Recent Floods and Salinity of the Murray River

Recent Floods and Salinity of the Murray River
Tapas Biswas, Asitha Katupitiya and Jason Alexandra, MDBA
River Symposium – Melbourne, 8-12 Oct 2012

Content
1. Murray Darling Basin
2. River Murray salinity (targets and
objectives)
3. Post flood-recession salt mobilisation and
key processes
4. River reaches contributing salt loads
5. Post-flood salinity exceedances at
Morgan, SA, after various floods
6. Salt Interception on post flood salinity
7. Key messages

Two River Systems
−Murray River 2,530 km
−Darling River 2,740 km
Murray-Darling Basin
Basin Area: 1,060,000 Square kilometers
14% of Australia; Four States and ACT
>2 million people
>40% Agricultural product value ~$10
billion per year
Home to 34 major Indigenous groups
The city of Adelaide located
just outside of the Basin at the
downstream end of the Murray-
Darling River System

River Murray – a saline minefield
Source: Ian Jolly (CSIRO)

Why salt matters
Stock
Urban
Irrigation
Industries
Human
consumption
Environmental
needs

Basin Salinity
Management Strategy
Basin Salinity Target
aims to maintain the
salinity at Morgan < 800
EC (µS/cm) for 95% of
the time
Murray accounts for
40% of Adelaide’s
water supply; in
drought year this can
increase to 80%.
Salinity targets and objectives
The proposed Water
Quality and Salinity
Management Plan
(to be tabled at the
federal parliament)
includes objectives
and targets to
maintain acceptable
salinity levels at key
locations and
flushing of salt out of
the Lower Murray
System.

Historic salinity records at Morgan, SA

River reaches for salt mobilisation study

Salt Inflow - Daily Average (t/day)
Salt loads from major reaches
during flood recession
3000
2500
2000
1500
1000
500
0
-500
-1000
Major Reach - Salt Inflows
BIGMOD - 1970 to 2009
Euston to Mildura Mildura to Lock 9 Lock 9 to Lock 5 Lock 5 to Morgan Morgan to Murray
Bridge
Longterm Average During Floods During 6 months Following Flood
IncreasingRisk
MDBA 2011

Recessions salt spikes possibly driven by ponded
water in Coombool Swamp (Backwater)

Recent flood in the Murray River
Flood waters spreading into the flood plain, recharges the groundwater systems
which pushes salt back to the river after the floods have gone past.
© MDBA 2011

70 dSm -1
Drought and Basin’s salt export past
Morgan, SA
Year Morgan Salt Load (t/yr)
2000-01 1,444,929
2001-02 624,941
2002-03 359,278
2003-04 430,043
2004-05 332,515
2005-06 425,373
2006-07 226,546
2007-08 152,451
2008-09 180,918
2009-10 239,621
2010-11 2,902,225 Flood
2011-12 1,723,786 High Flow

Salt Load (t/month)
600,000
500,000
400,000
300,000
200,000
100,000
Basin Salt Export at Morgan with Recent
Floods (July 2009- June 2012)
0
Morgan Salt Load (T/mth)
Averaged Monthly Flow (Locks 1&2
U/S) (GL/mth)
Jul-09
Aug-09
Sep-09
Oct-09
Nov-09
Dec-09
Jan-10
Feb-10
Mar-10
Apr-10
May-10
Jun-10
Jul-10
Aug-10
Sep-10
Oct-10
Nov-10
Dec-10
Jan-11
Feb-11
Mar-11
Apr-11
May-11
Jun-11
Jul-11
Aug-11
Sep-11
Oct-11
Nov-11
Dec-11
Jan-12
Feb-12
Mar-12
Apr-12
May-12
Jun-12
Dec’10– Jun’12 (1.5 years) ~ 4.25 million tons of salt export past Morgan
2500
2000
1500
1000
500
0
Flow (GL/month)

Flow (ML)
20000
18000
16000
14000
12000
10000
8000
6000
4000
2000
0
Morgan salinity exceedances
Flow (Lock 1) vs EC (Morgan)
800 EC
2.9%
13.8%
5000 ML/day
0 200 400 600 800 1000
EC
1200 1400 1600 1800
•Most exceedences occur
at flows below 5,000 ML/d
MDBA 2011

Morgan salinity exceedance – post
flood 1981
MDBA 2012

Morgan salinity exceedance –
post flood 2010-11
MDBA 2012

Engineering Solution: Salt Interception
Schemes
Diverts saline groundwater and
surface drainage in the landscape
away from an area of high in-river
impact to an area of very low in-river
impact.

Change in Salt loads (t/d)
100
0
-100
-200
-300
-400
-500
-600
-700
-800
-900
-1000
-1100
-1200
-1300
-1400
-1500
-1600
-1700
-1800
-1900
-2000
1968
Operating rules for Barr Ck
Actions that changed salt loads to the river
since 1968
Buronga and Mildura-Merbein
1980
Total average reduction
per year 465,281 t–salt
SIS since 2001)
206,987 t-salt
Other state actions
258,294 t-salt
Curlwaa
1983
1984
Rufus River and Noora Drainage Disposal Scheme
Baseline date for Basin Salinity Managemnt Strategy (1988)
Total average increase
per year 44,024 t-salt
Other increases due
to past (pre-1988)
actions?
1991
Woolpunda, Mildura-Merbein upgrade, New operating rules
for Barr Ck (1991) and Barr Ck CMP
Waikerie
1992
1994 1996 1999
Mallee Cliffs
Psyche Bend
New operating rules for Barr Ck (1999)
SA IIP and Rehabilitation
Qualco Sunlands GWCS
Waikerie 2A
NSW Sunraysia Irr Develop Nyah to SA
Border Irr Develop, SA Irr Develop
Pyramid Ck, Bookpurnong, Improved
Buronga, Churche's Cut, SA Component of
Bookpurnong, SA Irr Develop to 2009
2003 2004
2006
2000
2002
Loxton with SA component
Waikerie L2 with SA component, NSW
and Vic RISI, SA Irr Develop to 2012
Pike Stage 1and other remaining
register entries
2008
2010
2012

Murray River Salinity at Morgan
(Daily Salinity - EC uS/cm)
1600
1400
1200
1000
800
600
400
200
0
Effect of salinity management on water
quality at Morgan, SA
"No further intervention" salinity levels
(1975 conditions)
Recorded salinity levels Effect of salinity management

Murray River Salinity at Morgan
(Daily Salinity - EC uS/cm)
Average Flow
(Lock 2 and Lock 1) ML/d
600
550
500
450
400
350
300
250
200
150
100
60,000
50,000
40,000
30,000
20,000
10,000
0
"No further intervention"
salinity levels
(1975 conditions)
levels at Morgan 2011/12
Effect of salinity
management
Recorded
salinity levels
(Lock 2 and Lock 1) ML/d Measured and modelled mean daily salinity
MDBA BSMS annual report 2011/12

Key messages
Success of Basin’s salinity management came from good
policy and commitment of governments to implement them,
awareness or understanding of salinity processes leading
to effective engineering and land and water management
solutions
Salinity spikes occurred immediately post flood periods:
flows (4 million tonnes of salt in 1.5 years
Backwater & Groundwater are major salt accession sources
to the river
Current ‘flood’ is receding slowly and salt spike is expected
to be different than previous floods
Monitoring flood recession salinity is key to managing realtime
salinity spikes following floods