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Centroc 2010 Summit at the Mount
Recharging the Region
Understanding and Managing Australia’s Water Resources
Prof Ian AcworthUniversity of New South Wales
Director, Connected Waters Initiative
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Outline
1.
Water availability – Global and local
2.
Rainfall variability
3.
Measuring surface flow
4.
What is groundwater?
5.
Surface water and groundwater connectivity
6.
Wellington Field Training Centre
7.
Dryland
salinity (time permitting)
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Where data is required for 5 of these 6 variables:
P
precipitation,I
applied irrigation water
R surface run offET
evapotranspiration
D
deep drainage or rechargeΔW
change in soil moisture storage
To understand and monitor Australia’s water resources we need to solve the
The Water Balance Equation
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1. Water Availability – Global and Local
Some conflicting perceptions!
Water shortage? Dry as dust – on the surfacebut how about groundwater below?
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All of earth’s water is connected through the Hydrological Cycle
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The distribution of Australia’s rainfall
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2. Rainfall variability
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Spatial rainfall variability is determined by rainfall mechanisms
OrographicConvective
Frontal
Variable Rainfall DistributionUniform Rainfall Distribution
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Residual mass curves demonstrate rainfall also varies with time
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Lake George provides a good example of long term rainfall variability
16-Dec-59 13-Dec-69 11-Dec-79 8-Dec-89 6-Dec-99
0
10000
20000
30000
40000
50000
60000
70000
80000
90000
Flui
d EC
(μS/
cm)
0
1
2
3
4
5
Wat
er D
epth
(m)
Lake George, NSW
Water salinityWater depth
Sea water salinity
1810 1820 1830 1840 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010Time (years)
0
1000
2000
3000
4000
5000
6000
7000
8000
Wat
er d
epth
(mm
)
Lake George - water depth record
Data from Russel (1887)Data digitised from Jacobson and Schuett (1979)Data provided by Tim Ransley (pers comm, 2009)
No recordavailable
believed to be dry
Dryfrom2004
Wet WetDry Dry
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3. Measuring surface flow
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Flow gauging stations measure surface flow
Water level in the stilling well is recordedon a chart recorder or by a pressuretransducer. These stations are mostly managed by State authorities and the data made available through the BoM.
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However streamflow variability presents significant challenges
Major problem is handling the variability
Todd River at Alice Springs:
How do you know when to startmeasurements???
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4. What is groundwater?
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Beakers full of dry sand (1L)and 500mL of water
An sand aquifer is created when water saturates sand
Water was slowly added to
the sand until the water surface
just covered the sand
150mL of water was left in the beaker – 350mL now occupies the pore space in the sand indicating porosity of 35%
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How much water do the sands contain?
Perfect cubic packing
porosity is 47.8%
478 Liters in every cubic meter ofsand
Perfect rhombohedralpacking
porosity is 26%
260 Liters in every cubic meter ofsand
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Reality!Botany aquifer sands have a typical porosity of 35%
350 L for everycubic meter ofsand.
250 L can be drained from eachcubic meter – theresidual is left behind as soil moisture.
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Botany Sands is an example of a Australian Aquifer
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If the volume of sands is known – then a simple calculation tells how muchwater is held in the aquifer. The northern part of the aquifer holds approximately72 GL of water. But …. ….If we take out all of the water, then the wetlands will dry up completely, the parks will be brown – and the sand dunes that are left, will start moving again!
Groundwater moves from the recharge areas to Botany Bay at approximately 150 m/year. That is 50 years from Centennial Park to the Bay.
There is a record of more than 50 years of contamination in the southern andwestern parts of the aquifer.But …. ….The water quality in the northern 2/3 of the aquifer remains of extremely highquality, despite receiving storm water run off for the last 130 years!
Some Botany Aquifer facts
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150,000 years ago the ‘Botany Aquifer’
was a dry valley
Valleys in theHawkesburySandstone surface werecut during the Tertiary Periodthat ended 1.5myears ago.
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Tertiary valleyscrossing Botany Bay
(Albani, 1985)
The valleys still exist beneath Botany Bay
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40 30 18 10 0
-30 metres
HIGH
DRY COOL WET COOL DRY WARM
-40 metres
DUNE ACTIVITY
THOUSAND YEARS BEFORE THE PRESENT
SE A
UST
RA
LIA
LAK
E LE
VEL
S
TEM
PER
ATU
RE
(rel
ativ
e to
pre
sent
)
TEMP.SEALEVEL
After Chappell 2321
-75 metres
-150 metres
LAKE LEVELS, SEA LEVEL, TEMPERATURE ANDDUNE-BUILDING IN THE LAST 40 000 YEARS
Lake levels in Aust.from High to Dry
Sea level relativeto today
Temperature relativeto the present
Dune-building
Though were filled with sand during the last ice age ~ 18,000 years ago
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Legend
AlluvialSoils
Aeolian DuneSands
HawkesburySandstone
AshfieldShale
TidalSwamp
Filled andReclaimed Land
North
Scale0 3 km
AshfieldShale
Tertiary Pleistocene Recent
North
Sands in the Botany Aquifer are thought to have been blown from the floor of Botany Bay during the iceage
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Wind blown sand in the Namib desert – slowly moving to cover an old eroded and exposed rock surface.
This process is still occurring in other parts of the world today – for example Namibia…
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Copyright William Acworth
Sand dunes encroach on a townin Peru … … …
and swallow an oasis in Yemen
…Peru, and Yemen
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Two grain sizesmixed togethergreatly reduce porosity
A conglomerate is a mixture ofdifferent grain sizes and willhave a much reduced porosity.
Conglomerates, sands and gravels are deposited by rivers.
The Hawkesbury Sandstone is a fluvial deposit that has later been subject to compression and cementation.
The Hawkesbury Sandstone is another type of aquifer
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Photomicrographs of a sandstone rock
Note how the pore space is clogged with smaller grain size particles or new crystals growing in the pore space.
The lack of primary porosity explains the low yields of the Hawkesbury Sandstones and why it is necessary to search for areas where the sandstones have been broken and fractured by later earth movements.
The low porosity significantly reduces the water available for abstraction
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Sandstone exposed at Belrose, Sydney
Groundwater seepage from bedding plane in sandstone
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5. Connectivity between surface water and groundwater
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Stream Aquifer Water ExchangeMain Interactions• Groundwater discharge into stream
(e.g. baseflow)
• Stream discharge into aquifer
(recharge)
Hyporheic Zone•Interface between surface and groundwater•Water passes through this area•Flow affects water quality
What is the flow rate?
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Field Installations at Maules Creek
Temperature Installations•Apparently stagnant perennial pools•Arrays installed at 3 locations•Period: September & October 2007
Water Level Installations•Monitoring of surface water levels•Streambed water level logging
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River recharge from temperature data
16.0
20.0
24.0
28.0
32.0
Tem
pera
ture
[°C
]
Surface Water Temperature (probe 1)Sediment Temperature (depth = 0.45 m)
05/09 10/09 15/09 20/09 25/09 30/09 05/10 10/10 15/10 20/10 25/10Year 2007
-0.8
-0.6
-0.4
-0.2
Vel
ocity
[m/d
]
Amplitude RatioPhase Shift
Seepage Velocities, Probe 1/4 (spacing 0.45 m)
Recorded Temperatures in Streambed
The tool The principle
Some results
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Gaining →
losing
~ 2005
~ 1980‐1993
~ 1994
~ 40 yrs
~ 40 yrs
~ 40 yrs
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Groundwater residences times
Northern transect
Maules Creek transect
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% modern carbon – Northern transect
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000Distance, m
100
120
140
160
180
200
220
240
260
Ele
vatio
n, m
89.96
105.28
70.55
59.18
107.00
53.64
23.70
97.81
81.05
60.70
76.35
103.22
84.99
105.98
92.7789.32
West East
Namoi30231
3023230233
3023430235 30236
3023730133/30134
Sands and gravels
ClaysBedrock: sandstonesshales/coals
% modern carbon
5,000 yrs
12,000 yrs
ModernGroundwater Discharge
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% modern carbon – Maules Creek transect
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000Distance, m
120
130
140
150
160
170
180
190
200
210
220
230
240
250
260
270
280
Ele
vatio
n, m
103.9
65.6
97.1
108.1
105.6
99.3
106.0
100.9
7.2
101.5 98.8
107.2
104.4
36005
Namoi
36096
Har crx36186
36187
30129Maules 1
30130
96137MaulesElfin crx
UHA
Fassifern
3617936093 36164
30131
South-west North-east
Sands and gravels
ClaysBedrock: sandstonesshales/coals
% modern carbon
Modern River Recharge
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6. Wellington Field Training Centre
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Site LocationThe UNSW is establishing aField Training Centre on the400ha farm owned by the UNSW at Wellington. The funding is provided by theNSW Science Leveraging Fund as a part of the NSW Contribution to the newNational Centre for Groundwater Research andTraining.
Training courses will be run atthe Centre several times eachyear.
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Relocation of building
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Classroom configuration
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Installation of the Pumping test facility
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NCGRT Wellington Field Training Facility
The official opening of theFacility will take place at12:00 on Monday 8th
November, 2010
The first NCGRT field training school will bepresented at Wellington Monday to Friday8th to 12th November, 2010
Regular NCGRT field training schools will be presented at WellingtonRegular UNSW undergraduate training courses are also planned
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Wellington Research Sites
The Federal Government Super Science expenditure at Wellington willbe approximately $3.5 million over 2010 to 2013.
This will see the establishment of long-term groundwater and surfacemonitoring in the area.
The Wellington caves will become a major National and Internationalresearch site for palaeoclimate and fractured rock resource studies.
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The End! Thank you for your attention
Questions………
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7. Dryland Salinity
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Some Definitions
National Committee on Water Engineering (The Institute of Engineers, Australia)
Dryland salinity is fundamentally a groundwater problem, …
x
CRC for Plant‐Based Management of Dryland SalinitySalt occurs naturally at high levels in the sub soils of most Australian agricultural
land. As a result of clearing native vegetation, groundwater tables have risen,
mobilising the salt and causing adverse impacts to farmland, infrastructure, water
resources,……
?
NSW DIPNR 2004Salt is … a product of rock weathering…a natural part of some landscapes…
x
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Some Questions
Why does salt occur naturally in most Australian soils? Is this a true statement?
Why do the same conditions not exist on similar rocks, under similar cleared catchments, in similar climates in other countries?
Why is rising groundwater a problem? What is wrong with a spring? Spring water attracts a premium in the supermarket!
Is groundwater the problem – just a part of the problem ‐
or completely innocent?
Is the paradigm – that we teach in our Schools, let alone our
Universities, correct?
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Some Answers
Groundwater is a major Australian resource – it is not all salty – otherwise some 3 billion (annually) of agricultural exports
would not exist.
350 l/s of groundwater.
Good enough to drink!Salt content is half thatof Sydney tap water!!!!
Used here to floodIrrigate rice!?!
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The Water Balance
• Removing tree cover does lead to rising water levels.
• Planting trees does lead to falling water levels – as proven in South Africa.
• In other countries – these processes DO NOT
lead to salinity, why?
• What are we missing in the current paradigm?
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Water Level Changes
• Between 1950 and 2000 (approximately) rainfall was higher than the long term average – and water levels rose in
response. More dryland salinity was reported during this time –
but dryland salinity did not start then.
• In many areas, levels have been falling for the last 5 years. Has dryland salinity improved?
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What is dryland salinity?
Groundwater discharging from an abandoned artesian bore.
Salt deposits! What type of salt?Not sodium chloride but, in manycases, sodium bicarbonate.
What is the most serious aspect of this site? The white deposits, the gully erosion, or maybe the Paterson’s Curse weed infestation?
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Textbook Example
Dicks Creeksite at Yass,NSW.
The major problem iserosion.
Is groundwatera feature?
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Seeps and Springs
Seepage at Dicks Creek – note the ironstaining and the lack of salt
Major surface seepage causing clay to be carried tothe surface. Is this drylandsalinity?
Belata mud mounds
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Erosion – The Main Problem
No salt – no groundwater – stilla major problem as the result ofdispersion of recent ‘soil’ deposits.
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What is eroding? – Is it salty?
• At Yass, a recent (perhaps 30,000 year old) deposit has high 1:5
extract values, is strongly dispersible and shows evidence of an extensive aeolian
component.
• At Wellington, a red soil is of a similar recent age, is susceptible to erosion by dispersion and also occurs inside limestone caves!
• At Coleambally, a peak in salinity at 2m depth has been correlated with dust input dated to 20,000 years ago.
• In Western Sydney, new housing is being developed on similar dispersible soils.
• Why are they dispersible? How can they be dispersed by rainwater
if they were alluvial deposits in the first place?
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Salty clays in caves mixed with bones!?!
Snake Gully – SE of Dubbo
Deposit fallen through a hole in the top of a limestone cave at Wellington
The bone beds from thephosphorous mine at
Wellington
Recent megafauna fossils
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Could dust be the source of the salt?
Loess deposits in China
Ozdustfrontin2004
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Desert sands and dust
Sand dunes covering bedrock in the Namib
Ephemeral streams discharging into the Namib Desert, and drying up – Note the lack of salinity!
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Sediments recently mobile in AustraliaSilt deposits at Yass, mobile en masse In the past 1000 years. Charcoal disseminated throughout the deposit.
All the characteristics of a mud flow.
Massive movementof silt during flooding
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Could the source of salt be dust?
• In Australia, the winds that transport dust blow over salt lakes. The lunnets that are found on the windward side of the salt lakes in Western
NSW are composed of clay and salt derived from the clay pans.
• This salt and dust has been transported eastward to form the dispersible soils that result in dryland salinity.
• Salt in the Shepparton Formation has also accumulated in the soil profile so that when water levels rise due to excess irrigation – the salt is
released – giving rise to salinity.
• Groundwater can mobilise salt but is NOT
the main cause of salinity
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A Different Paradigm
• If aeolian processes have resulted in an accumulation of salt in
silt, then exposure to rainfall will cause this material to disperse, releasing the salt and silt into the river system.
• Rising water levels may cause saturation of this material, mobilising (dissolving or releasing) the salt.
• Rising water levels where there is no salty clay are not a problem.
• Clays with no salt are not a problem.
• Mapping and understanding the clay accumulation process becomes fundamental to management.
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In Conclusion
• Water levels may have begun to fall – but, as they are not the main driver for salinity, the risk has not disappeared!
• The focus needs to move from groundwater to the source of salt and to mapping the occurrence of these deposits.
• As they may be expected to be locally very variable, this implies a locally focused management strategy.
• Planting trees may have many benefits, but reduced groundwater recharge is not necessarily beneficial in times of drought!