South-West Western Australia Sustainable Yields Project Don - - PowerPoint PPT Presentation

South-West Western Australia Sustainable Yields Project

Don McFarlane Project Leader

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Acknowledgements

• DEWHA – funding and policy guidance
• Department of Water – data, models, researchers, report review
• Water Corporation – data, report review
• Department of Agriculture and Food WA – soils data
• Bureau of Meteorology – climate data, surface water modelling
• Queensland Department of Environment and Resource Management – SILO

data

• Contracts and consultancies
• URS – Peel Harvey groundwater model
• CyMod Systems Pty Ltd – groundwater model calibration
• Resource Economics Unit – demand estimation
• Geographic Information Analysis – model data preparation
• Jim Davies and Associates – yield and demand analyses
• External reviewers:

Peter Davies (University of Tasmania); Andy Pitman (University of New South Wales); Tony Jakeman (Australian National University): Don Armstrong (Lisdon Associates) and Murray Peel (University of Melbourne)

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Broad terms of reference

• Estimate the current and 2030 yield of water in

catchments and aquifers for the south-west of WA considering climate change and development (plantations, farm dams, groundwater abstraction)

• Compare the estimated current and future water

yields to those needed to meet the current levels of extractive use, future demands and environmental needs

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Publications

Main reports Executive summaries Factsheets Web:

www.csiro.au/partnerships/SWSY.html

USB Sticks

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Project context

• The project does not determine sustainable yields or set new

allocation limits

• The project is regional and doesn’t address local issues
• The results are scenarios based on assumptions about the future

climate, landuses, abstraction levels and demands Water resource planning, management and investment This Project Assessments

• f current and

future water yields and demands Environmental impacts of alternate allocation regimes Socio-economic impacts of alternate allocation regimes Stakeholder and community consultation

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Sustainable Yields Projects – 2007 to 2009

Murray-Darling Basin Northern Australia South-West Western Australia Tasmania

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Location of the project area

• All fresh, marginal and

brackish surface water catchments between Gingin Brook and the Hay River

• All aquifers within the

Perth and Collie basins, plus the western Bremer Basin

• Area = 62,500 km2

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Project area topography

• Short streams that arise in

the Darling Ranges are fresh

• Darling Fault separates Perth

Basin from Darling Plateau

• Coastal plains are flat and

low lying – Swan Coastal Plain; Scott Costal Plain; South Coast

• Perth Basin Plateaux are

higher in elevation

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Land cover

• Surface water catchments

are mainly forested

• About 60% of the Perth

Basin is cleared about 56% of this being under dryland agriculture

• The uncleared areas

include coastal areas north of Perth, the Gnangara Mound and the Blackwood Plateau

Gnangara Mound Blackwood Plateau

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Climate – 1975 to 2007

Potential evapotranspiration Rainfall - APET

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

South-west WA has had reduced rainfall since 1975

100 200 300 400 500 600 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 Total rainfall (mm) May – July August October –

The 1975 to 2007 period is the baseline for all subsequent comparisons

• 18%
• 8%

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Scenarios

• The ‘historical climate’ or Scenario A assumed that the climate of the

last 33 years (1975 to 2007) would continue. This was used as a base case for comparison of other climate scenarios

• The ‘recent climate’ or Scenario B assumed that the climate of the last

11 years (1997 to 2007) would continue.

• The ‘future climate’ or Scenario C used 15 GCMs with 3 GHG

emission levels which would result in 0.7, 1.0 and 1.3oC of warming by 2030 = 45 possible climates. They are reported as

• wet extreme future climate (Cwet)
• median future climate (Cmid) and
• dry extreme future climate (Cdry)
• Current levels of abstraction and land use were assumed to continue

for all scenarios above

• The ‘future climate and development’ or Scenario D assumed a

median future climate and full groundwater abstraction, new plantations and farm dams (where important)

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

14 of 15 GCMs predict it will get drier

Mid warming Low warming High warming

• Median future
• 7%

climate

• Wet extreme future
• 1%

climate (90 percentile)

• Dry extreme future
• 14%

climate (10 percentile) Change in annual rainfall

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Geographic scope

• 13 surface water

basins covering 39,000 km2

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Rainfall runoff modelling

• Runoff simulated using five simple conceptual models
• Sacramento
• IHACRES
• SIMHYD
• AWBM
• SMARG
• One catchment model
• LUCICAT (in about half the catchments)
• The calibrated model output was compared with
• bserved data and an average of runoff from

Sacramento and IHACRES was the best

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Catchment representation

Collie Basin

• 0.05o x 0.05o grid (~ 5 x 5 km)
• Each cell mapped into a catchment
• Flow accumulated for 204 defined streamflow reporting nodes

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Calibration results – examples

100 200 300 400 500

Modelled annual runoff (mm)

NSE = 0.82

100 200 300 400 1975 1985 1995 2005

Annual runoff (mm) . Scott River - Brennan's Ford

Observed Modelled 100 200 300 400 500

Annual runoff (mm) . Harvey River - Dingo Road

Observed Modelled 100 200 300 400 100 200 300 400

Modelled annual runoff (mm) Observed annual runoff (mm)

NSE = 0.87

Average model efficiency = 0.84, >0.8 in 80% of catchments

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Averaged across the surface water basins 15 global climate models project less runoff

• 50
• 40
• 30
• 20
• 10

inmcm ncar_pcm iap cccma_t63 ipsl miroc cnrm cccma_t47 ncar_ccsm mri mpi gfdl csiro giss_aom miub Change in runoff from historical (%) Global climate models Mid warming Low warming High warming

Wet future climate

• 10%

Median future climate -25% Dry future climate

• 42%

Runoff change across all basins

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Rainfall, runoff and runoff coefficient under historical climate

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Projected change in mean annual rainfall relative to the historical climate

• Rainfall declines by 8% under median future climate and 14% under dry climate
• Proportion of area receiving over 900 mm is: 37% under historical climate, 34% under

recent and wet future, 22% under median future, and 16% under dry future climate

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Projected change in mean annual runoff relative to the historical climate

• Runoff declines by 25% under median future climate and 42% under dry climate
• Proportion of area generating 110 mm runoff is: 37% under historical climate, 34% under

recent and wet future, 22% under median future, and 16% under dry future climate

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Projected changes in rainfall and runoff

Historical Percent change relative to historical climate Surface water modelling area mm Recent Wet Median Dry Mean annual rainfall 837

• 2%
• 2%
• 8%
• 14%

Mean annual runoff 98

• 7%
• 10%
• 25%
• 42%

Frequency of rainfall exceeding 900 mm generating more than 130 mm runoff 1 in 5 years 1 in 9 years 1 in 8 years 1 in 14 years <1 in 33 years

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Percent decline in runoff in all basins

• Decline under recent climate is greatest Gingin to Collie
• Decline under median future climate more uniform across the area
• 40
• 30
• 20
• 10

G i n g i n S w a n C

• a

s t a l M u r r a y H a r v e y C

• l

l i e P r e s t

• n

B u s s e l t

• n

C

• a

s t L

• w

e r B l a c k w

• d

D

• n

n e l l y W a r r e n S h a n n

• n

K e n t D e n m a r k Change in mean annual runoff (%) Recent climate Median future climate Northern region Central region Southern region

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Surface water – Key Findings

Relative to the historical climate, under the median future climate:

• Rainfall declines by an average of 8% and runoff by 25%
• Climate impact on projected streamflows is much greater

than that of increase in plantations and farm dams after 2007

• Across all surface water basins, there is a decline in

mean annual runoff of 24 mm and streamflow of 800 GL in addition to the decline that has occurred since the mid- 1970s

• Declines in runoff are proportionally greater in the

northern surface water region but greater volumetrically in the central and southern regions

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Groundwater results

Geomorphic landforms affect groundwater response to climate change

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Groundwater models

• All together 24 GWAs

considered for groundwater modelling and/or assessment

• Recharge modelling in

GWAs of the Northern Perth Basin and Albany area

• Recharge and

groundwater modelling for all remaining GWAs

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Groundwater models

• The PRAMS model as

used in the Gnangara Sustainability Strategy was used

• A new model (PHRAMS)

was developed for the Peel Harvey area

• The SWAMS model was

linked to a recharge model and recalibrated

• The Collie model was

linked to a recharge model and recalibrated

Perth Regional Aquifer Modeling System (PRAMS) Peel Harvey Regional Aquifer Modeling System (PHRAMS) South West Aquifer Modeling System (SWAMS) Collie model

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Groundwater objectives

• Project groundwater levels in 2030 under future

climate and development scenarios

• Understand why some areas and aquifers may be

less sensitive to climate change than others

• The groundwater results are later used to:
• assess the impacts of levels on groundwater

dependent ecosystems (GDEs); and

• estimate future groundwater yields

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Land cover likely to affect recharge / discharge

Groundwater areas

• 56% dryland agriculture
• 38% native vegetation
• 6% plantations, urban,

irrigated, open water

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Maximum depth of the watertable in the southern half of the Perth Basin in 2007

• Coloured areas are potential

GDEs if not cleared

• Coastal plain soils have very

shallow watertables except Gnangara and Spearwood Dunes

• Plateaux areas mainly

have deep watertables

22% 14% 10%

46%

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Change in groundwater levels between 2008 and 2030 under climate and development scenarios

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

South to North cross section across the Southern Perth Basin

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Historical climate Median Future Climate

Long term monitoring bores

Change in superficial aquifer levels between 2008 and 2030

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Groundwater trends on the Blackwood Plateau since 1987

CL2C

• 65
• 64
• 63
• 62
• 61

Apr-88 Jan-91 Oct-93 Jul-96 Apr-99 Jan-02 Oct-04 Jun-07 Date CL2C Linear (CL2C) CL6W

• 5
• 4
• 3
• 2

Jun-87 Dec-92 Jun-98 Dec-03 Date CL6W Linear (CL6W) CL7W

• 20
• 19.5
• 19
• 18.5
• 18

Apr-88 Jan-91 Oct-93 Jul-96 Apr-99 Jan-02 Oct-04 Jun-07 Date Depth (m) CL7W Linear (CL7W) CL8C

• 24
• 23
• 22
• 21
• 20
• 19

Feb-87 Nov-89 Aug-92 May-95 Jan-98 Oct-00 Jul-03 Apr-06 Jan-09

Date CL8C Linear (CL8C)

Historical Recent Wet Future Dry Future Median Future Development

Change in groundwater levels in the Leederville Aquifer 2008 to 2030

Historical Recent Wet Future Dry Future Median Future Development

Change in groundwater levels in the Yarragadee Aquifer 2008 to 2030

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Collie groundwater basin level changes between 2008 and 2030

Groundwater levels are less affected near rivers

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Level of confidence in the 2030 projections of groundwater levels

• Central and Southern

Perth Basin groundwater models are generally better than others

• Northern Perth Basin and

Albany Area require models

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Groundwater – Key Findings

• A future drier and hotter climate is likely to lower

groundwater levels, especially where there is perennial vegetation

• Groundwater levels under cleared, sandy coastal

plains are expected to be fairly resilient except under the dry extreme climate and high abstraction

• As groundwater levels fall in these areas,

evapotranspiration and drainage losses decrease and there is room in the aquifer to accept recharge

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Groundwater – Key Findings (cont.)

• Interactions between surface water and groundwater

may change in both volume and direction as a result

• f lower water levels in rivers and surrounding

aquifers

• Confidence in model predictions varies depending on

calibration error, hydrogeology, data quality, model maturity and other factors

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Environmental assets in the project area

• Ramsar listed

wetlands

• Wetlands of

national significance

• Conservation

category wetlands

• Wild rivers
• Caves

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Ecological significance Maintain pool habitat in summer Minimum flow to maintain pool quality Upstream migration of small native fish Summer habitat for invertebrates Winter habitat for invertebrates Inundate trailing vegetation Inundate low elevation benches Inundate high elevation benches Ecological function flow threshold (ML/day)

1 6 10 16 60 120 320 1080

Based on data from DoW

Lefroy Brook Flow threshold exceeded (%) 20 40 60 80 100

Frequencies of daily river flow under the historical climate: fhist

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Ecological significance Maintain pool habitat in summer Minimum flow to maintain pool quality Upstream migration of small native fish Summer habitat for invertebrates Winter habitat for invertebrates Inundate trailing vegetation Inundate low elevation benches Inundate high elevation benches Ecological function flow threshold (ML/day)

1 6 10 16 60 120 320 1080

Change in the frequencies of daily river flow under future climate scenarios: (fhist - fscenario

)

Recent climate Wet extreme future climate Median future climate Dry extreme future climate

• 16
• 12
• 8
• 4

4 Difference (%) Lefroy Brook

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Ecological significance Maintain pool habitat in summer Minimum flow to maintain pool quality Upstream migration of small native fish Summer habitat for invertebrates Winter habitat for invertebrates Inundate trailing vegetation Inundate low elevation benches Inundate high elevation benches Ecological function flow threshold (ML/day)

1 6 10 16 60 120 320 1080

Relative frequency difference under dry extreme future climate (relative to historical climate): (fhist - fscenario )/fhist

• 100
• 80
• 60
• 40
• 20

Relative difference Lefroy Brook

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

• 2. Variation in runoff during high runoff and low

runoff periods under future climate

• More than 80% percent of annual runoff is generated during the high runoff period
• Runoff during this period decreases under future climates relative to historical data

Lefroy Brook

Runoff decrease for all rivers 5–20% 20–30% 40–50%

High runoff period Low runoff period

Historical climate Recent climate Wet extreme future climate Median future climate Dry extreme future climate 10 20 30 40 50 60 70 Streamflow (GL/y)

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Change in runoff under the median future climate

(relative to historical climate)

• Climate impacts on runoff are greater in southern (Kent and Denmark) and northern

rivers (Gingin)

• There is a slightly greater percentage decrease in summer runoff compared

to winter

• 70
• 60
• 50
• 40
• 30
• 20
• 10

Denmark Kent 5 Kent 4 Kent 3 Kent 2 Kent 1 Lake Muir Shannon Deep Lefroy Warren Donnelly Chapman 2 Chapman 1 Margaret 4 Cowaramup Wilyabrup 2 Wilyabrup 1 Margaret 3 Margaret 2 Margaret 1 Thomson Ferguson Preston Collie Brunswick 2 Brunswick 1 Bancell Harvey Serpentine Canning Gingin 2 Gingin 1 Change in flow (%) High runoff period Low runoff period

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

• 3. Change in “no-flow” days

Perennial rivers

No-Flow days Change in number of no-flow days

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Areas of potential GDEs

• Only regional risk assessments

were undertaken

• The analyses were carried out

where groundwater models were available and where potential GDEs may occur (coloured areas)

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

GDEs ecological risk assessment

*Depth to watertable

(Froend and Loomes, 2004)

0.2 0.4 0.6 0.2 0.4 0.6 1 2 3 Rate of decline (m/y) 1 2 3 Magnitude of groundwater decline (m) Severe risk High risk Moderate risk Low risk Wetland Vegetation (0–3 m*) Vegetation (3–6 m*) Vegetation (6–10 m*) 0.4 0.6 1 1 2 3 0.2 0.8

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Risks to GDEs in the Peel Harvey area under a median future climate (in addition to current conditions)

The risk to some wetlands is moderate but other categories are low to nil

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Risks to GDEs in the Southern Perth Basin under a median future climate (in addition to current conditions)

The risk to GDEs from a median future climate is mainly low or non existent

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Key findings

• For surface water dependent ecosystems
• Runoff during both the wet and dry seasons is expected to

decrease by 20 to 30 percent under a median future climate

• The impact of a drier climate is greater for low frequency-

high flow events, but ecosystems are less sensitive to such conditions

• For groundwater dependent ecosystems
• About 40% of potential GDEs may be affected to some

degree under a median future climate

• There are some localised high risk areas under the dry

future climate and development scenarios

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Water use in the project area

• Total use is about 1200 GL/y of which 71% is self

supplied (on-site bores and farm dams) and three quarters is groundwater

• About 35% is used for irrigated agriculture – elsewhere in

Australia it is 66 to 75%

• There is relatively little ‘low value’ agricultural water use

compared with elsewhere in Australia

• Can be competition for water between water sectors –

residential, industry, mining and agriculture

• The fact that so little agricultural water is in schemes,

most is groundwater and it is used on high value crops, makes transfers and trading less feasible

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Water demand was assumed to grow because of:

• population growth;
• economic growth; and
• industry growth – some industries have high water use coefficients

1.0 1.5 2.0 2.5 3.0 3.5 2006 2010 2014 2018 2022 2026 2030 High growth Medium growth Low growth Population (Million) Year

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Yield and demand areas

• 21 surface water

management areas

• 23 groundwater areas
• 8 demand regions

Perth Demand Region

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Surface water use is highest in central catchments and these will grow in future

Current use = 299 GL/y Growth in demand

Metro basins are fully used and growth in demand was assumed to be zero

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Current surface water yields

Total yield Yield per unit area

Total yield = 425 GL/y

• Public Water Supply 24%
• Irrigation schemes 27%
• Self supply 49%
• Harvey and Collie

contribute 43% of total yield

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Surface water yields are projected to change by -24% under a median future climate. Range of -4 to -49%

IWSS yields reduced by 18% to 77 GL/y under a median future climate

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Gaps in surface water yields and demands in areas where irrigation is important

Deficit Surplus

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Current groundwater yields as estimated by adding the 2009 Allocation Limits

Total yield Yield per unit area Total yield = 1556 GL/y

(3.6 x surface water yield)

Main aquifers:

• Superficial 58%
• Leederville 12%
• Yarragadee 26%

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Groundwater use and future demand is highest near Perth and Bunbury

Current use = 808 GL/y

(2.2 x surface water)

Perth – Peel area Bunbury

Additional

Growth in demand

Current groundwater use

Current Allocation Limits

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Future groundwater yield method

• Almost all groundwater areas are proclaimed and

have an annual allocation limit set under an allocation plan

• This limit was assumed to be the best estimate of the

aquifer’s current yield

• The limit was assumed to be related to the historical

climate (Scenario A) and 2008 aquifer storage volumes (groundwater levels)

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Groundwater yields are projected to change by -2% under a median future climate. Range = +2 to -7%

Yield reductions are low because

• 1. Drain and ET losses reduce as watertables fall
• 2. Areas under dryland agriculture (56% of Perth Basin) have rising levels
• 3. Allocation Limits account for a future drier climate

Recent climate Median future climate Dry future climate

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Groundwater deficits may develop near Perth, Collie and Albany

Recent climate 2030 gap Median future climate 2030 gap Dry future climate 2030 gap

Surplus Deficit

50 100 150 200 250 Current yield A B Cw et Cmid Cdry Available SW/GW yield (GL/y) Yarragadee Mirrabooka Leederville Superficial Fractured rock Other aquifer SW self-supply SW dams 50 100 150 200 250 2005 2010 2015 2020 2025 2030 2035 Total demand v Total available yield (GL/y) 2030 Low demand 2030 Scenario B 2030 Medium demand 2030 Scenario Cwet 2030 High demand 2030 Scenario Cmid 2030 Scenario A 2030 Scenario Cdry

Yields and demands in the Harvey to Preston surface water region

50 100 150 200 250 300 350 400 Current yield A B Cw et Cmid Cdry Available SW/GW yield (GL/y) Yarragadee Mirrabooka Leederville Superficial Fractured rock Other aquifer SW self-supply SW dams 50 100 150 200 250 300 350 400 2005 2010 2015 2020 2025 2030 2035 Total demand v Total available yield (GL/y) 2030 Low demand 2030 Scenario B 2030 Medium demand 2030 Scenario Cwet 2030 High demand 2030 Scenario Cmid 2030 Scenario A 2030 Scenario Cdry

Yields and demands in the Preston Demand Region

20 40 60 80 100 120 140 160 180 200 2005 2010 2015 2020 2025 2030 2035 Total demand v Total available yield (GL/y) 2030 Low demand 2030 Scenario B 2030 Medium demand 2030 Scenario Cwet 2030 High demand 2030 Scenario Cmid 2030 Scenario A 2030 Scenario Cdry 20 40 60 80 100 120 140 160 180 200 Current yield A B Cw et Cmid Cdry Available SW/GW yield (GL/y) Yarragadee Mirrabooka Leederville Superficial Fractured rock Other aquifer SW self-supply SW dams

Yields and demands in the Southern Perth Basin

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

500 1000 1500 2000 2500 C u r r e n t y i e l d H i s t

• r

i c a l R e c e n t W e t e x t r e m e M e d i a n D r y e x t r e m e Available SW/GW yield (GL/y) 500 1000 1500 2000 2500 2005 2010 2015 2020 2025 2030 2035 2030 Low demand Recent 2030 Medium demand Wet extreme 2030 High demand Median Historical Dry extreme Total demand v Total available yield (GL/y) Yarragadee Mirrabooka Leederville Superficial Other aquifer Self-supply dams Scheme dams Fractured rock

The project area can meet all except high demands until 2030 under a median future climate

• A 250 GL/y deficit may develop under a dry extreme climate and

high demand

250 GL

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Key findings

• 1. South-west Western Australia has experienced a

significant climate shift since 1975 which is thought to be mainly climate change. Climate models project that rainfall could decline further by about 7% by 2030 (up to 14%)

• 2. Surface water yields are projected to decrease by

about 24% (up to 49%)

• The yields have already decreased in northern catchments

and may decrease further by 2030

• Central catchments are higher yielding and the decrease

could be less

• Streamflows are projected to decrease the most in the

Southern catchments

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Key Findings (cont.)

• 3. Groundwater levels are projected to fall most under

areas of perennial vegetation, e.g. Gnangara, Blackwood Plateau, Collie and Albany. Levels are least affected in areas with high watertables such as coastal areas under dryland agriculture, e.g. Swan and Scott Coastal Plains; Dandaragan Plateau As watertables fall, drainage and evaporation from GDEs fall and allows more recharge to enter

• 4. Water dependent ecosystems have already been

impacted and these impacts are projected to worsen, especially for high streamflows and GDEs with a watertable depth of 6 to 10m

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Key Findings (cont.)

• 5. Water deficits between yields and demands are

likely in:

• Surface water irrigation catchments
• Aquifers near Perth, Collie and Albany
• 6. Overall there is enough water to meet all except

high demands under a median future climate. However if there is a dry extreme climate and a high demand the deficit may be as much as 250 GL/y

CSIRO South-West Western Australia Sustainable Yields Project – Bunbury

Contributors

Project Director Tom Hatton Sustainable Yields Coord. Mac Kirby Project Leader Don McFarlane Project Support Frances Parsons, Therese McGillion, Paul Jupp, Josie Grayson Data Management Geoff Hodgson, Jeannette Crute, Christina Gabrovsek, Mick Hartcher, Malcolm Hodgen DOW – Aidan Belouardi DAFWA – Damien Shepherd, Dennis van Gool, Noel Schoknecht Climate Stephen Charles, Francis Chiew, Randall Donohue, Guobin Fu, Ling Tao Li, Steve Marvanek, Tim McVicar, Ian Smith, Tom Van Niel NSW Dept of Water and Energy – Jin Teng Surface Water Richard Silberstein, Santosh Aryal, Neil Viney, Ang Yang DOW – Mark Pearcey, Jacqui Durrant, Michael Braccia, Kathryn Smith, Lidia Boniecka, Simone McCallum BOM – Mohammad Bari Geographic Information Analysis – Geoff Mauger Groundwater Riasat Ali, Warrick Dawes, Sunil Varma, Irina Emelyanova, Jeff Turner, Glen Walker, John Byrne, Phil Davies, Steve Gorelick, Mahtab Ali DOW – Chris O’Boy, Binh Anson, Phillip Commander, Cahit Yesertener, Jayath de Silva, Jasmine Rutherford Water Corporation – Mike Canci, Chengchao Xu Cymod Systems – Neil Milligan URS Australia – Wen Yu, Andrew Brooker, Amandine Bou, Andrew McTaggart Water Yields and Demands Olga Barron, Natalie Smart, Michael Donn DOW – Roy Stone, Phillip Kalaitzis, Rob Donohue, Fiona Lynn, Adrian Goodreid, Andrew Paton, Susan Worley, Kylie La Spina Resource Economics Unit – Jonathan Thomas Jim Davies and Associates – Sasha Martens, Kate Smith Reporting Viv Baker, Becky Schmidt, Susan Cuddy, Simon Gallant, Heinz Buettikofer, Elissa Churchward, Chris Maguire, Linda Merrin Communications Anne McKenzie, Helen Beringen, Mary Mulcahy

Questions?