Artesian Springs Report - Summary Excerpt by ecocreative

Summary of Findings for Natural Resource Management

of the Western Great Artesian Basin Allocating Water and Maintaining Springs in the Great Artesian Basin

Volume

VII

Volume VII: Summary of Findings for Natural Resource Management of the Western Great Artesian Basin Allocating Water and Maintaining Springs in the Great Artesian Basin

Background

viii

Volume VII: Summary of Findings for Natural Resource Management of the Western Great Artesian Basin

Chapter 1: Background

Allocating Water and Maintaining Springs in the Great Artesian Basin

1. Background 1.1 The Great Artesian Basin

1.1.1 Cultural and economic significance GAB groundwater resources are of great national

The Great Artesian Basin (GAB) is an iconic

and societal importance for Australia.

aquifer system of both national and international significance. One of the largest groundwater

The GAB springs hold a deep cultural

basins in the world, it underlies 22% of the

significance for Aboriginal Australians (Hercus

Australian continent. The diverse landscape

& Sutton 1985). This connection is reflected

overlying the GAB extends from the wet/dry

through an extensive collection of dreaming

tropics in Australia’s Carpentaria region of

stories associated with mound springs and other

Queensland to the arid zone of Lake Eyre in

prominent topographic features in the GAB

South Australia.

(Hercus & Sutton 1985). For thousands of years, GAB springs were the only reliable water source

Artesian springs are a surface water expression

for Aboriginal people in central Australia.

of the GAB. There are more than 170 spring groups in South Australia with approximately

The GAB springs also set the boundaries for

5000–6000 vents. However, the springs have

early European exploration and development

decreased in flow by an estimated 30% since the

through the central inland during the 19th and

development of the basin, with some drying out

early 20th centuries. Groundwater from GAB

completely. Reductions in water flow pressure

aquifers and springs contributed notably to the

of even 1–2 m are significant enough to cause

opening of the dry interior of Australia to the

extinction of many of the low-flow springs in

pastoral industry (ANRA 2009) and has been the

South Australia.

main driver of settlement within the GAB (Cox & Barron 1998).

Groundwater-dependent ecosystems extend across the GAB and occur mostly around the

Over much of the basin, groundwater provides

margin of the basin, with springs clustering into

the only reliable source of fresh water for

13 major regional spring supergroups. In the

human activities, including the pastoral, mining,

south-western GAB, springs have persisted as a

petroleum and tourism industries, as well as

wetland ecosystem within the arid landscape for

outback towns and their associated businesses.

more than one million years, their isolated nature

Hence, while GAB springs have great ecological

resulting in the preservation of many endemic

and cultural value, the utility of the region’s

(Fensham et al. 2010), endangered (Environment

groundwater results in a number of competing

Protection and Biodiversity Conservation Act

interests that have the potential to threaten the

1999, or EPBC Act) and relict species of great

springs and the dependence of their associated

ecological and evolutionary significance (Ponder

ecosystems.

1986; Byrne et al. 2008; Gotch et al. 2008; Murphy et al. 2009). Due to reductions in spring flow, GAB springs are listed as endangered ecological communities under the EPBC Act.

Photo on facing page: Volmer Berens

Chapter 1: Background

1 1.1.2 Management

and management to address shortcomings in

The GAB water resources have not always

estimates of the sustainability of groundwater

been well managed. Since its discovery by

resources as well as protection of significant

Europeans in 1878, thousands of bores have

ecological assets. The project commenced in

been drilled into the complex aquifers. Currently

April 2008 and finished in June 2012.

there are over 14 000 artesian bores (also known as free-flowing wells) and non-artesian bores

The aims of the AWMSGAB Project were to

(which must be pumped to extract water) that

improve understanding of complex surface and

access the GAB aquifers. Most of the older

groundwater interactions and mound spring

artesian bores were uncontrolled pastoral bores

characteristics in the western GAB (Figure

that flowed freely into open bore drains where

1.1). The project investigated groundwater

more than 95% of the water was lost through

recharge, hydrodynamics and discharge along

evaporation and seepage. These free-flowing

the western margin of the GAB; mapped the

bores have the potential to cause substantial

spatial locations and elevations of the GAB

pressure reductions over much of the basin.

springs; and developed capacity to determine water requirements for the environmentally

The need for government intervention to control

significant mound springs. The project brought

the extraction of water from the GAB was

together multiple disciplines from hydrology,

recognised as early as 1913. Since that time,

hydrogeology, ecology and remote sensing.

governments have worked with landholders to control the waste of GAB water and reverse the

Benefits of the AWMSGAB Project include:

reduction in artesian pressure (GABCC 2008).

• enhanced capacity for the management and protection of sensitive water-dependent

Effective management of the GAB springs

ecosystems, in particular the internationally

and their associated groundwater-dependent

significant GAB springs

ecosystems requires increased knowledge

• contributions to the development of a

and understanding of the source and origin of

recovery plan for threatened ecosystems

spring water as well as the relationship between

dependent on natural discharge of

spring vent pressures and artesian groundwater pressure. Also, increasing the efficient use of

groundwater from GAB springs • building the capacity of water managers

GAB groundwater resources has important

and users to sustainably manage water

economic consequences at a national scale.

allocations from the GAB in this region • returning an estimated minimum of 300 ML

1.2 AWMSGAB Project overview

a year to Dalhousie Springs in the form of environmental flows

A limited understanding of the GAB and its

• advancing the National Water Initiative

relationship with the natural environment

objectives of recognising the connectivity

hampers authorities’ ability to protect and

between surface water and groundwater

manage it effectively.

resources and managing connected systems as a single resource.

To help address this, the National Water Commission provided funding to establish the Allocating Water and Maintaining Springs in the Great Artesian Basin (AWMSGAB) project, with the specific objective of providing a blueprint for future groundwater investigations

Volume VII: Summary of Findings for Natural Resource Management of the Western Great Artesian Basin

Chapter 1: Background

Allocating Water and Maintaining Springs in the Great Artesian Basin

Preparation for in-field water sampling. Photo: Vincent Post

As well as improving management of the GAB

1.2.1 Funding and support

groundwater resource, the scientific knowledge

The AWMSGAB Project was funded by the

obtained during the AWMSGAB Project may

National Water Commission with support from

have wider use, including:

the following project partners:

• providing guidance on future policy direction

• South Australian Arid Lands Natural

with respect to groundwater resource management in arid and semi-arid regions • providing a knowledge base upon which future economic development of the GAB, either as a supply of water or petroleum product, can be based—this is particularly pertinent in relation to coal seam gas and open-cut coal mining developments (SAALNRMB 2009)

Resources Management Board • Flinders University of South Australia • The University of Adelaide • South Australian Department for Environment, Water and Natural Resources • Northern Territory Department of Natural Resources, Environment, the Arts and Sport • Commonwealth Scientific and Industrial Research Organisation.

• developing new methodologies and novel techniques that can serve as a blueprint

The project attracted national and international

for future research studies and adoption

scientific collaborators including the University of

throughout the GAB

New Mexico, Oklahoma State University and the

• providing a potential source of data for

University of Bern.

palaeo-hydrology, palaeo-climatology and neotectonic studies (e.g. Andrews 2006; Hancock et al. 1999; Love et al. 2009; Miner et al. 2007).

Chapter 1: Background

1 Figure 1.1: Overview of important hydrogeological characteristics of the western margin of the GAB Legend

Produced by Flinders University Map Datum: Geocentric Datum of Australia 1994 Date: February 2012 Data source: GAB Boundary/ Waterbodies Department for Water. Geology courtesy of GA (Whitaker et al., 2008)

Great Artesian Basin Dalhousie Supergroup

Western Margin Lake Eyre Supergroup

100km

Western Margin

Lake Frome Supergroup

Volume VII: Summary of Findings for Natural Resource Management of the Western Great Artesian Basin

Chapter 1: Background

Allocating Water and Maintaining Springs in the Great Artesian Basin

1.3 Volume series

This summary volume provides an overview of the detailed technical volumes and outlines

The AWMSGAB Project has produced this

the key tools, methods and information arising

summary volume along with six technical

from the research. This document briefly

volumes that provide new information and

summarises outcomes that have implications

conceptual understanding of groundwater flow

for natural resource management (NRM) in the

systems and ecology of the GAB springs:

GAB, however the reader should refer to the

• Volume I: Hydrogeological Framework of the

six individual scientific volumes for full details,

Western Great Artesian Basin • Volume II: Groundwater Recharge, Hydrodynamics and Hydrochemistry of the

including background information, scientific investigations and rationale for findings and conclusions.

Western Great Artesian Basin • Volume III: Groundwater Discharge of the Western Great Artesian Basin • Volume IV: Spatial Survey and Remote

The simplified schematic diagram below (Figure 1.2) shows how each of the volumes contribute to improved understanding for future

Sensing of Artesian Springs of the Western

management of the GAB (note that complete

Great Artesian Basin

linkages are substantially more complicated).

• Volume V: Groundwater-dependent Ecosystems of the Western Great Artesian Basin • Volume VI: Risk Assessment Process for Evaluating Water Use Impacts on Great Artesian Basin Springs • Volume VII: Summary of Findings for Natural Resource Management of the Western Great Artesian Basin.

Groundwaterdependent Ecosystems

Hydrogeological Framework

of the Western Great Artesian Basin

Figure 1.2: Schematic diagram showing relationship between volumes

of the Western Great Artesian Basin

Groundwater Recharge, Hydrodynamics and Hydrochemistry

HYDROGEOLOGY

of the Western Great Artesian Basin

Risk Assessment Process for Evaluating Water Use Impacts

ECOLOGY

on Great Artesian Basin Springs

III Groundwater Discharge

of the Western Great Artesian Basin

IV Spatial Survey and Remote Sensing of Artesian Springs of the Western Great Artesian Basin

Volume VII: Summary of Findings for Natural Resource Management of the Western Great Artesian Basin

Allocating Water and Maintaining Springs in the Great Artesian Basin

Summary of the volumes

Volume VII: Summary of Findings for Natural Resource Management of the Western Great Artesian Basin

Chapter 2: Summary of the volumes

Allocating Water and Maintaining Springs in the Great Artesian Basin

2. Summary of the volumes 2.1 Volume I: Hydrogeological Framework of the Western Great Artesian Basin

Chapter 1: Introduction Mark Keppel, Karl Karlstrom, Andrew J Love, Stacey Priestley, Daniel Wohling, Samantha De Ritter

Hydrogeological Framework

Chapter 2: Overview of study area

of the Western Great Artesian Basin

Mark Keppel, Simon Fulton, Daniel Wohling, Stacey Priestley, Karl Karlstrom,

Allocating Water and Maintaining Springs in the Great Artesian Basin

Laura Crossey, Samantha De Ritter, Jennie Fluin, Andrew J Love Volume

Chapter 3: Summary of hydrogeology and hydrostratigraphy Mark Keppel, Daniel Wohling, Simon Fulton, Lloyd Sampson, Karl Karlstrom, Gabriel Nelson, Tim Ransley, Andrew J Love Chapter 4: Structural and tectonic history Karl Karlstrom, Mark Keppel, Laura Crossey, Andrew J Love, Chris Boreham Chapter 5: Conclusions and development of the conceptual model

Editors: Mark Keppel, Karl

Mark Keppel, Karl Karlstrom, Andrew J Love, Stacey Priestley,

Karlstrom, Andrew J Love,

Daniel Wohling, Samantha De Ritter

Stacey Priestley, Daniel Wohling and Samantha De Ritter

2.1.1 Volume I summary

A summary of historical exploitation helps

Volume I: Hydrogeological Framework of

determine the efficacy of data sets to describe

the Western Great Artesian Basin presents

the â&#x20AC;&#x2DC;naturalâ&#x20AC;&#x2122; system as well as providing a

a summary of background knowledge in

starting point to quantify human impacts on the

relation to the climate, physiology, geology and

resource. Furthermore, describing the value of

hydrogeology in the western Great Artesian

the resource in historical as well as scientific

Basin (GAB). This background information

terms helps the reader understand stakeholder

is necessary to understand the issues

related issues, impacts and concerns.

concerning the GAB resource and the impact of extractive use.

Photo on facing page: Volmer Berens

Chapter 2: Summary of the volumes

Breakaways at William Creek, SA. Photo: Mark Keppel

The volume also presents a description of the

The main confining layer to the J Aquifer is a

physical and climatological nature of the basin in

massive shale unit that comprises geological

relation to investigating potential recharge zones

units of the Bulldog Shale / Rumbarala Shale,

and recharge event histories within the study

Oodnadatta Formations and lateral equivalents

area.

that can be up to 1000 m in thickness. Measured vertical hydraulic conductivity values

The present climatic conditions of the region

indicate that this confining layer is extremely

are arid, with episodic rainfall events. The area

impermeable.

is generally flat and featureless in nature, and surface water systems are ephemeral. A review

The term ‘upper’ aquifer describes, collectively,

of palaeo-climatological studies conducted

the shallow groundwater occurrences in aquifer

in Australia indicates that recharge along the

units above the J Aquifer.

western margin is likely to have been greater during periods in the Pleistocene than today.

A description of the sedimentology, spatial distribution and known hydrogeology of

The main aquifer in the western GAB is the

basins bordering the GAB provides a guide to

J Aquifer, an unconfined to confined artesian

understanding inter-basinal connectivity and

aquifer, comprised mostly of the Cretaceous

potential risks to the GAB groundwater

Cadna-owie Formation and the underlying

resource not directly associated with

Jurassic Algebuckina Sandstone. The aquifer

groundwater extraction.

comprises unconsolidated gravels, sands and silts and consolidated sandstones with inter-

A summary of structural and basinal studies

bedded shales and mudstones. It can reach a

highlights the deformational history of the

thickness in excess of 1000 m.

GAB that led to its development and current architecture. Deformation may not only affect

Aquifer units are not continuous but are instead

groundwater flow and hydrochemistry, such

interrupted by interleaving clay horizons and

as in the vicinity of the Birdsville Track Ridge

faults forming preferential pathways and

(Figure 2.1), but may also help shape a better

impermeable or leaky barriers to groundwater

understanding of the tectonic and structural

flow. Groundwater flow paths have complex

nature of the Australian continent.

horizontal and vertical components.

Innamincka

Coober Pedy

Volume William Creek VII:

Summary of Findings for Natural Resource Management of the Western Great Artesian Basin

29°S

31°S

GM IR

28°S 29°S

30°

Cooper Basin

Chapter 2: Summary of the volumes 24°S

Oodnadatta

idg e

28°S

Marla

Bi rd sv ill

Marree

139°E

24°S

135°E 135°E

136°E 136°E

26°S 25°S 25°S 25°S

rid sie ou -D lls

Marla

. Marla .Marla .

. Oodnadatta .Oodnadatta . Coober Pedy

Innamincka

Poolowanna trough Poolowanna trough

William Creek

. William Creek .William Creek .

. Coober Pedy .Coober Pedy .

Innamincka Cooper Basin . Cooper Basin Innamincka Innamincka .

William Creek

Coober Pedy

30°S 29°S 29°S 29°S

Cooper Basin

Oodnadatta Oodnadatta

27°S 26°S 26°S 26°S

Marla

30°S 29°S 29°S 29°S

Marree Marree

. Marree Leigh Creek .Marree . . . Leigh Creek Roxby Downs . Roxby Downs . Leigh Creek .Leigh Creek .Roxby Downs . .

134°E

135°E

136°E

137°E

138°E

139°E

140°E

25°S 24°S 24°S

Marla

180

240

Coober Pedy

Coober Pedy .Coober Pedy

William Creek

.William Creek . .

31°S 30°S 30°S

Innamincka Innamincka .

Roxby Downs

Marree

Roxby Downs

.Roxby Downs . 135°E

135°E 135°E

136°E

136°E 136°E

137°E

137°E 137°E

138°E

138°E 138°E

Leigh Creek

Thickness of J Aquifer Value High : 1588 Thickness of J Aquifer Low : -378 Thickness of J Aquifer Value ValueHigh : 1588 High : 1588 Low : -378 Low : -378

120 Kilometres

180

240

´ ´´

Produced by Flinders University | Map Datum 0 60 120 180 240 Geocentric Datum of Australia 1994 | Date February 0 60 120 180 240 2012 | Data source Data/GAB Boundary/ Kilometres Waterbodies Department for Water and PIR SA Kilometres

Produced by Flinders University | Map Datum Produced Flinders University1994 | Map Datum GeocentricbyDatum of Australia | Date February Geocentric Australia 1994 | Date February 2012 | DataDatum sourceofData/GAB Boundary/ 2012 | Data source Data/GAB Boundary/ Waterbodies Department for Water and PIR SA Waterbodies Department for Water and PIR SA

.Leigh Creek . 139°E

139°E 139°E

140°E

140°E 140°E

Coobe

Produced by Flinders University | Map Datum

Marree Leigh Creek

.Marree . .

30°S 29°S 29°S

120 Kilometres

31°S 30°S 30°S

29°S 28°S 28°S

.Oodnadatta .

28°S 27°S 27°S

Innamincka

Oodnadatta

134°E 134°E

Geocentric Datum of Australia 1994 | Date February Produced by Flinders University 2012 | Data source Data/GAB Boundary/ Map Datum: Geocentric Datum of Waterbodies Department for Water and PIR SA Australia 1994 Date: February 2012 Data source: Data/GAB Boundary 133°E 134°E Waterbodies Department for Water and PIR SA

Oodnadatta

29°S 28°S 28°S

Marla .Marla

133°E 133°E

31°S 31°S

28°S 27°S 27°S

134°E

27°S 26°S 26°S

26°S 25°S 25°S

B B

133°E

Legend Figure 2.1: Elevation of the top of the Aquifer . JTownships Interpreted Lineaments Roadsof J Aquifer Legend Thickness Legend boundaries Value Townships . State Townships Major lakes : ephemeral 1588 Lineaments . High Interpreted Marla Interpreted Lineaments GAB Boundary Roads Low : -378 Roads Elevation of top of J Aquifer State boundaries Value State Majorboundaries ephemeral lakes High : 528 Major ephemeral lakes GAB Boundary GAB Boundary Elevation top of J Aquifer Low :of-1952 Elevation of top of J Aquifer (mAHD) Value Value High : 528 High : 528 Low : -1952 Low : -1952

31°S 30°S 30°S 30°S 24°S 31°S 31°S 31°S

31°S 30°S 30°S 30°S

Roxby Downs

133°E

28°S 27°S 27°S 27°S

Poolowanna trough

29°S 28°S 28°S 28°S

Bi Bi B rd rd ird sv sv sv ille ille ill Tr Ter T ac acra kR k Rck GM GMG idg R idgid I M e Ri I RI g e e R dg idgid e e ge

South Australia South Australia

24°S 31°S 31°S 31°S 25°S 24°S 24°S

140°E 140°E

South Australia Northern Territory Northern Territory

31°S 31°S

139°E 139°E

alh

Northern Territory

27°S 26°S 26°S

26°S 25°S 25°S

138°E 138°E

B A A

137°E 137°E

25°S 24°S 24°S 24°S

134°E 134°E

25°S 24°S 24°S 24°S 26°S 25°S 25°S 25°S 27°S 26°S 26°S 26°S

133°E 133°E

29°S 28°S 28°S 28°S

28°S 27°S 27°S 27°S

25°S

30°S

140°E

26°S

138°E

27°S

137°E

28°S

136°E

29°S

135°E

Leigh Creek

30°S

134°E

24°S

133°E

Roxby Downs

31°S

30°S

Allocating Water . and Maintaining Springs in the Great Artesian Basin

135°E

Chapter 2: Summary of the volumes

2 2.2 Volume II: Groundwater Recharge, Hydrodynamics and Hydrochemistry of the Western Great Artesian Basin

Chapter 1: Introduction Andrew J Love, Daniel Wohling, Simon A Fulton, Pauline Rousseau-Gueutin,

Groundwater Recharge, Hydrodynamics and Hydrochemistry

of the Western Great Artesian Basin

Samantha De Ritter Chapter 2: Diffuse recharge Daniel Wohling, Simon Fulton, Andrew J Love, Bridget Scanlon

Allocating Water and Maintaining Springs in the Great Artesian Basin

Chapter 3: Ephemeral river recharge

Volume

Simon Fulton, Daniel Wohling, Andrew J Love, Volmer Berens

Allocating Water and Maintaining Springs in the Great Artesian Basin

Chapter 4: Mountain system recharge Daniel Wohling, Simon Fulton, Andrew J Love, Meghan Dailey, Todd Hallihan, Volmer Berens, Roland Purtschert, Paul Shand Chapter 5: Groundwater flow and hydrodynamics Editors: Andrew J Love,

Pauline Rousseau-Gueutin, Szilvia Simon, Andrew J Love, Vincent Post,

Daniel Wohling, Simon Fulton,

Camille Doublet, Craig T Simmons, Daniel Wohling, Simon Fulton

Pauline Rousseau-Gueutin, Samantha De Ritter

Chapter 6: Hydrochemistry Stacey Priestley, Paul Shand, Andrew J Love, Laura Crossey, Karl Karlstrom Chapter 7: Conclusions Andrew J Love, Daniel Wohling, Simon A Fulton, Pauline Rousseau-Gueutin, Samantha De Ritter

2.2.1 Volume II summary

recharge, discharge and aquifer flow and of the

Volume II: Groundwater Recharge,

status of the water balance within the western

Hydrodynamics and Hydrochemistry of the

margin of the GAB. This new understanding

Western Great Artesian Basin examines three

implies that the overall recharge and inflow into

forms of groundwater recharge processes in

the basin is less than assumed or estimated by

the western margin of the GAB: ephemeral river

previous studies.

recharge; diffuse recharge; and mountain block recharge. The volume presents when and how

The only recharge to the J Aquifer that occurs

recharge currently occurs and concludes that

in the western margin under the current

present-day rates of groundwater recharge are

climatic conditions is via monsoonal flow

much less than in the past.

events in defined arid zone rivers. This recharge mechanism contributes between 6 and 20% of

2.2.1.1 Summary of key findings

the actual natural discharge, meaning current

Together with Volume III, this volume provides

day recharge is significantly less than natural

a new understanding of the relative quantities

discharge.

of the main water balance components of

Volume VII: Summary of Findings for Natural Resource Management of the Western Great Artesian Basin

Chapter 2: Summary of the volumes

Allocating Water and Maintaining Springs in the Great Artesian Basin

2 Figure 2.2: Ephemeral river recharge from a defined river channel

Stream

Fig 3.11

Unsaturated zone

Capillary zone Water table

The majority of recharge in the western margin

These potential recharge zones are larger than

occurred over 10 000 years ago in the wet

previously thought, however it is important to

periods of the Pleistocene—with virtually no

note that these larger potential recharge zones

recharge over the last 10 000 years. This means

do not necessarily correspond to increased

that the basin is in a state of (natural) long-term

recharge to the system.

pressure decline and not in steady state, as previously thought. This does not imply that the

Estimates of diffuse recharge are calculated

springs will dry up in the near term—the basin

using the chloride mass balance method for

has gone through many iterations of waxing and

groundwater and the unsaturated zone, as well

waning—but the study does indicate that the

as radiocarbon dating. Researchers observe

basin is in a natural state of decline at this time.

recharge values of 0.01 to 1.8 mm/year with

This leads to the conclusion that all groundwater

a mean value of approximately 0.15 mm/year.

extractions from the system are ultimately at

For groundwater management purposes, this

the expense of natural discharges but over an

value can be considered to be zero. Residence

uncertain timescale.

time in the unsaturated zone can be in the order 20 000 to 30 000 years, indicating that the

An improved understanding of groundwater flow

majority of diffuse recharge occurring today is a

paths reveals that flow systems from the eastern

result of rainfall that occurred in the Pleistocene.

states into South Australia is potentially up to

Therefore, any significant volumes of diffuse

20% less than previous estimates.

recharge would have been the result of much wetter climate conditions in the past.

2.2.1.2 Diffuse recharge Diffuse recharge is defined as recharge in

2.2.1.3 Ephemeral river recharge

response to rainfall infiltrating the soil surface

Ephemeral river recharge describes the indirect

and percolating through the unsaturated zone to

recharge resulting from episodic flow events in

the water table.

defined arid zone rivers (Figure 2.2).

The diffuse recharge chapter identifies zones

Active recharge to the J Aquifer along the Finke

of potential recharge to the GAB aquifers

and Plenty Rivers occurs across 16 km2 of river

and maps them in the South Australian and

bed. Estimated recharge rates along the Finke

Northern Territory sections of western GAB.

River are between 5100 to 11 300 ML/year

Chapter 2: Summary of the volumes

2 across the recharge zone. Estimated annual

Contemporary recharge identified at Marla

recharge to the J Aquifer from the Plenty River is

is linked to monthly rainfall totals exceeding

between 50 to 260 ML/year. Stable isotopes of

180 mm, however the majority of mountain

water link recharge to the J Aquifer with summer,

system recharge identified is considered

monsoonal rainfall that occurs in months with a

palaeo-recharge.

total rainfall in excess of 100 mm. The potential for ephemeral river recharge to the J Aquifer

Distinct hydrochemical signatures in

is limited from the Hale, Todd, and Alberga

groundwater collected from the J Aquifer either

Rivers and Stevenson Creek systems, while no

side of the Peake and Denison Inlier indicates

recharge potential exists beneath the Hay River

a partitioning of groundwater flows systems

and Illogawa Creek.

and that the Peake and Denison Inlier acts as a barrier to east–west flow.

The investigation indicates that an upper limit for this recharge source is an average of only 13 GL/

2.2.1.5 Groundwater flow and

year, which is very small compared to the overall

hydrodynamics

scale of flows and capacity of the GAB in South

The correction of hydraulic head to include

Australia and the Northern Territory.

variations in groundwater density for groundwater, temperature, salinity and pressure

2.2.1.4 Mountain system recharge

provides a new interpretation of groundwater

Mountain system recharge describes the

flow across the western GAB (Figure 2.4). A large

contribution of recharge derived from mountains

regional groundwater divide occurs in the central

to adjacent aquifers and can be categorised

portion of the western GAB that extends from

into two processes: mountain block recharge

the northern rivers recharge area in the Northern

(subsurface inflows from the consolidated

Territory to the Lake Eyre South / Marree region

mountain block) and mountain front recharge

of South Australia. To the east of this divide,

(infiltration from streams at the mountain front)

groundwater flows from the Northern Territory

(Figure 2.3).

towards Queensland, where likely discharge occurs in the Mulligan River Spring Group and

The investigation concludes that mountain

diverges in a south-easterly direction through

system recharge mechanisms were in operation

South Australia. This reveals that groundwater

in the past and are likely to still be in operation

flow from the eastern states to the eastern

today along the western GAB. Specifically,

portion of South Australia is up to 20% less

they identify recharge to the J Aquifer east

than suggested by previous potentiometric

of the Peake and Denison Inlier, and to the P

surfaces. To the west of this large regional divide

Aquifer west of the Peake and Denison Inlier.

is another groundwater divide that occurs on an

Additionally, recharge to the J Aquifer occurs

approximate line between Marla, Oodnadatta

at Marla. Regional mixing models indicate

and William Creek, extending to the southern

between 10 and 15% of groundwater flow in the

margin. From Oodnadatta southwards, this

J Aquifer to the east of the Peake and Denison

divide corresponds to part of the mound spring

Inlier is a contribution from mountain system

line and Peake and Denison Inlier. Groundwater

recharge mechanisms. A local mixing model

flows from the north-west of South Australia

at the Freeling Spring Complex infers a 1–12%

and south-west of the Northern Territory in a

mountain block contribution to spring flow.

generalised south-easterly direction until it is partitioned either side of the Peake and Denison Inlier. South of Marla, groundwater flows in a west south-westerly direction.

Volume VII: Summary of Findings for Natural Resource Management of the Western Great Artesian Basin

Chapter 2: Summary of the volumes

Allocating Water and Maintaining Springs in the Great Artesian Basin

2 Figure 2.3: Conceptualised section of mountain system recharge at the Peake and Denison Inlier

Precipitation

MFR

Faults

MBR

Water flow

MOUNTAIN BLOCK

LEGEND Mountain block

Q and T formations

MFR Mountain front recharge

J Aquifer

P aquifer

MBR Mountain block recharge

Direction of water movement

Potentiometric surface

Confining beds

Springs

Several isolated depressions of the

variation. Groundwater levels across the western

potentiometric surface occur to the east and

GAB are undergoing re-equilibration in response

south-east of the major regional northâ&#x20AC;&#x201C;south

to a reduction in recharge at the margins of the

groundwater divide. The depression near

basin. Potentiometric levels, which are not in

Innamincka is a reflection of groundwater

equilibrium with the contemporary recharge

extraction associated with the petroleum and

rate, drive groundwater discharges via springs

gas industries. A depression, approximately

and diffuse discharge pathways. Hence,

200â&#x20AC;&#x2030;km to the east of Marree, most likely

current discharge from the basin is greater than

represents a conversion of groundwater

recharge and the system is in a state of ongoing

recharge from the Northern Flinders Ranges

pressure decline in the western margin of the

and a spring discharge zone associated with

GAB. This is contrary to the assumption of a

Lake Blanche.

steady-state condition that has underpinned earlier numerical models of the basin, and

Hydrodynamics research shows that the western

implies that these earlier models may have over-

GAB is not in steady state, but is undergoing a

estimated the amount of water available in the

change in state in response to long-term climate

system.

Chapter 2: Summary of the volumes

2 Figure 2.4: Potentiometric surface of the main J Aquifer in the western margin of the GAB

Produced by Flinders University Map Datum: Geocentric Datum of Australia 1994 Date: February 2012 Data source: Data/GAB Boundary/ Waterbodies Department for Water

A transient numerical analysis suggests that

2.2.1.6 Hydrochemistry

a new equilibrium would take in the order of

The groundwater hydrochemistry study

50 000 to 60 000 years to be established.

delineates groundwater flow paths over long

However, in large regional aquifer systems

time periods. This is possible because, in effect,

where changes to recharge rates are induced by

the water retains a ‘geochemical memory’ of

geological climate cycles that are smaller than

its recharge and flow history. Groundwater

the time it would take to reach a new equilibrium,

chemistry along inferred flow directions

steady-state conditions are unlikely to ever

reflects myriad potential processes and

occur. Therefore, transient analysis is most

water–rock interactions, including variations

appropriate for modelling of large arid aquifer

in evapotranspiration over time, periods of

systems such as the GAB.

increased rainfall, and interruptions in the horizontal flow path by upward or downward flow.

Volume VII: Summary of Findings for Natural Resource Management of the Western Great Artesian Basin

Chapter 2: Summary of the volumes

Allocating Water and Maintaining Springs in the Great Artesian Basin

Regional variations across the aquifer can be

The GAB springs display a large range of

explained as a series of discrete flow systems

chemistry similar to that of the groundwaters.

from the margins (recharge areas) towards a

The hydrochemistry study reveals a new

regional discharge zone south of Lake Eyre

understanding of the origin of spring waters,

South, which represents a convergence of

with fluids sourced from different regional flow

flow systems. Fresh groundwater flow from

paths (horizontal) and depths (vertical). The

Queensland occurs along the Birdsville Track

new conceptual understanding of the source

Ridge (Figure 2.1). The chemistry of the

of spring water indicates they are not simply

discharge water from the springs suggests a

a mixing of western and eastern waters but

mixing of water from different flow paths at a

may have an important vertical component.

range of scales; regional flow systems converge

Interpretations of sesimic, noble gases and

towards the south and it is likely that cross-

CO2 analyses imply a potential for connection

formational flow occurs along faults throughout

with aquifers much deeper than the Eromanga

the basin as well as in the discharge areas.

Basin formations.

The new hydrochemical data interpretation provides information on the origin of water and flow pathways, with implications for predicting impacts of groundwater development.

Project feature

Groundwater recharge

This imbalance results from climate forcing,

…under the current

where the actual discharge is induced by wetter

climate conditions,

Ephemeral river recharge (ERR) is the only

past climate conditions. This imbalance, or

recharge mechanism providing modern recharge

transient hydraulic state, should last for 50 000

the modern recharge

to the J Aquifer. Indeed, diffuse recharge and

to 60 000 years since the last climate change.

mountain system recharge are negligible under

Since the onset of the last climate change

current climate conditions. Recharge under

in the Holocene (approximately 6000 years

natural discharge. Under

ephemeral rivers is approximately three times

ago), recharge has been in disequilibrium with

the current climate,

smaller than spring discharge on the western

discharge and hydraulic heads in a state of

recharge is much

GAB, which is estimated to represent around

natural decline.

less than present-day

20% of the total natural discharge of the western GAB (springs and upward leakage). Under the

Groundwater storage in the western GAB is a

current climate conditions this means that the

legacy of recharge that occurred under wetter

modern recharge represents between 6 and

climatic conditions than today and, as a result,

20% of the actual natural discharge. Under the

can be considered to be a fossil resource. This

current climate, recharge is much less than

does not imply that the springs will dry up in the

present-day discharge.

near term—the basin has gone through many

represents between 6 and 20% of the actual

discharge.

cycles of waxing and waning—but at this point in time, the basin is in a natural state of (natural) long-term pressure decline.

Chapter 2: Summary of the volumes

2 Figure 2.5: Western margin of the GAB showing chloride concentration (mg/L)

Produced by Flinders University Map Datum: Geocentric Datum of Australia 1994 Date: February 2012 Data source chemistry: Flinders University, Department for Water, BHP Billiton, 2006, Collerson et al., 1988, Herczeg et al., 1991, Love et al., 2000, Mahara et al., 2009, Pirlo, 2004, Radke et al., 2000, Torgersen and Clarke, 1985, Torgersen and Clarke,1987, Torgersen et al., 1991, Zeider and Ponder, eds., 1989, Zhang et al., 2007 springs/towns/ Boundaries/Watercourse/Waterbodies/ geology Department for Water Potentiometric surface: Flinders University

Volume VII: Summary of Findings for Natural Resource Management of the Western Great Artesian Basin

Chapter 2: Summary of the volumes

Allocating Water and Maintaining Springs in the Great Artesian Basin

2.3 Volume III: Groundwater Discharge of the Western Great Artesian Basin

Chapter 1: Introduction to groundwater discharge Andrew J Love, Paul Shand, Laura Crossey, Glenn A Harrington, Pauline Rousseau-Gueutin

Groundwater Discharge

of the Western Great Artesian Basin

Chapter 2: Source and origin of western GAB

Allocating Water and Maintaining Springs in the Great Artesian Basin

spring water Laura Crossey, Stacey Priestley, Paul Shand, Karl Karlstrom, Andrew J Love, Mark Keppel

Volume

III

Chapter 3: Formation and evolution of mound springs Mark Keppel, Todd Halihan, Andrew J Love, Vincent Post, Adrian Werner, Allocating Water and Maintaining Springs in the Great Artesian Basin

Jonathon Clarke Chapter 4: Formation of acid sulfate soils Paul Shand, Andrew J Love, Stacey Priestley, Mark Raven, Travis Gotch Chapter 5: Palaeo-discharge inferred from U-series dating of

Editors: Andrew J Love,

spring travertine deposits

Paul Shand, Laura Crossey,

Stacey Priestley, Karl E Karlstrom, Andrew J Love, Laura J Crossey,

Glenn A Harrington and

Victor Polyak, Yemane Asmerom

Pauline Rousseau-Gueutin

Chapter 6: Hydrogeology of Dalhousie Springs Brad Wolaver, Mark Keppel, Andrew J Love Chapter 7: Relationship between aquifer pressure changes and spring discharge rates Graham Green, Volmer Berens Chapter 8: Diffuse discharge Glenn A Harrington, Brian D Smerdon, Payton W Gardner, Andrew R Taylor, Jim Hendry Chapter 9: Conclusions Andrew J Love, Paul Shand, Laura Crossey, Glenn A Harrington, Pauline Rousseau-Gueutin

2.3.1 Volume III summary

the formation of acid sulfate soils, and the

Volume III: Groundwater Discharge of the

hydrogeology of Dalhousie Springs. It also

Western Great Artesian Basin bridges a number

presents the results of the first successful

of knowledge gaps in the understanding of

uranium-series dating on GAB spring

groundwater discharge in the GAB, including

travertine deposits.

the source and origin of spring water, the formation and evolution of the mound springs,

Chapter 2: Summary of the volumes

2 2.3.1.1 Summary of key findings

contrast, uses the hydrochemistry of the springs

Aquifers recharged by arid zone rivers near Finke

to decipher GAB groundwater sources and

(Apatula Community) in the Northern Territory

flow paths and the mixing of fluids from

are the source of groundwater discharging at

different aquifers.

Dalhousie Springs. The GAB springs display a large range in Spring flow rates are dependent on both the

chemistry similar to that of the regional

groundwater pressure level above the spring

groundwater. The hydrochemistry study

elevation and the conductivity of the vent. It

presents a new understanding of the origin of

is possible that the capacity of spring vents

spring waters, with fluids sourced from different

to transmit flows may reduce when flows are

regional flow paths (horizontal) and depths

reduced, thereby reducing their potential to

(vertical). Western GAB spring waters reflect

recover if groundwater levels are restored. To

mixing of western, northern and southern GAB

understand the risks to springs from aquifer

flow paths. Furthermore, some previously

pressure changes it is necessary to know the

denoted GAB springs are in fact sourced from

spring flow rate, elevation salinity and the current

mountain block recharge adjacent to the Peake

pressure level.

and Denison Inlier. The presence of primordial helium and mantle-derived carbon dioxide in

In certain areas, a decrease in flow has resulted

GAB springs indicates a linkage between the

in the development of acidic soils due the

mantle and spring discharge along long-lived

oxidation of acid sulfate soils, with many spring

deep crustal fractures. Interpretation of seismic

sediments having pH values equivalent to or

and noble gas data implies connection with

more acidic than battery acid. This may have

aquifers much deeper than the Eromanga Basin

severe consequences for spring ecosystems, in

formations. The new conceptual understanding

particular the flushing of acid and metals into the

of the source of spring water indicates they

pool and wetland.

are not simply a mixing of western and eastern waters but may have an important vertical

Some of the basic assumptions of the current

component.

Far North Wells Prescribed Wells Area Water Allocation Plan have proven to be flawed. For

2.3.1.3 Formation and evolution of

example, diffuse leakage (water permeating

mound springs

slowly upwards where it is evaporated from the

The hydrochemistry of mound spring wetland

soil) is much less than estimated in the current

environments changes significantly along mound

plan, whereas vertical leakage via preferential

tails, affecting how mound structures form.

flow paths is much greater. The implication of

The variations in hydrochemistry may also have

this for management is that the location and

important consequences for the distribution of

volume of extractions is critical to the extent and

aquatic flora and fauna. Cyanobacteria play an

timescale on which spring discharges will be

important role in the deposition of calcareous

affected.

mound spring structures. This highlights an instance in which a form of native vegetation is

2.3.1.2 Source and origin of spring waters

critical to mound spring environments, but little

Traditional GAB models assumed that spring

is known about it in the scientific community. In

waters were from the J Aquifer, neglecting

addition, researchers observed deformation as

vertical movement of fluids along faults from

a consequence of tectonic activity, implying an

above or below the GAB. This research, in

important role for tectonics in spring formation and maintenance.

Volume VII: Summary of Findings for Natural Resource Management of the Western Great Artesian Basin

Chapter 2: Summary of the volumes

Allocating Water and Maintaining Springs in the Great Artesian Basin

2 Figure 2.6: Conceptual model for mound formation (from Keppel et al. 2011)

Carbonate precipitation Carbonate precipitation Carbonate precipitation Fig 3.11 Fig 3.11

Spring conduit

Fig 3.11

Spring conduit

A. Discharge from a new spring conduit forms a circular swamp after radial flow away from vent. Spring conduit

Carbonate precipitation triggered at the point where sufficient PCO 2 degassing has occurred.

Carbonate precipitation Carbonate precipitation Carbonate precipitation

Spring conduit Spring conduit Spring conduit

B. Continued precipitation eventually builds a mound barrage structure, enclosing a central spring pool. Carbonate precipitation Carbonate precipitation Break-out Carbonate precipitation Break-out

Break-out Spring conduit Spring conduit Spring conduit

C. Sustained mound growth deepens pool and dampens turbulence, slowing PCO 2 degassing that results in development of carbonate under-saturation in spring pool waters. A break-out subsequently develops and travertine precipitation shifts to the tail environment.

Chapter 2: Summary of the volumes

2 Mound spring structures may be used to provide

the spring sediments display the highest sulfide

information regarding historical climate and

contents recorded in any acid sulfate soil world-

hydrogeological conditions of the GAB, although

wide. Acidification has strongly impacted local

consideration of morphological and depositional

areas of vegetation and has probably affected

conditions is required before this is attempted.

the soil biota. This highlights a potential risk to associated rare ecosystems, in particular due

2.3.1.4 Formation of acid sulfate soils

to flushing of acid and metals to the spring pool

Acid sulfate soils are a ubiquitous feature of

and tail environments.

most mound springs, forming in the discharge zone where iron and sulfate from groundwater

Much of the acidification observed in springs is

interact with organic-rich sediment to form pyrite

probably a recent phenomenon, occurring due

(FeS2). The acidification hazard for most springs

to changes in aquifer pressure and consequent

is low due to high acid neutralising capacity in

spring flow reductions. However, the presence

the soils. However, in some areas, a decrease

of brecciated iron-stained travertines in

in flow has led to the exposure of highly sulfidic

some spring mounds may be evidence that

soils and oxidation of the soils has occurred,

acidification also occurred in the past (prior to

generating significant acidity. A range of rare

human influence on aquifer pressures).

iron- and aluminium-rich mineral efflorescences (salts) have formed due to evaporation and

These findings have major implications for

concentration of acidic soil solutions. In some

management of springs and assessing the

cases, the soil pH is extremely acidic. Many soil

risk to springs from aquifer draw-down. Future

profiles have pH values less than 1, and some of

decreases in aquifer potentiometric levels

Project feature

Extremely rare mineral efflorescences (salts) in Australia The long-term discharge of spring waters with

led to the precipitation of surface mineral

elevated sulfate concentrations through organic-

efflorescences (salts). Bright yellow,

rich sediments has allowed the development

yellow-green, brown and white mineral

of highly sulfidic soils to form in the spring

efflorescences are present at a number

discharge areas, particularly west of Lake Eyre.

of springs, along with a strong smell of

A decrease in flow in these springs has led to the

sulfur-rich gases (Figure 1.1). In the worst

exposure and oxidation of these acid sulfate soils

affected areas, a range of rare iron-and

(containing pyrite, FeS2), and in some springs

aluminium-rich mineral efflorescences have

the generation of significant soil acidity. In the

formed. Many of these are extremely rare

The highest sulfide

most extreme cases, the soil pH is extremely

(e.g. ferrinatrite, Jurbanite, metavoltine,

contents for any such

acidic, with pH values less than 1. The highest

sideronatrite) and some represent the first

acid sulfate soils world-

sulfide contents for any such acid sulfate soils

known occurrences in Australia.

wide were recorded at two of the springs.

world-wide were recorded at two of the springs. Evaporation and concentration of these acidic soil solutions in the arid interior of the GAB has

Volume VII: Summary of Findings for Natural Resource Management of the Western Great Artesian Basin

Chapter 2: Summary of the volumes

Allocating Water and Maintaining Springs in the Great Artesian Basin

2 Figure 2.7: Acidic mineral efflorescences (yellow, brown and white) noted at a number of springs

Big Perry

Vaughn

Hawker

Strangways

may cause severe acidification of spring soils

Comparison of the timing of travertine deposition

and channel waters as well as dissolution and

with climate proxy data for Australia suggests

mobilisation of metals and metalloids in spring

that variations in the flow of springs in the

surface water environments. The impacts on

western margin of the GAB respond to changes

soils and biota are likely to be irreversible on

in recharge on the western margin, rather than

short time scales.

recharge to the eastern margin along the Great Dividing Ranges.

2.3.1.5 Palaeo-discharge inferred from uranium-series dating of spring travertine

The results also indicate that the majority of

deposits

recharge for the western GAB occurred during

Researchers conducted isotopic dating using

glacial periods. These findings support the

the uranium-series on samples of travertine

outcomes of the hydrodynamic analysis that

(carbonate rocks formed around springs)

suggest the GAB is now in a transient state and

throughout the western GAB. The range of

that western margin recharge rates are much

U-series ages indicates that spring discharge

lower than they were in the past during different

has been episodic, but has occurred in the same

climatic periods.

general locations for at least 465 000 years. The periods of high travertine growth suggest higher

The palaeo-hydrogeology evidence also shows

past groundwater discharge, which may reflect

springs can turn on and shut off abruptly in

periods of increased recharge, possibly

response to natural cycles of climate change.

due to regional wet intervals during wetter

For example, Sulphuric Springs had an on-off

climatic periods.

history about 10â&#x20AC;&#x201C;12 thousand years ago. It is

Pacoota Sst.

Bulldog Shale

mn.

Cadna-owie Fmn.

Algebuckina Sst.

Chapter 2: Summary of the volumes ?

n Point mn.

Polowanna Fmn. Peera Peera and Walkandi Fmns.

? Finke River recharge area

Eringa Trough McDills-Dalhousie Ridge Crown Point Fmn.

Aâ&#x20AC;&#x2122;

Witcherrie 1

Purni 1

Legend Purni Fmn.

-1000

Metres (AHD)

-2000

Purni Fmn.

Bulldog Shale Cadna-owie Fmn.

Algebuckina Sst.

-2000

Fmn.

Crown PointCrown Fmn. Point

Polowanna Fmn.

Finke Grp.

Peera Peera and Walkandi Fmns.

? Dullingari Group 40

100

Proterozo. Seds.

V/H = 6/1

Crown Point Fmn.

Mesozoic Eromanga Basin Mesozoic Simpson Basin Paleozoic Pedirka Basin Paleozoic Southeast Amadeus Basin Paleozoic Western Warburton Basin Paleozoic and older undifferentiated

Cenzoic and Mesozic undifferentiated Lake Eyre and Eromanga basins

Walkandi 1

Undifferentiated Lake Eyre and Eromanga Basins

Kilometres Undifferentiated Paleozoic and older rocks

Finke Grp.

Dullingari Group

-3000

Simplified stratigraphy

Macumba 1

Peera Peera and Walkandi Fmns.

Mokari 1

Polowanna Fmn.

Undifferentiated Paleozoic and older rocks Well -3000

Algebuckina Sst.

Unconformity

Inferred groundwater flow direction

Aâ&#x20AC;&#x2122; Purni 1

Pacoota Sst.

Metres (AHD)

? ?

Crown Point Fmn.

Poolowanna Trough

Cadna-owie Fmn.

Algebuckina Sst.

Fault Finke River and other ephemeral river recharge

Walkandi 1

Bulldog Shale

Conformable contact (queried where inferred)

Macumba 1

Proterozo. Seds. Eringa Trough McDills-Dalhousie Ridge Undifferentiated Lake Eyre and Dalhousie Springs Eromanga Mt. Hammersley 1 Witcherrie 1 Basins

Finke River recharge area Mereenie Sst.

Dullingari Group

Mokari 1

Mereenie Sst.

Mt. Hammersley 1

Figure 2.8: Hydrogeological 40 0cross-section, 20 60 80 100 Algebuckina west to east in V/H = 6/1 Sst. DalhousieKilometres Springs region

-1000

Poolowanna Trough

Dalhousie Finke Springs Grp.

Pacoota Sst.

Legend Conformable contact (queried where inferred) Fault Simplified stratigraphy

100

Proterozo. Seds.

V/H = 6/1

Kilometres

Legend

Finke River Cenzoic and Mesozic and other ephemeral undifferentiated Lake Eyre and river recharge Eromanga basins Mesozoic Unconformity possible that spring flows shut off in response Eromanga Basin

Conformable contact (queried where inferred) Fault

Formation and Algebuckina Sandstone permit

to natural climate change and in response to Finke River both mixing of and other ephemeral Well Mesozoic anthropogenic changes. However, if and when (Figure 2.8). river recharge Simpson Basin springInferred flow recommences, it may not occur in groundwater Paleozoic

groundwater and discharge

Unconformity

flow Pedirka direction the exact sameBasin location as prior to shutting off.

The analyses indicate that groundwater

These results may have implications for restoring Paleozoic Well

discharges at Dalhousie Springs are sourced

flow to GAB springs.

from water recharged from ephemeral rivers

Southeast Amadeus Basin Paleozoic Western Warburton Basin

2.3.1.6 Dalhousie Springs

Inferred groundwater that intersect flow direction

Paleozoic and older

the Algebuckina Sandstone and

the Crown Point Formation of the underlying

The Dalhousie Springs supergroup is subject to undifferentiated

Pedirka basin near Finke (Apatula) Community,

individual attention in Volume III because of its

approximately 150 kilometres northwest of

exceptional status among spring groups within

Dalhousie Springs.

the western GAB. Spring discharge at Dalhousie represents approximately 90% of the discharge

The identification of the role of western

occurring via GAB springs in the western GAB.

margin ephemeral river recharge in Dalhousie Springs discharge highlights the importance of

Dalhousie Springs is formed by fault-associated

managing extractions in this region to maintain

fractures in the McDills-Dalhousie Ridge Anticline

potentiometric levels in both the Great Artesian

(Figure 2.1). Uplift in the anticline formed a

(Eromanga) and Pedirka basins. Natural resource

topographic high and eroded the Bulldog

management in the ephemeral river recharge

Shale confining bed and exposed the Cadna-

zones of the Finke and Plenty Rivers and limited

owie Formation. Fractures in the Crown Point

in the Hale River should take account of this dependence.

Volume VII: Summary of Findings for Natural Resource Management of the Western Great Artesian Basin

Chapter 2: Summary of the volumes

Allocating Water and Maintaining Springs in the Great Artesian Basin

Water chemistry sampling at Dalhousie Springs. Photo: Szilvia Simon

2.3.1.7 Spring flow and aquifer pressure

Spring flow rates measured at the Freeling

changes

Spring Group indicate a much greater variation

The quantitative relationship between aquifer

exists in spring vent conductances than in the

pressure and spring discharge is conceptually

aquifer potentiometric head levels on the scale

modelled and explained in this volume. The

of this spring group. This implies that spring flow

model illustrates that under ideal hydrogeological

rates are much more likely to exhibit variations

conditions, changes in the elevation of aquifer

between springs due to vent conductance

head level above the elevation of a spring

differences than due to aquifer pressure

discharge point will result in a proportional

variations.

change in spring discharge rate. There is a distinct risk that this relationship is non-linear

The implication of this is that the rate of flow from

in springs where the conductance (ability to

a spring does not provide a useful indication

transmit water) of the spring vent is affected

of how robust its flow rate is against aquifer

by the rate of flow through the vent. However,

pressure reductions. A spring with a high vent

insufficient data are available on historic flow

conductance can exhibit a high flow rate, even

rates and aquifer pressure variations to identify

if it has a relatively low level of potentiometric

linearity or non-linearity of the relationship in any

head above the spring discharge point. This is

specific spring groups.

significant for resource management and risk assessments of springs.

This conceptual understanding applies to all springs of a form similar to those in the

In assessing the risks of aquifer drawdown to

south-west springs zone (i.e. springs with an

springs, knowledge of the elevation of aquifer

identifiable discharge point and sourced from a

potentiometric head level above the spring

confined aquifer underlying the springs). This is

discharge point provides a primary measure of

the form of many of the springs throughout the

the vulnerability of springs to aquifer drawdown.

GAB.

Equilibriu

12000

10000

8000

6000

4000 Chapter 2: Summary of the volumes 2000

6000

10%

20%

30%

40%

50%

60%

Spring flow reduction 4000

20000

2000 mg/L 3000 mg/L

Figure 2.9: Changes in equilibrium 4000 mg/L salinity of surface pool water with spring 0 reductions in 5000 mg/Ldischarge for a0%range of scenarios 10% 20%

2000

18000 A. Spring discharge salinity 20000 16000 30%

6000 mg/L

Equilibrium poolEquilibrium salinity (mg/L) pool salinity (mg/L)

20000

3000 mg/L 4000 mg/L

18000 5000 mg/L 16000

40%

50%

60%

Spring flow reduction

2000 mg/L

6000 mg/L

14000 20000

Equilibrium pool salinity (mg/L)

12000

18000 10000

18000 14000

16000 12000

14000 10000

12000 8000

10000 6000

8000 4000

6000 2000

16000 8000

40000

14000

6000

10%

20%

30%

40%

50%

60%

40%

50%

60%

40%

50%

60%

40%

50%

60%

Spring flow reduction

2000

12000

2000 mg/L

4000 10000

3000 mg/L 0%

2000

10%

20%

4000 mg/L

8000

30%

Spring flow reduction

5000 2000 mg/L 0

6000

10%

20%

30% 6000 3000 mg/L

40%

60%

50%

B. Evapotranspiration/outflow ratios Spring flow reduction 4000 mg/L

4000

5000 mg/L

20000

ET/Outflow 0.11 2000

6000 mg/L

ET/Outflow 0.25 18000

ET/Outflow 3.0 0

ET/Outflow 10%0.43

20%

20000 30% 16000

40%

50%

60%

Spring flow reduction

ET/Outflow 1.0

18000 14000

ET/Outflow 0.11 ET/Outflow 0.25 ET/Outflow 3.0 ET/Outflow 0.43 ET/Outflow 1.0

Equilibrium poolEquilibrium salinity (mg/L) pool salinity (mg/L)

Equilibrium pool salinity (mg/L)

14000

16000 12000

14000 10000

12000 8000

10000 6000

8000 4000

6000 2000

4000 0 0%

10%

20%

2000

ET/Outflow 0.11 0% ET/Outflow 0.2510%

ET/Outflow 3.0 ET/Outflow ET/Outflow 0.43 0.11

30%

Spring flow reduction

ET/Outflow ET/Outflow 1.0 0.25 ET/Outflow 3.0 ET/Outflow 0.43

20%

30%

Spring flow reduction

Volume VII: Summary of Findings for Natural Resource Management of the Western Great Artesian Basin

Chapter 2: Summary of the volumes

Allocating Water and Maintaining Springs in the Great Artesian Basin

Spring discharge

Diffuse discharge

Preferential leakage through fractures and faults

2 Figure 2.10: Conceptual diagram of groundwater discharge mechanisms

Slow leakage through massive aquitard

However, this approach should only be taken

2.3.1.8 Diffuse discharge

with an understanding that a linear relationship

Diffuse groundwater discharge from the

between spring flow and aquifer potentiometric

J Aquifer on the western margin of the GAB

head may be a best-case scenario for a spring

occurs by a combination of very slow upward

flow rate vulnerability assessment.

leakage through massive sections of shale aquitard and comparatively fast preferential

The study provides a further conceptual model

flow along fractures and faults (Figure 2.10).

that describes the relationship between changes

Both mechanisms discharge water to the upper

in spring discharge rate and the salinity of

aquifer.

water in the spring surface environment (Figure 2.9). The relationship and model indicate that

The diffuse discharge investigation provides the

the surface water environment of springs that

first ever estimates of diffuse discharge through

have both a high ratio of evapotranspiration to

the Bulldog Shale aquitard. The analysis found

outflow and high spring discharge salinity are

that upward leakage through massive sections

particularly susceptible to salinity increases

of shale aquitard is approximately 0.0003 mm/

as a result of reductions in spring discharge

year, or 3 mm per 10 000 years.

rate. This understanding may be applied for natural resource management purposes in the assessment of the risks to spring surface environments that may result from changes in spring discharge rates.

Chapter 2: Summary of the volumes

(A) (B)

(B) The study also gives evidence of a far more significant ‘preferential’ discharge mechanism, with groundwater discharging via fractures and faults in the aquitard to the overlying shallow unconfined aquifer. Results of noble gas analysis of the unconfined aquifer indicate effective hydraulic conductivity of this ‘preferential’ discharge is two to three orders of magnitude higher than diffuse discharge through the aquitard. The estimate of preferential discharge is not able to be up-scaled, but a methodology for regional assessment has been developed to quantify the discharge occurring via this process, providing an opportunity for important future

(C)

Subcore of Bulldog Shale

(D)

research. However, even a rate of preferential

(D)

discharge that is three orders of magnitude greater than diffuse discharge through the aquitard would equate to only approximately 0.3 mm/year. For the regional discharge areas of the GAB in South Australia, this estimate of preferential discharge could total between 20 and 300 ML/day. Although the relative importance of the preferential discharge at the regional scale is not quantified, the results suggest the total diffuse discharge rate, via both the preferential

Photos: Brian Smerdon

discharge mechanism and diffuse migration through the aquitard, is very low. Overall, diffuse discharge is likely to be substantially less than estimated in previous studies on which current water resource management is based. Stainless steel vacuum canister used for noble gas sampling

Volume VII: Summary of Findings for Natural Resource Management of the Western Great Artesian Basin

Chapter 2: Summary of the volumes

Allocating Water and Maintaining Springs in the Great Artesian Basin

2.4 Volume IV: Spatial Survey and Remote Sensing of Artesian Springs of the Western Great Artesian Basin

Chapter 1: Introduction Megan M Lewis, Travis Gotch, Davina White

Spatial Survey and Remote Sensing of Artesian Springs

Chapter 2: Spatial survey of springs Travis Gotch

of the Western Great Artesian Basin Allocating Water and Maintaining Springs in the Great Artesian Basin

Chapter 3: Characterising spring groups Davina White, Travis Gotch, Yuot Alaak, Michelle Clark, Joshua Ryan,

Volume

Megan M Lewis

Davina White, Caroline Petus, Megan M Lewis Chapter 5: Associating wetland extent and spring flow rates

Allocating Water and Maintaining Springs in the Great Artesian Basin

Chapter 4: Temporal dynamics of spring complexes

Davina White, Megan M Lewis Editors: Megan M Lewis, Chapter 6: Evaluation of remote sensing approaches

Davina White, Travis Gotch

Megan M Lewis, Davina White Chapter 7: Conclusions and recommendations

2.4.1 Volume IV summary

Analysis of airborne hyperspectral imagery

Volume IV: Spatial Survey and Remote Sensing

provides the first mapping of different vegetation

of Artesian Springs of the Western Great Artesian

communities for a range of GAB springs, as

Basin presents the results of spatial surveys and

well as evaporative crusts and standing surface

remote sensing activities, as well as describing

water. Such mapping provides a baseline that

the new tools, information resources and

can be used to monitor change in GAB springs

methodologies developed as part of this work.

as a result of water resource management.

2.4.1.1 Summary of key findings

High temporal frequency satellite imagery

Maps of 4516 spring vents in 103 spring groups

indicates that different wetland vegetation

in South Australia were produced, with elevations

communities have characteristic seasonal

of the outflow points. Of these, 40% of springs

phenological patterns of greening, drying and

have partially to completely ceased flows.

growth, and that these are quite different from those of dryland communities and watercourse

Researchers present a relationship between

vegetation.

the flow rates of springs and the total vegetated wetland area that can be used to estimate and

Satellite imagery is used to document changes

monitor flow in springs with objectivity and

in wetland area / development for Dalhousie and

repeatability.

Finniss complexes over the past 11 years with fortnightly time-steps.

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Freeling Springs & Mount Denison Chapter 2: Summary of the volumes

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Francis Swamp

Focal Spring Complex

Hermit Hill

Spring Comp

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Figure 2.11: Location of study spring complexes in the western GAB, highlighting the four complexes on which this report focuses

Strangways & Beresford

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Chapter 2: Summary of the volumes

Volume VII: Summary of Findings for Natural Resource Management of the Western Great Artesian Basin Allocating Water and Maintaining Springs in the Great Artesian Basin

Photo: Erika Lawley

This is the first documentation of the dynamic

hydraulic head potential above the spring

nature of the wetland vegetation communities.

discharge point for each of the surveyed springs.

The wetlands fluctuate in greenness and area

This quantity provides a primary indicator of

seasonally, largely as a result of the growing

the vulnerability of a spring-to-aquifer pressure

cycles of the dominant plants. Localised

reduction, for example due to groundwater

changes in wetland distribution and area are

extraction, and is essential to the assessment of

caused by changing spring flow paths and

risks to springs and spring ecosystems

occasional fires. Rainfall in the preceding six

(Volume VI).

months to one year strongly influences longer term fluctuations in wetland area.

A record of springs which were flowing and extinct in February 2012 provides an objective

2.4.1.2 Spatial and elevation survey of

baseline against which to monitor any future

springs of the western Great Artesian Basin

changes in spring flows due to groundwater

This study surveys a total of 4516 spring

extractions. With this information, future spring

vents within 103 spring groupsâ&#x20AC;&#x201D;the most

extinctions can be quantified with no uncertainty

comprehensive and accurate survey of spring

as to when the extinction took place.

vent position and elevation ever undertaken in the GAB. Prior to this work, the locations and

In addition, the spring survey data are used

condition of most GAB springs had not been

extensively with the remotely sensed imagery

accurately recorded, with many still unknown to

and associated field data presented in the

current natural resource managers.

subsequent sections of this volume.

The elevation data are a valuable resource for

2.4.1.3 Remote sensingâ&#x20AC;&#x201D;characterisation

GAB spring management and will significantly

of spring wetlands and surrounding

advance management of the western

landscape

margin GAB springs through use of the Risk

Mapping and monitoring of GAB spring wetlands

Assessment Framework. In combination with

has previously been confined to selected springs

the interpolated potentiometric surface of

in the western margin of the GAB.

the GAB aquifer, these spring elevation data allow estimation of the elevation of the aquifer

Chapter 2: Summary of the volumes

2 Monitoring methods have relied on visual

The imagery acquired for these studies includes

interpretation and classification of aerial

very high spatial resolution multispectral satellite

photography combined with considerable

imagery (1.85 m to 2.62 m spatial resolution)

field work. This approach to GAB spring

and hyperspectral airborne imagery with many

monitoring is costly, time-consuming, and has

spectral wavebands (over 120 wavebands

limited capacity to differentiate spring wetland

in the visible to short-wave infrared range,

vegetation communities or discriminate them

with a spatial resolution of ≥ 3 m). Dalhousie,

from surrounding dryland vegetation.

Francis Swamp, Mt Denison and Hermit Hill complexes provide showcases for environmental

In contrast, this study obtains new baseline

information derived through analysis of this

information about the current status of the

imagery. This image-based mapping provides

western margin GAB springs (in particular the

the first thorough documentation and baseline

extent of spring-fed wetland vegetation and its

information about the geomorphic context

floristic composition) from analysis of satellite

and surface expression of the springs, their

and airborne images coupled with field studies.

associated wetlands and environments. This

The nature of hyperspectral imagery: the detail is in the spectra

The extensive suite of collected hyperspectral

Project feature

data provides new insights into the characteristics of spring vegetation distribution

Plants, soils and minerals have distinctive

and composition as well as substrate and saline

reflectance characteristics, often called spectral

surfaces. Field spectra was collected to assist

signatures, in the visible to near-infrared part of

with and validate hyperspectral image analysis

the spectrum. These are caused by differential

for mapping of spring characteristics, as well

absorption, scattering and reflection of light by

as providing new spectral information about the

the molecules and structures that make up the

GAB springs.

materials. Hyperspectral remote sensing is able to record these spectral signatures and can be

The rapidly growing field of hyperspectral remote

used to provide information about land surfaces,

sensing is a valuable tool for mapping GAB

including vegetation condition and types, soil

springs because:

variations, minerals and moisture.

• the rich spectral detail (many narrow wavebands) enables discrimination of

In-situ measurement of spectral reflectance. Photo: Erica Lawley

Hyperspectral data contain many narrow

different vegetation communities and types,

wavebands, usually more than 100, within the

which were found to have unique spectral

visible to near-infrared parts of the spectrum.

characteristics that could be differentiated at

One ground-based and two airborne sensors

• spectral signatures also enabled discrimination

the spring-group scale were used in this study:

of surface water, minerals and substrate

• HyMap airborne sensor (450–2500 nm)

surface expressions

• ASIA Eagle airborne sensor (400–970 nm) • Analytical Spectral Devices (ASD) full-range

• two epochs of hyperspectral image capture enable changes in the characteristics of

FieldSpec® 3 spectroradiometer (400–

the springs and their surroundings to be

2500 nm).

investigated at an unprecedented level of detail.

Chapter 2: Summary of the volumes

Volume VII: Summary of Findings for Natural Resource Management of the Western Great Artesian Basin Allocating Water and Maintaining Springs in the Great Artesian Basin

includes spring-fed wetland extent and dominant

complexes investigated have been described

vegetation types, surface evaporative crusts

in previous literature, none have been mapped

and their mineralogy, wetted areas and standing

or their spatial characteristics documented and

surface water.

quantified.

This very detailed baseline information about

Case studies illustrate how this new, very

the western margin GAB springs provides

detailed spatial and spectral baseline data about

new insights about the surface expressions

the GAB springs can be used for a range of other

of these unique ecosystems in terms of the

applications of importance to natural resource

vegetation they support and their surrounding

managers. Examples include monitoring the

landscapes. It provides an objective baseline of

influence of bore capping on springs in Mt

spring character and condition in 2009â&#x20AC;&#x201C;2011

Denison (see break-out box and Figure 2.13),

for comparison with future assessments. This

and the use of surface water delineation to

new information is particularly significant given

estimate native fish populations and their risk of

that, although some of these spring groups and

invasion by Mosquito Fish.

A. Spectral profiles

B. Hyperspectral image cube

1 0.9 0.8 0.7

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A. Examples of spectral signatures of GAB wetland plants measured with field spectroradiometer and corresponding features in HyMap airborne hyperspectral imagery (Dalhousie, March 2009).

Bare soil

Ephemeral sedgelands

Phragmites reeds

B. The image cube illustrates both the spatial and spectral detail achievable with this type of imagery: every pixel in the highresolution image is recorded in 126 spectral bands, highlighted in rainbow colours behind the colour image.

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Produced by The University of Adelaide School of Earth & Environmental Background image: HyMap, Sciences | Map Projection UTM 665.7 nm, March 2009. Background images: HyMap, Inset image: Landsat True Colour, 2006 Transverse Mercator | Map Datum Geocentric Datum of Australia 665.7 nm, March 20091994 | by The University of Adelaide DateProduced January 2012 Inset image: True School of EarthLandsat & Environmental Sciences2006 | Map Projection UTM Colour, Transverse Mercator | Map Datum Produced by The Geocentric Datum of University Australia 1994 | January 2012 ofDate Adelaide, School of Earth &

Background image: HyMap, 665.7 nm, March 2009. Metres True Colour, 2006 Inset image: Landsat

300

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0 Legend 100 200

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Geocentric Datum of Australia 1994 | Legend

Figure 2.12: Distribution of wetland vegetation Background image: HyMap, 665.7 nm, March 2009. types, Inset image:from Landsatspectral True Colour, 2006 analysis of HyMap Produced by The University of Adelaide School of Earth hyperspectral & Environmental airborne Sciences | Map Projection UTM imagery (March Transverse Mercator | Map2009) Datum

Chapter 2: Summary of the volumes

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Chapter 2: Summary of the volumes

Volume VII: Summary of Findings for Natural Resource Management of the Western Great Artesian Basin

! .

Allocating Water and Maintaining Springs in the Great Artesian Basin

Project feature 604000

Legend

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Big Blythe Bore Extent of wetland 2.13: ! .Figure

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605000 from Big Blyth Bore supported an estimated

Uncontrolled artesian water flowing from

424.8 ha of wetlands, comprising a large,

bores can reduce aquifer pressure and have

relatively homogenous expanse of Bulrush

adverse impacts on nearby natural springs.

(Typha domingensis), extending north-west

Studies at Freeling Springs and Big Blyth

from the bore into the nearby ephemeral

Bore 15 km to the east (latitude 28.05° S,

creek system (Figure 2.13). Interpretation

longitude 136.06° E) aim to quantify these 604000

of archival Landsat satellite imagery helped 605000

impacts. Satellite and airborne remotely

identify the vegetation fed by flows from

sensed imagery were acquired near-

the bore.

simultaneously with field data in April and May 2011 to provide baseline measurements of the area of wetland associated with the

Chapter 2: Summary of the volumes

2 2.4.1.4 Remote sensingâ&#x20AC;&#x201D;spring wetland

Very high spatial resolution satellite images

change over time

of vegetation greenness allow highly detailed

This research, for the first time, documents

delineations of the extent of spring-fed wetland

seasonal growth cycles of dominant spring

vegetation. This research documents short-

wetland vegetation and monitors changes in

term variability in wetland extent at Dalhousie

wetland greenness and area since 2000. This

Spring Complex and links it to influences from

is achieved through analysis and interpretation

rainfall, land management practices and natural

of moderate spatial resolution (250â&#x20AC;&#x2030;m ground

hazards such as fires started by lightning strikes.

resolution), high temporal frequency (16-day

The dynamic nature of spring tails is particularly

composites) MODIS satellite imagery.

notable: they are highly mobile, moving tens of metres in short intervals of 1 to 3.5 years (Figure

Findings show that different wetland

2.14). Airborne spectral mapping techniques

communities have characteristic seasonal

revealed changes in the extent and species

growth patterns of greening and drying, quite

composition of spring-fed wetland vegetation

distinct from those of dryland and intermittent

and surrounding wetted area and diffuse

watercourse vegetation. This information will be

evaporative discharge in 2009-2011.

useful for future spring monitoring, as it identifies the variation in wetland greenness throughout

The outcomes of this study provide a highly

the year and can be used to recommend

valuable baseline documentation of the recent

appropriate timing of image and field data

extent and condition of several major spring

collection. For example, monitoring when

groups and complexes, against which future

spring vegetation is at maximum greenness

change can be assessed. Additionally, the

improves discrimination of spring vegetation

techniques developed can be used to survey,

from surrounding dryland vegetation and allows

map and monitor these poorly documented

more consistent comparisons between years. In

ecosystems.

addition, their characteristic seasonal patterns of greenness may be used to detect spring-fed

2.4.1.5 Area of spring wetland vegetation as

wetlands in broad-scale inventories that seek to

a surrogate for spring flow

locate and document the occurrence of spring

Historically, direct monitoring of flow from

ecosystems.

springs has been limited in extent and duration, and has been logistically difficult.

This research documents changes in wetland area for Dalhousie and Hermit Hill complexes

In this volume, researchers use detailed mapping

over the past decade with fortnightly time-steps.

of spring wetland extent from very high spatial

The findings have important implications for

resolution (from 1.85 to 2.62â&#x20AC;&#x2030;m) multispectral

assessing spring and wetland responses to

satellite imagery to successfully develop a strong

changes in aquifer pressure. Rainfall, ecological

linear relationship between spring-fed wetland

cycles and processes, and changes in spring

extent and spring flow rates at Dalhousie and

flow all influence annual and longer-term trends

Mt Denison Spring complexes. Figure 2.15

in wetland area. Consequently, the baseline

illustrates this relationship for the Mt Denison

against which impacts might be measured is not

Complex. These two complexes vary markedly

a single value, but a range of variation observed

in spring spatial extent, flow rates and number

under natural conditions, which may be used

of springs, along with differing geomorphic

to establish acceptable limits or thresholds of

settings. In addition, comparison of satellite

change.

images of the same site from different dates allows an estimate of the range of variation in the wetland area / flow relationship.

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Vegetation Index

NDVI increase NDVI decrease

DCA001 from analysis of QuickBird multispectral satellite Low imagery

timeHigh of spring

Metres Vegetation Index Figure 2.14: Change over

NDVI decrease

Volume VII: Summary of Findings for Natural Resource Management of the Western Great Artesian Basin Chapter 2: Summary of the volumes

Allocating Water and Maintaining Springs in the Great Artesian Basin

Chapter 2: Summary of the volumes

2 This relationship is significant because spring-

Moderate resolution MODIS imagery with high

fed wetland area can be used as a surrogate

frequency (16-day) and a long archive (11

for spring flow volume, providing an objective

years) is ideally suited to determining seasonal

and cost-effective means of monitoring GAB

and longer term changes in spring wetland

spring response to any aquifer changes. New

vegetation at large spring complexes. Very

techniques have now been developed and are

high resolution multispectral satellite imagery

easy to reapply to newly captured imagery.

provides the fine detail necessary to map and

These findings have important implications

quantify wetland vegetation extent to relate

for natural resource managers given that this

to spring flow rates. Hyperspectral airborne

new technology and technique can be used

imagery contains fine spectral detail about

effectively for monitoring GAB spring flows and

the reflectance properties of vegetation, soils

can be collected for time-sensitive situations.

and minerals, ideally suited to discriminating dominant spring vegetation types and

2.4.1.6 Evaluation of remote sensing

associated spring surface features. Visible and

approaches

near-infrared colour digital aerial photography

This volume applies and evaluates a wide range

with very fine spatial resolution is a staple

of remote sensing, spatial information and field

image product for validating mapped outputs,

measurements for spring characterisation,

particularly important for these remote sites. This

assessment and monitoring. After testing over

review will enable managers to select the most

a range of spring contexts, spatial and temporal

appropriate techniques to survey and monitor

scales, researchers make recommendations

GAB springs.

about the appropriateness and utility of various remote sensing and spatial technologies for these purposes.

Figure 2.15: Relationship between wetland area and spring flow rate at 21 springs, Freeling Springs, Mt Denison

3.5

Spring wetland area (ha)

2.5

1.5

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Volume VII: Summary of Findings for Natural Resource Management of the Western Great Artesian Basin

Chapter 2: Summary of the volumes

Allocating Water and Maintaining Springs in the Great Artesian Basin

2.5 Volume V: Groundwater-dependent Ecosystems of the Western Great Artesian Basin

Chapter 1: Introduction Travis Gotch

Groundwater-dependent Ecosystems

Chapter 2: Biology and ecology of South Australian GAB springs Travis Gotch

of the Western Great Artesian Basin Allocating Water and Maintaining Springs in the Great Artesian Basin

Chapter 3: Palaeo-ecological analysis of artesian springs in the GAB of South Australia

Volume

Jennie Fluin, Nicholas De Rozario, John Tibby, Travis Gotch, Andrew J Love

GAB spring invertebrates Michelle Guzik, Nicholas Murphy

Allocating Water and Maintaining Springs in the Great Artesian Basin

Chapter 4: Fauna of the GAB springs: Comparative phylogeography of

Chapter 5: Flora of the GAB springs: Ecology of GAB vegetation Laurence Clarke, Molly Whalen, Duncan Mackay

Editor: Travis Gotch

Chapter 6: Phragmites australis: Knowledge to support its management on GAB springs Jane Roberts Chapter 7: Grazing management Travis Gotch, Michelle Denny, Mellissa Horgan Chapter 8: Date Palms and the return of environmental flows Travis Gotch, Denise Noack Chapter 9: Conclusions and recommendations Travis Gotch

2.5.1 Volume V summary

2.5.1.1 Summary of key findings

Volume V: Groundwater-dependent Ecosystems

This work confirms and extends knowledge of

of the Western Great Artesian Basin explores

the high genetic diversity and high degree of

the ecological communities and organisms that

endemism present in the GAB springs. Twenty-

depend on GAB spring discharge. It describes

five new species of invertebrates are found in the

the genetic diversity and distribution of flora and

South Australian springs that are found nowhere

fauna and established a 37â&#x20AC;&#x2030;000-year ecological

else in the world.

history at Warburton Spring. In this context, it then examines three of the most pressing current

GAB spring-dependent plant species

management issues affecting the ecological

exhibit complex responses to different land

balance of mound spring communities: Common

management factors and zonation in spring

Reed control, grazing pressure and Date Palm

habitats.

infestation.

Chapter 2: Summary of the volumes

2 Researchers found that Common Reed

It is unclear therefore whether the regular

(Phragmites australis) has existed at GAB

burning was due to natural or anthropogenic

springs for many thousands of years and

causes. In either case, the new data gained from

should be viewed as a native species that can

this study suggest that burning and Common

become out of balance due to changes in land

Reed have coexisted for many thousands of

management.

years. This new information is useful when considering the effectiveness of prescribed

Removal of exotic vegetation is shown to be

burning as a strategy for the control of Common

an effective method to return environmental

Reed at GAB spring sites.

flows and restore groundwater-dependent ecosystems.

The age of the palaeo-environment record at Warburton Spring adds scientific value to this

2.5.1.2 Palaeo-ecology

and other GAB spring sites that should be

Radiocarbon analyses of sediments from

a consideration when assessing the risks of

Warburton Spring shows this site has among

disturbance to GAB springs.

the oldest palaeo-ecological evidence of any palaeo-environment record in Australia, with a

2.5.1.3 GAB spring fauna

basal age of greater than 37â&#x20AC;&#x2030;000 years. A history

The springs of the western GAB contain aquatic

of Common Reed (Phragmites australis) was

fauna that have existed for many thousands

constructed for Warburton Spring, covering the

of years in what are essentially aquatic islands

extent of this period. This is the longest record of

within a sea of desert. Genetic analysis of GAB

Common Reed growth in Australia.

spring aquatic invertebrate fauna (Figure 2.16) identified up to 42 likely new species of endemic

The presence of Common Reed over

isopods and hydrobiid snails. Based on these

37â&#x20AC;&#x2030;000 years can be used as a guide when

results, the biodiversity represented by cryptic

considering future management practices for

species has been vastly underestimated to date.

GAB springs. Current management practices often assume that this species is a post-

The research shows that each of the taxa

European introduction to the GAB springs,

demonstrated distinct lineages between spring

however this study concludes that the species

groups and complexes, suggesting dispersal

is actually a natural occurrence in the region.

between springs is low to absent. The genetic

This new understanding should be taken into

differences correspond with geographical

consideration when determining ecological

features in the landscape and are dependent on

baselines and condition targets for GAB springs.

the dispersal mechanisms (or lack thereof) of individual species for most taxa. The research

The study determines the fire history at

identifies specific locations of high vulnerability

Warburton Spring from analysis of charcoal in

based on diversity of ecologically significant units

sediment cores, which indicates the occurrence

and endemism, including Coward and Neales

of regular burning throughout the 37â&#x20AC;&#x2030;000-year

spring complexes.

history of this spring. It is difficult to correlate this record with Indigenous occupation of the

2.5.1.4 GAB spring flora

area, as archaeological investigations are not

GAB springs support many endemic and

conclusive about when occupation commenced.

threatened species of flora, as well as populations of species not otherwise found in the arid zone.

Chapter 2: Summary of the volumes

Volume VII: Summary of Findings for Natural Resource Management of the Western Great Artesian Basin Allocating Water and Maintaining Springs in the Great Artesian Basin

2 Figure 2.16: Endemic aquatic GAB springs fauna from southern Lake Eyre

B. Austrochiltonia sp. (Amphipoda)

C. Ngarawa sp. (Ostracoda) and

D. Haloniscus (Isopoda: Oniscidea)

Photos: Nick Murphy

A. Phreatomerus latipes (Isopoda)

terrestrial

Analysis of vegetation and environmental data

conditions across spring groups and complexes,

from over 1000 springs in the Lake Eyre and

and is also significant for management at the

Lake Frome supergroups (Figure 2.17) finds

local spring scale. Reductions in spring flow that

that a range of physical and chemical factors

result in a reduction in the spring tail environment

influence the abundance and diversity of

and zones of different hydrochemistry may

vegetation at the GAB springs. Of particular

result in loss of flora diversity. A key determinant

interest is a focal group of species that are found

of flora diversity is the number of spring vents;

predominantly on GAB springs in the study area

therefore, losses of spring vents (through flow

to the west and south of Lake Eyre. The focal

reduction) may result in loss of flora diversity.

group of flora are more abundant at springs with high flow rates and species richness is positively

Correlation of plant species richness and

associated with springs that have flowing water

abundance against stock impact show some

in their tails.

species-specific associations. Focus group species richness in general is negatively

The study also demonstrates species-specific

correlated with stock impact; however, when

but variable associations with conductivity. This

fenced springs are excluded from the analysis,

has important implications for preserving suites

the maximum number of focus group taxa occur

of species associated with different conductivity

in lightly grazed springs (these relationships are

700000

800000

Wangianna

Hermit Hill

LAKE EYRE

Neales River

Mt Margaret Mt Denison

Coward Peake CreekMt Dutton Neales Springs River

700000

Beresford Lake Eyre South 800000

800000

500000

600000

700000

800000

Francis Mt Swamp Margaret Strangways LAKE EYRE Beresford Lake Lake Eyre South Cadibarrawirricanna Billa Kalina Hermit Hill Coward Strangways Francis Swamp Springs Wangianna Beresford Lake Eyre South Billa Kalina Hermit Hill Coward 500000 600000 700000 800000 Springs Wangianna

500000

700000

LAKE EYRE

Strangways

Mt Denison 600000 Billa Kalina

600000 Lake Peake Creek Cadibarrawirricanna

500000

MtSwamp Dutton Francis

Lake 500000 600000 Cadibarrawirricanna

6800000

6900000

6900000 6700000

6800000

6700000

900000

Mt. Hopeless

900000

Reedy

Mt. Hopeless Lake Blanche

Reedy

Lake Blanche

900000

Mt. Hopeless

Reedy

900000

Lake Blanche

900000

1000000

6800000

6900000

1000000

6900000 6700000 6800000 6800000 1000000

6700000

40 1000000

6700000

Mt Margaret

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Map Projection: UTM Transverse Mercator Map Datum: Geocentric Datum of Australia 1994 Date: January 2012

2006 by The University of Adelaide Produced School of Earth Environmental Produced by&The University Sciences | Map Projection UTM of Adelaide, School ofDatum Earth & Transverse Mercator | Map Geocentric Datum of Australia 1994 | Environmental Sciences Date January 2012

Background image: Landsat 2006 Background image: Landsat

Produced by The University of Adelaide 0 40 80 School of Earth & Environmental Sciences | Map Projection UTM Kilometres Transverse Mercator | Map Datum Geocentric Datum of Australia 1994 | Date January 2012

Background image: Landsat 2006

Springs Kilometres

0 Legend

Springs area and location of spring complexes

Produced by The University of Adelaide School of Earth & Environmental Sciences | Map Projection UTM Transverse Mercator | Map Datum Geocentric Datum of Australia 1994 | Date January 2012 Flora study Legend Figure 2.17:

Chapter 2: Summary of the volumes

Volume VII: Summary of Findings for Natural Resource Management of the Western Great Artesian Basin

Chapter 2: Summary of the volumes

Allocating Water and Maintaining Springs in the Great Artesian Basin

further explored in later chapters; see 2.5.5 and

Roberts (Chapter 6, Volume V (Gotch 2013))

2.5.6). An abundance of focal group species

shows that the possibility of Common Reed

including Cutting Grass (Gahnia trifida) and

invading sites from which it has been eliminated

Bare Twig-rush (Baumea juncea) are generally

is low (though not impossible), and that this

negatively associated with the presence of

species is unlikely to be actively colonising new

stock. However, the abundance of the nationally

sites, but much more likely to be re-establishing

endangered spring-dependent Salt Pipewort

its canopy.

(Eriocaulon carsonii) is positively associated with grazing. This species is also found to

The specific adaptations of Common Reed

be dependent on sites with low salinities and

are such that it is a vigorous competitor for

therefore efforts to conserve this species can be

space and nutrients on GAB springs. Common

targeted and should take into consideration the

Reed has an impact on endemic and relict flora

requirements of other species.

species and is perceived as a threat to native plant and animal communities on GAB springs

The study also explores the genetic structure of

in northern South Australia. These plant and

GAB spring and coastal wetland populations of

animal species are listed as endangered under

the sedges Cutting Grass and Bare Twig-rush.

the Environment Protection and Biodiversity

Both species are found to show significant

Conservation Act 1999. Taking into account the

genetic differentiation and restricted connectivity

results of the palaeo-ecology study (Chapter 3,

between spring groups.

Volume V (Gotch 2013)) that found Common Reed has been present at GAB springs for many

The genetic component of the study helps

thousands of years, Common Reed may be

to determine the appropriate spatial unit

viewed as a native species that is out of balance

for managing GAB spring-dependent flora.

due to changes in land management.

Understanding the nature and ecology of the GAB spring-dependent vegetation and the

2.5.1.6 Grazing management of GAB springs

degrees of isolation between spring groups

Many GAB springs provide water and feed

and complexes is critical to the management of

for stock and there is concern that both the

endangered ecosystems.

presence and removal of stock may have negative impacts on GAB springs. This chapter

2.5.1.5 Common Reed (Phragmites

presents a review of the effects and impacts

australis)

of grazing in riparian and spring environments

In this section, a literature review and ecological

along with a community survey into the values

synthesis provides a knowledge platform to

of GAB springs to a wide range of stakeholders.

guide and inform future decisions on managing

It is found that grazing and spring management

the threats imposed by Common Reed

are not mutually exclusive, however grazing must

(Phragmites australis). This work is in response

be carefully managed to reduce its impactsÂÂâ&#x20AC;&#x201D;

to the findings of grazing exclosure monitoring

especially in GAB springs where there is high

and the anecdotal reports of land managers that

diversity of short-range endemics.

find Common Reed grows strongly following lifting of grazing pressure, apparently to the detriment of other species, notably the nationally endangered spring endemic Salt Pipewort.

Chapter 2: Summary of the volumes

2 2.5.1.7 Date Palms and return of

The work has been highly successful and cost-

environmental flows

effective, however it is imperative to follow up

A series of on-ground works enabled the

regeneration in treated areas and to continue

return of environmental flows to the Dalhousie

treatment in the untreated areas. Any use of

Spring Complex by removing invasive Date

fire as a management tool to achieve a specific

Palms (Phoenix dactylifera) from the springs

management outcome (e.g. reduction in

(Figure 2.18) and monitoring the recovery. A

abundance of Date Palms) must consider both

total of 2458 palms were removed, resulting

the probability of success and the risks to non-

in an estimated return of environmental flow of

target species and ecological processes.

between 307 and 442 ML/year. The work shows that a program of integrated and staged on-ground management works can return significant environmental flow and habitat availability to GAB springs.

Photo: Travis Gotch

Figure 2.18: Green Date Palms on fire at Old Man Spring, Dalhousie, South Australia

Volume VII: Summary of Findings for Natural Resource Management of the Western Great Artesian Basin

Chapter 2: Summary of the volumes

Allocating Water and Maintaining Springs in the Great Artesian Basin

2.6. Volume VI: Risk Assessment Process for Evaluating Water Use Impacts on Great Artesian Basin Springs

Chapter 1: Introduction Chapter 2: Risk identification

Risk Assessment Process for Evaluating Water Use Impacts

Chapter 3: Spring classification

on Great Artesian Basin Springs Allocating Water and Maintaining Springs in the Great Artesian Basin

Chapter 4: Risk analysis

Volume

Chapter 5: Case study: Freeling Spring Group

Allocating Water and Maintaining Springs in the Great Artesian Basin

Chapter 6: Conclusions

Editors: Graham Green, Melissa White, Travis Gotch, Glen Scholz

2.6.1 Volume VI summary

• a system of ratings for the likelihood of

Volume VI: Risk Assessment Process for

impacts arising, the specific vulnerabilities of

Evaluating Water Use Impacts on Great Artesian

springs and specific ecological values of their

Basin Springs builds on the findings of the

ecosystems

previous volumes to provide a guideline for structured analysis and evaluation of risk factors associated with reductions in groundwater pressure in the GAB.

• a simple visual summary of the overall assessment outcomes and the ratings applied • acknowledgement of uncertainties in the risk evaluation process and recommendations

To enable risk assessment of such complex environmental assets, a multi-stage process is described that facilitates: • classification of springs and spring groups

for further information required to reduce uncertainties • assessment of the controls, either existing or necessary, to mitigate assessed risks.

according to their morphological types • identification of the degree of threats

The risk assessment process includes

presented by proposed groundwater

individual assessments of the various defined

developments and the likely impacts on spring

risk components, while a table displays the

flow rates

assessed ratings for each (Table 2.1). The table

• assessment of the vulnerabilities of springs

provides an overall summary of the level of risk

and spring groups to identified threats

presented to the subject spring or spring group

according to their typology and degree of

and enables easy identification of which risk

exposure to the threat

components are considered to be contributing

• assessment of the specific ecological values of

the majority of overall risk.

springs and spring groups

Chapter 2: Summary of the volumes

2 Figure 2.19: Six stages of risk assessment for evaluating water use impacts on GAB springs

A. Likelihood assessment

1. Spring flow impact likelihood

a. Determine aquifer pressure above spring level versus predicted drawdown b. Apply spring flow reduction likelihood matrix

B. Vulnerability assessment 2. Spring surface environment vulnerability

a. b. c. d.

Assess surface water salinity Assess acid sulfate hazard Assess morphology Assess wetland extent

3. Ecosystem connectivity vulnerability

a. Identify ecological focal zone b. Determine vulnerability of connected ecosystems to fragmentation

C. Consequence assessment 4. Ecological values

a. Assess ecological values

D. Uncertainty assessment 5. Confidence

a. Indicate the level of certainty for steps 1â&#x20AC;&#x201C;4 b. Address knowledge gaps for future risk assessments to consider

E. Controls analysis 6. Existing controls and protections

a. Determine if current statutory controls demand or provide mitigation of risks

Volume VII: Summary of Findings for Natural Resource Management of the Western Great Artesian Basin

Chapter 2: Summary of the volumes

Allocating Water and Maintaining Springs in the Great Artesian Basin

Table 2.1: Risk assessment summary for Freeling Spring Group for a hypothetical impact Risk assessment step

Component

Rating8

Likelihood assessment

1a. Aquifer pressure above spring level versus predicted drawdown (number of spring vents in each rating category)

1b. Spring flow reduction likelihood matrix (number of spring vents in each rating category)

2a. Surface water salinity

Medium

High

2b. Acid sulfate hazard

Medium

Medâ&#x20AC;&#x201C;High

2c. Morphology (typology)

High

Medâ&#x20AC;&#x201C;High

2d. Wetland extent (number of spring vents in each rating category)

3a. Ecological focal zone

Refer to Figure 2.19

High

3b. Wetland connectivity vulnerability

Moderate

High

Low

Med

High

Distinctiveness

High

Vital habitat

High

Evolutionary history

High

Naturalness

High

Vulnerability assessment

Risk of ecosystem fragmentation Consequence assessment

4a. Diversity

Confidence High

High

* Rating options are: extreme (E), high (H), moderate (M), low (L), based on assessments

The process for the assessment of the likelihood

The risk assessment process is informed and

of impacts to the springs makes use of new

underpinned by a sound scientific understanding

information provided for the first time by the

of the ecological and physical characteristics of

outcomes of the AWMSGAB Project, including

springs and the response of these to identified

the potentiometric surface map of the main GAB

threats. It brings together new understanding

aquifer and accurately surveyed elevations of the

provided by the AWMSGAB Project of the

artesian springs in South Australia.

nature and hydrogeology of GAB springs, their physical, hydrological, chemical and ecological vulnerabilities, and their ecological values.