Irrigation Controller Scheduling – one of the keys to successful landscape water management.
Properly scheduling irrigation is complicated. Consideration of many factors are needed to properly program an irrigation controller.
- ET° (Weather Conditions)
- Kc (Crop Coefficient)
- Sprinkler DU (Distribution Uniformity)
- Precipitation Rate (Sprinkler Type and Spacing/Placement/Area Dimensions)
- Drip EU (Emission Uniformity)
- Drip Emitter Output, Number of Emitters, and Spacing/Placement (Canopy/Root-Zone Footprint)
- SC (Scheduling Coefficient)
- Soil Type/Infiltration Rate/Water Holding Capacity
The above list is not intended to be a comprehensive list; rather it is intended to be a starting point for scheduling irrigation controllers.
Use of a comprehensive Landscape Water Budget to monitor water use, along with visual observations/confirmation of landscape health ongoing, is necessary to periodically update controller schedules for seasonal landscape water needs.
WatrWise Consulting does not recommend using Percent Scaling, or Run Time Minute adjustments as a scheduling tool/shortcut for properties located in arid climates.
Percent Scaling adjusts “run time minutes”; often used to reduce the amount of time that a valve, zone/area, or station runs (watering time). Watering for varying amounts of time changes the depth of watering; longer run times water deeper, shorter run times water shallower. Salts gather at the perimeter of the watered profile. Reducing watering run time minutes will deposit salts in the middle of plant root zone profiles (established during longer run times), affecting plant health and water availability; see the post “Salinity Effects on Plant Growth“.
Run times should be established for each valve, zone/area or station based on the list above. Water consistently the same run time minutes throughout the year, only changing the frequency or interval between watering; the exception to this rule is to increase run time minutes (for one watering) periodically throughout the year to leach salts from root zone profiles.
Watering By the Numbers – guide to watering in arid climates.
Published By Water Use it Wisely