Chapter 2
Background
Introduction
2.1
This chapter provides an overview of the physical characteristics of the
Coorong and Lower Lakes, including its geography and ecosystems. The chapter
then provides an overview of water management within the Basin before setting
the Coorong and Lower Lakes within the wider context of the Murray-Darling Basin.
Geography
2.2
The Coorong, Lower Lakes and Murray Mouth are a system of lakes, lagoons
and wetlands which form the terminus of the River Murray. The diverse
environmental, economic, social and cultural values offered by the Coorong and
Lower Lakes has been formally recognised by the declaration of portions of the
system as a wetland of international importance under the Ramsar convention and
the area's nomination as an Icon Site under the Living Murray Initiative. The
system covers approximately 140 500 hectares (ha) and contains both fresh water
and estuarine ecosystems. There are three major bodies of water – Lake Alexandrina,
Lake Albert and the Coorong.
Lake Alexandrina
2.3
Lake Alexandrina is the largest of the lakes with an area of 76 000ha. The
lake is relatively shallow, with a maximum depth of approximately 4 metres (m),
and is fed by fresh water from the Murray River and rivers from the Mt Lofty
ranges. The Murray passes through Lake Alexandrina to the sea. The lake receives
the majority of its fresh water from the Murray, although local rainfall and
runoff from the Mt Lofty Ranges also contributes substantial inflows.
Historically, the lake has been a predominantly fresh to brackish water system
which, in the pre-European period would have occasionally become saline for
short periods during extreme droughts. Currently the water in the lake is highly
saline near the barrages and brackish in the centre.
Lake Albert
2.4
Lake Albert is a smaller fresh water lake connected to Lake Alexandrina.
It has an area of 16 800ha and is shallower than Lake Alexandrina. It has no
other significant inflows and is not connected to the sea.
The Coorong
2.5
The Coorong is a chain of lagoons which stretch along the coast for
approximately 140 kilometres (km) and is divided into the North Lagoon and the South
Lagoon by the narrows at Parnka Point. The two lagoons are distinct from the
Murray Estuary leading from the mouth to Goolwa Barrage. The aquatic environment
ranges from estuarine in the North Lagoon to hyper-saline in the far reaches of
the South Lagoon. The Coorong relies on river flow, tidal exchange, runoff and
ground water from the Upper South East Drainage scheme area and wind mixing for
water to balance evaporation. As a consequence of low or no inflows over the
past ten years, reduced tidal prism and silting of the mouth, hypersalinity in
the South Lagoon has been increasing beyond natural limits.
Fig 1. Coorong, the Lower Lakes and Murray Mouth.[1]
Ecosystem
2.6
The region contains a variety of wetland ecosystems which are home to a
number of threatened or endangered bird, fish and plant species.[2]
The region's natural values have resulted in it being listed as a Ramsar
convention protected wetland.[3]
The Lower Lakes have historically been a predominantly fresh water environment,
although there is evidence of periodic intrusion of salt water.
2.7
Sediment sampling indicates that the tidal prism regularly extended into
Lake Alexandrina throughout the last 6000 years[4]
Murray-Darling Basin Commission (MDBC) modelling based on data from 1891 to
2007 indicates that under natural conditions without human modification of the
river flow, there would have been periodic reverse flows of sea water into the
lakes resulting in high salinity in 17 per cent of years and in 5 per cent of
years these reverse flows would have exceeded 70 gigalitres (GL).[5]
Accounts from Charles Sturt's 1829 expedition indicate that there was a
gradient of salinity on entering the lake, with the lake becoming more saline
as he approached the mouth.
2.8
Despite this evidence of past salinity, the Lakes have been
predominantly fresh since the construction of the barrages and are maintained
as a fresh water ecosystem.
2.9
The Coorong lagoons support a variety of ecosystems, ranging from an estuarine
environment in the North Lagoon, to a specialised hypersaline ecosystem in the
far reaches of the South Lagoon. Some of the estuarine fish species of the
north end of the Coorong are adapted to live in both the Coorong and Lower Lakes
and a fishway has been constructed in the barrages to allow these species
access to the lakes. The hypersaline species in the South Lagoon are adapted to
live in water approximately three times as saline as sea water.
The Barrages
2.10
Lake Alexandrina is separated from the Coorong by a system of barrages
constructed in the 1930s. These are low dams across the channels leading from Lake
Alexandrina to the Coorong. The purposes of the barrages are to: reduce salinity
levels in the lower reaches of the River Murray and associated lakes caused by
tidal effects and salt water intrusion during periods of low flow; stabilise
the river level, and normally maintain it above the level of reclaimed river
flats between Wellington and Mannum for irrigation; concentrate releases to the
ocean to a small area in order to scour a channel for navigation; and maintain
pool water that can be pumped to Adelaide and the south-eastern corner of South
Australia.
2.11
The barrages reduce the tidal prism through the Murray Mouth by
approximately 90 per cent.[6]
Fig 2. Barrages separating Lake Alexandrina
from the Coorong.[7]
2.12
There are 5 barrages: Goolwa Barrage, Mundoo Barrage, Boundary Creek
Barrage, Ewe Island and Tauwitchere Barrages. Goolwa Barrage, located 8km
upstream of the Murray Mouth, is the deepest of the barrages and is constructed
on fine sand and silt. It is founded on timber piles and sheet piling up to 14m
deep. Ewe Island and Tauwitchere Barrages are wide and shallow barrages built on
a calcareous reef, with earth embankments at both ends. The Mundoo Barrage and
Boundary Creek Barrage are the shortest of the barrages and are founded on a
limestone reef.
2.13
Goolwa contains a lock chamber 30.5m by 6.1m and Tauwitchere has a lock
of 13.7m by 3.8m but no provision was made in the other barrages to allow the
passage of shipping. The barrages also contain fishways which, when operational,
allow passage for estuarine species that require access to the fresh water
environment of the lakes. These fishways begin to operate effectively when the
lakes are above 0.3 metres higher than mean sea level, formally known as
Australian Height Datum (AHD).
2.14
In normal operation, as designed, the barrages raise the level of fresh
water in the Lower Lakes to approximately 0.75 metres AHD. The barrages cause
an increase in water level of approximately 50cm as far upstream as Lock 1 at
Blanchetown (274km upstream).[8]
2.15
At full supply the lakes hold approximately 2200GL. Estimates of
evaporation vary, but the lakes probably require 700-950GL to maintain their normal
level. When flow exceeds this volume it is released to the Murray Estuary and
flows into the Coorong North Lagoon or out the Murray Mouth.[9]
Water management
2.16
Water levels in the Lower Lakes have followed an annual cycle of
drawdown during the summer/autumn period, when extraction and evaporation
exceed entitlement flows, and refill during winter and spring as flows increase
and extraction and evaporation decreases.
2.17
The main operating rule for the Lower Lakes has been to maintain an average
water level of 0.75m AHD. This is compared to a mean sea level of -0.03m AHD at
Victor Harbour. This level is regulated through the opening and closing of
barrage gates.
2.18
When flows from the Murray are limited to entitlement flows, evaporation
from the lakes exceeds inflow and lake levels drop unless some action is taken
to reduce the drawdown. To mitigate this effect, in normal operation the
barrages are closed and the lakes surcharged to 0.85m AHD at the beginning of summer
to allow for evaporation dropping the level to an average minimum of 0.60m AHD in
autumn.
2.19
Irrigation development and management of salinity and algal blooms have
all placed operational constraints on the management of the Lower Lakes.
Irrigation development around the lakeshore is generally based on gravity
systems that rely on water levels being maintained above a minimum level of 0.6m
AHD. Current operating rules have aimed to maintain the water level within a
narrow band of 0.6m‑0.85m AHD for the purpose of water supply, irrigation
and bank stability.
2.20
Several small communities rely on pumping water from the lakes for
domestic supply. High salinities and algal counts are of concern to these
communities and water users. The salinity of the Lower Lakes can increase
substantially during low flow periods. Salinity in the Lower Lakes has been
managed in the past by decreasing the water level to 0.65m AHD to allow
flushing. Reclaimed irrigation areas in the Lower Murray can be a source of
nutrient loads to the river, but rehabilitation of these areas to minimise such
returns is well advanced.[10]
The Murray-Darling Basin
2.21
The Murray-Darling Basin (the Basin) covers approximately 1 059 000
square kilometres or 14 per cent of Australia’s land area. Two million people
(10 per cent of Australia’s population) live in the Basin and are dependent on
it for their drinking water, as are another 1.1 million residents of the
city of Adelaide.
Fig 3. the Murray-Darling
Basin.[11]
Water availability
2.22
The Basin is one of the driest catchments in the world. By way of comparison,
the catchment of the Mississippi River contributes 20 times more runoff per square
kilometre, and the Amazon catchment 75 times more runoff per square kilometre, than
the Basin. The average annual flow of the rivers of the Murray-Darling would
pass through the Amazon River in less than a day.
2.23
The estimated long term average annual runoff into all rivers in the Basin
is approximately 23 609GL which is approximately 4 per cent of the average
annual rainfall of 530 618GL. There is considerable variation in runoff from
one part of the Basin to another.
2.24
The catchments draining the Great Dividing Range on the south-east and
southern margins of the Basin make the largest contributions to total runoff.
For example, the Murrumbidgee and Goulburn, Broken and Loddon river catchments
account for 35 per cent of the Basin's total runoff from 12 per cent of its
area. The Upper Murray catchment alone accounts for 17.3 per cent of runoff
from just 1.4 per cent of the Basin. In contrast, and further illustrating the Basin’s
climatic differences, runoff in the Darling Basin is estimated to be just 30
per cent of total runoff in the entire Basin, despite the Darling Basin
accounting for 70 per cent of the Basin’s total area.
2.25
Runoff variability in the Basin over time is considerably high. Over the
period from 1894-1993, the annual discharge at the mouth of the Murray-Darling
system ranged from 1626GL to 54 168GL. Except during very wet years, some 86
per cent of the Basin contributes virtually no runoff to the river systems.
2.26
The MDBC noted that it has been estimated that under natural conditions
almost 11 000GL/year were contained in wetlands, on the floodplains or lost to
evaporation from the river surface and that only 12 890 GL/year or 54 per cent
of the runoff reached the sea. Some of the water that would have been consumed
by wetlands and the floodplain under natural conditions is now used for
irrigation or is evaporated from reservoirs.[12]
2.27
The CSIRO Sustainable Yield Project has modelled the aggregated flow impacts
through the connected rivers of the Basin and identified (under the current
climate and development scenario) that the current development of the water
resources in the Basin has reduced the flow to the Murray Mouth by 61 per cent
and that the river now ceases to flow 40 per cent of the time compared to 1 per
cent of the time without the current level of development.[13]
2.28
To regulate the River Murray system, River Murray Water utilises four
major storages, sixteen weirs, five barrages and numerous other smaller
structures. Major storage capacity in the Murray system (Dartmouth, Hume, Lake
Victoria, and Menindee) is approximately 9000GL and in all Basin storages is
approximately 23 000GL.
2.29
The total net open water evaporation from major water bodies within the Basin
is in the order of 3000GL/year. Of this, the Menindee Lakes account for about
460GL/year, Lake Victoria 120GL/year, and Lake Hume accounts for about
60GL/year of evaporation. The Lower Lakes account for net evaporation of approximately
700-950GL per year, almost a third of the total estimated evaporation.
2.30
Inter-Basin transfers are also a feature of the system with water being
transferred into the Basin via the Snowy Mountains scheme. However, these flows
are only equivalent to less than 5 per cent of the natural runoff.[14]
Land use
2.31
The Basin accounts for 40 per cent of the value of Australia’s
agricultural output.[15]
It should be noted however, in previous years this percentage has been higher. Some
84 per cent of the land in the Basin is owned by businesses engaged in
agriculture and 67 per cent of this land is used for growing crops and pasture.
The vast bulk of agricultural land in the Basin is not irrigated, with only 2
per cent of Basin land under irrigation – this produces 44 per cent of the
value of Australia’s irrigated agricultural output.[16]
2.32
The total gross value of production of agricultural crops in the Basin
in 2005‑06 was $15 billion, which is nearly 39 per cent of the total
Australian gross value of agricultural production.
2.33
Irrigated agriculture covers a total of almost 1.65 million hectares in
the Basin and is the single greatest water user. Average annual diversions in
the Basin are about 11 500GL per year; about half of the annual flow in the Basin.
Around 95 per cent of this diversion is for irrigation. In 2006-07, water
diverted from the Murray, Murrumbidgee and Goulburn Rivers accounted for about
72 per cent of all the water diverted in the Basin.[17]
2.34
Irrigation within the Basin can be broadly characterised by several main
industries with different patterns of water use. These are:
- pasture in the southeast which is often flood-irrigated and
occurs throughout much of the year (17 per cent);
- rice in the Murray and Murrumbidgee which is flood-irrigated
(standing water) for about three months in the summer (16 per cent);
- dairy farming (17 per cent);
- cotton in the northern Basin catchments which is flood-irrigated
for about three months in the summer (20 per cent); and
- Horticulture, including grapes, other fruit, nuts and vegetables
(13 per cent).[18]
Environmental conditions
2.35
The Coorong and Lower Lakes are one of fifteen wetlands and one of six
Icon Sites under the Living Murray Initiative in the Basin that are recognised
internationally for their environmental significance.[19]
For example, it provides habitat for more than 30 per cent of the migratory
waders summering in Australia.[20]
2.36
It should also be noted that there are numerous other wetlands of
significance across the Basin and that the rivers themselves support important
environmental values.
2.37
The prolonged dry period across the southern half of the Basin continues
to severely impact on wetland and floodplain ecosystems across the Basin.
Whilst portions of the Barmah-Millewa Forest have received limited flooding as
recently as 2005, there has not been any significant flooding in the mid and
lower floodplains of the Murray downstream of Euston for many years. Floodplain
vegetation is under severe stress. The 2007 Living Murray Icon Site condition
report indicates that up to 80 per cent of River Red Gums are declining or dead
significant wetlands along the Murray, such as the Koondrook-Perricoota Forest
and the Chowilla floodplain.
2.38
In November 2007, aerial surveys of waterbirds along the Murray
indicated that the drought had greatly reduced the availability of wetland and
floodplain habitat and this had a severe impact on waterbird abundance and
breeding. The greatest number of birds was recorded in the Lower Lakes, Coorong
and Murray Mouth where a total of about 250 000 birds and 42 species were
observed. Most of the other Living Murray Icon Sites supported low numbers and
very little breeding.
2.39
In May 2008 a small volume of environmental water (7.7GL) was delivered
to Gunbower Forest and this has stimulated an encouraging response from plant
and animal life. The MDBC noted that this response emphasises the importance
of using the small volumes of environmental water available to maintain drought
refuges along the river and avoid loss of threatened species.
2.40
Overall, however, the riverine environments across the southern and
central regions of the Basin are in severe decline and this is not expected to
improve until there is a very significant improvement in rainfall and system
inflows.
2.41
In the northern Basin, the benefits of good summer rainfall and
associated flooding are still evident at some sites. Although most wetlands and
lakes along the Warrego and Paroo Rivers are drying up, those still containing
some water are supporting large concentrations of waterbirds.[21]
Water management in the Basin
2.42
Water resources in the Basin are managed through the Murray-Darling Basin
Agreement (the Agreement). The Agreement sets out the arrangements for sharing
water between New South Wales (NSW), Victoria and South Australia (SA). Part X
of the Agreement regulates the sharing of the waters of the 'upper River
Murray' (water upstream of the SA border) the waters of the Murray tributaries
below Albury and the waters for the Darling River and its tributaries upstream
of Menindee Lakes remain under the control of the relevant state, although only
when below an agreed level for the Menindee Lakes. [22]
Water sharing arrangements
2.43
Under the basic sharing provisions of the Agreement, SA is entitled to
receive a minimum volume of 'entitlement' water from the upper States (1859GL
per year). The upper states retain access to their own tributary inflows to the
Murray except for inflows upstream of Albury/Wodonga (including Snowy Scheme
releases) and inflows to Menindee Lakes when under MDBC control. The inflows
above Albury and into Menindee Lakes are 'shared' equally between NSW and Victoria.[23]
2.44
The Agreement provides each state with flexibility to manage its water
share as it wishes within certain limits. Each state can manage its water use
according to its own water security profile. Victoria and NSW have equal access
to the storage capacity of the major MDBC reservoirs upstream of the SA border.
Victoria, NSW and SA can each, by way of its own policy, choose to consume its
share or hold it in storage for a future time. Each of the three states may
also permit an individual water license holder to 'carry over' water from one
year to the next.
2.45
Security of water for SA is provided via three key mechanisms under the Agreement.
SA's dilution and loss component is the most secure water in the Agreement,
together with system losses upstream of the SA border. Special accounting
provisions in the Agreement also apply during drier times and a concept of a
minimum reserve of water held in major MDBC storages reserves a proportion of
water for SA's access in the following year once SA's share reaches full
entitlement.[24]
Interim water sharing arrangements
2.46
The record low inflows observed in 2006-07 combined with record low
storage levels both in the Snowy Scheme and MDBC storages have required interim
water sharing arrangements to be agreed to by the Murray-Darling Basin Ministerial
Council (Ministerial Council) in 2007-08 and 2008-09.
2.47
In 2007-08 the agreed interim arrangements meant that SA's share was
initially reduced to ensure availability of critical water to the upper states.
Initial improvements in water availability were shared between all states,
instead of going solely to SA, to protect industry and permanent plantings in
all three states. The arrangements then directed further improvements towards
increasing SA's share.[25]
2.48
In 2008-09 a new set of arrangements were agreed which included
contingency arrangements to ensure availability of SA's full dilution and loss
entitlement. The arrangements permitted all three states to carryover water to
meet critical human needs as well as those volumes carried over by individual
license holders in each state.
2.49
Under both sets of arrangements SA's share was higher than it would have
otherwise been under normal sharing arrangements and SA owed a debt in the form
of 'drought imbalance' to the upper states.[26]
Water entitlements
2.50
Approximately 350GL of River Murray Water is used by urban and domestic consumers
each year. The largest consumer of this water in dry years is SA (200GL), near
the end of the River Murray.[27]
2.51
Water use throughout the Basin is managed through the granting of some
form of water access entitlement and water allocation.[28]
A 'water access entitlement', such as a water licence, is defined in the
National Water Initiative (NWI) as 'a perpetual or ongoing entitlement to
exclusive access to a share of water from a specified consumptive pool as
defined in the relevant water plan'. A 'water allocation' is defined as 'the
specific volume of water allocated to water access entitlements in a given
season, defined according to rules established in the relevant water plan'. [29]
2.52
Ms Jenni Mattila, coordinator of the Bondi Group[30]
explained to the committee the distinction between water entitlements and water
allocations by likening permanent water entitlements to an empty glass in so
far as they represent a maximum capacity but not a physical asset. She said:
At the start of each season, the state crown determines the
percentage of the glass that will be filled with the annual allocation. That is
the physical water. [31]
2.53
Long term average water diversion in the Murray system is approximately
4068GL. However, there is a total of 5280GL of River Murray water entitlements.
There is 2487GL of high reliability water entitlements and 2793GL of low
reliability water entitlements.
2.54
From 1955 consumptive use of Murray-Darling water rose extremely rapidly
and by 1965, according to the Wentworth Group, was exceeding sustainable
yields. Consumptive use continued to rise in the 1970s and 80s.[32] In 1995, in response to the
findings of an audit of river use, a cap was imposed on the volume of water
which could be diverted from the rivers for consumptive uses, and was put into
effect from 1 July 1997.
2.55
For NSW and Victoria, the cap is defined as 'The volume of water that
would have been diverted under 1993/94 levels of development.' For Queensland
and the Australian Capital Territory, the cap arrangements are still being
finalised, but Queensland has had a moratorium on new development in place
since 2000.[33]
2.56
The type of entitlement and the share of water for a given water
resource system is established through water sharing plans. As a result, the
specific attributes of high and low reliability irrigation water entitlements
vary between states and river valleys. On the River Murray, the long term
average allocation against the high reliability Victorian entitlement is called
a 'high reliability water share'. The long term average allocation against the
low reliability Victorian entitlement is called 'low reliability water share'.[34]
In NSW a distinction is made between 'high security' and 'general security'
users.
2.57
Ms Mattila explained the practical difference in security or reliability
of entitlements for the committee with reference to NSW. General security
growers in NSW do not receive any annual allocation until the high security
growers receive 80 per cent of their entitlement.[35]
Water trading
2.58
Under the NWI, water trade is the transfer of water access entitlements
(permanent) and seasonal water allocations (temporary) between different
entities including irrigators, environmental water managers and infrastructure
operators. Water trading is intended to allow access to scarce water resources
to be reallocated over time to their most productive uses. The 1994 Council of
Australian Governments (COAG) water reforms sought to open up trading
arrangements, including interstate trading. Through the NWI, COAG has agreed to
'an expansion of permanent trade in water bringing about more profitable use of
water and more cost effective and flexible recovery of water to achieve
environmental outcomes'.[36]
2.59
Temporary or permanent trading of access entitlements is provided for
under state and territory legislation. In many cases, statutory water access
entitlements are held by irrigators. In these circumstances the irrigators have
clearly defined water rights that can be traded. However, in NSW and SA water
entitlements are typically held by irrigation infrastructure operators on
behalf of member irrigators.[37]
There is evidence to suggest that the actions of such operators can impede
trading processes.
2.60
The Australian Competition and Consumer Commission (ACCC) is considering
the form of water market rules and water charge rules as part of its new
functions under the Water Act 2007 (the Act). In particular, the ACCC
has noted how the actions of operators may impede the development of efficient
water markets and has considered ways to improve transformation and/or trading
processes and outcomes.[38]
2.61
In the southern Murray-Darling Basin the amount of water that can be
permanently traded out of an area is limited to four percent of the total water
entitlements of that area, per annum (the four per cent cap). Evidence suggests
that the cap is impeding structural adjustment in the agricultural sector,
making it more difficult for those who can most productively use water to buy
it and constraining environmental water purchases. Under the NWI, such caps on
permanent trade are required to be removed altogether by 2014 at the latest.[39]
The Water Act 2007
2.62
The Act, which came into effect on 3 March 2008, creates new institutional and governance arrangements to address the sustainability and
management of water resources in the Basin. The Act builds on earlier reform
initiatives including the NWI, and the Murray-Darling Basin Agreement.
2.63
The key elements of the Act are:
- the establishment of the Murray-Darling Basin Authority with a
range of function and powers;
- the preparation of a Basin Plan for the integrated and
sustainable management of water resources in the Murray-Darling Basin,
including:
- limits on the amount of water that can be taken from Basin water
resources;
- identification of risks to Basin water resources;
- an environmental watering plan
- a water quality and salinity management plan; and
- rules about trading of water rights in relation to Basin
resources.
- The establishment of a Commonwealth Environmental Water Holder to
manage the Commonwealth's environmental water to protect and restore the
environmental assets of the Murray-Darling Basin, and outside the Basin where
the Commonwealth owns water;
- The development and enforcement of water charge and water market
rules by the ACCC; and
- Authorisation of the Bureau of Meteorology to collect and publish
high-quality water information, including the National Water Account and
periodic reports on water resource use and availability.[40]
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