Design Considerations (continued)

4. Scheduling coefficient

The scheduling coefficient is another measure of uniformity. It is the ratio between the average precipitation rate (application rate) and the lowest precipitation rate in the sprinkler layout. Catchment data from can tests are used to calculate this value. The scheduling coefficient has a value equal to or greater than 1.0 and can be thought of as a multiplier to determine sprinkler system timing. For example, if the average application rate for a system was 12 mm/hr and the driest area had an application rate of 7 mm/hr, the scheduling coefficient would equal 12/7 1.7. This means that if a group of plants required 9 mm of water per day, this irrigation system would have to be operated for 1.3 hours per day (1 hr/12 mm × 9 mm/day × 1.7) to insure that all plants received an adequate supply of water. This illustrates the point that a scheduling coefficient closer to 1.0 is desireable indicating a more uniform irrigation system.

5. Infiltration rate

The infiltration rate is the rate in which water moves through the soil. It is best to have an infiltration rate that is greater than the irrigation system's application rate so that water does not accumulate in puddles or overflow the container. This can become important in the landscape on poorly drained or compacted soils.