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RIVER MURRAY - SOUTH AUSTRALIA
A more detailed review of the status of River Murray water availability for South Australia is provided for the current 'drought year' (latter half of 2006 and the beginning of 2007 (the 2006-07 year)).
The six aspects of River Murray water considered in this article are the:
Rainfall in the cooler winter-spring seasons provides the main inflows into South Australia's reservoir catchment areas. The winter-spring period of 2006 was the driest on record experienced in South Australia (and Adelaide), resulting in Adelaide's reservoir levels being very low at the commencement of summer.
Adelaide's water supply is supplemented by water diverted from the River Murray. About 40-45% of the annual delivery of water to SA Water customers is derived from the River. Under drought conditions SA Water's reservoir shortfalls are overcome by increasing the amount of water extracted from the River Murray.
In addition, considerable quantities of the River Murray's water are diverted by: irrigators in the Lower Murray Swamps (which lie between Wellington and Mannum) and the higher lands; pastoralists; industries; households and environmental requirements in South Australia's Murray Valley.
SOUTH AUSTRALIAN WATER DIVERSIONS FROM THE RIVER MURRAY
Diversions for the Adelaide metropolitan area and country centres
Graph 1 shows the relative amounts of River Murray and reservoir and ground-water delivered by SA Water to the Adelaide metropolitan area and country centres for the period 2000-01 to 2005-06. River Murray diversions by type of user over the period 2000-01 to 2005-06 are shown in Graph 2.
In the dry 2002-03 period, lower annual inflows to the local reservoir catchments in the Mount Lofty Ranges resulted in an increased demand for water from the River Murray with 72% of the water delivered by SA Water in this period obtained from this source (Graph 1). Furthermore the 2002-03 summer had a large number of days with temperatures in excess of 32oC, which contributed to an increased demand for water by SA Water's customers (SA Water, Annual Report 2002-03). In 2002-03, 282 GL of water were delivered by SA Water, compared with 266 GL in 2001-02 and 246 GL in 2003-4.
SA Water's River Murray water diversions to South Australian metropolitan area and country towns users in 2002-03 amounted to 204 GL; in 2001-02 the volume of diversion was 118 GL, and 117 GL in 2003-04 (Graph 2). The average annual diversions for the metropolitan area and country towns users for the five years 2000-01 to 2004-05 was 138 GL per year.
Graph 1. WATER DELIVERED BY SA WATER, proportions of water derived from the River Murray and reservoir/ground-water sources, 2000-01 to 2005-06
Sources: SA WATER, Annual Reports, Operations Overview
Murray-Darling Basin Commission, Annual Water Audit Monitoring Reports, Table 2
In South Australia's dry year of 2002-03, about 64% of water diverted by all states and territories for predominantly mains distribution was extracted by South Australia; in 2001-02 and 2003-04 the proportions were 40% and 49% respectively (Graph 1).
Irrigators (and irrigation water providers) in the Lower Murray Swamps and in the higher ground of the Murray Valley accounted for approximately 80% of the South Australian diversions of River Murray water over the period 2000-01 to 2004-05 MDBC, Annual Water Audit Monitoring Reports, Table 2. For the dry period 2002-03, the estimated diversions were 531 GL; the 2001-02 and 2003-04 diversions were 494 GL and 490 GL respectively. The average annual diversion for irrigation usage for the five years 2000-01 to 2004-05 was 508 GL per year. The irrigation diversions include an Environmental Land Management Allocation for the Lower Murray Swamps of 22.2 GL/year.
Graph 2. WATER DIVERTED FROM THE RIVER MURRAY TO SOUTH AUSTRALIAN USERS, 2000-01 TO 2005-06.
In terms of the total irrigation diversions from the River Murray, South Australian irrigators accounted for 16% of these water diversions in 2004-05. In South Australia's dry year of 2002-03, the proportion was 18%; in 2001-02 and 2003-04 the proportions were 12% and 16% respectively (Graph 3).
In 2002-03, all South Australian diversions amounted to about 22% (737 GL from 3,317 GL) of the total water extracted from the River Murray; in 2001-02 this proportion was about 15% (662 GL from 4,388 GL), and in 2003-04 it was 18% (612 GL from 3,366 GL) (Graph 3).
Graph 3. SOUTH AUSTRALIA'S SHARE OF RIVER MURRAY DIVERSIONS, by purpose, 2000-01 to 2004-05 (a)
Conditions of low rainfall and reduced reservoir levels necessitate increasing the amounts of water diverted from the River Murray to meet South Australia's water demand. When available, a temporary increase in demand from South Australia can be readily accommodated from the River Murray. However, the Murray-Darling Basin (MDB) is suffering its sixth consecutive year of drought and water storage in the basin's reservoirs has been seriously reduced MDBC, River Murray System - Drought Update July 2006.
MURRAY-DARLING BASIN RAINFALL AND INFLOWS
The Murray-Darling Basin Commission (MDBC) reported in July 2006 MDBC, River Murray System - Drought Update July 2006 that the River Murray system is entering its sixth consecutive year of drought. Over the five years from July 2001 to June 2006 average inflows to the River Murray system were 4,800 GL/yr, which is about 40% of the long-term average of 11,200 GL/yr.
From January 2006 through to early 2007, the MDBC reported
Extreme conditions have also affected the Snowy Mountains:
The long term average total monthly storage in MDBC reservoirs fluctuates between peaks of about 75% capacity at the end of June (start of July), and troughs of about 55% capacity at the end of December (beginning of January) MDBC, River Murray System - Drought Update No. 5, December 2006, Figure 3. Approximately 98% of the total storage capacity is active storage, that is, water which can be distributed to users; the residual 2% is known as dead storage.
River Murray water demand tends to be highest during the summer months, largely because the irrigation season extends from the start of November until mid-May. The proportions of active water storage capacity in the MDBC reservoirs at the start of summer (the first week in December) are shown in Graph 4.
Of particular interest are the levels of Lake Victoria which is located downstream of the major demands and channel capacity constraints in the River Murray. South Australia's flow of River Murray water is set by releases from Lake Victoria. This means that during periods of peak demand, water can be released from the Lake to continue to supply flows to South Australia. Lake Victoria plays a strategic role in helping the Murray-Darling Basin Commission meet its responsibilities to deliver a uniform water supply to South Australia in accordance with its water entitlements defined in the Murray-Darling Basin Agreement MDBC, River Murray Water, Lake Victoria.
Of the total 677 GL capacity of Lake Victoria, 577 GL, or about 85%, is active storage. Lake Victoria active storage is seen to have been maintained at relatively high levels (generally greater than 75% of active storage capacity) regardless of the depletion of other reservoirs during drought conditions. For example, at the beginning of December 2002 (the start of the 2002-03 summer), Lake Victoria active storage was at 76% capacity, while active storage for all MDBC reservoirs was at 35% capacity. At the beginning of the 2006-07 summer, after prolonged drought in the MDB, Lake Victoria's active holdings were at 70% of capacity, with combined MDBC reservoirs at 23% capacity.
Graph 4. ACTIVE (a) WATER STORAGE IN MDBC RESERVOIRS AT THE BEGINNING OF DECEMBER (SUMMER), proportion of active capacity, 2000-01 to 2006-07.
Source: MDBC, Natural Resource Management, Archived Weekly Reports
Active water storage levels of MDBC reservoirs at the first Wednesday of each month are expressed as proportions of active capacity in Graph 5. Graph 6 shows the same information for Lake Victoria.
At the beginning of 2006-07 (July 2006), active water storage levels in the main MDBC reservoirs (Dartmouth Reservoir, Hume Reservoir, Lake Victoria and Menindee Lakes) were higher than one year earlier (Graph 5), but the failure of winter/spring rains and record low inflows in the MDB brought rapidly falling storage levels. The rate of fall in storage levels over the 2006 winter/spring period was similar to that seen in the 2002-03 drought MDBC, River Murray System Operational Update December 2006.
Graph 5. ACTIVE (a) WATER STORAGE IN MDBC RESERVOIRS AT THE BEGINNING OF THE MONTH, proportion of active capacity, 2005-06 and 2006-07
At the beginning of 2006-07 (July 2006), active water storage levels in Lake Victoria were higher than one year earlier (Graph 6). However, for the ten months from June 2006 to March 2007 when inflows to the River Murray had been at record lows, the upstream availability of water for the lake declined. Combined MDBC reservoirs were at 8% of active capacity at the beginning of April 2007 while Lake Victoria was at about 23% active capacity; correspondingly, at the beginning of April 2006, active storage for all MDBC reservoirs was 39%, and Lake Victoria was at 27%.
Graph 6. ACTIVE (a) WATER STORAGE IN LAKE VICTORIA AT THE BEGINNING OF THE MONTH, proportion of active storage capacity, 2005-06 and 2006-07
SOUTH AUSTRALIA'S RIVER MURRAY ENTITLEMENT FLOWS
Water entitlement flows aim to meet the needs of users of water and to maintain the river's health and natural environment. South Australia receives an agreed amount of water from the River Murray as a legal entitlement (security entitlement) and has a very high reliability of supply. The entitlement flow reflects the amount necessary to meet South Australia's water requirements and is ensured by maintenance of adequate water supplies in Lake Victoria. River Murray entitlement flows are highest during the summer months, largely because of the greater water demands of irrigators.
Flows to SA
As a result of the continuing drought across the MDB South Australia undertook a reduction of its water entitlement flow by 500 ML/day from 1 September 2006 MDBC, River Murray System - Drought Update, September 2006. On December 15 2006, the South Australian Minister for the River Murray announced press release that South Australia should receive a minimum entitlement flow of 1,470 GL for 2006-07; this is about 30% below the regular minimum of 1,850 GL. Flows will be kept higher over the 2006-07 summer months when water demand is greatest, and a large cut in entitlement flow will be made for the March to May 2007 period. By the end of February 2007, 174 GL of South Australia's entitlement flow remained to be delivered before the end of May MDBC, Media Release, March 16 2007. South Australia's water entitlement flow for March 2007 was 88 GL, compared with the normal March entitlement of 186 GL.
On 12 January 2007 it was announced that the Acting Prime Minister and the Premiers of South Australia, Victoria and New South Wales had agreed to the immediate implementation of River Murray measures that would ensure the critical demands of urban areas, towns and other households reliant upon River Murray water. These measures include lowering the target end of season reserves in Lake Victoria, reduced minimum flow targets, early pumping to build reserves in Mt Lofty Ranges storages, and disconnecting selected permanent wetlands that are artificially inundated Media release - Joint Media Statement - Water contingency planning in the southern Murray-Darling Basin.
Water entitlements and actual flows of River Murray water to South Australia for 2005-06 and 2006-07 are shown in Graph 7. The significantly higher flows between September and December 2005 are seen to correspond with near capacity volumes of water in Lake Victoria (refer Graph 6) that allowed for greater than entitlement flows to occur.
Graph 7. SOUTH AUSTRALIAN MONTHLY RIVER MURRAY WATER ENTITLEMENT AND FLOWS, 2005-06 and 2006-07.
THE CAP AND RIVER MURRAY WATER ALLOCATIONS FOR SOUTH AUSTRALIA
In July 1997 the Murray-Darling Basin Ministerial Council (the "Council") confirmed a permanent Cap on MDB water diversions. The Council defined the Cap as the volume of water that would have been diverted under 1993-94 levels of development. For reasons of equity, the cap may be adjusted for certain developments that occurred after 1993-94. South Australia's Cap is slightly greater than the diversions for 1993-94 because of high security entitlements MDBC, The Cap Brochure, 2004.
The Cap does not attempt to reduce basin diversions, it merely prevents them from increasing. New developments can occur provided that their water needs are met by improving water use efficiency or by purchasing water from existing developments.
In early 2004, the South Australian Department of Water, Land and Biodiversity Conservation (DWLBC) implemented a drought response strategy using the draft River Murray Drought Water Allocation Policy to provide advice to the High Level Taskforce on the River Murray and the River Murray Drought Liaison Committee. These bodies make recommendations to the South Australian Minister for the River Murray on the appropriate level of allocations of the Cap for South Australian River Murray water users. The operating version of the Policy was published in January 2006 DWLBC, South Australian River Murray Drought Water Allocation Policy, 2006.
South Australian allocations for irrigators were reduced from 80% of the legal entitlements to 70% in mid-October 2006, and a further reduction to 60% was made on 2 November 2006. On 15 December 2006 the South Australian Minister for the River Murray said that "the 60% allocation figure should be sustainable but it will be necessary to micro-manage the river and inflows over summer and evaporation of storages must be closely monitored".
Irrigation allocations have also been significantly reduced in NSW, where both high security and carry over allocations were reduced by a further 32% on 2 November 2006, after a 20% reduction in October. Victoria, which has adopted a different strategy in water allocation, has not reduced allocations MDBC, River Murray System - Drought Update No. 5, December 2006. Nevertheless, both NSW and Victoria are planning an early end to the 2006-07 irrigation season to ensure internal losses within the distribution systems of irrigation districts remain within target levels MDBC, River Murray System Operational Update February 2007.
OUTLOOK FOR THE FUTURE
The following section provides a summary of the outlook for the future as reported by the various agencies that have responsibility over the Murray-Darling Basin/River Murray system:
Rainfall in the MDB 2007-08 MDBC, River Murray System - Drought Update No. 6, February 2007
The Bureau of Meteorology advised that the current El Nino is beginning to weaken and that the rainfall outlook for February to April 2007 (inclusive) is for a 55% to 60% chance that rainfall in the Basin would be above the median. Nevertheless, catchments are extremely dry and flows into streams in the higher yielding upper catchment areas have virtually dried up. Consequently, rainfall would need to be well above average in order to produce average inflows to MDBC storage reservoirs, and inflow conditions throughout 2007-08 would need to be at a level experienced (over the long term) in only about one year in ten in order to raise storage to near average levels.
Flows and allocations 2007-08 MDBC, River Murray System - Drought Update No. 6, February 2007
Currently, flows in the River Murray are being maintained to meet diversion requirements and the requirements for transfer of water to Lake Victoria. South Australia's revised allocation of 60% of licensed entitlement should continue as there has been no significant increase in water available to the States for 2006-07. If the 2006-07 dry conditions are repeated in 2007-08 new minimum flow rates could be implemented and it is likely that there would be just enough water to meet the critical water needs of all towns and cities that rely on River Murray water. Recent announcements by State water agencies have indicated that the opening irrigation allocations for 2007-08 would be zero, Seasonal improvement in irrigation allocations will very much depend on rainfall to the end of spring (the start of the irrigation season).
Water Proofing Adelaide
As part of South Australia's Strategic Plan of 2002 the SA Government recognised the need to address challenges to water supply. In October 2003 a 20-year water strategy, Water Proofing Adelaide A thirst for change 2005 - 2025, aimed at management of existing resources, responsible water use, and developing additional water supplies, was launched. The importance of this strategy was emphasised by the dry period of 2002-03, coupled with the on-going drought in the Murray-Darling Basin, when Adelaide's Reservoir supplies and the River Murray flows were reduced and water restrictions were introduced in South Australia from 2003.
Water Proofing Adelaide plan aims to provide sufficient mains water to meet Adelaide's needs beyond 2025 (even in drought years) without putting higher demands on the River Murray.
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