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SAMPLE WATERING GUIDE

Below are a couple examples of how you might program your controller. A key component of these schedules is the use of a cycle and soak method.

  • This involves using two or more short watering cycles, with brief resting times in between, rather than a single long sprinkling time.
  • Many sprinklers apply water more quickly than soil can absorb it. Using multiple short cycles, water from one round of sprinkling can soak in before the next cycle starts.
  • These short cycles should be spaced only an hour or two apart (not split up between morning and evening) in order to obtain deep watering and healthier roots.

 

LAWN SCHEDULE
Biweekly Period Approximate Lawn Water Needs (ET)
(Inches Per Week)(1)		 Total Watering Time
Per Week
for Standard Spray Heads(2)		 Total Watering Time
Per Week
for Rotary Heads(2)
May 1-15 0.94 38 Minutes 90 Minutes
May 16-31 1.21 48 Minutes 116 Minutes
June 1-15 1.39 56 Minutes 134 Minutes
June 16-30 1.60 64 Minutes 154 Minutes
July 1-15 1.71 68 Minutes 164 Minutes
July 16-31 1.70 68 Minutes 164 Minutes
Aug 1-15 1.49 60 Minutes 144 Minutes
Aug 16-31 1.33 54 Minutes 128 Minutes
Sep 1-15 1.08 44 Minutes 104 Minutes
Sep 16-30 0.85 34 Minutes 82 Minutes


(1) Plant water need is often described as inches of water needed per week. Evapotranspiration (ET) is the sum of evaporation and plant transpiration from the Earth’s land surface to the atmosphere.

(2) These run times are based on an average application rate of 1.5 inches per hour for standard spray heads, and 0.625 inches per hour for rotating sprinklers.

SHRUB AND TREE WATERING: The sample schedule above applies only to lawns. Most shrubs and trees prefer deeper, less frequent watering.

The following is a recommendation for determining vegetation water needs:

  • Vegetables: 75-100% of lawn requirement (ET)
  • Shrubs & Perennials: 50-60% of lawn requirement (ET)
  • Waterwise plants: 30-40% of lawn requirement (ET)
  • Trees: Newly planted trees need regular water for up to the first couple of years, while established trees may need only a deep soak or two in summer.

Example water requirement calculation:

Weekly irrigation = 1.70 in. (ET)) / 1.5 (application rate of sprays) x 60 = 68 minutes per week.

You should utilize any City of Hillsboro recommended schedules as a starting point only. While this proposed schedule is based on long-term weather conditions, actual weather will vary somewhat from averages. Also, water needs vary from site to site according to such factors as vegetation, soil characteristics, slope, and how much sun an area receives.

When making adjustments to your schedule, it is probably best to make modifications a little at a time, and evaluate results before making further adjustments.

Drip Irrigation is an ideal alternative for shrub areas. Scheduling drip zones varies according to the size and number of emitters serving various plants. Monitor soil moisture around plants using an inexpensive moisture meter to determine appropriate watering schedules.

Please note:

  • Watering times for rotating sprinklers are different from sprays.
  • Zones that receive shade should be run for less time than areas in full sun.
  • Reduce sprinkling when rain has occurred, especially in spring when showers are common.