Distribution Uniformity (DU)

is a measure of how evenly water is applied across a field during irrigation. For example, if one inch of water is applied in one part of the field and only half an inch is applied in another part of the field, that is poor DU. DU is expressed as a percentage between 0 and 100%, although it is virtually impossible to attain 100% in practice. DUs of less than 70% are considered poor, DUs of 70 - 90% are good, and DUs greater than 90% are excellent.

Hydro Zoning

refers to the separation of areas with different water requirements so that they can operate completely independent of one another. Some examples of areas with very different water needs are: grass, flowers, shrubs and groundcover, sunny areas, shady areas, exposed areas, enclosed areas, pots, hedges, slopes...etc. Your shrubs generally do not need to be watered nearly as often as your lawn, and your shady areas not nearly as often as your sunny areas. Therefore, the irrigation designer will have at least one automatic valve to control the flow of water to the sprinklers in the sunny lawn area, an area of like need. The sprinklers for a cedar hedge would be controlled by another valve. The vegetable garden is another area where individual control is needed and another automatic valve would be required. It is not unusual to have nine independent zones of sprinklers in order to achieve the objective of being able to have the means to apply the correct amount of water. By means of the automatic controller, each irrigation valve can be programmed for its own unique watering schedule.

Irrigation Efficiency

is different than DU. One example of IE is where an irrigation designer has matched the application rate of the sprinklers to a sloped lawn area. Sprinklers that apply the water slowly, such as rotor sprinklers, will allow the water to soak into the soil. Conversely, the use of spray sprinklers that have a comparatively very high water application rate, will likely result in having a significant portion of the water simply running off the slope and into a storm drain.

Reliability

Economical –

Cost of Water

Comparative water rates and trends