Glossary of Irrigation Terms

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.

The name given to pollution which can’t be traced to a single clear source, such as a waste-water pipe. Non-point source pollution is generally caused by rainfall or snowmelt moving through and over the ground, picking up and carrying pollutants such as fertilizers, pesticides, bacteria, sediment and other forms of man-made pollution. The pollutants are then introduced to water sources such as rivers, lakes, ground water, wetlands and the sea.

The hole in a sprinkler or emitter through which water is passed into the atmosphere. The size, shape and positioning of the nozzles in an irrigation system can have a clear impact on factors such as the distance over which water is applied, the placement of the water and the efficient distribution of irrigation in general.