Archive for May, 2012

Perth is a city with variable water quality. There are places in Perth with great water – I am lucky enough to live in one of those places. The EC of my water is good (<500 mg/L or an EC of about 0.8 dSm-1) and it doesn’t have iron or calcium problems. Its just acidic and eats out valve seats in taps. But there are other places, some nearby, that have quite salty water. And over near the coast also there is sea water encroachment into a lot of the shallow aquifers (where people have their bores) which means their water is getting progressively salty -twice what mine is or more.

Other areas of Perth, notably coastal and northern suburbs have calcium in their water which means they may get white deposits on the foliage after a period of overhead watering. This is mostly cosmetic but also can also affect photosynthesis. The EC of the water is often good.

Many areas around Perth have iron in their water – were the water has that ‘rotten egg smell’. The quality of the water is usually good but the iron oxidises and can block up drippers if not removed. The easiest way to remove iron is by exposing the water to air so it can oxidise and drop out – use a water feature or some sort or simply spray water into the air before you tank it or distribute it to your garden. There are filters but they are a more expensive option.
It is useful to know the pH of your water – not that you’d often want to treat it but it can give you an idea of whether you may need to lime your garden over time. Using fertilisers generally depresses pH so having acid water as well may make that worse. Conversely, if your water is alkaline and you use fertilisers you may not have to lime at all!

If your water is salty then that will cause problems with any overhead watering. As the salty water evaporates the residual salt burns the leaves. Over time, with sprinkler irrigation the salt may accumulate in the root zone and that can also cause problems. If you can get through summer then winter rains may do the required leaching, otherwise you may periodically have to do a heavier irrigation to wash the salts down out of the root zone. Commercial growers generally work on a 10-20% ‘leaching factor’.

You can get your water tested simply at a Pool shop, they can do pH and EC for you and that’s often all the infomration you need.  If you suspect you have bigger issues, then the Chemcentre  is one place that will comprehensively test it for you.

There are a heaps of good references out there if you can to know more about water quality. The first is probably The Perth Groundwater Atlas which tells you what your water quality is likely to be for a particular location and how deep it is to the water table.

The Department of Agriculture and Food WA has a number of publications about water. Water quality in home gardens, gives good information on you can grow according to your water quality.

Other publications are:

The latest version of the Australian Drinking Water Guidelines are here and here.


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