Glossary of Irrigation Terms

An irrigation sprinkler is a device that distributes water through the air to the ground. Water is delivered to sprinklers through a network of pipes and valves and distributed through a series of nozzles, which can be adjusted to provide a range of spray patterns and water droplet sizes.

An arrangement of equipment, such as pipes, pumps, and valves, used to deliver water to an area for irrigation.

An area within a landscape or field with a distinct irrigation requirement based on factors such as plant type, sun exposure, microclimate, and soil characteristics. These distinct areas are known as zones and are divided and controlled separately, usually by a single control valve. Creating zones means water application can be tailored around need, thus making more efficient use of water.

An isolation valve is a mechanical valve used to isolate one section of a piping system from another to control and thus regulate water flow. Often used for maintenance or safety purposes, the isolating valve is not named for being a particular type of valve, but because of its function within a system.

These are generally smaller pumps that provide pressure and flow assistance in a larger pump system. They are extremely useful for handling smaller, (constant or intermittent) flows of water in a system, thus removing the need for a larger pump to constantly turn on and off. For this reason they can be an excellent cost saving feature of a system - in energy savings or maintenance cost savings for example.

The landscape coefficient is a measure of the type and density of vegetation in a given landscape, as well as the presence of microclimates (such as areas which are shaded or exposed to wind and sun). It enables us estimate of the evapotranspiration which is likely to occur as water evaporates from the soil or through the plant surface. An accurate landscape coefficient makes it easier to plan for water loss and ensure that irrigation is neither too little nor too much.

Magnetic flow meters (sometimes called electromagnetic or mag meters) are a flow measurement technology used in applications where a highly accurate measurement of volumetric flow of a liquid is required. In simple terms, as liquid is moved through an induced voltage the meter can measure flow, liquid velocity and the rate of flow. They can only measure liquids that conduct electricity.

The pipe used to carry water from the chosen water source (i.e. an irrigation lake or well) to the irrigation system itself. The mainline will than carry water through the irrigation system to the points of delivery. In high pressure systems the pipe will probably be made of PVC. 

A unique set of environmental conditions applying to a specific area. Factors which help to create a microclimate include the soil type, the wind, the sunlight available and how much shade there is. Microclimates can occur naturally or can be designed into a landscape.

A type of centrifugal pump which combines features of axial and radial pumps. Water pressure within the pump is generated by a combination of centrifugal force and the lifting action of the pump impellers. Mixed flow pumps generate a high flow rate and high water pressure at the point of discharge.

The difference between the amount of moisture present in the soil and the amount of water the soil is actually capable of holding, once gravitational forces have drained it. The latter is referred to as the field capacity of the soil. 

A device placed in the soil of an area which is being irrigated. It measures the amount of water present in the soil at the root zone, and this figure can then be used to vary the amount of water being delivered through irrigation. Moisture sensors can be stationary or portable. Also known as a moisture meter. 

A pump which takes water in and then pushes it through two or more impellers mounted in a single shaft. Each stage of the pump is made up of an impeller, a diffuser and return guide vanes within a single casing. As the water is fed from impeller to impeller the pressure increases.

A measure of the depth of water required by a particular landscape, once factors such as moisture stored in the soil and effective precipitation have been taken into account. The amount will be the water needed to satisfy requirements such as transpiration and evaporation while irrigating the soil.

This figure represents the difference between the pressure of water taken into the irrigation system and the pressure of water inside the pump. If the net positive suction head (NPSH) is less than that required (due to insufficient water pressure) it can cause cavitation – vapor bubbles which damage the pump.