The availability of an adequate water supply is usually the key determinant in any decision to create a settlement. Natural sources of water in Australia are the sea, lakes, rivers, captured rain and the Great Artesian Basin (though this last is somewhat compromised due to the prodigal and wasteful manner in which its resources were accessed in times past). Generally speaking, water supplies are (and should be) sourced locally. However, there are two substantial conflicts of interest which must be resolved. The first relates to rivers, which are conduits of water from the places where rainfall occurs, to places where rainfall is much reduced, or non-existent. There is an ongoing debate as to the rights of access of upstream and downstream users, especially when some of those users engage in very water-hungry activities such as growing cotton. The second relates to capital cities which, because of their huge concentration of people, often need to draw their water from distant sources. This would not be a problem if these sources were not used by other communities or to maintain flora and fauna habitats. However, as the new pipeline serving Melbourne’s water requirements has shown, arbitration between conflicting demands has proved very divisive.
A NATIONAL WATER PLAN.
If we are going to encourage human settlement in the more remote parts of the country, we urgently need a national water plan. This will consist of an inventory of all possible water resources, identification of areas which have excess water to contribute to other areas needs and the identification of all storage and flows required to transfer excess or generated water capacity (e.g. desalination plants) to areas which are short of water
Such a plan would need to address the following issues:
- Determination of the quantities of water which must be allowed to traverse the entire length of each river in order to maintain its health. This should take into account that the natural habitats served by some rivers assume a seasonal rainfall and would not prosper if the flows were changed to be more uniform.
- If the river flows are inadequate to meet all requirements, identify natural or artificial sources which are conveniently located to supplement these flows.
- Average and minimum water requirements per hectare for all types of activity to be serviced by a river. This would include riparian properties plus any more distant land supplied through dams, pipelines, etc.
- Determine the storages, such as tanks, dams, pipework, etc. which will be required to capture excess flows (if any) for future use or support of more distant communities or other river systems and transmit them to points of need.
- Identify “hot spots” where there are singular difficulties in providing enough water and take steps to provide a constructed water supply (e.g. pipes from a desalination plant.). Note 1.
Some policies on the implementation and management of such a plan should include the following:
- Where the water usage would be distorted by industries of high water demand, insist that water in excess of average agricultural or domestic requirements be met from desalination plants or sea water.
- Engagement in extensive research to address the problem of evaporation. Solutions could include floating panels of insulants (providing environmental factors were not a concern), or in the case of dams, constructing roofs which would support agricultural activities over the dam (Note 2).
- Current water rights should, where the water plan indicates that the water drawn exceeds that conferred by such rights, be exchanged for rights falling within the range permitted by the plan. Grants or other assistance should be available to the relevant agribusiness to modify its processes or products.
Much of the information required could be supplied through the mapping exercise described in my earlier post. Appropriate sites for desalination plants would also be identified as another type of land usage.
THE GREAT ARTESIAN BASIN
The Great Artesian Basin offers some interesting possibilities as a water source. It is recharged naturally by excess rainwater in the northern latitudes and is transmitted very slowly to the south and west through porous sandstones (this is one theory, anyway !). The supply from this source is dwindling due to excessive and wasteful drawing-down in the past. If left alone for a few hundred years, no doubt it will fill up again. (Note 3).
I believe that the order of priority for the allocation of water should be:
- The health of rivers and other storages.
- Agricultural use (especially direct food-growing operations).
- Urban and domestic use, particularly cities close to the sea and not directly related to the foregoing.
With regard to the last item, there are substantial opportunities for economising or finding alternative sources of water. Cities have huge paved areas which could be used to capture rainfall. While this and waste water would required recycling, the output would normally be potable, if not quite to the high quality that we have become accustomed to. Alternatively, water for human consumption could be stored in tanks on the property and replenished by tankers (why not;: we have no problem buying bottled water at exorbitant prices), leaving the other mains-supplied water for washing dishes and clothes, bathing, garden maintenance and so forth.
Consider the Underground Car Park at Melbourne University. The roof over the car park consists of about 120 umbrella-shaped concrete structures, each consisting of four hyperbolic paraboloid shapes. The significance of the HP geometry is that it supports nearly 2 metres depth of soil over the columns reducing to about 40cm at the midpoint between columns. The project was extremely economical to build as six sets of forms were each used more than 20 times. Laying the concrete was also very easy, because the HP shape is formed from intersecting straight lines, thus facilitating the tamping of the concrete into place. The lawn above the car park contains a number of substantial trees (whose weight, as well as that of the supporting soil is taken directly by the columns below). If similar structures were constructed over dams with a suitable topography, there is scope for leasing out the area over the dams for plantation-type agriculture, such as fruit or nuts.
One wonders whether one could speed up the process by artificially recharging the basin by directing water from desalination plants into the aquifer. For several hundred years, London (in UK) drew its water by pumping it from aquifers trapped between dense clay layers. Recharge was effected by pumping waste water and excess river flows back into the aquifers.