle was approachingfull allocation, including possibleexpansion into the NorthernTerritory and new CockatooSands areas in Western Australia

• how much water was left inthe lower Ord to maintain theenvironment, suitable waterquality and water-basedrecreation and how we wouldmonitor biological impacts

• how water release rules andhydropower, irrigation andenvironmental water restrictionswould apply in dry years and beevaluated over time

1 SunWater was the preferred water service provider for the Goomig farmlands, but has since withdrawn.


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• water supply options if/whendemand exceeded the allocationlimits

• how the plan related to theNational Water Initiative andclarity on the department’sposition to recoup unusedentitlements

• a need to better communicatethe key technical conceptsbehind the plan.

We have discussed and clarifiedthese issues raised in submissions withrespondents and addressed them infinalising the plan, as appropriate.For further information on stakeholderinterests and how they were consideredin finalising the plan, see theOrd surface water allocation plan:statement of response (DoW 2013).

1.6 Plan timeframe

The Ord surface water allocation planis in effect until it is replaced by a newwater allocation plan, amended orrevoked by the Minister for Water.

We will assess whether to amend orreplace this plan in 2019, or earlier if the

annual evaluation process (Section 7.2)identifies the need. When additionalnew agricultural expansion areas areagreed and their water supply needsare clarified, we may amend parts ofthe plan.

We are assessing and advisinggovernment on water supply options,should more water be required forirrigation expansion. If there are majorchanges to the current dam

infrastructure or supply system,changes to licences and a newplan will be needed.


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Chapter TwoWhat the plan will achieve

The Department of Water is responsible

for managing water resources in WesternAustralia consistent with the objectsof Part III of the Rights in Water andIrrigation Act 1914, specifically:

a. to provide for the managementof water resources, and inparticular:

i. for their sustainable use anddevelopment to meet theneeds of current and future

users; and

ii. for the protection of theirecosystems and theenvironment in which waterresources are situated,including by the regulation ofactivities detrimental to them

b. to promote the orderly, equitableand efficient use of waterresources

c. to foster consultation withmembers of local communitiesin the local administration ofthis Part, and to enable them toparticipate in that administration

d. to assist the integration of themanagement of water resourceswith the management of othernatural resources.

Allocation plans are developed so

that water resources across the stateare managed consistent with theseobjectives while addressing area-specific issues.

This chapter outlines the framework

for how the Ord River’s surface waterresources will be managed. It clearlystates:

• the outcomes we expect to see

• how the water resource shouldperform to meet the outcomes –the water resource objectives

• the strategies we will use todeliver the water resource

objectives.

2.1 Outcomes

Outcomes are the broad ecological,social and economic consequences ofour water resource management. Theexpected outcomes of this plan are:

• secure and reliable watersupplies for a strong and

expanding irrigation industry

• a healthy lower Ord Riverenvironment

• as much hydroelectricityproduction as possible, withinthe limits of the water needed byirrigators and the downstreamenvironment

• traditional Indigenous access,water-based tourism and

recreational opportunities thatcomplement the irrigation,environmental and poweroutcomes.


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2What the plan will achieve

Ord


2.2 Resource objectives

Water resource objectives state howwe want the water resource to performas a result of the management weput in place. They are specific andmeasurable, and ensure the outcomescan be met. This plan’s resourceobjectives are as follows:

a. flows measured at Tarrara Barmeet the environmental waterprovision, including:

i. the baseflow component forwet and dry seasons

ii. annual and inter-annual wetseason peak flows

iii. infrequent wet season floodevents

b. water levels in Lake Argyle aremaintained above irrigationrestriction levels in 95 per centof years.

2.3 Strategies

We have identified five key strategies tomeet the resource objectives and deliverthe outcomes. They are:

• issue licence entitlements withinthe allocation limits for eachsubarea

• manage water releases atthe Ord River and KununurraDiversion dams through thisplan’s release rules

• adjust releases over time asirrigation development proceeds

• adjust releases in periods ofdrought

• optimise the water available fornew development and powergeneration by recouping unusedwater entitlements.

These strategies are described in detailin chapters 4 and 5.

2.4 Measuring the successof the plan

The department will evaluate the planannually and publish an evaluationstatement at least every three years. Wewill assess how we have implementedthe strategies and whether the resourceobjectives and outcomes are beingmet. If necessary we will adapt our

management.

We will communicate the results ofevaluations to key stakeholders at theannual Ord River stakeholders meeting(see Section 5.6).

More information about how wewill monitor the Ord River’s surfacewater resources and evaluate theperformance of the plan is given inchapters 6 and 7.


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Chapter ThreeCurrent and projected water demands

The Ord River and its tributaries provide

water for the regionally importantirrigated agriculture and miningindustries. The river also provides waterfor other significant demands such ashydroelectricity and the environment. Attimes the demands are complementaryand at other times they are incompetition.

Competition for water will increase asnew irrigation areas are developedand as more power is needed to supplyunderground mining. This competitionwill become more intense in dry years,as water released for hydroelectricitygeneration draws down storage for thenext season’s irrigation.

This chapter provides the water demandcontext for the plan and includes:

• irrigation demands now and intothe future

• power supply demands now andinto the future

• environmental, social, tourismand cultural water demands

• how to balance all thesedemands.

3.1 How water isdistributed in the Ord

The approach to managing differentdemands for water from the Ord Riveris influenced by where the demandpoint is located and how water isdistributed. The distribution of water andthe location of demands is shown inFigure 3.


24/941 1

Current and projected water demands

Figure 3How water is distributed from the Ord River a nd Kununurra Diver sion damsOrd surface water allocation plan

Lake Argyle

Lake Kununurra

Spillway Creek

Rainfall/Evaporation

Inflow

Upper Ord River

Inflow between dams

Ord River Dam


Tarrara Bar (end of Main Ord subarea)

Lower Ord River

Start of Carlton-Mantinea subarea

House Roof Hill

Riverside pumpers

Supply to Carlton-Mantinea

Releases or diversions specifically

to meet demand of:

Irrigation

Hydropower

Environment

Surplus spillage,

inflows,

hydropower

station releases

and specific

releases to meet

the environmental

water provision

Hydropower

generators

Irrigation Valves

Gauging station

Ord River estuary


25/9412

3 Current and projected water demands

Ord


Water from the upper Ord catchmentis stored in Lake Argyle and releasedthrough the Ord River Dam to LakeKununurra. Above the KununurraDiversion Dam, water is diverted to theStage 1 irrigation area and the newM2 supply area (Figure 4, Section 3.2).Self-supply pumpers take water directlyfrom the river above and below thediversion dam. Further downstream,

past House Roof Hill, more water maybe directly pumped from the river forirrigation. The release of water fromLake Argyle and Lake Kununurra servesmultiple purposes, but the volumeand timing of releases needed forhydropower are not always the sameas those needed for irrigation, the riverenvironment or other demands.

Releases from Ord River Dam for

hydropower and irrigation

Most of the water used in the Ord areais stored in and released from LakeArgyle by the Water Corporation. TheWater Corporation owns, operates andmaintains the Ord River Dam and islicensed by the Department of Waterto store and release (but not divert)the water in the reservoir. Pacific Hydroowns and operates a 30 MW powerstation constructed on the outlet works

of the Ord River Dam.

Through contract arrangements withthe Water Corporation, Pacific Hydroreleases water through the powerstation to generate electricity. The WaterCorporation can also release waterfrom Lake Argyle through the irrigationvalves that bypass the power station(Figure 3). Water is released throughthe power station whenever possible.Releases via the irrigation valves usuallyonly occur when the hydropower stationis undergoing maintenance.

The water released through the powerstation or irrigation valves flows downthe Ord River and into Lake Kununurra.Riverside pumpers (self-suppliers)abstract water directly from LakeKununurra, as well as from the lowerOrd River downstream of the KununurraDiversion Dam.

Diversions from Lake Kununurrafor irrigation

Above the diversion dam, the OIC takeswater from Lake Kununurra for irrigationby either:

• diverting it under gravity into theM1 supply channel (Figure 3) tosupply members on the IvanhoePlain

• pumping it into the Packsaddlesupply channel (Figure 3)to supply members on thePacksaddle Plain.

By 2014 additional water is expectedto be diverted into the M1 channel tosupply the new Goomig farmland area(Figure 4). This is the first phase of theOrd irrigation expansion project todevelop the larger M2 channel supplyarea, including land on Knox Creek and

Keep River plains in the Northern Territory(Figure 4).

The M1 supply channel’s capacity hasbeen increased to enable delivery ofthe additional water for the first 17 kmtowards the Goomig farmland. Thenew M2 channel will carry water for theremaining distance and will be extendedfurther when subsequent developmentphases proceed. When complete, theM2 channel will transport water from

Lake Kununurra to supply 30 000 ha ofthe M2 supply area.


26/9413

3Current and projected water demands

Ord


Ord Irrigation Cooperative’s supplyfor Stage 1 irrigation

The Stage 1 area includes the Ivanhoeand Packsaddle plains (Figure 4).The OIC supplies water to 15 363 haof farmland on 111 separate properties(as at June 2012) on the Ivanhoe andPacksaddle plains (Figure 5). The OICholds a licence to take 335 GL/ yr

(in force until 2014).

Most water for the Stage 1 areas isdiverted at the M1 offtake into theM1 supply channel for the Ivanhoe Plainand about 10 to 12 per cent is divertedat the Packsaddle pump station toPacksaddle Plain. In recent years, theOIC has taken less than 200 GL/yr fromLake Kununurra, largely due to changedcropping and the closure of the sugar

mill since the licence was first issuedin 2004.

Releases from Lake Kununurra tomaintain the lower Ord River

The Water Corporation releases waterfrom Lake Kununurra into the lower OrdRiver by raising some of the 20 gatesof the Kununurra Diversion Dam. Thereleases are made up of:

• surplus spillage from Lake Argyle

• surplus inflows from the LakeKununurra catchment

• surplus hydropower releases

• when necessary, releasesspecifically to meet theenvironmental water provision forthe lower Ord River.

3.2

Irrigation demands

Irrigation is the dominant consumptiveuse of water from Lake Argyle. Waterfor irrigation is either self-supplied byindividual users or scheme-supplied bythe OIC.

Current demand for irrigation

More than 80 licensed self-supply

irrigators abstract a total of 9.3 GL/yrof water from the Main Ord subarea,mainly from Lake Kununurra andbetween the Kununurra Diversion Damand Tarrara Bar (Figure 3).

In addition, the Water Corporation islicensed to abstract 3.1 GL/yr from theM1 offtake to supply some irrigationcustomers (within the first 12.8 km of theM1 channel) in the Stage 1 area, and toflush and dilute treated wastewater that

discharges into the M1 channel.


27/94


Ò Ð

!(

^



Legend

0 8 16

Kilometres

D u n h a m

R i v e r

E i g h t

M i l e

C r e

e k

K n o x C r e

e k

W e s t e r n A u s t r a l i a

N o r t h e r

n

T e r r i t o

r y

Carlton Plain

Mantinea

Ord WestBank

Green Swamp

Ivanhoe Plain

PacksaddlePlain

Keep River Plain

Knox CreekPlain

Kununurra

!( Towns

^ Streamflow gauge Ò Ð Dam site

Roads

Rivers

M1 channel

M2 channel

M2N supply channel

Govt EOI 2011

Sorby Hills Mining Area

Stage 1 areas

Stage 2 areas

Goomig farmland

Vegetation management area

Non irrigation areas

Land not available


!(

!(

KUNUNURRA

HALLS CREEK

Locality Map

WESTERNAUSTRALIA

NT

SA

±

Tarrara Bar streamflow gauge

Goomig farmland

Figure 4Cur rent (Stage 1) and proposed ir r igat ion development areas in t he plan areaOrd surface water allocation plan

14


28/9415


Ord


Irrigation expansion

Since the 1950s the vision for the Ordirrigation project has been to developall the irrigable soils on the greaterOrd and Keep River floodplains.Expansion beyond the Stage 1 areaswas promoted in the mid 1990s,culminating in a proposal to developmore than 30 000 ha of irrigatedagriculture to the north of the Stage 1area, in what became known as theM2 channel supply area.

The M2 channel supply area wasthoroughly investigated and grantedconditional environmental approvalby the state and Northern Territorygovernments in early 2002. Althoughthe project lapsed, the approvalsremained and the Western Australian

Government committed financialresources to develop the first phase ofthe M2 supply area.

The Goomig farmlands – firs t phaseof the M2 supply area

In 2008 the state governmentcommitted to developing 7400 haof serviced irrigated farmland, nowknown as the Goomig farmlands(Figure 4). The Goomig farmlands

form the first phase of the greater(30 000 ha) M2 channel supply areadevelopment. Construction of the off-farm infrastructure began in 2010 andis scheduled to be completed by theend of 2013.

In November 2012, the stategovernment announced thatKimberley Agricultural InvestmentPty Ltd (KAI) had been selected todevelop the Goomig farmlands2.

Subject to contract negotiations ofKAI to obtain relevant (federalgovernment) approvals, KAI intendsto develop subsequent phases ofthe M2 supply area (see below) andconstruct a sugar refinery to processsugarcane. The first water is to besupplied in 2014, with demand growingover the subsequent four years as moresugarcane is grown.

The Knox Plain area in Western Australia – second phase of M2supply area

KAI has also been appointed thepreferred developer for approximately5000 ha of the Knox Creek Plainin Western Australia. This involvescompleting final designs for irrigationinfrastructure, seeking the remainingenvironmental approvals and

constructing the infrastructure withinthe next five years.

Extension into the Northern Territory– third phase of M2 supply area

The Northern Territory, WesternAustralian and federal governmentsrecently signed a Memorandumof Understanding on the proposedexpansion of the Ord River AgriculturalArea over the remaining 14 000 haof the M2 supply channel area in theNorthern Territory. Development ofthe area will require further approvalsfrom the Northern Territory and federalgovernments. More detail on theapprovals required under differentlegislation and the status of thoseapprovals is provided in Section 1.2.8of the Ord surface water allocation planmethods report (DoW 2012b).

2 The Miriuwung Gajerrong Corporation has been offered two lots (675 ha) in the Goomig farmlands –

in accordance with the Ord Final Agreement and the Aboriginal Development Package negotiated

for the Goomig development.


29/9416


Ord


Infill areas in the Sorby Hills miningtenement – final phase of the M2supply area

In the longer term there is scopeto irrigate up to 3000 ha of land,undisturbed by mining in the Sorby Hillsmining tenement, after mining andrehabilitation is complete.

Ord West Bank

In November 2012, the state governmentannounced it would develop the OrdWest Bank area (Figure 4). It expects tobring approximately 1000 ha of irrigablefreehold land to the market during thenext several years. A mix of horticulturaland broadacre crops is expected to begrown across this area in the next threeto five years.

The Carlton Plain and the Mantineaareas – the downriver developments

Downstream in the Carlton-Mantineasubarea, there are proposals todevelop more than 8000 ha on theriver’s north side (Carlton Plain). Thereis also the potential to develop 4000 haon the south side (Mantinea area).Development of these areas could takeplace in five to 10 years. Given recentchanges in planned areas and croptypes, demand could be up to155 GL/yr.

New areas on the Packsaddle Plain,Ord East Bank and Stage 1 infill areas

Variable soils on new areas ofPacksaddle Plain are likely to limitdevelopment to about 200 ha.A further 1000 to 1100 ha of landcould be developed on land known as

the Ord East Bank area and other areasadjacent to existing Stage 1 lots.

While subject to native title and otherapprovals, together the demand fromthese areas could be up to25 GL/yr (Table 2).

Cockatoo Sands

DAFWA is investigating whether thesoils of Cockatoo Sands are suitable forirrigation. Between 4000 and 6000 ha

of Cockatoo Sands is sufficiently closeto the Ord River to warrant assessmentof whether it can be economicallysupplied with water from the river. Thedevelopment is a longer-term proposaland possible demand is likely to beabout 40 to 60 GL/yr.

Water demand for irrigationexpansion and supply options

A range of irrigation demands arepossible in the Main Ord subarea(Table 2). If each of the developmentareas proceed, and water demand inthese areas is consistent with the rangeof demand listed, then water demandwill be greater than the allocation limitset by this plan. Should a decision bemade to meet all of these demands intothe future, with consequent changes tothe current dam infrastructure or supplysystem, then a new water allocationplan will be needed.


30/9417


Ord


Once the system reaches full allocation,and there are no further managementimprovements to effectively distributereliable water supply across competingdemands, a market may develop forwater for consumptive use.

Irrigation demand may exceed thereliable allocation limit in this plan inthe medium to long term. While beyondthe scope of this plan, the Departmentof Water is leading a cross-governmentapproach to investigate additionalwater supply options to meet this larger

demand.

Table 2 Wa ter demand for i r r igat ion developments in the Main Ord subarea

Development area

Gross

developmentarea (ha)

Nominal

farmlandarea (ha)

Range of possible

water demand*(GL/yr)

Ord Stage 1 irrigation area

Ivanhoe and Packsaddle plains,

riverside pumpers

19 000 16 000 230–350

Ord expansion area supplied by the M2 channel

Goomig farmlands 9500 7400 80–170

Knox Plain (in WA) 6000 5000 60–110

Sorby Hills area (post mining) 4000 3000 30–60

Northern Territory ~16 000 14 000 140–270

Ord expansion area not supplied by the M2 channel

Ord West Bank 1700 1000 16–25

East Bank and other miscellaneous 1200 1100 8–20

New Packsaddle Plain area 1700 200 4–5

Cockatoo Sands Not defined 4000–6000 40–60

Total >59 100 51 700–53 700 608–1070

* At the point of diversion from the Ord River

3.3

Water demands for

power

Pacific Hydro supplies hydropower toHorizon Power for towns and the ArgyleDiamond Mine. When hydropoweris not available, backup dieselgenerators are used.


31/94


32/9419


Ord


By 2015, we expect demand to be 150 per cent or greater than the 210 GWh/yrminimum guaranteed by the 1994 agreement. The electricity demand on the EastKimberley electricity grid beyond 2017 is highly uncertain, but is likely to decreaseafter 2018 (as advised by Argyle Diamonds). The hydropower station on the Ord RiverDam cannot meet the full projected electricity demand (Figure 5). However, thepower station will remain the main and cheapest source of electricity in the region.

A new source of electricity generation or greater reliance on the existing dieselpower stations at Argyle Diamond Mine and Kununurra will be required to meet thebulk of the growing electricity demand. A possible source of extra power would be toconstruct a 10 MW capacity hydropower station at the Kununurra Diversion Dam. Thestation would generate electricity from water released from Lake Kununurra to thelower Ord River. Appendix D shows the average electricity that could be generatedif two hydropower stations (at both the Ord River and Kununurra Diversion dams)supplied to the East Kimberley electricity grid.

With a 10 MW station at the Kununurra Diversion Dam, the average additionalelectricity generated would be more than 60 GWh/yr under the current waterlicences (350 GL/yr) and 50 GWh/yr if all water for allocation from the Main Ordsubarea were licensed (750 GL/yr). With this additional power option, less waterwould need to be released from Lake Argyle, and the severity of irrigation restrictionswould reduce – especially as full allocation for irrigation expansion approaches.

Figure 5Recorded and projected demands on the East Kimberley elec tr icity gr id

0

100

200

300

400

2000 2002 2004 2006 2008 2010 2012 2014 2016 2018 2020

E l e c t r i c i t y d e m a

n d ( G W h / y r )

Year

Horizon ADM ADM est imated

Recorded Projected


33/9420


Ord


3.4 Environmental, socialand cultural water

demands

Water that remains in the Ord Riverprovides for environmental, socialand some cultural needs as well asfor tourism.

Environmental water

The Ord River Dam’s constructionin the early 1970s greatly changedthe flow regime of the lower OrdRiver. These hydrological changes inturn dramatically altered the river’senvironment.

Before the dam, the lower Ord Riverflooded regularly in the wet season,

inundating large areas of the river’sfloodplain. In the dry season the riverdried out to a series of isolated pools.After the dam was built, average wetseason flows in the lower Ord Riverreduced by 67 per cent, and averagedry season flows increased by430 per cent (based on data from1974–75 to 2003–04).

In 1999 the EPA, in line with the COAGWater Reform Framework of 1994,recognised the importance of thepost-dam environmental values thathad developed in the lower Ord Riverand required that these be protected.In response to this, the Department ofWater has established the environmentalwater regime required to maintain thepost-dam riverine environment of thelower Ord River (Braimbridge & Malseed2007). This process is consistent withthe changes made in 2000 to the Rightsin Water and Irrigation Act 1914 andwith contemporary water managementpolicy.

Determining water for theenvironment

To meet the legislative requirementsand the EPA’s requirements, we tookinto account the post-dam ecological,social, cultural and economic factorsin providing water for the downstreamenvironment.

To determine the ecological flowrequirements of the lower Ord River weconsidered the water regimes neededto maintain:

• populations of fish andmacroinvertebrates

• vegetation community structureand composition

• water quality

• ecosystem processes

• channel morphology.

The method used to determine therequired ecological flow regime(Flow Events Methodology) recognisesthat different parts of the flow regime –low, high, bankfull and overbank flows– are important to river health and havedifferent ecological functions. These flowcomponents reflect the seasonality of

the flow regime which, although altered,remains important to the ecology ofthe lower Ord River. In recent years, thebaseflows have been well above whatthe riverine ecology needs. Flows in thelower Ord will decrease noticeably asdiversions for irrigation increase towardsthe full allocation limit.

For more information on environmentalvalues and the ecological waterrequirements, see Environmental values,

flow related issues and objectives forthe lower Ord River (DoW 2006a) andEcological water requirements for thelower Ord River (Braimbridge & Malseed2007).


34/9421


Ord


Water to support traditional Aboriginal laws and customs

Native title consent determinationsof the Federal Court of Australia in2003 and 2006 determined the culturaland spiritual importance of the lower OrdRiver to the Miriuwung Gajerrong peoplein law. For details of the Miriuwung

Gajerrong determinations (Number 1on 9 December 2003 and Number 4 on24 November 2006) see the Ord surfacewater allocation plan methods report (DoW 2012b).

The views of the Miriuwung Gajerrong inrelation to flows in the lower Ord Riverare reported in the Ord River watermanagement plan (DoW 2006b):

At the community workshop in 2000,

representatives of traditional ownersindicated that access to the river forfishing and ceremonial activities wereimportant to Miriuwung and Gajerrongpeople, and suggested short periodsof ‘dry out’ and ‘wash out’. Subsequentdiscussions with traditional ownersconfirmed that having access to theriver so they can pursue their traditionalactivities associated with the river, wasimportant to the Miriuwung and Gajerrongpeople.

Short periods of low (‘dry out’) flows

are important to (pre-dam) Dreamingstories of the Miriuwung Gajerrong.Such low flows are now very rare in thelower Ord River and usually only occurduring periods of dam or power stationmaintenance.

The Department of Water and WaterCorporation recognise the importanceof low-flow periods to the MiriuwungGajerrong and will ensure they aremade aware of maintenance likely tocause such low flows so that customarypractices can be undertaken.

Water for recreation and tourism

Water-based recreation on Lake Argyle,Lake Kununurra and the lower Ord Riveris important to the local economy andcommunity. Most fishing and boatingactivity is only possible because theriver is now regulated through the OrdRiver Dam so the river flows during thedry season (when it would previouslyhave dried out). High releases andrelatively low irrigation diversions haveallowed boats to navigate betweenthe Kununurra Diversion Dam and theOrd River Dam, and below the diversiondam along much of the lower Ord River.

Impacts of changes to flows in thelower Ord River

The decrease in dry season flows in

the lower Ord River as more wateris diverted to supply new irrigationareas will affect the water availableto meet tourism and recreationalneeds. However, previous communityengagement has shown acceptanceof reduced flows given the economicbenefits of diverting water foragriculture and as long as some flowis maintained (DoW 2006a).

Dry season flows in the lower Ord were

typically around 50 m3

/sec after LakeArgyle first filled in 1974, and increasedto 60 to 70 m3/sec after 1996 whenthe spillway was raised and the OrdRiver Dam power station became fullyoperational. The average dry seasonflow rate is expected to be about55 m3/s once the irrigation allocation(750 GL/yr) is fully utilised. However, inmore than a third of dry seasons, flowswill be around 42 m3/s, which is theminimum dry season environmeqntal

flow when restrictions are not in force.


35/9422


Ord


Releasing water from Lake Argyleto raise water levels in the lowerreaches of the lower Ord River is notfeasible given water levels fluctuateconsiderably based on river bed andbank conditions, changes in channelform due to floods, and tidal influencescloser to the estuary. Modelling showsa considerable amount of water wouldneed to be released to have any impact

on water levels in the lower Ord River– to the detriment of storing water foragriculture. As such, we do not supportreleases from Lake Argyle specifically fornavigational purposes on the lower OrdRiver (see Section 5.6).

Recreation on Lake Argyle and LakeKununurra

Most water-based recreation on LakeKununurra and Lake Argyle takes place

during the dry season and involvescommercial boat tours and privateboating for recreational fishing.

The water needed for boating isprovided by lake storage. However,tour boat operations on Lake Kununurratravel upstream, to where the spillwayreaches the lake (40–45 km) andnormally continue further upstream(another 15 km) to the base of the

Ord River Dam. Flow rates of 50 m

3

/sare needed for the boats to navigateto the base of the dam.

Hydropower station releases normallyexceed this flow rate, except at timesof low power demand. In the past, theWater Corporation has made additionalreleases for navigation via the Ord RiverDam irrigation valves when the powerstation is releasing less than 50 m 3/s.

We support these releases given thebenefits for tourism, but only consider itacceptable when water storage in LakeArgyle is high. At times of low storage,especially when other restrictions apply,releases specifically for navigationwould compromise other demands andare not supported (see Section 5.6).

3.5

Balancing thedemands for water

A major part of managing water inthe Ord River is balancing the releaseof water from Lake Argyle to meetthe different seasonal and short-termpatterns of water demand. For this plan,the department’s approach to meetingdemand is to maximise water forirrigation and hydroelectricity, and meetecological needs given the existinginfrastructure.

Our water release rules provide a veryreliable and secure water supply forirrigation (see Chapter 5). Throughlicences issued under the Rights inWater and Irrigation Act 1914 , we willmanage the timing and volume of waterreleases, restrictions and diversions tooptimise water availability for competingdemands.

To guide management, we used aniterative modelling approach (using theOrd River-Lake Argyle reservoir model) toexamine different water allocation andrestriction options. We modelled futurescenarios representing the irrigationand hydroelectricity demand likely todevelop during the plan’s life. Scenariosranged from 350 GL/yr for irrigation andmoderate power demand, to 750 GL/yrfor irrigation and high power demands.


36/9423


Ord


We based modelling on recorded andestimated dam inflow for the period1906–07 to 2003–04. Through theprocess, we recognised the importanceof managing for drought periods –such as those that occurred in the1930s, 1950s and 1980s – by specifyingrestricted releases when inflow declines.

We used the modelling to:

• identify the most effective wayto release water for irrigation,hydropower and the environmentso that consumptive and non-consumptive demands were metin as many years as possible

• specify water release rulesfrom Lake Argyle and developrestriction policies for eachdemand during droughts

• estimate the number of years thatthe different demands were likelyto be restricted.

To do this, we modelled the scenariosto meet three target criteria:

• the full irrigation supply of750 GL/yr to be met in95 per cent of years

• a minimum irrigation supply of25 per cent of water demand inthe driest year

• a minimum operating level forLake Argyle of 70 mAHD.

Within these constraints, we selectedthe optimal water releases to maximisepower generation and meet theenvironmental water provision.The modelling was used to confirmallocation limits and establish licensing

rules for water releases, and irrigation,hydropower and environmental waterrestrictions, for each demand scenario.

As irrigation developments proceed,we will revise restrictions using theOrd River-Lake Argyle reservoir model(see Section 5.3). If new developmentsproceed rapidly and the high demandprojections of Table 2 are realised, andthere is agreement that the current daminfrastructure will be changed, we willrevise our management accordingly(see Section 1.6).

For more information on the Ord River-Lake Argyle reservoir model simulationsand demand scenarios for this plan,see the Ord surface water allocationplan methods report (DoW 2012b) andReservoir simulation in the Ord Rivercatchment (Smith & Rodgers 2010).


37/9424

Ord


Chapter Four Water allocation

This chapter sets out the:

• water allocation limits in eachsubarea

• water allocation approach

• water regime provided tomaintain the lower Ord Riverenvironment.

The Department of Water has setallocation limits for each of the fivesubareas in the Ord plan area. For eachsubarea we will license and manageto the allocation limits, which were setto achieve the outcomes and resourceobjectives stated in Chapter 2.

Together, allocation limits andlicensing guide how we managewater for irrigation purposes and otherconsumptive uses. The environmentalwater regime is provided throughwater releases for hydroelectricity

generation and environmental flows,which are managed through the WaterCorporation’s Ord River Dam licence.

For more information on how wedeveloped the allocation limits, waterrelease rules and environmental flowregime for this plan, see the Ord surfacewater allocation plan methods report(DoW 2012b).

4.1 Water allocation limits

Generally, an allocation limit is theannual volume of water set aside foruse from a water resource. In the Ord,allocation limits represent the annualvolume of water that can be taken forconsumptive use from each subarea.

Water is available for licensing in fourout of the five subareas. The departmentwill grant licensed entitlements up to the

annual allocation limits at the definedreliability for each of the surface watersubareas (Table 3).

The Ord allocation limits are divided intocomponents for accounting purposes,including:

• water available for licensing (thegeneral licensing component)

• water set aside for potential

irrigation expansion into theNorthern Territory (the NorthernTerritory component).

Allocation limits do not include waterreleased for hydroelectricity generationor the downstream environment.

The allocation limits for the Main Ordand Carlton-Mantinea subareas wereset in the 2006 plan and remain inplace. Water allocation limits for the

Upper Ord and Dunham River subareasare newly set in this plan (Table 3).


38/9425

4Water allocation

Ord


Table 3 A l locat ion l imit s for t he Ord surface water a l locat ion plan a rea

Subarea

Allocationlimit (total

entitlements)

(GL/yr)

Allocation limitcomponents (GL/yr) Annual

reliability ofsupply

Water available forlicensing in WA

(GL/yr)

(at January 2013)General

licensing Northern Territory

Upper Ord 15 15 0 variable 6

Main Ord 750 590 160* 95% 242

Tarrara-Carlton 0 0 0 N/A 0

Carlton-

Mantinea115 115 0 95% 115

Dunham River 25 25 0 variable 5

Total 905 745 160 368

* The Northern Territory component may be used in Western Australia if demands in this state grow rapidly

before extra supply options are approved.

As at February 2013, there is anapplication seeking an annual water

entitlement of 98 GL from the Carlton-Mantinea subarea. If it is approved, itwill significantly reduce the remainingwater available in that subarea.

4.2 Allocation approach

Allocating water for irrigationexpansion

The irrigation demands dependenton Lake Argyle will change over timeas new irrigation expansion areasare approved and the demandfor hydroelectricity increases. Wewill stage the issuing of licensedentitlements for irrigation water bynot issuing more entitlements thanare needed for efficient irrigation ofplanned crop types. This will allowirrigation developers to

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