Irrigation Control

 

The simplest form of irrigation control is turning the tap on and off, the operator of the tap needs to be present this presents a number of disadvantages. Manual irrigation control is subject to forgetfulness and wasted water. In addition, it is generally accepted that the best time to water is dawn, when most people are in bed.

 

 

Control equipment ranges from simple single zone controllers to sophisticated multi zone controllers with mini weather stations to predict the exact amount of water required.

Single zone controllers

For small systems a battery operated timer can be fitted to the tap, turning the system on and off several times a day. These are ideal for small hanging basket drip systems.

Multi zone control

Different areas will need separate control to ensure each planting type receives the correct amount of water. Borders can be watered every couple of days, whereas planters will require water several times a day.

Zoning of the irrigation also helps ensure that irrigation does not exceed the available water. A large lawn, for example, could be watered as one zone, but would need large diameter pipes and a very high flow of water. By dividing the lawn into several zones, pipe sizes and water requirements are kept more manageable.

Weather sensitivity

The simplest controllers are operated purely on the basis of time. Regardless of the weather conditions the controller will irrigate for a pre-determined length of time, leading to watering in the rain. For very small scale projects this is acceptable, but larger schemes need improved weather sensitivity.

Mains powered controllers generally have an input for a rain sensor and the ability to easily increase or decrease the watering duration as the seasons change.

The most sophisticated irrigation controllers incorporate an on-site mini weather station. Using temperature, humidity, solar radiation and optionally wind speed, the unit can then calculate a highly accurate on-site evapo-transpiration (ET) figure. As the planting type and soil type are programmed in for each zone, the controller will automatically calculate the optimum watering requirements. Studies show that ET calculations provide a highly realistic model of plant needs, and can provide water savings of up to 50%.