Page 21 - Landscape SA Issue 107

ADVERTORIAL

IMPLEMENTATION OF THE LANDSCAPE

IRRIGATION MODEL FOR SOUTH AFRICA (LIMSA)

This model was produced with input from

a range of workshops held around South
Africa with members of the Green Industry,
who volunteered their time to contribute
valuable ideas to it. Added to this, a range of
wholesale nurseries in South Africa provided

feedback on plant hydrozones that were
specific to the plants they grow and sell.

spects for the model were obtained from these workshops, It is also important to note that as the landscape matures and as
and models in other countries. Data for the plant list was the environment around it changes over time, so too will the water
Aobtained from South African and international sources, as requirements. For example, new landscapes younger than three years
well as growers in South Africa. Through this research process, the will need to be re-assessed after three years. The same will apply for
intention was to ensure that as far as practically possible, aspects the application of, for example, water retention granules. If they are
were gathered from around the country to ensure applicability. designed to last for 18 months in the soil, then the model should be
For landscapes that are already in-situ and being maintained, this redone at that stage, unless the user is going to continuously replenish
model can be used as an “as built” irrigation calculator, allowing them. The same thinking will apply to mulch and replenishing of
for changes to be made over time to ensure that the landscape mulch as it slowly breaks down into the soil, forming compost. Other
slowly moves towards being a more water conserving one. Any aspects of how watering should be adjusted considers the site as it
improvements to the design and management of the in-situ matures, including aspects such as age, density and canopy copy in
landscape could result in water, cost and labour savings for the site. the model. It is therefore advised that the model be redone for the
site every three years. This will allow for more accurate watering and
The intention of this model is to allow for a more accurate water changes to the irrigation requirements for each hydrozone of the site
use on any landscape site to be determined. This is particularly over time.
important for sites that will rely on any form of supplementary
irrigation over and above rainfall of the area where the landscape For the model to be effective the assessor will need to:
is located. This will also apply to sites that require additional • Assess each hydrozone/hydrostation individually against all
watering beyond the initial establishment period. The period could aspects.
be as long as two years and will be influenced by, amongst other • Ensure that each hydrozone/hydrostation is to be watered as
things, the type of landscape being developed, soils, plant types a unit.
chosen and size of plants used. This period could, however, be • Choose one of 160 towns or the closest town to one on the
much shorter depending on the landscape, methods employed list (rainfall and potential evapotranspiration is automatically
and plants used. included).
• Each one of the questions (factors/elements) must be answered
In all cases, it is critical that each and every hydrozone (hydrostation) to allow the model to calculate water use accurately.
must be assessed individually. A hydrozone in this context is each • The model makes use of drop-down menus.
section of the landscape that is watered using the same valve i.e. • For best results, plants must be planted in the correct location
the hydrozone in question is watered as a unit. Hence each area on site, suited to that plant species.
that is individually watered must be assessed separately. • Experience and professional judgement will play a vital role in
some of the assessments required and therefore it is imperative
that the assessor draw on this experience and understanding of
landscapes to arrive at the decisions to be made.
• The guide below should be used to help explain each of the
elements and categories.

Some general considerations for the site and model use:
• It applies equally to indigenous and exotic plants;
• Watering for establishment (two year period);
• For single trees (planted as street trees) where no irrigation is
used at all, this model has limited use.

For more information, visit the Rand Water website www.
randwater.co.za and click on the Water Wise logo. Alternatively,
email us at waterwise@randwater.co.za or call us at 0860 10 10 60.
We also have YouTube, Twitter, and Facebook! n
Text and photos supplied by Rand Water. Images were taken from the
Garden World summer Festival and show hydrozoning practices.

Landscape SA • Issue 107 2021 19