SpencerGulfCanal
|
There have been proposals in the past to build a canal from Spencer Gulf to permenantly fill Lake Eyre and Lake Torrens.
This idea is has its merits, as it may alter the climate of Australia's dry interior by incresing rainfall through evaporation from the lake waters. In the current global climate change model, the interior of southern Australia is expected to get even drier than at present, and additional precipitation would be essential for argicultural production. Therefore the reason for dismissing ideas such as this may no longer be valid. Should we reconsider? ...discuss
What
The basic idea is a canal to Lake Torrens which is approximately 100km overland from sea. Lake Torrens has been naturally dry for all but one of the last 150 years of white settlement in the area. This lake, if filled, would then provide vast amounts of water (saline, but evaporation/precipitation would bring clean water) to the area. A further canal to Lake Eyre would easily fill this below-sea-level lake to become permenantly full. (currently it has water approximately one year in three)
Places
- Lake Torrens
- 28 m above sea level
- Lake Eyre
- up to 15 m below sea level
- Lake Frome
- 3 m above sea level
How
- A 'sea canal' from the top of Spencer Gulf would link sea waters to Lake Torrens. Approximately 80km in length.
- A 'lakes canal' to link Lake Torrens to Lake Eyre. Approximately 80km in length.
- Gradually undermining the surface of and dredging a canal to Lake Torrens until tidal forces can begin shifting sediment.
This would be an engineering work in the same magnitude as the Panama and Suez canals.
Note that Lake Torrens is above sea level, and would have to be excavated to at least 50m below the surface in order to fill. Lakes Eyre and Frome could fill naturally.
Letting sea water into Lake Eyre by means of a channel cut from Spencer Gulf was considered by the Government in 1883 and rejected. The length of a canal would be 400 km, its slope 3 x 10-5 and required bottom width 1.5 km. With estimated 10 km3 of excavations, the magnitude of earthworks would be without precedent in the world.[1]
Arguments For
- Extra water in Australia's interior will vastly increase the possible land use
- evaporation -> clouds -> rainfall on the western dividing range. (note that this cycle would rely on inflow from the ocean for a long period. The hope however is that longer-term the altered local ecosystem would begin to be more self-sustaining)
- There has been an inland sea there before (approx 100million years ago), so who is to say that environmental preservation should preserve the 'now' over the 'then'?
Arguments Against
- unpredictable outcome
- massive money spent
- extra water in the Australian interior does not nescessarily make the land any more fertile. Most of the land in Australia has poor quality soil, regardless of water availability.
- would the inflow of sea water INCREASE the local salinity levels?
- ALOT of water from the ocean is needed to offset current levels of evaporation!
Alternative: Lake Frome
According to the sea level predictor (linked below), Lake Torrens is at least 14m above sea level. However Lake Frome to the east is below sea level, as are several connecting lakes between Frome and Eyre. The Frome canal would appear to be a larger undertaking than either canals around Lake Torrens however, and the terrain skirting the southern edge of the flinders ranges may by more difficult. In addition, one of the lakes between Frome and Eyre is Lake Callabonna - which is a fossil reserve.
Nonetheless, it is an attractive alternative purely by virtue of its elevation. Plus, it may be a fair assumption that if Lake Eyre was full, that the change in climate/rainfall in the local area may flood these lakes routinely anyway, in which case they may as well be a deliberate part of the cycle.
Alternative: Water from eastern Australia
There have also been suggestions that rainwater from the east coast could be diverted into the waterways that now fill Lake Eyre on a sporadic basis. This would not lead to rapid accumulation of salt in the basin from evaporation, and might lead to a permanent level of the lake above sea level. The current accumulation of salt might then be reduced by allowing the lake water to drain into the ocean. Diverting dam overflows might reduce the coastal flooding that has recently been experienced as well as providing an assessment of what a permanent large body of water in central Australia would do to rainfall, cloud cover and thus average temperature.
