Irrigation control is a technique which is used to manage an irrigation system. Historically, it was accomplished by hand, with technology such as sluice gates to block or permit the passage of water. Today, it's often managed with electronic programs which control the flow of water. These programs may be highly sophisticated, with the ability to adapt their behavior to changing circumstances such as oncoming storms or a rising water table.
The goal of irrigation is to provide a crop or a garden with sufficient water to thrive. Waste is generally viewed as undesirable, both because water can be expensive and because it is bad for the environment. Irrigation needs change over the course of the year, both in response to rain and to the growing patterns of the plants being grown. Irrigation needs also vary depending on the plants being grown. Some plants are very water hungry, while others are more tolerant, with lower water requirements.
When an irrigation control system is developed and installed, the designer thinks about the existing needs of the garden or farm, and attempts to foresee some additional needs. Irrigation control includes timers which automatically start watering at set intervals, along with computer programs which can be used to remotely control irrigation systems, sensors which detect water and override automated settings to prevent irrigation systems from operating while its raining or when the soil is damp, and many other measures.
For large farms, irrigation control must be automated, because the manual labor required to operate a manual system would be very expensive. These systems must also be flexible, to allow for crop rotation. Many come with sensors and alarms which will sound when a leak is detected, when temperatures drop dangerously low, or when other problematic conditions emerge. Such systems can even be programmed to call someone such as a foreman or farm supervisor when there is a problem.
For a smaller farm or home garden, less automation is needed, because someone can physically take care of the system. It may use a series of timers which someone can manually override in the event that it becomes necessary, and it often lacks the bells and whistles such as alarms and sensors. An irrigation control system can also be tied into a smart house system, allowing someone to control a variety of automated systems pertaining to the administration of a house and garden from a central control panel.