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Part 2: Deliver water efficiently and equitably for domestic consumption, sustainable economic use and environmental benefit

Strategy 2.3
Sustain and improve physical asset base to contemporary best practice

The assets controlled and managed under the Murray-Darling Basin Agreement are investigated, designed, constructed, operated and maintained, for and on behalf of the MDBC by state constructing authorities from New South Wales, Victoria and South Australia. They are, respectively:

  • State Water Corporation (State Water NSW) and Department of Water and Energy (DWE NSW) (the agent was previously the Department of Natural Resources)
  • Goulburn–Murray Water (G–MW), and
  • the South Australian Minister for the River Murray (including the operating agent for South Australia, South Australian Water Corporation – SA Water).

Within the MDBC, River Murray Water Division exercises the Commission’s responsibilities in relation to management of the assets. A strong relationship has developed between the Commission and the state constructing authorities, so that maintenance is pro-active, decision making is almost always by consensus, and issues are raised by the constructing authorities at an early stage.

Drought-related record low inflow has resulted in historically low water storage levels in Lake Hume. Photo: Mark Vanner

Drought-related record low inflow has resulted in historically low water storage levels in Lake Hume.

(Photo: Mark Vanner)

Compliance with Australian National Committee on Large Dams Guidelines

Compliance of all its assets with Australian National Committee on Large Dams Guidelines is a key performance indicator for the MDBC. Each year there is clear evidence of working towards that goal and 2006–07 was no exception. The guidelines are focused upon reducing risks associated with dams and weirs to an acceptable level, to the community first and the owner’s business next.

During 2006–07, a portfolio risk assessment of the Commission’s five major assets (Dartmouth, Hume, Yarrawonga, Torrumbarry and Lake Victoria) was undertaken to improve compliance with the guidelines. Draft reports on the five major MDBC structures were available by the end of 2006–07 but planning in response to the recommendations had not yet commenced. The assessment will show how improvements in infrastructure need to be prioritised. More significantly, it will also recommend a dam improvement strategy for the Commission to follow over the next decade.

Setting the target for standard of maintenance

During 2006–07, a consultancy was let to gather data from three enterprises that own an extensive portfolio of large dams with a view of providing benchmarks for measuring the MDBC’s standard of maintenance performance. This benchmarking has been difficult, as there are commercial sensitivities and a lack of uniformity in how major dam owners classify the tasks and structures involved. The consultant is currently collating the data available to identify performance indicators and targets against each of those indicators.

Major works across MDBC assets

The Bethanga Bridge painting and deck upgrade project was completed. Transfer of ownership to New South Wales and Victorian road authorities was finalised, resolving an issue first raised in the 1940s.

Deck replacement at Tauwitchere and Ewe Island barrages is well under way, with 22 of a total of 860 new units installed. The project is expected to take 15 to 20 years to complete, as new units will only be installed to replace old units that have reached the end of their useful life.

Sections of the National Parks and Wildlife Act 1974 (NSW) relating to the protection of Aboriginal cultural heritage on the foreshore of Lake Victoria (the Lake Victoria Section 89 Permit and Section 90 Consent) were reviewed by the Advisory Committee under the guidance of the Department of Environment and Conservation. The department re-issued the Section 89 Permit and Section 90 Consent in August 2006 for a further eight years.

Stage 2 of the Pyramid Creek Salt Interception Scheme is near completion and Stage 3 is well under way. Because of the drought, Stage 1 and completed works on Stage 2 were placed in ‘asset protection mode’. Hot weather and high winds meant evaporation was exceeding the rate of disposal of saline water, leading to exposure of plastic liners to damaging winds.

Murray Mouth Barrages team wins 2006 Collings Trophy

ian sinclair- collins trophy.jpg

MDBC President Ian Sinclair AC (right) presenting the Collings Trophy to SA Water’s Peter Lewis.

It is the sense of ‘this is our structure’ adopted by the staff at each site that makes the competition for the Senator Collings Trophy so keen. The trophy has been awarded in most years since 1943 to the team looking after the asset judged to be the best maintained lock and weir. Since 2003, all storage assets of the Murray River system have been included. The judging criteria have been extended over recent years to include not only maintenance and care of the works and their surrounds but also the application of contemporary asset management practice.

In 2006, the Senator Collings Trophy was awarded to SA Water’s Peter Lewis and the Murray Mouth Barrages team based at Goolwa and Mundoo depots. The team has undertaken the site works for a number of major projects in recent years. In 2005–06, it completed the installation of a fishway at Goolwa Barrage, commenced work on the major deck replacement program at Tauwitchere and Ewe Island barrages and continued a major gate and stoplog refurbishment program. At the same time, the team made significant improvements to the grounds and site infrastructure.

The failure of a component common to every bore pipehead at Bookpurnong Salt Interception Scheme and a number of bores constructed in the early stages of the Loxton Salt Interception Scheme led to a replacement program at both sites. The Bookpurnong scheme is once again operational, and construction at the Loxton scheme is now back on track.

Maintain and renew river assets

Dartmouth Dam

For the second time in the past six years of drought, Lake Dartmouth has underpinned the diversions from the Murray system. To meet demand, water had to be transferred from Dartmouth Dam to Hume Dam near or slightly in excess of the maximum capacity of the Mitta Mitta River channel for about five months. There was an extra cost involved of more than $700,000 over approximately five months in 2006–07.

One benefit of the low reservoir levels was that a number of opportunistic works could be undertaken.

Hume Dam

Between 1993 and 2004, major dam improvement works were undertaken at Hume Dam. Part of the works included installation of a large array of supplementary instrumentation. The performance of the dam, and in particular of the remedial works, is assessed by monitoring and interpreting data from the instrumentation, routine surveillance and more formal inspections.

The results of the ongoing, extensive monitoring also help in planning the next stage of remedial works. A significant finding of the monitoring to date is that the extent and rate of settlement of the main earthen embankment following the most recent major remedial works is higher than allowed for in the remedial works design. A team of experts is considering the implications of this ongoing settlement and preparing advice to the Commission as to the most effective response.

Yarrawonga Weir

The most significant maintenance work at Yarrawonga Weir in 2006–07 was the replacement of the bearing pads under the road bridge beams and replacement of the seals in the bridge deck. Significant progress was also made in implementing the land and on-water management plan. Public amenity and safety have been improved.

Other locks and weirs

Planning has begun for two major programs, they are the refurbishment of the lock gates and operating values, and replacing rock protection eroded from downstream of weirs covering the majority of the locks and weirs on the Murray River. Both projects will involve planning by, and cooperation among, the three constructing authorities as they require the sharing of critical pieces of equipment and valuable knowledge of lock staff who have undertaken similar works in the past, as well as regulation of flows by other locks and weirs at critical times in the projects.

Navigable Pass Upgrade and Fishways Project

The construction phase of the Navigable Pass Upgrade and Fishways Project, managed by SA Water, started in mid-2001. A fish passage taskforce oversees the design and functional specifications for the fishways program and provides advice to MDBC on fish passage throughout the Basin.

The full program of fishways construction and navigable pass upgrade is scheduled for completion by mid-2010.

Lake Victoria

The face protection works to repair storm damage at Lake Victoria were completed in November 2006. At the end of the financial year, tenders were being assessed for replacing the inlet regulator service deck (the inlet regulator controls flow from the Murray River via Frenchman’s Creek into Lake Victoria).

Following the re-issue of the Section 90 Consent under the NSW National Parks and Wildlife Act (see above), a review of the Lake Victoria Cultural Landscape Plan of Management was undertaken. The main goal for the review is to simplify the plan so it is more user-friendly.

In addition, a Scientific Review Panel is to undertake a thorough review of the vegetation and erosion monitoring data collected over the past eight to ten years and report to the MDBC through the Lake Victoria Advisory Committee.

Barrages

As a consequence of the very low water levels in the Lower Lakes, there have been prolonged periods of ‘reverse heads’ against the barrages, where seawater levels are higher than freshwater levels. In response, the SA Water Barrages team has undertaken a number of tasks to ensure barrages are as watertight as possible.

A low concrete nib across the full length of the Tauwitchere spillway was constructed to prevent a mass flow of seawater from the Coorong into the Lower Lakes under a king tide and/or adverse winds.

The replacement of the concrete decking of the Ewe Island and Tauwitchere barrages is in its second year. The replacement program is now a routine operation involving replacement of more than 860 concrete deck units over a period of 15 to 20 years.

Menindee Lakes

The MDBC has a lease arrangement that gives it access to the stored water at the Menindee Lakes structures, which are State Water NSW assets. Part of the lease arrangements requires the Commission to contribute 75 per cent of the cost of operations and maintenance.

The arrangement permits the Commission to direct operations when total storage exceeds defined limits. With the prolonged drought, and in particular the lack of flow in the upper Darling, there has been no water available under the lease for the past five years. The low reserves of water have led to an extensive review of the operation of the complex Menindee Lakes system.

Over the past two years, substantial resources have been made available to fully document operations, maintenance procedures, and safe work method statements for Menindee Lakes.

Mitta Mitta River channel improvements

As in 2002–03, operations during the 2006–07 season required very large volumes to be transferred from Dartmouth Reservoir to Hume Reservoir. Erosion was monitored and, where necessary, emergency works initiated. Overall, the erosion protection and repair works completed in the previous four seasons performed satisfactorily and the extent of the erosion that occurred in 2006–07 was less than in 2002–03.

Hume to Yarrawonga River Management Plan

Works continued under the 2002 River Management Plan for the Hume to Yarrawonga reach of the Murray River. The advisory group, with wide representation, continues to meet regularly to review progress and provide advice to the MDBC on future directions for the program.

With seven years of on-ground works behind it, the outcomes from this program are now highly visible.

Hume to Yarrawonga reach physical works

By the end of 2006–07, condition assessments had been completed for 12 of the 15 reaches. Following MDBC acceptance of a proposal to accelerate the River Management Plan implementation works for three years from 2007–08, it is expected that the capital works component of the plan will be complete by 2010.

A variety of on-ground works were completed in 2006–07 across all programs. Erosion control works were undertaken at 38 sites on the Murray River and its New South Wales and Victorian anabranches between Hume Dam and Lake Mulwala. Other works involved vegetation management and replanting along the riverbank using local native species of trees, shrubs, reeds and grasses.

Hume to Yarrawonga reach land management review

Significant progress continued in 2006–07 towards purchasing easements in the Hume to Yarrawonga reach to confirm the Commission’s rights to pass regulated flows within existing channel capacity on affected properties in Victoria and New South Wales. By the end of June 2007, all 106 offers had been issued or re-issued and 76 accepted. Eleven landowners had confirmed that the offers would not be accepted, leaving 19 offers outstanding. The offers will lapse 12 months after issue.

Murray Mouth dredging

The prolonged dry spell, including the lowest inflows on record in 2006–07, combined with the level of extraction from the Murray River, has led to significantly reduced flows through the Murray Mouth. There were no releases from the barrages from February to June 2007 and, for much of the time that releases were made, they were small flows restricted to the fishways.

In spite of these severely restricted or nonexistent flows, dredging operations at the Murray Mouth have been successful in keeping the channel open between the sea and the Coorong. Tidal range targets are being maintained. The key performance indicators for dredging are being met even though only one dredge has been required to operate during 2006–07.

This success has been due to the establishment of channels from the Coorong and Goolwa that mimic what the shape of the Mouth would be under natural flows. As a consequence, the tidal flows are assisting the dredging rather than undoing it. Computerised modelling is used to determine the correct shape of the channels. The single dredge operation has led to cost savings in excess of $1.5 million in 2006–07 compared with the past few years. In May 2007, the Ministerial Council approved the award of a new contract to undertake the dredging operations for the next three years. Dredging will not take place if there is sufficient run-off from the Basin to keep the Mouth open.

The total cost of dredging for 2006–07 is $4.6 million.