Australian Inland Sea II

An alternative method of creating a permanently-full Lake Eyre in central Australia. [see link - The Australian Sea - for background] Also applicable to the various similar proposals such as "Lake Death Valley".

Lake Eyre fills naturally with floodwaters approximately every seven years, after heavy rains in the vast catchment area stretching up through South Australia, Queensland and the Northern Territory. While full, the lake is a haven for wildlife, particularly migratory birds, and contributes to estimated billions of dollars in extra agricultural production by encouraging rains* downwind.

Then, within a few months, it evaporates, leaving the more familiar barren salt plain (below sea level).

The enemy is the vicious heat and sun of the Outback. So let's do something about that - shade the sun from striking the water, and slow the rate of evaporation. While we're at it, let's put that solar radiation to good use.

Let's begin with a pilot project.

"Even in the dry season there is usually some water remaining in Lake Eyre, normally collecting in a number of smaller sub-lakes on the playa." [wikipedia - link]

Picture small square or rectangular barges carrying an array of photovoltaic panels, a small wind turbine and tower, a high voltage inverter, and connecting cables. The sun does not fall vertically, even at noon in midsummer, so raise the panels a couple of meters up - this way, the barge and the array together will be shading the largest possible area. Use the cheapest panel technology available, as efficient conversion as measured by area is not an issue - in fact, shading a larger area is a positive, not a negative. Therefore we can aim for efficiency in dollar terms instead.

All equipment will need to be suitably toughened against the brutal environment - salt, high winds, sandstorms, highly saline water, and extreme temperatures.

Dot a number of these pontoons across the remnant lake. Aim to cover a proportion of the lake's surface at midday midsummer - perhaps 25%, 50%, 75% - whatever your calculations show is desirable, or whatever your funding allows. Start with a small area, or a small proportion, and add to it over time.

100% shade, although effective, would be the deathknell of any biological activity in the water. Spacing between the barges also allows for towing barges in between for installation and maintenance, access by small craft, and to send in skimmer craft to harvest any blue-green algae outbreaks as bonus biomass.

(Calculations to follow, maybe. Of course we will need to take into account that part of the evaporation due to high ambient temperatures, rather than direct insolation)

The pontoons are linked in a chain by cables or rods to maintain their spacing, and to carry the HV transmission lines. These are fed to a substation on the shore which boosts the voltage once more for transmission to the national grid.

Each barge consists of a ring (round, square, rectangular) of pontoons with a void in the centre. Across this void stretches a polymer mesh or gridwork, which is planted with salt-tolerant grasses, shrubs and other plant species. This will infill the void with shade, as well as providing a wetland-like habitat for birds, insects and eventually other animals (initally, probably reptiles). The animal life attracted to these shaded, floating grassy islands will provide manure to make the micro-environment self-sustaining. The cool, shaded, nutrient-rich water underneath will encourage fish and other aquatic species to take up residence, or they can be introduced (mussels for example). In addition, the halophile plants draw salt from the water, lowering the salinity. Seeding with high-value ocean fish species is a future option.

Periodically the plantlife is harvested and returned to a facility at the natural shoreline, where it is used as, or converted into, biofuel. It can either be burnt directly to generate steam for a conventional electricity turbine, or fed into a methane digester and the methane so used. If suitable species are chosen, it can be converted into liquid biofuels for transport (ethanol and/or biodiesel), using the abundant sunshine as process heat. Here again, efficiency by cropped area is a secondary consideration to efficiency by cost. Process waste (ash or sludge) is used on-site as a soil improver for landscaping around the facility and any worker residences. As production expands, this waste stream is turned to aid in the plantation, afforestation and stabilization of the Lake Eyre shoreline.

The grid arrangement and standardization of barges lends itself well to mechanized harvest.

Now you are up and running, and generating a diversified income stream. This aids you in funding future expansion. Observe, monitor, take copious notes. Adjust grid spacing and proportion of shade as observation and theory dictate.

New barges are added to the edges of the grid, expanding outwards from the pilot area, one ring at a time. These are added continuously during dry periods, simply trucked into place, dropped onto the saltpan and connected up to their neighbours. They are wired into the grid, and immediately begin contributing to your electrical sales. Upstream infrastructure to the national grid is upgraded as required.

Initially, these added barges will be resting on the salt pan. Over the approximate seven years between flood events, a large area is thus shaded. When the next flood arrives, they will float with their neighbours, and can be similarly planted. Once the flood has passed, a larger lake stays behind.

Continuous barge manufacture provides a small but steady regional industry and employment opportunity, synergistic with local (South Australian) industry strengths such as small boatbuilding, electrical contracting and skills from the mining industry (welding, fabrication, logistics etc). This helps to stabilize employment against the boom/bust cycle of the mining sector. Standardized barge and component design allows for a broad and competitive supply stream.

Lather, rinse, repeat. Your green, island-dotted lake expands. Fish, birds and small animals abound. Perhaps another playa lake or two nearby have also been thus developed, either by your project or an independent one (though standardized to ensure compatibility), and they meet and merge.

Over a few decades, it should be possible to eventually shade the whole of Lake Eyre, and create a permanent body of water with all of the benefits detailed at [The Australian Sea], along with viable and ongoing export industries in energy, food and biomass.

As the permanent lake approaches the edges of the salt basin, work begins on dredging out the (cheap, shallow) barge canal from Lake Eyre to Spencer Gulf. Once open, this will allow the flow of water from the lake to the ocean, and begin the process of permanently removing the salt from the lakebed. In addition, a direct freight channel will be opened up for the export produce of the Lake Eyre Corporation, and the import of new infrastructure.

Grand thoroughfares are opened up between the rows of barges, and their connecting structures submerged, to allow the passage of both freight and maintenance vessels, and pleasure craft for tourists, bird watchers, anglers, hunters and holidaymakers. Double- and quadruple-sized (and so on) barges are added to the grid to create small forests and space for holiday cabins, and eventually permanent homes and farms. As the salinity drops, plant species are adjusted (or, in barge zones set aside as wilderness, selected) to suit the new, less saline environment.

Judging by the experience of similar island-dotted lakes (whether floating, as in South and Central America and south-east Asia, or dredged and sculpted out of marshlands like the pre-Columbian chiñampa system of Mexico City), the new, permanent, inland sea could become one of the most agriculturally productive sites on the planet, as well as contributing to stable and productive agriculture throughout the south-eastern Australian agricultural region. Plus, abundant renewable energy.

*I am aware that by lowering the rate of evaporation, we are lessening the potential for downwind rainfall during flood events. I posit that the permanence of the lake more than makes up for this. Rather than a short-term rain boost, the permanent lake should provide a more steady climate with more even rains over the years, and help to break the cycle of drought and flood which has so characterised Australian agriculture, and contributed to its economic and environmental instability.