Drip Irrigation – How Many Separate Taps Should You Install for Maximum Water Conservation?
 (Read 500+ times)
By Jonathan Yaakobi
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The number of separate taps needed for drip irrigating the garden plants is a matter of pressure and efficient water management. In parks and large gardens, the irrigation designer will have calculated the diameter of pipe required and the number of separate stations that are needed, so that all the drippers emit water properly.
In small gardens however, the gardener can often judge these things by sight, and simply divide the area into a couple of stations; say a line for the front garden, and one for the plants in the back. This might be enough as far as pressure is concerned, but hardly adequate in terms of managing water as efficiently as possible.
The factor, other than pressure calculations, that should determine the number of taps is the type of plants that make up the garden. The first rule of water conserving gardening is to estimate the annual water consumption of the different plant groups. The second rule is to plant these groups separately, so that thirsty plants like annuals or citrus trees are not next to drought-resistant plants. The third rule, obviously, is to install a separate irrigation line for each plant group, so that an independent watering regime can be applied to each one.
The important thing to remember is that plants differ not only in the quantities of water they need, but also in the frequency of the watering. To take two extreme examples; annual flowers might require watering every three days in the summer, while many drought-tolerant shrubs and bushes, are not only able to survive on a once-a-month-schedule, but actually suffer from over frequent irrigating.
Many of the irrigation controllers available to the private garden market consider this, by having three programs that allow for three separate watering schedules. Effectively, this provides for one schedule for the lawns, one for trees and shrubs, and another for flowers. It appears reasonable at first sight, because even if the lawn irrigation (for example) requires dividing into two or more stations to ensure sufficient working pressure, the watering frequency should be the same for all the stations. Such a configuration is insufficient however, for the purpose of optimal water management, and saving as much water as possible.
Let’s look at the question in a bit more detail, by seeing how the drip irrigation could be organized in a typical dry climate garden.
*The garden has a small lawn, irrigated by sprinklers on their own tap.
*There are two types of woody plants. Most are drought-tolerant shrubs and trees, such as Melaleuca, Grevillea, Juniper, Olive, Pomegranate, and Leocophyllum. We have determined that they need water to the extent of 200 liters per square meter a year, spaced out over 3-4 waterings during the summer. They will have a separate tap.
*The second group of woody plants is comprised of sub-tropical ornamentals such as Jacaranda, Duranta, Plumeria, Orange, and Lemon trees. They will need 400mm a year, being irrigated every three weeks through the summer. Do you not agree that a tap independent of the dry plants would be preferable?
*We can now divide the herbaceous plants into the modest consumers like ornamental grasses, Agapanthus and Liriope, and the water guzzling summer annuals. The former may need 400-500mm a year, on a weekly schedule, while the annuals would need 1,000 mm, on a schedule of every three days. A separate tap for each? I think so.
*The garden also has decorative pots and containers on the balcony and patio. These are planted with flowers and need watering every day in the hot, dry months. Ideally, the container plants should have their own watering schedule. They can be grown on the same regime as annual flowers, if these are in light, sandy soil. However, if the annuals are growing in heavy clay soil, the interval between each watering should be extended to permit sufficient oxygen in the root zone. As the pot plants may need water every day, it is not difficult to see why they need a separate tap for themselves.
In this imaginary but representative case, it is clear that a three-program controller does not offer enough options for optimal water use. It is for this reason that you should be looking for a timer that allows for each tap to be entirely independent in terms time and frequency.
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Author Bio Box: Jonathan Yaakobi
 My name is Jonathan Ya'akobi.
I've been gardening in a professional capacity for 25 years.
I am the former head gardener of the Jerusalem Botanical Garden, but now concentrate on building beautiful gardens for private homeowners.
My job is to help you get the very best from your garden,
so visit me at http://www.dryclimategardening.com
Take the opportunity and download FOR FREE, the first chapter of my book
How to Garden in a Dry Climate
Go to http://www.dryclimategardening.com/Products/tabid/55/Default.aspx
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