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

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)

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

1. Water Availability – Global and Local

Some conflicting perceptions!

Water shortage? Dry as dust – on the surfacebut how about groundwater below?

All of earth’s water is connected through the Hydrological Cycle

The distribution of Australia’s rainfall

2. Rainfall variability

Spatial rainfall variability is determined by  rainfall mechanisms

OrographicConvective

Frontal

Variable Rainfall DistributionUniform Rainfall Distribution

Residual mass curves demonstrate rainfall also  varies with time

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

3. Measuring surface flow

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.

However streamflow variability presents  significant challenges

Major problem is handling the variability

Todd River at Alice Springs:

How do you know when to startmeasurements???

4. What is groundwater?

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%

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

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.

Botany Sands is an example of a Australian  Aquifer

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

150,000 years ago the ‘Botany Aquifer’

was a  dry valley

Valleys in theHawkesburySandstone surface werecut during the Tertiary Periodthat ended 1.5myears ago.

Tertiary valleyscrossing Botany Bay

(Albani, 1985)

The valleys still exist beneath Botany Bay

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

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

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…

Copyright William Acworth

Sand dunes encroach on a townin Peru … … …

and swallow an oasis in Yemen

…Peru, and Yemen

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

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

Sandstone exposed at Belrose, Sydney

Groundwater seepage from bedding plane in sandstone

5. Connectivity between surface  water and groundwater

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?

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

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

Gaining  →

losing

~ 2005

~ 1980‐1993

~ 1994

~ 40 yrs

~ 40 yrs

~ 40 yrs

Groundwater residences times

Northern transect

Maules Creek transect

% 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

% 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

6. Wellington Field Training Centre

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.

Relocation of building

Classroom configuration

Installation of the Pumping test facility

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

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.

The End! Thank you for your attention

Questions………

7. Dryland Salinity

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

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?

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!?!

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?

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?

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?

Textbook Example

Dicks Creeksite at Yass,NSW.

The major problem iserosion.

Is groundwatera feature?

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

Erosion – The Main Problem

No salt – no groundwater – stilla major problem as the result ofdispersion of recent ‘soil’ deposits.

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? 

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

Could dust be the source of the salt?

Loess deposits in China

Ozdustfrontin2004

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!

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

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    

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.

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!