your existing water source is not suitable for gardening and it is not
possible to successfully treat its problems, you will need to find an
alternative source. The choice will usually depend on availability and
Common water sources include:
- Scheme water: Public water supplies
are unlikely to be contaminated with industrial pollutants. They are also
sterilized and treated to remove color, turbidity, iron and excess CO2.
suppliers may even treat for problems such as excessive hardness (causes
dripper blockages) and low alkalinity (causes corrosion). However, EC
(salinity) may be an untreated problem. Suppliers are usually willing to
provide a copy of the water’s typical analysis free of charge.
- Rainwater: Rainwater is invariably
of low EC and a preferred source if available. To maximize purity, ensure
that the run-off area (e.g. roof, gutters) is cleaned prior to the ‘wet’
season, and place a screen on the inlet to the storage reservoir (Fig
6.9). Note also that storage conditions and reservoir design are critical
considerations - see section below on “Long term storage of water”.
- Reverse osmosis (RO) water: This
requires a high initial capital outlay along with ongoing maintenance
expenses. However, it may be the only option if good quality water is not
otherwise available (Fig 6.10). For waters that are hard, alkaline,
contain iron, color or turbidity, pretreatment is required to avoid
damaging the expensive membranes.
- Bore or ground water: Although bore
waters are usually sterile when fresh, they can have high EC; contain high
levels of CO2; hardness; alkalinity; color; turbidity and iron. Other
‘undesirables’ can also be present if the bore is located close to septic
tanks, rubbish dumps and industry – including leaky underground petrol
station tanks and areas of intensive horticulture.
- Surface water (e.g. rivers, streams,
lakes, dams, soaks): These sources are least likely to produce iron
and CO2 problems. However, bacteriological quality, turbidity and slimes
are key concerns. High turbidity (cloudiness) usually correlates with poor
bacteriological quality and potential problems with root borne diseases.
Over the warm or dry months there is often an increase in TDS (salinity)
because high evaporation rates will concentrate the salts. Surface waters
should be dosed prior to use with a suitable disinfectant - see section
below on “long term storage of water”.
Long term storage of water
Water, regardless of its source, deteriorates
when stored. To minimize this problem, the reservoir should be:
- Covered with a lid to prevent the ingress of dirt, light (causes algae
and slimes) and airborne bacteria.
- Opaque in color to prevent the ingress of light.
- Located in a cool, dark place. In hot climates, consider burying
Treat the water weekly using a disinfectant -
disregard this for waters that are due to undergo reverse osmosis