GARDENING WITH LESS WATER?
GARDENERS STRUGGLE WITH WATER RESTRICTIONS
MANY readers of these articles will know that I’m a passionate advocate of maximising water holding capacity of garden soils and keeping it there for as long as possible in order to grow healthy, quality plants and lawns.
It’d be an understatement to say that among the 312 articles I’ve written that I’ve devoted many to promoting water-efficient methods and practices.
With water restrictions imposed on all locations within our regional council boundary, and periods of hot, dry weather interspersed with sporadic days of rainfall, it’s still vitally important that we understand what our restrictions are and how we can still water our gardens based on those restrictions.
Apart from Cambooya, Cecil Plains, Clifton, Vale View and Yarraman (all on high level restrictions at this time), all other locations in the Toowoomba Region are currently on medium level water restrictions (according to Toowoomba Region website this week).
This asks all users to attempt to restrict usage to 175 litres per person per day.
Garden watering restrictions also apply, with set days for odd and even numbered premises (Tue, Thur, Sat and Wed, Fri, Sun respectively), and set times on those days (currently 5.30pm to 6.30pm until March 31).
No garden watering is allowed on Mondays.
Watering methods for established gardens are restricted to a “handheld hose with trigger or twist nozzle, efficient irrigation system or efficient sprinkler”.
Today’s article will take a look at the definition of “efficient” when applied to irrigation systems and sprinklers and will suggest a few products that may fall within this definition.
Bear in mind that, at the moment, both Toowoomba Region and SEQWater still rely on the definition of “efficient irrigation” as it is stated in guidelines from the now defunct Qld Water Commission (QWC).
Let’s look at sprinklers firstly.
This generally applies to portable sprinklers that are moved around the garden from time to time.
According to the QWC document, an “efficient” sprinkler is one that has a maximum output capacity that does not exceed more than nine litres of water a minute (540L/hr), is connected via a pipe or hose of 15mm diameter or less, is used with a timer (max 30min), and has an adjustable distribution pattern so that hard surfaces are not watered.
Phew! I won’t list the other “musts” and “shoulds” from the document, otherwise 99% of sprinklers would not be compliant.
The first point to be made is that if a sprinkler’s output is around 9L/min, then the average person’s daily 175L limit will be used in slightly less than 20 minutes.
I have drawn figures from products listed on the Smart Approved WaterMark website (www.smartwatermark.org), which is recommended in the QWC document.
Portable sprinklers listed on this website are able to comply with the efficiency limit, applying between 6.5L and 9L (with pressure reduction) of irrigation in a minute.
If used over the three allowed watering days for 30 min each, they’d use 585L and 810L respectively of water each week.
So, even water efficient sprinklers can use plenty of water if used according to current restriction guidelines.
An important factor to consider when water restrictions apply is whether the water applied to the garden actually penetrates well into the root zone of the plants we’re irrigating.
My calculations show that one hour of application from the above sprinkler delivering 6.5L/min will only apply around 3.5mm of irrigation (equivalent rainfall), which will be likely to only penetrate a few centimetres into a sandy loam soil, much less in a clay-based soil.
This is not effective irrigation as it will encourage shallow roots on plants, making them more susceptible to hot, dry days such as we’ve been experiencing during our recent summers.
I was surprised to see only one drip line product listed on the Smart Approved WaterMark website.
From my perspective, drip systems are the epitome of efficient irrigation products.
They apply water where it’s needed, and don’t suffer the losses that sprinklers do during hot, windy weather.
Unfortunately, the current 9L/min flow maximum for “fixed” irrigation systems in our water restriction guidelines means that a drip system is unlikely to apply enough water if only operated for the specified three hours per week (three days x one hour each day).
Some professional calculations show that a drip system with 4L/hr drippers over a garden area of about 10sqm (3m x 3.5m) needs to be operated for up to 10 hours every three days to effectively irrigate, say, a couple of fruit trees during our mid-January heat.
The upshot of all these baffling figures (sorry) is that there is no simple solution to the conundrum of matching water restrictions to maintaining a garden in a satisfactory condition.
Councils MUST attempt to have enough water for we humans to live comfortably in their cities and towns, so it will mean that gardens may suffer in the short term until rain once again replenishes our soils and hopefully our regional dams.
What can gardeners do?
1. Install a water tank.
2. Improve your garden soil.
3. Mulch.
4. Choose garden plants wisely.
5. Utilise drip irrigation wherever it’s practical to do so.
But above all, don’t stop gardening.