the future for water availability in south-west …• we are relatively isolated from other...

The future for water availability in South-west Western Australia in a drying climate

Don McFarlaneProject Leader

CSIRO South-West Western Australia Sustainable Yields Project

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

This talk will cover the main findings but concentrate on water for irrigated agriculture especially


Sustainable Yields Projects – 2007 to 2009

Murray-Darling BasinNorthern AustraliaSouth-West Western AustraliaTasmania

Presenter

Presentation Notes

This is the one of four Sustainable Yield projects carried out by CSIRO around Australia. The Murray Darling Basin project was completed in 2008, the Northern Australia project was launched at the River Symposium in 2009, and the Tasmanian and SWWA projects in early 2010. By using a consistent methodology we are now able for the first time to say what impacts climate change and development may have on water resources for all of the main water regions of Australia. The rest of this talk will focus on the blue area shown on the map.


South-West WA Sustainable Yields – Publications

Main reports Executive summaries

FactsheetsWeb: www.csiro.au/partnerships/SWSY.html

Presenter

Presentation Notes

The results are contained in three main reports of 170 to 330 pages in length – one on surface water; one on groundwater and one on water yields and demands. There are also three executive summary reports of 12 to 16 pages in length. The third one of these contains results from all there areas Finally there are four 4-page Factsheets with the Key Findings summarised for each area of work.


The ‘south-west’ as defined in this talk

• 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

• Combined area = 62,500 km2

Presenter

Presentation Notes

The project area includes all of the fresh, marginal and brackish water resources in SWWA The surface water basins are shown in blue and extend from Gingin Brook to the Denmark and Hay catchments. The saline Avon, Murray, Blackwood and Frankland Rivers were not modelled The groundwater resources are shown in red and include the Perth Basin west of the Darling Fault, the Collie Basin and the western part of the Bremer Basin near Albany.

CSIRO South-West Western Australia Sustainable Yields ProjectCSIRO 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

Presenter

Presentation Notes

The yellow line shows the project boundary. The blue (cooler) colours are areas with a low elevation and the hotter colours are high. Only short streams that arise in the Darling Ranges are fresh and were modelled. Not all of the Perth Basin has a low elevation. The Swan Coastal Plain is very low and flat as a result of ocean inundation in the Pleistocene but the northern plateaux, and to a lesser extent the Blackwood Plateau, are moderately elevated.


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

Presenter

Presentation Notes

Surface water catchments are mainly forested whereas most of the Swan Coastal Plain has been cleared. Areas on the Perth Basin that remain under perennial vegetation are the coastal strip north of Jurien Bay, the Gnangara Mound and the Blackwood Plateau. The Collie and Albany groundwater areas are also mainly vegetated.


Landforms

Geomorphic landforms affect groundwater response to climate change

Presenter

Presentation Notes

This map shows important features of the Perth Basin which lies to the west of the Darling Scarp and considered for groundwater modelling and assessment. As was shown earlier, the blue Swan Coastal Plain is flat, sandy and a large part of it has been cleared for dryland agriculture. The orange area is the Gnangara Mound which has Banksia Woodland and pine plantations as important land uses, and there are high levels of abstraction from this area. The northern plateaux of Dandaragan, Arrowsmith and Yarra Yarra are elevated and contain soils which are gravelly and less sandy than the coastal plain. The Blackwood Plateau is slightly elevated and contains more clayey soils. The Scott Coastal Plain is sandy, flat and waterlogged. Some of it has been cleared, especially in the west.


Features of south-west WA

• We are relatively isolated from other irrigation areas • South Australia – lower Murray and Lower SE ca. 3000 road kms• Carnarvon mainly groundwater – sub-tropical crops – 900 km• Ord – sub-tropical crops – 3200 km

• Has experienced a drier, hotter climate in the last 35 years which has impacted on surface and groundwater yields

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Features of south-west WA (cont.)

• Is experiencing some of the fastest growth in the economy and population in Australia, and in its own short history

• Aspects of water use and irrigation are different in south-west WA so we need to find our own solutions in some cases

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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

Presenter

Presentation Notes

First some interesting facts about current water use in the project area

Current agricultural irrigation water use

Presenter

Presentation Notes

About 35,000 ha of agricultural land is irrigated in the project area each year using about 443 GL. This does not include irrigation of public and private open space (eg urban lawns and ovals). The relative size of irrigation water used on three agricultural industries – pastures in green, perennial crops in brown and vegetables in red – are shown for 8 demand regions that cover the south west Two regions use more than 100 GL per year – Moore which is a groundwater-based area and Preston where there is surface water from the Harvey, Collie, Waroona and Preston schemes, and groundwater from Myalup. Groundwater is also the water source in Perth peri-urban areas and in Greenough. The Blackwood and King use surface water on-farm dams while Vasse is a mixture of both sources. Pastures are the main use of water in the Preston area (dairy, beef) while vegetables are the main water users in Manjimup and Perth. Perennial fruit crops including olives and paulownia trees are the main water users in the Moore and Greenough demand regions. Vasse has a mixture of vegetables (eg potatoes at Jindong), dairy pastures, lucerne and vineyards.


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

Presenter

Presentation Notes

Current surface water use is shown on the left hand map with areas of high use in the hotter colours. The units are ML per square kilometre per year, or mm – as has been used in previous maps to take account of the different sizes in the areas shown. Interestingly, the highest use per unit of catchment area is in the central basins around Dandalup, Harvey and Collie. Growth in demand for surface water is shown in the other two maps. Under both the medium and high growth in demand scenarios, the estimated demand pressures are highest in the central basins as well as the Warren. These are all horticultural areas and the growth in demand estimates result from assumed increases in demand for surface water to help meet the demands for horticultural products by a growing population and economy.


Current abstraction by groundwater areas

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

Presenter

Presentation Notes

These maps show where groundwater is currently being abstracted from groundwater areas. The hot colours are areas of high abstraction. The units are ML per square kilometre per year or mm (the same as rainfall is measured) The very high levels of abstraction around Perth – over 100 and up to 500 mm per annum, reflects the presence of very high yielding aquifers – the Superficial, Leederville and Yarragadee especially - and the high demand for water for public and private users. Currently abstraction is modest away from Perth – often 50 mm or less per year


Scenarios

• The ‘historical climate’ assumed that the climate of the last 33 years (1975 to 2007) would continue until 2030. Used as a base case

• The ‘recent climate’ assumed that the climate of the last 11 years (1997 to 2007) would continue until 2030

• The ‘future climate’ used 15 GCMs with 3 greenhouse gas 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


Some terminology clarification

• Runoff = amount of surface water flow expressed as a depth (mm)

• Streamflow = amount of surface water flow 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 of economic, demographic and industry growth. Unmet demand may result in higher water prices, reuse, water conservation, trading, desalination, etc. as well as the curtailment of growth

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

Rainfall, runoff and runoff coefficient under historical climate

Presenter

Presentation Notes

Under the Historical Climate: The highest rainfall is in the southern basins and along Darling Scarp The highest runoff is in in Harvey Basin and some basins in south west and south Note that the higher rainfalls along the northern parts of the Darling Scarp do not produce high runoff as in the southern basin. The highest runoff coefficients are in the Harvey Basin and some areas around Margaret River. Northern and inland areas have low runoff coefficients due to their lower rainfalls and high evaporative demands


14 of 15 GCMs predict it will get drier

Mid warming

Low warmingHigh warming

• Median future climate -7%

• Wet extreme future -1% climate (90 percentile)

• Dry extreme future -14% climate (10 percentile)

Change in annual rainfall

Presenter

Presentation Notes

This graph shows what 15 global climate models project for 2030 rainfall in the project area. The models are ranked on the vertical axis and the estimated change in annual rainfall is shown on the lower axis. Three global warming scenario are also shown – high warming or 1.3o C which would be expected if GHG emissions are high, mid warming or 1.0o C which equates to median emissions and low warming or 0.7o C which assumes that GHG emissions will be lower. Almost all models projects a drier climate with the median being a reduction of about 7% compared with the Historical Climate and with a range of 1 to 14 percent reduction. It must be remembered that the baseline already includes a reduction in rainfall and this projection is in addition to that which has been recorded since 1975. For comparison the median projected reductions in the Murray Darling Basin and Tasmania are about 3 percent with no net reduction being estimated for northern Australia.


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

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Runoff change across all basins

Presenter

Presentation Notes

We are now presenting scenario modelling results This plot shows projections of change in runoff for 2030 rainfall for 15 global climate models. The vertical axis shows the names of the climate models. The models are ranked on the vertical axis in order of magnitude of change and the estimated change in annual runoff is shown on the horizontal axis. The leftmost end of the orange bar shows the percent change in runoff due to the high warming climate scenario. The right end of the green bar shows the same for the low warming scenario. The middle point, where the orange and green bars join, shows the change in runoff due to mid warming climate scenario. All models project less runoff with the median being a reduction of about 25% below that under the Historical Climate and with a range of 5 to 49 percent reduction. The symbols on the plot show runoff change for the wet and dry extremes and median future climates given by 10th, 90th and 50th percentile runoff.


Projected change in runoff relative to the historical climate

• Major decline in north and central region under recent climate • Major impact in high rainfall areas under median and dry future climate

Presenter

Presentation Notes

The four maps show that as the climate dries up the runoff is also decreased. Interesting to note that areas in Darling Scarp and Southern basins are affected more (in absolute terms) than inland areas. These changes may not show same pattern for the percentage change. Under the Median Future Climate, rainfall is projected to decline by an average of 8% and runoff by 25%


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 Basins contribute 43% of the total yield

Presenter

Presentation Notes

These maps show surface water yields – or the amount of water than can be safely diverted for use – in two ways The left map shows yields in volumes per year from each of the 13 basins while the right map show them in ML per square kilometer per year (or mm per year) The highest yielding basins are in the centre with those to the north and south with low yields, either because there is little streamflow (north) or because the streamflow may be within areas that contain nature reserves or national parks (south) as well as having lower streamflows per area. The total yield of all basins is about 425 GL/yr with about 43% of this coming from the central Harvey and Collie Basins. Currently surface water is used by self-supply irrigators with dams on streams within their property (about half), and by irrigation schemes (mainly Harvey Water) and public water supply dams which each use about a quarter.


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

Presenter

Presentation Notes

These three maps show the projected percentage change in surface water yields under three climate scenarios – a continuation of the Recent Climate, the Median Future Climate and the Dry Extreme Future Climate Under the Median Future Climate, surface water yields are estimated to decrease by about 24% compared with the Historical Climate with the range being between 4% (under the Wet Extreme Future Climate) and 49% decrease (under the Dry Extreme Future Climate). The projected future reductions in yields are not uniform across all basins. Interestingly the high yielding Harvey and Collie Basins also appear to have lower reductions compared with basins to both the north and south. The Gingin, Donnelly, Warren and Denmark catchments appear to be most affected. The estimated reduction in 2030 yield to the metropolitan dam catchments which supply water to the Integrated Water Supply Scheme is 18% or 77 GL/y. These estimates are very similar to those in Water Corporation’s Water Forever plan


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

Presenter

Presentation Notes

Having estimated future demands and yields it is possible to map gaps between them. A positive gap represents a surplus of water – shown here in cool colours, and a negative gap is a potential deficit of water – shown here in hot colours. Under the Median and Dry Extreme Future Climates, surface water deficits are evident in the Harvey and Dandalup Basins. Deficits are apparent wherever horticultural demand is expected to grow by 2030 and yields are projected to decline.


Yield and demand gap in the Harvey, Collie and Preston surface water basins

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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

Presenter

Presentation Notes

Four groundwater models were used to estimate groundwater levels in 2030 under climate and development scenarios; Perth Regional Aquifer Modelling System or PRAMS as used in the Gnangara Sustainability Strategy but over the whole domain and with more climate scenarios A new model was developed by URS under guidance from CSIRO and DoW for the area between Mandurah and Bunbury – PHRAMS The South West Aquifer Modelling System (or SWAMS) was updated and upgraded by linking a vertical flux model to the groundwater system Likewise the Collie groundwater model was updated and upgraded. Neil Milligan from Cymod Systems helped re-calibrate the SWAMS and Collie models.


Land cover likely to affect recharge / discharge

Groundwater assessment areas

• 56% dryland agriculture

• 38% native vegetation

• 6% plantations, urban, irrigated, open water

Presenter

Presentation Notes

This map shows the main landuses over the whole project area Perennial vegetation is shown in green and cleared dryland agricultural land in bronze. The areas of pines on the Gnangara Mound, Myalup and Donnybrook Sunkland areas are shown in purple. For the Perth Basin, dryland agriculture occupies 56% and about 38% is under native vegetation. About 60% is cleared and 40% vegetated to some extent.


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%

Presenter

Presentation Notes

This map shows areas in the modelled domain with a shallow watertable – green is within 3m, yellow 3 to 6m and pink, 6 to 10m. Almost half of this area has the potential to contain groundwater dependent ecosystems if they are not cleared. The Swan and Scott Coastal Plains have especially shallow watertables whereas the plateau areas (Dandaragan, Blackwood) usually have deep watertables.


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

Presenter

Presentation Notes

These maps are the main groundwater findings from the project They show the change in groundwater levels between 2008 and 2030 under four climate scenarios – the historical climate (1975 to 2007), the recent climate (1997 to 2007), and the median and dry extreme future climates. If the climate of the past 33 years were to continue until 2030 groundwater levels are projected to rise under the Dandaragan Plateau, the Swan Coastal Plain near Lancelin and where the pines are removed at Gnangara and on the Swan and Scott Coastal Plains in the south. Areas under the Blackwood Plateau and the crest of the Gnangara Mound however would continue to fall. If the climate of the past 11 years were to continue until 2030 more areas would record a fall in levels but the pattern remains very similar. Under the future climate scenarios this trend continues such that under the dry extreme future climate, even removing the pines on Gnangara will not be enough to prevent groundwater levels from falling. Interestingly, groundwater levels are projected to rise under the Dandaragan Plateau even under a dry extreme future climate. This area has a relatively poorly calibrated model so this may be optimistic. However it is an area under dryland agriculture and sandy soils with modest levels of abstraction and we know that similar areas in the wheatbelt would be recording rises in groundwater levels under a annual rainfall of about 500 mm or we would not have a dryland salinity problem in the state. The Swan Coastal Plain between Perth and Bunbury changes relatively little compared with many areas. You will recall that these areas had groundwater levels within about 3 metres of the soil surface indicating that the aquifers were relatively full. It is believed that these areas are comparatively resistant to a drier climate because drainage and evaporation losses decrease as watertables fall. The lower watertables also enable more recharge to enter the aquifers. This reduction in evaporation losses will be accompanied by a loss of wetlands so there is a price to be paid for in having ‘climate resilience’. Like the Gnangara Mound, groundwater levels under the Blackwood Plateau have been falling for the last 40 or so years and this trend is projected to continue even under an historical climate. Both areas are under perennial, native vegetation and in the case of the Blackwood Plateau, the soils are clayey.


Current groundwater yields as estimated by adding the 2009 Allocation Limits

Total yield Yield per unit area

Total yield = 1556 GL/y

Main aquifers:

• Superficial 58%

• Leederville 12%

• Yarragadee 26%

Presenter

Presentation Notes

To estimate current groundwater yields we added all of the allocation limits for all aquifers in each groundwater area. The total yield of these aquifers was 1,556 GL per year with 58% contained in the Superficial Aquifer,12% in the Leederville and 26% in the Yarragadee The left map shows the yields in GL per groundwater area and the right map in ML per square kilometer per year or mm per annum. The highest yielding areas shown in blue on the right map are located around Perth and in the SW Coastal area around Preston. These areas have multiple aquifers which are high yielding – over 200 mm per annum being able to be abstracted. In comparison the aquifers in the northern and southern Perth Basins, and near Albany, are much lower yielding as defined by this method. Perth is very fortunate to have been located in a water-rich area. Its is also possible that the resources in this area of high demand have been more fully investigated and exploited and therefore they appear relatively high.


Groundwater use and future demand is highest near Perth and Bunbury

Current use = 808 GL/y (2.2 x surface water)

Perth – Peelarea

Bunbury

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Growth in demand

Presenter

Presentation Notes

The map on the left shows current groundwater use reflects the current water yield map that was just shown with high concentrations near Perth and around Bunbury and Collie. Everything ‘hotter’ than yellow has an annual use of more than 50 mm per annum. The other two maps show the expected growths in demand for groundwater under medium and high demand scenarios. Future growth in demand for groundwater is expected to be substantial near Perth and Bunbury with demand growing by 25 to 50 % of current use in these areas. This does not mean that all of this demand will be met but it does show that there may be requirements for increased efficiencies of use, other water sources may need to be developed or imported and there may be significant unmet demand.


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

Yield reductions are low because1. Drain and ET losses reduce as watertables fall 2. Areas under dryland agriculture (56% of Perth Basin) have rising levels3. Allocation Limits account for a future drier climate

Recentclimate

Median future climate

Dryfuture climate

Presenter

Presentation Notes

Using this method it was estimated that future groundwater yields would decrease by about 2% under a Median Future Climate with a range of +2% under the Wet Extreme Future Climate or a decrease of about 7% under a Dry Extreme Future Climate. Areas with the greatest decreases in yield were Gnangara, the Blackwood, Collie groundwater basin and the Albany Area All of these areas are overlain by perennial vegetation which reduces recharge compared with cleared dryland agricultural land, the areas where yields were less affected. While the average reduction in groundwater yields is relatively small, some resources have substantial projected decreases under the Dry Extreme Future Climate – e.g. by between a quarter and a half for the four areas just mentioned


Groundwater deficits may develop near Perth, Collie and Albany

Recent climate 2030 gap

Median future climate2030 gap

Dry future climate2030 gap

Presenter

Presentation Notes

This slide shows surpluses in blue and deficits in ‘hot colours’ under three scenarios – Recent Climate, Median Future Climate and Dry Extreme Future Climate The main groundwater deficits are expected to develop near Perth, Collie and Albany A limitation of the method used to estimate future water demands is that new industries are not included in the estimates of growth, e.g. a paper pulp mill or a new mine. It is therefore feasible that the apparent surplus of water in the Northern Perth Basin may be used if demands by mid-west iron ore companies eventuate. These demands can be incorporated into the method that was developed by this project if the demands are known, but they were not been included in this analysis.


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climate yield

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

Presenter

Presentation Notes

The left graph shows what may happen to surface water and groundwater yields in the Perth demand Region by 2030 for each climate scenario. Surface water scheme dams and Superficial Aquifer yields are projected to decline, especially under the Dry Extreme Future Climate. Confined aquifers such as the Leederville and Yarragadee appear more stable however. Water from the two desalination plants at Kwinana are not included in this assessment but they add an additional 50 GL/year at present. The right hand graph shows that the growth in demand for water (blue lines) is expected to be very substantial which mainly reflects the grown in residential, peri-urban agriculture, council and industrial water demands. Under the Median Future Climate and Median Demand a deficit for the region is expected by 2025. This may seem optimistic but it is important to remember that the Perth Demand Region includes provision for increased recharge after the pines are removed from Gnangara and includes water which is currently reserved for future drinking water supplies. It is expected that there will be increased competition between public and private water supplies in future. A high rate of growth in water demand and a Dry Extreme Future Climate would result in this cross-over occurring about eight years earlier

Current agricultural irrigation water use

Presenter

Presentation Notes

Summarising what may happen in each water demand region: In the Greenough Demand Region there is unallocated groundwater but also growing demand from residential and mining interests. The project did not model the groundwater resources so we are unable to make a useful comment on future potentials Moore Demand Region. The areas with rising groundwater levels on the Swan Coastal Plain and Dandaragan Plateau appear to have the potential for more irrigation assuming that dryland agriculture remains the predominant landuse. The Perth Demand Region has been shown to have very high demands from multiple users and peri-urban agriculture may continue to be displaced to outer regions both to the north and south. The Peel Demand Region has little irrigation and this is unlikely to change Surface water resources in the Preston Demand Region are the highest yielding and appear to be slightly less impacted by a drier climate than areas to the north and south. The reason for the high yields in unknown. Increased demand for irrigation products by an expanding population and for industry and mining is expected put high demands on these water resources. Groundwater resources (e.g. Myalup) appear relatively secure but some of the available groundwater is of poor quality and the impacts of abstraction on Lakes Clifton and Preston may limit development. Surface water yields in the Vasse Demand Region are projected to be affected by a drier climate and groundwater may become increasingly important as a source of irrigation water. Competition from other demand centers does not appear to be significant. Surface water yields in the Blackwood Demand Region are also expected to decline but the absence of groundwater makes the switch to an alternative source of water not feasible. Demand for vegetables is expected to grow so the water deficit may become significant. There is little irrigation in the King Demand Region and this is not expected to change by much in future. A water deficit is expected to develop by about 2020.


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

250 GL

A 250 GL/y deficit may develop under a dry future climate and high demand

Presenter

Presentation Notes

These graphs show the yield and demand gaps for the entire project area. The decrease in surface water yields is very apparent in the left graph, along with a substantial decrease in yields in the Superficial Aquifer. Groundwater, which currently supplies about three quarters of all water needs, may become even more important in future, along with other water sources such as desalination and water reuse. The right graph shows how both demand and yields are projected to change between 2008 and 2030. If there is median grown in demand and a Median Future Climate, there is enough water to meet all growth in existing industries until 2030. This assumes that water quality is adequate and transportations cost are not prohibitive. This situation is possible largely because of the large groundwater reserves that are contained within the Perth Basin. In reality there will be local deficits and alternative sources will be developed, as is occurring already through desalination, and there will be an increasing need for increased water efficiencies, reuse and trading. If we experience a Dry Extreme Future Climate and demand growth is high there could be a 250 GL per year deficit by 2030. Obviously these estimates are approximate only and are based on a set of assumptions which affects estimates of both future yields and demands. This project has developed some tools that could be adapted and used over time as both data and assumptions are improved.


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


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


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


Key findings – agriculture focus

7. Competition for available water for irrigating agricultural crops and pasture is likely to become more intense as Perth, Bunbury and Busselton expand and require more residential water. This includes water for outdoor use

8. There appears to be available groundwater with increasing distance from Perth for irrigation, especially where dryland agriculture is currently raising groundwater levels. Lower value irrigation uses may also be replaced by crops that can be transported to urban centers

9. Water, not land, seems to be the main constraint to irrigation, although the fertile and well-drained Spearwood Dune system is a premium landform for many uses.


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)

Presenter

Presentation Notes

It is important to acknowledge the very substantial contributions made by people and groups outside CSIRO DEWHA provided funding and policy guidance; the DoW provided significant assistance from the provision of data and models to being partners in the research and review – about 25 DoW people had some input. Water Corp, DAFWA and the Bureau of Met provided data and technical assistance; SILO data were used in the modelling. Five consulting groups were used to provide important technical input as shown in the slide. Finally the results and reports underwent extensive review – internally, with the DoW and Water Corporation; then through a national Technical Reference Panel and also an external group of reviewers as shown on the slide. As a result, hundreds of suggestions were incorporated into each of the three main reports.


Contributors

Project Director Tom HattonSustainable Yields Coord. Mac KirbyProject Leader Don McFarlaneProject Support Frances Parsons, Therese McGillion, Paul Jupp, Josie GraysonData Management Geoff Hodgson, Jeannette Crute, Christina Gabrovsek, Mick Hartcher, Malcolm Hodgen

DOW – Aidan BelouardiDAFWA – 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 NielNSW Dept of Water and Energy – Jin Teng

Surface Water Richard Silberstein, Santosh Aryal, Neil Viney, Ang YangDOW – Mark Pearcey, Jacqui Durrant, Michael Braccia, Kathryn Smith, Lidia Boniecka, Simone McCallumBOM – Mohammad BariGeographic Information Analysis – Geoff Mauger

Groundwater Riasat Ali, Warrick Dawes, Sunil Varma, Irina Emelyanova, Jeff Turner, Glen Walker, John Byrne, Phil Davies, Steve Gorelick, Mahtab AliDOW – Chris O’Boy, Binh Anson, Phillip Commander, Cahit Yesertener, Jayath de Silva, Jasmine Rutherford Water Corporation – Mike Canci, Chengchao XuCymod Systems – Neil MilliganURS Australia – Wen Yu, Andrew Brooker, Amandine Bou, Andrew McTaggart

Water Yields and Demands Olga Barron, Natalie Smart, Michael DonnDOW – Roy Stone, Phillip Kalaitzis, Rob Donohue, Fiona Lynn, Adrian Goodreid, Andrew Paton, Susan Worley, Kylie La SpinaResource Economics Unit – Jonathan ThomasJim 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?

the future for water availability in south-west …• we are relatively isolated from other...

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