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Rain Water

South Australia is described anecdotally as the driest state in the the driest continent on this planet.
That suggests that this land area is poorly resourced with naturally occurring water sources; be they artesian (below ground), stationary or flowing (ground level streams, dams, lakes) or airborne (rain).
Most streams in the region flow seasonally only, ground water bodies are subject to high evaporation rates in summer, and rain falls predominantly over a short winter season only.

In this situation, capture, retention and potability of naturally occurring waters is a high priority in development and settlement decisionmaking.
South Australia encompasses a substantial portion of the plains which in geological times were covered with ocean. The soil's high salinity content thereby contaminates both below ground and on-ground water sources.

Rain water becomes a desirable source of unpolluted waters; however air pollutants and pollutants on run-off surfaces particularly in urban areas further contaminate this water source. Low rainfall levels in the region becomes one of the natural land capacity limits where in the past development of greater density now depends on importation of waters from elsewhere.
Major watershed diversion schemes and pipeline distribution have been undertaken in the past to make large portions of the region habitable.
In addition to their energy and recurrent maintenance demands, there is doubt about the sustainability of this approach to land settlement in the long term.
Already large areas of irrigation abutting rivers has increased held salinity levels; and areas cleared for grazing abutting riparian zones of some streams have become salt logged and unuseable.
Abutting urban areas waste and stormwater pollutant discharge has measurable detrimental effects on swamp and ocean areas.

Environmental projects

limit the use of land to within occupancy levels where local resources, particularly water supply, will suffice.
This includes allowing for poor rainfall periods, drawing on on-ground and in-ground sources only to the extent where replenishment from local good season rains is then possible.

Water use strategies within developments become integral to such regional development philosophy, in particular low water use appliances, waste water treatment and re-use, and disposal of waters to avoid land damage.

This particularly includes development design to avoid changes to in-ground waterflows (underground courses), avoid concentrations of stormwater flows and nutrients and contaminants in waste waters.
Development creates roof and pavement areas where previously natural soil absorption dissipated water flows. Concentrations from such hard surfaces need to be dealt with to avoid damage to land elsewhere.
Conventional stormwater systems pipe such damage sizeable distances from collection points in concentrated and high flow speed form.

    Environmental projects therefore consider water in categories including:-
  • potable waters - from unpolluted collecting surfaces or where basic treatment including UV filter suffices
  • stored waters - from mains or on-ground sources where carbon filter restores potability
  • stormwaters - from traffiked surfaces, where treatment even with carbon filter may not restore potability
  • grey waters - waste waters from bathroom, kitchen, laundry where grease trap and biological treatment achieves standards suitable for garden watering
  • black waters - septic waste waters unsuitable for human contact and requiring disposal segregated.

With seasonal water generation, rain water too becomes a stored water, though usually in covered tanks limiting contamination by salinity or pollutants; although tanin from Australian native vegetation retained on collection surfaces can colour and taint taste.

Development practice therefore includes:-

- screens to gutters
- maintenance obligations to clear collection surfaces
- 'first rain' diversion piping and syphon delivery piping diversion and cleaning pipes
- filters

Sizing water storage is limited by available rainfall and roof area. Some calculations allow for top up by out of seasonal rain thereby reducing storage volume required.
This approach doesn't allow for storing opportunity water from higher than average seasons against use in drought conditions.
Rain water systems will include mixtures of delivery/storage/ supply infrastructure complete with gravity feed and pumped sections. These need to be matched to other development features:-

  • There is limited size to DC electrical motor pumps suitable to operate from renewable energy systems without inverter
  • various appliances have varied pressure requirements
    - while pressure hot water services will operate at low pressure (<20psi) some low flow shower heads (particularly with aerating heads) require high pressures (>60psi).
    A compromise between delivery pressure and water saving can be made (removing some of the waterflow restrictors in such a showerhead).
  • water saving strategies includes the use of pressure balancing tap systems, dual plumbing to allow connection by separate rain water and bore water supplies
  • waste water treatment and re-use is described on the separate page

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