Desert Landscape Irrigation

Even the most drought-resistant xeriscape plants do sometimes need help getting enough water, especially during those first years while their still establishing their root systems.

Irrigation systems are available in two main types:

• Stationary sprinkler systems
  A system of rigid pipes mounted with fixed sprinklers and sprays.
• Drip irrigation system
  Flexible pipe with holes at regular intervals which release water directly onto the ground.

Which type to use depends on the type of area to be watered, plants' requirements, and the time you want to spend. Sprinklers work best for lawns, ground covers, and other low-growing plants. Pop up sprinklers, 3 to 6-inch high heads that produce a tight pattern and emit a constant flow of water in a short period of time, are ideal for small lawns. The area of coverage can be adjusted from 5 to 15 feet, the nozzles are adjustable from 90 to 360 degree sprays, and they’re recessed when not in use.

In areas where water isn't a problem, flow-regulated flood bubblers are used near trees and shrubs and in planters, which require more water than flower beds. In the hot, dry air of a desert landscape, though, any watering method where the water passes throught the air before reaches the plant is highly inefficient and drip irrigation is often a better choice. Drip systems are excellent for plants on hillsides, because of the low precipitation rate of these systems means they rarely cause any run-off .

Drip or trickle systems

A drip irrigation system is not only simple to install, at 90% efficiency, it's also the most efficient type of irrigation available. It can also reduce disease problems that some plants develop due to high levels of moisture. This system applies water directly to the soil through a polyvinyl tube, with the volume of water determined by the size of an "emitter" on the tube. Emitters range in size from 1/2 gallon per hour to 5 gallons per hour of delivery, with 4 liters (1 gallon) per hour being the most common. Emitters that regulate flow rates can be positioned near each plant.

Drip systems work at low pressure (10-30 PSI). There are also spray-mist emitters and other specialty emitters. These systems require a main waterline (from water source to the valves), valves, a submain line (from valves to the connection point of the tubing), drip tubing (polyethylene tubing) a backflow preventer, filter, emitters (these release water to the plant. Small plants need two, trees need three or more) and an end cap. Most systems will require a 20 mm (3/4-inch) valve. Drip tubing is a thin-wall tube and is generally produced in metric sizes. The length of drip hose should not exceed 60 meters (200 inches) from the point the water enters the tube to the end of the tube.

To avoid leaks and damage the system, be sure to choose fittings in precisely the right size and avoid very thin tubing. Total length of the mainline and the sub-main together should exceed 120 meters (400 feet).

Other irrigation ideas

A sprinkler system can be fitted with a programmable timer to more efficiently control the amount of water plants receive. Irrigation times and duration can be controlled at by a solar powered photovoltaic timer

If you find that you do need to water your plants occasionally, do it late in the evenings, to slow evaporation, and allow the plants to make the best use of the water. To slow evaporation and cool the soil, try an organic mulch made from bark or cotton by-products.

Improperly designed irrigation systems are a major cause landscape problems as poor drainage can damage plants and run-off can affect the foundation of your house. For detailed information about how to properly design and install an irrigation system, consult an irrigation specialist or landscaper. Your local water company may also offer free publications about irrigation and water conservation.