The Murray-Darling Basin Commission
Visit the Murray-Darling Basin Commission website
A succession of dry years from 1895, culminating in the record
drought of 1902, brought general acceptance that some drought
protection was required to allow further development of the
Murray Valley. Thirteen years of negotiation ensued before
agreement was reached between the four Governments on the
control of waters. In 1911 the three Premiers met in Melbourne
for an Interstate Conference and appointed leading engineers
from each State. Their task was to present to the Premiers
a report and recommendation which might lead to a settlement
concerning the question of utilisation of the River Murray
and its tributaries.
There was some difference of opinion among the engineers as
to the scope of their enquiry, but when their report was presented
on 24 July 1913 there were sufficient points of agreement
to enable their recommendations to be finalised. The engineers
had concluded that what was most needed to permit further
irrigation development was regulation by storage. The flow
from year to year was so erratic that no scheme for securing
complete control was feasible, and so in order to regulate
the water supply it would be best to provide for the building
of dams
or weirs – firstly, to construct a storage of 1
million acre-feet on the upper Murray, and secondly, to convert
Lake Victoria into a storage basin.
The River Murray Waters Agreement (later changed to The Murray-Darling
Basin Agreement) was ratified in 1915 by the Commonwealth
and State Governments by Acts, and proclaimed on 31 January
1917 by the Commonwealth Government. These Acts specified
the works which would be constructed under the provisions
of the Agreement (including storages on the upper Murray and
at Lake Victoria), and set up the River Murray Commission
(later to become the Murray-Darling Basin Commission - MDBC)
consisting of a representative nominated by each of the contracting
Governments.
The water-sharing principles adopted then, remain fundamentally
unchanged today:
- Flow at Albury is shared equally between New South Wales and Victoria;
- Victoria and New South Wales retain control of their tributaries below Albury;
- Victoria and New South Wales supply South Australia with a guaranteed minimum quantity of water, or “entitlement”.
The agreement also provided for construction of:
- A storage on the upper Murray (the site of the Hume Reservoir was selected from 25 alternatives);
- A storage at Lake Victoria;
- 26 locks and weirs extended up to Echuca;
- 9 locks and weirs on either the Murrumbidgee or Darling River (New South Wales later chose the Murrumbidgee).
The Murray-Darling Basin Agreement provides the basis for
managing water under Commission control. The most fundamental
requirement has not changed since 1915 – the MDBC must
conserve water, as well as share and supply it to the three
States with minimum wastage. Water controlled by the Commission
is shared between New South Wales and Victoria, with both
States contributing half of South Australia’s minimum
entitlement flow from their share. The States may use their
share of water as they like, which has traditionally been
for irrigation and water supply purposes. They may, however,
choose to use their water for other purposes.
The Murray-Darling Basin Commission is responsible for regulating
flow in the River Murray, its anabranches and the Darling
River downstream of Menindee Lakes. Water is shared between
New South Wales, Victoria and South Australia, according to
the provisions of the Murray-Darling Basin Agreement. The
Commission does not own any water; it manages water for the
three States. MDBC responsibilities were extended in 1970
to provide dilution flows in the Murray to reduce river salinity.
Further amendment of the Agreement in 1982 enabled the Commission
to consider other water management objectives in its operations.
The Agreement still gives precedence, however, to the efficient
allocation and supply of water to the States.
Amendment of the Agreement in 1982 enabled the Commission to
consider other water management objectives in its operations,
such as recreation and environmental needs. This means that
operations aimed at meeting objectives other than conserving
water and supplying it to the States, must not significantly
reduce the volume of water under Commission control.
The MDBC is required under the Agreement to provide a dilution flow at Torrumbarry and Euston Weirs to reduce downstream river salinity levels. Although this may result in some “loss” of water resources, this is accepted.
Water Allocation
During each irrigation season, the Commission assesses the volume of water expected to be under its control so that it can be allocated to the States. Only one assessment may be necessary if resources are ample and the reserve of water held in storage at the end of the season is forecast to exceed 2,500 GL.
River Operations
The MDBC meets State water requirements along the Murray with minimum wastage by:
- Storing water in the wetter winter/spring months and later releasing it during the drier summer/autumn months to meet supply requirements.
- Making releases from the most downstream storage first to minimise loses due to spill.
- Making timely releases from major storages to accurately
match water supply with demand, with close attention paid
to the time it takes for flow to travel along the Murray.
The upper States assist by estimating and advising the Commission
of their future requirements at each water offtake point
along the Murray, and also by estimating future tributary
inflows.
- Using a network of flow gauging stations along the Murray and its tributaries to continuously monitor river flows.
- Utilising mid-river storages to re-regulate flows if supplies do not exactly match demand.
Other operational objectives defined in the Agreement include:
- Providing dilution flows up to 2,450 ML/day and 3,900 ML/day past Euston and Torrumbarry Weirs respectively to prevent the salinity of river water at Merbein and Swan Hill from exceeding 500 EC units as far as possible. These flows are in addition to downstream water supply requirements.
- Providing a depth of water at locks and weirs sufficient for navigation by vessels drawing 1.4m of water.
There are numerous other, often conflicting requirements that the MDBC attempts to meet in its operations. It does this provided that the water conservation objective is not significantly prejudiced. The MDBC would release stored water to meet such objectives, however, at the request of a State, with the water being taken from that State’s share of MDBC available water. Other requirements include:
- Providing flood protection
- Forest irrigation and flooding
- Improving water quality
- Protecting and enhancing the river environment
- Allowing electricity generation
- Meeting recreational needs.
For more information visit the Murray-Darling Basin Commission website.
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