Climate Variability and Freshwater Systems

Lessons for protecting freshwater systems from climate change impacts

Fran SheldonAustralian Rivers Institute

Griffith School of Environment Griffith University

We know Australia’s rivers are variable…..

from Puckridge et al. (1998). Mar. Freshw. Res. 49, 55-72

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Cooper

Diamantina

Burdekin

DarlingVaalFitzroyLimpopo

Danube

MississippiMekong Colorado

Rhine

Summary medians (23 hydrological measures)

Predictions are that variability will increase with climate change…….

Rainfall & consequently river flow will become more variable There will be less frequent, but perhaps larger, floods Rivers will be influenced by longer, and more severe, no flow or

drought conditions There will be an increase in the number of highly variable rivers Understanding flow variability and its influence on rivers will

become important for o looking at resilience of systems in the face of climate changeo determining environmental flows and o assessing ecosystem health

Scales of Variability in Dryland Rivers

Reach scale responses to ‘boom and bust’ cycles

Within channel

water level fluctuations

Catchment scale responses to

flood – drought cycles

Temporal Scale (years)

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m)

Within channel variability:Lower River Murray

BlanchtownEuston

MorganOverlandCorner

Renmark

Loxton

Mildura

Menindee

MenindeeLakes

1 2 3 45 6 7 8 9 10

ADELAIDE

SouthAustralia

New South Wales

RiverMurray

DarlingRiver

0 100km

Water level variability changes along the channel

Time

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UP LPMP

UP LPMP

Assemblage differences along the channel reflect different levels of variability

Discrete assemblages between channel sections

Overall diversity very low compared to other large rivers

Differences in assemblages reflect different microhabitats

MDS Plot, Bray-Curtis Dissimilarity, log10(x+1) abundance data

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is 2

Lower Pool

Middle Pool

Upper Pool

Axis 1

Ax

is 2

Lower Pool

Middle Pool

Upper Pool

Reach scale responses to Boom & Bust

Data from CRCFE Dryland River Refugia Project

Photo by Peter Unmack

Photo by Stephen Balcombe

• We know that:– Temporal changes in flow (boom and bust)

have strong influences on dryland river ecosystems

April 2001September 2001October 2002May 2003January 2004 March 2004 June 2004 October 2004 December 2004

Flow variability drives water quality - Cooper Creek

Windorah Water Quality

PCI – 47%Conductivity, Total Hardness, TDS

-2 0 2 4

PCII – 27%Total NTotal P

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Dry Samples

Flow Samples

Flood Samples

PCA Plot, Water Quality Data from Windorah reach

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Temporal Variability Cooper Creek - Invertebrates

TanbarApril 2001

SpringfieldApril 2001

NoonbahApril 2001

WindorahApril 2001

Sept 2001

Oct 2002

May 2003

Stress = 0.16

Data from CRCFE Dryland River Refugia Project: Marshall, Sheldon, Thoms & Choy 2006

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MDS Plot, Bray-Curtis Dissimilarity, log10(x+1) abundance data

Temporal shifts in community composition driven by hydrological connection

Connection Disconnection

Prolonged Disconnection

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Sequential flooding

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1950 1951 1952 1953 1954 1955 1956 1957 1958 1959

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Mungindi

Darling Bourke

Darling Wilcannia

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Darling River

Larger catchment

scale responses

A large scale sequence of wetlands

Upper Middle LowerWetlands

The BIG ‘booms’

Removing water from the top end…..

The BIG ‘booms’

Upper Middle LowerWetlands

Protecting variability at all scales

• We recognise variability is important in driving large river ecology across a range of scales

• To protect large rivers we need to protect this variability

• Intrinsic resilience to variability – adapted to cope with climate change, but

• Climate change + human pressure may be too much……

Summary

Photo by Peter Unmack

Photo by Jon Marshall