Hume and Dartmouth Dams Operations Review Design and Operation of Dartmouth DamThe Governor General, the R. Hon. Sir Paul Hasluck, officially opened work on the Dartmouth Dam project on 15 February 1973. The commencement ceremony took place at the Dartmouth township downstream of the dam site. Construction of the Dam was completed in 1979 by the Rural Water Commission, on behalf of the River Murray Commission - the authority responsible for regulating the waters of the River Murray. The cost in 1979 was $139 million and was shared equally by the Commonwealth and the States of New South Wales, Victoria, and South Australia.
Design featuresThe Dartmouth Dam embankment is a zoned earth and rockfill structure 180 metres high from the lowest part of the foundation to the roadway across the top of the dam. It consists of
The embankment has a crest length of 670 metres and a base width of 700 metres.
SpillwayThe rock for the construction of the Dam wall was quarried immediately downstream of the dam site. This quarry now forms the spillway through which floodwaters pass when the Dam is full The crest of the spillway is approximately 91 m long. When the Dam is full, water breaches the crest and falls down a concrete chute for about 80 metres. The flood then returns to the river via an open rock cascade which gradually widens to 300 m at river level. The spillway is subject to erosion and considerable work has been done to spread flood waters evenly across the face of the upper spillway steps. It was recognised, when the spillway was designed, that it might eventually need to be concrete lined. It was decided, on economic grounds, that concrete lining should be deferred for as long as possible.
Outlet worksWater can be released through either of two outlet tunnels. One, part of the high level outlet works, is situated with an inlet at a relatively high level on the left abutment and is connected to a 150 MW power station located at the toe of the Dam. Whenever possible, releases for irrigation are made through the power station in order that advantage can be taken of the high energy of the stored water. The second and lower tunnel, part of the low level outlet works, is located in the right hand abutment and is used when the water level is below the operating level for the high level outlet.
The high level outlet worksWater for hydro-electric generation and irrigation is released through the high level outlet works. The intake structure for the high level outlet works has been built to a first stage height of 32 metres, which is 31 metres below full supply level. There is provision in the design of the structure to allow it to be extended to full height above full supply level with shutters installed to provide more control over selection of the draw-off level. This will allow control of the temperature of water released into the Mitta Mitta River. Studies are planned shortly to determine likely benefits from such an extension. As an alternative to releases through the power station located at the foot of the dam, releases can be made for irrigation supplies by means of a bypass and two fixed-cone dispersion valves that have been installed in a valve house adjacent to the power station. Discharge fluctuations due to peak load power station operation are smoothed out by the Banimboola re-regulating pondage of 8 500 megalitres capacity formed by a small dam constructed some nine kilometres downstream.
The low level outlet worksNormally releases from the Dam are made through the high level outlet works. When the storage water level has fallen below the sill of the high level outlet works, the low level outlet works enable releases to continue, discharging through what was previously the diversion tunnel during construction of the dam embankment. This outlet was designed to release water at any storage level. However, vibration due to cavitation at the outlet gates currently may restrict operation of the low level outlet works. The low level outlet works include an intake tower and a concrete lined tunnel. The intake tunnel is submerged below the water and is only visible when the reservoir contains less than 14% of its capacity. The tunnel is 6 metres in diameter and 900 metre long. It discharges water downstream of the Dam. Slide gates mid-way along the tunnel control water releases. The intake tower houses a bulkhead. The bulkhead is similar to a large plug. It provides the means for sealing and dewatering the low level outlet tunnel for inspection and maintenance. Major rehabilitation works at the intake tower were completed in 1996.
For more information regarding the operation of Dartmouth Dam refer to the "Review of the Operations of Hume and Dartmouth Dams" (link)
Dartmouth Power StationHydro-electricity which is generated from the 150 MW power station, provides around 330 million kilowatt-hours of power to the operators, Southern Hydro |
RIVER MURRAY WATER
