Glossary of Irrigation Terms

An increase in pressure in the downstream piping of an irrigation system that causes it to be greater than the supply pressure is known as back pressure. It can result in many and varied problems including a reversal in the normal direction of water flow.

When backflow (a reversal of flow) happens because of a reduction in system pressure and this in turn causes a negative or sub-atmospheric pressure to exist at any location in a system, back siphonage can occur.

Any water moving the wrong way through an irrigation system is referred to as backflow. Backflow can lead to contaminants in the water - or debris from the surface - infiltrating and damaging your irrigation system. Backflow prevention involves equipping a system with devices such as valves that only allow water to move in one direction.

Many factors influence the amount of water needed by plants. The Blaney-Criddle Method is a formula used to estimate water loss due to evapotranspiration in crops. At its simplest level, the calculation takes into consideration such factors as consumptive water use, mean monthly temperatures, and percentage of total annual daylight hours that were available over the period being measured. There are several other formulae employed to assess the amount of water plants need and it's an important aspect of the science of irrigation - whether in agriculture or for domestic and leisure purposes. Given the growing need to conserve water supplies and the increasing number of restrictions governing how much water we use for irrigation, knowing how much and when to water is a critical aspect of landscape management.