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 – Overview

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 – Overview

Broad terms of reference

• Estimate the current and 2030 yield of water for

catchments and aquifers in 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 – Overview

Publications

Main reports Executive summaries Factsheets Web:

www.csiro.au/partnerships/SWSY.html

CSIRO South-West Western Australia Sustainable Yields Project – Overview

Project context

• The project does not attempt to 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 – Overview

Sustainable Yields Projects – 2007 to 2009

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

CSIRO South-West Western Australia Sustainable Yields Project – Overview

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 – Overview

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 – Overview

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 – Overview

Climate – annual averages, 1975 to 2007

Potential evapotranspiration Rainfall - APET

CSIRO South-West Western Australia Sustainable Yields Project – Overview

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 – Overview

Scenarios

• The ‘historical climate’ 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’ assumed that the climate of the last 11 years

(1997 to 2007) would continue

• The ‘future climate’ 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 future climate
• median future climate, and
• dry future climate
• Current levels of abstraction and land use were assumed to continue

for all scenarios above

• The ‘future climate and development’ assumed a median future climate

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

CSIRO South-West Western Australia Sustainable Yields Project – Overview

Annual rainfall and inflow into Perth dams

Runoff is affected by climate and other factors

Yearly rainfall at Jarrahdale

500 1000 1500 2000 2500 1911 1914 1917 1920 1923 1926 1929 1932 1935 1938 1941 1944 1947 1950 1953 1956 1959 1962 1965 1968 1971 1974 1977 1980 1983 1986 1989 1992 1995 1998 2001 2004 2007

Annual Rainfall at Jarrahdale (mm)

Annual Total 1911 to 1974 (1251mm) 1975 to 2009 (1047mm) 1997 to 2009 (1003mm)

Yearly streamflow for major surface water sources - IWSS

100 200 300 400 500 600 700 800 900 1000 1911 1914 1917 1920 1923 1926 1929 1932 1935 1938 1941 1944 1947 1950 1953 1956 1959 1962 1965 1968 1971 1974 1977 1980 1983 1986 1989 1992 1995 1998 2001 2004 2007

Annual Inflow to Perth Dams (GL)

Annual Total 1911 to 1974 (338GL) 1975 to 2009 (151GL) 1997 to 2009 (107GL)

Note: A year is taken as May to April (Data courtesy of the Water Corporation)

16% reduction 55% reduction

Historical Recent

CSIRO South-West Western Australia Sustainable Yields Project – Overview

Annual rainfalls have been even drier since 1997

1997 to 2007 rainfall compared with 1975 to 1996 rainfall

CSIRO South-West Western Australia Sustainable Yields Project – Overview

14 of 15 GCMs project it will get drier

Mid warming Low warming High warming

• Median future climate
• 7%
• 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 – Overview

Subsequent talks

• Surface water

Richie Silberstein

• Groundwater

Riasat Ali

• Environment

Olga Barron

• Water yields and demands

Don McFarlane Short period for questions after each talk

• Meet the Team – informal session over afternoon tea

Rainfall and runoff in south-west Western Australia

Richard Silberstein Surface Water Team Leader

CSIRO South-West Western Australia Sustainable Yields Project – Surface Water

Objectives – Surface Water

• Project future quantity, duration and seasonal

distribution of runoff (mm) and streamflow (ML) for conditions in 2030

• under specified climate scenarios, and
• with future plantations and farm dams
• These results were used in estimating divertible

yields and impacts on ecosystems

CSIRO South-West Western Australia Sustainable Yields Project – Surface Water

Geographic scope

• 13 surface water

basins covering 39,000 km2

CSIRO South-West Western Australia Sustainable Yields Project – Surface Water

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 – Surface Water

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 – Surface Water

106 Calibration catchments

Criteria for use in calibration:

• Catchments larger than 10 km2
• At least 10 years of available

streamflow data between 1975 and 2007 (average record length 27 years)

CSIRO South-West Western Australia Sustainable Yields Project – Surface Water

100 200 300 400 500

Modelled annual runoff (mm)

NSE = 0.82

Calibration results – examples

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 – Surface Water

Calibration results

• In about half of catchments, runoff coefficients have reduced over the recent

past (1995 to 2007) – i.e. the same amount of rainfall produces less runoff

• Our rainfall-runoff models are over predicting runoff during the recent period

Annual runoff vs rainfall Model – observed runoff

150 300 450 600 600 800 1000 1200 1400 1600 Rainfall (mm) Runoff (mm) 1975-1994 1995-2007 Bancell Brook – Waterous

• 100
• 50

50 100 1970 1980 1990 2000 2010 Modelled – observed (mm) Bancell Brook – Waterous Year

CSIRO South-West Western Australia Sustainable Yields Project – Surface Water

Rainfall, runoff and runoff coefficient under historical climate

CSIRO South-West Western Australia Sustainable Yields Project – Surface Water

• 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

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

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 – Surface Water

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 – Surface Water

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 – Surface Water

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 – Surface Water

Percent decline in runoff in all basins

• Decline under recent climate is greatest from 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 – Surface Water

Key Findings – Surface water

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

• Rainfall declines by an average of 8% and runoff by 25%
• Mean annual runoff declines by 24 mm and streamflow

declines by 800 GL in addition to the decline 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

• Climate impact on projected streamflows is much greater

than that of projected increase in plantations and farm dams after 2007

CSIRO South-West Western Australia Sustainable Yields Project – Surface Water

Questions?

Groundwater in south-west Western Australia

Riasat Ali Groundwater Team Leader

CSIRO South-West Western Australia Sustainable Yields Project – Groundwater

Landforms

Geomorphic landforms affect groundwater response to climate change

CSIRO South-West Western Australia Sustainable Yields Project – Groundwater

Groundwater areas

• 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 – Groundwater

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 – Groundwater

Objectives – Groundwater

• 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 – Groundwater

Recharge estimation

• The project developed an estimate of net recharge /

discharge for combinations of:

• Climate
• Soil types
• Land cover
• Depth of the watertable
• These estimates were linked to the groundwater

models

CSIRO South-West Western Australia Sustainable Yields Project – Groundwater

Climate zones

• 15 climate zones in the

groundwater assessment area

• Representative stations

in each zone were used

CSIRO South-West Western Australia Sustainable Yields Project – Groundwater

Soil types used in models likely to affect recharge

• Coastal plain soils are

sandy except Guildford which is clayey

• Plateau soils are mainly

gravelly (north) or clayey (Blackwood Plateau)

CSIRO South-West Western Australia Sustainable Yields Project – Groundwater

Land cover likely to affect recharge / discharge

Groundwater assessment areas

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

irrigated, open water

CSIRO South-West Western Australia Sustainable Yields Project – Groundwater

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 – Groundwater

Current abstraction by groundwater areas

Most groundwater abstraction currently occurs close to Perth because of high demand and water availability

CSIRO South-West Western Australia Sustainable Yields Project – Groundwater

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

CSIRO South-West Western Australia Sustainable Yields Project – Groundwater

The additional impact on 2030 groundwater levels of allowing full abstraction under a median future climate

• There are a few areas

where additional abstraction will cause a decline in levels

• This may not be a problem

where groundwater levels are projected to rise

• There are many areas

already fully allocated

CSIRO South-West Western Australia Sustainable Yields Project – Groundwater

Collie groundwater basin level changes between 2008 and 2030

Groundwater levels are less affected near rivers

CSIRO South-West Western Australia Sustainable Yields Project – Groundwater

Northern Perth Basin bore hydrographs

Slight fall in groundwater levels under native vegetation Rising levels under dryland agriculture since 1978

GS1B

• 25
• 20
• 15
• 10

1995 2000 2005 2010 2015 2020 2025 2030 OB1-75

• 60
• 55
• 50
• 45
• 40

1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 2025 2030 Historical climate Recent climate Median future climate Observed level Fitted 1975-2007 Range between wet and dry extreme future climate

• 30

Groundwater level (m) Groundwater level (m)

CSIRO South-West Western Australia Sustainable Yields Project – Groundwater

Albany Area bore hydrographs

Groundwater levels are projected to decline under all future climates

CST-99-78

• 45
• 40
• 35
• 30

1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 2025 2030 CST-W78

• 15
• 10
• 5

1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 2025 2030 Groundwater level (m) Groundwater level (m) Observed level Fitted 1975-2007 Historical climate Recent climate Median future climate Range between wet and dry extreme future climate

CSIRO South-West Western Australia Sustainable Yields Project – Groundwater

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 – Groundwater

Key findings – Groundwater

• 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 less sensitive to climate change except under the dry future 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 – Groundwater

Key findings – Groundwater (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

• Groundwater models are needed to estimate the

impact of climate change and development for the Northern Perth Basin and Albany Area to extend the results of this project

• 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 – Groundwater

Questions?

Water Dependent Ecosystems

Olga Barron Environment Team Leader

CSIRO South-West Western Australia Sustainable Yields Project – Water Dependent Ecosystems

Objective

• Assess the impact of climate change on hydrologic

regimes likely to affect water dependent ecosystems This was applied to:

• Surface water dependent ecosystems (SDEs)
• 33 rivers
• Groundwater dependent ecosystems (GDEs)
• Four types of ecosystems assessed –

wetlands and vegetation with various depths to the watertable

• Only future risks were assessed

CSIRO South-West Western Australia Sustainable Yields Project – Water Dependent Ecosystems

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 – Water Dependent Ecosystems

Surface Water Ecosystems

CSIRO South-West Western Australia Sustainable Yields Project – Water Dependent Ecosystems

Assessing the effects on ecologically significant surface water flows

• 1. Rivers where Ecological

Water Requirements were available (9 rivers shown in blue)

• 2. Rivers where Ecological

Water Requirements were not available (shown in red)

• 3. Duration of “no-flow”

periods under future climate scenarios

CSIRO South-West Western Australia Sustainable Yields Project – Water Dependent Ecosystems

• 1. Frequencies of daily river flow under the historical

climate: fhist

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

CSIRO South-West Western Australia Sustainable Yields Project – Water Dependent Ecosystems

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 – Water Dependent Ecosystems

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 – Water Dependent Ecosystems

• 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 – Water Dependent Ecosystems

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 – Water Dependent Ecosystems

• 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 – Water Dependent Ecosystems

Groundwater Dependent Ecosystems

CSIRO South-West Western Australia Sustainable Yields Project – Water Dependent Ecosystems

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 – Water Dependent Ecosystems

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 – Water Dependent Ecosystems

Risks to GDEs in the Central Perth Basin under a Median Future climate (in addition to current conditions)

CSIRO South-West Western Australia Sustainable Yields Project – Water Dependent Ecosystems

Projected risk to wetlands

Historical climate Median future climate Dry extreme future climate Full abstraction under a median future climate

CSIRO South-West Western Australia Sustainable Yields Project – Water Dependent Ecosystems

High and severe ecological risk to GDEs in the southern half of the Perth Basin

• Dry future climate scenario results in significant increase in risk to GDEs
• There appears to be a threshold between median and dry future climates

10 20 30 40 Percent area greater than high risk Central Perth Basin Peel Harvey Area Southern Perth Basin 10 20 30 40 Historical climate Recent climate Wet extreme future climate Median future climate Dry extreme future climate Future climate and future development Historical climate Recent climate Wet extreme future climate Median future climate Dry extreme future climate Future climate and future development

Wetland Vegetation (0–3 m) Vegetation (3–6 m) Vegetation (6–10 m)

CSIRO South-West Western Australia Sustainable Yields Project – Water Dependent Ecosystems

Key findings – water dependent ecosystems

• 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 – Water Dependent Ecosystems

Questions?

Water yields and demands

Don McFarlane Project Leader

CSIRO South-West Western Australia Sustainable Yields Project – Water Yields and Demands

Some terminology clarification

• Runoff = amount of surface water expressed as a depth (mm)
• Streamflow = amount of surface water expressed as a volume (runoff

x area)

• Surface water yield = streamflow that can be diverted for use. Takes

account of water for the environment and the location of nature reserves, national parks, irrigable land etc.

• Use = water that is currently being used (metered, estimated)
• Yield = the amount of surface water and groundwater that is available

for use – either under license and as unlicensed ‘stock and domestic’

• Demand – as estimate of the future requirement for water as a result
• f economic, demographic and industrial growth. Unmet demand may

result in higher water prices, reuse, water conservation, trading, desalination, etc. as well as a curtailment in growth

CSIRO South-West Western Australia Sustainable Yields Project – Water Yields and Demands

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%

• Can be competition for water between water sectors –

residential, industry, mining and agriculture

• Most irrigation water in south-west is used for high value

products

• This, in addition to it being self supply and mostly

groundwater, makes transfers and trading less feasible

CSIRO South-West Western Australia Sustainable Yields Project – Water Yields and Demands

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 – Water Yields and Demands

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 – Water Yields and Demands

Surface water use is highest in central catchments and demand 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 – Water Yields and Demands

Current surface water yields

Volumetric yield Yield per unit area Total yield = 425 GL/y Licensed allocations

• 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 – Water Yields and Demands

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 – Water Yields and Demands

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

Deficit Surplus

CSIRO South-West Western Australia Sustainable Yields Project – Water Yields and Demands

Current groundwater yields as estimated by adding the 2009 Allocation Limits

Volumetric 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 – Water Yields and Demands

Groundwater use and future demand is highest near Perth and Bunbury

Current use = 808 GL/y

(2.2 x surface water use)

Perth – Peel area Bunbury

Additional

Growth in demand

CSIRO South-West Western Australia Sustainable Yields Project – Water Yields and Demands

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 and 2008 aquifer storage volumes (groundwater levels)

CSIRO South-West Western Australia Sustainable Yields Project – Water Yields and Demands

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 – Water Yields and Demands

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

CSIRO South-West Western Australia Sustainable Yields Project – Water Yields and Demands

Current yield Historical Recent Wet extreme Median Dry extreme Available SW/GW yield (GL/y) 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 400 500 600 700 800 100 200 300 400 500 600 700

Combined yield and demand for the Perth Demand Region

Potential gap under median future climate and medium demand within 15 years

Median demand = median future climate yield

CSIRO South-West Western Australia Sustainable Yields Project – Water Yields and Demands

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 future climate and high demand

250 GL

CSIRO South-West Western Australia Sustainable Yields Project – Water Yields and Demands

Key findings

• 1. South-west Western Australia has experienced a

significant climate shift since 1975 which is thought to include a component of 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 – Water Yields and Demands

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 decrease and this slows the rate of fall

• 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 10 m

CSIRO South-West Western Australia Sustainable Yields Project – Water Yields and Demands

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 – Overview

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

CSIRO South-West Western Australia Sustainable Yields Project – Water Yields and Demands

Questions?