Irrigation Scheduling Tool – User Guide
Introduction – The Irrigation Scheduling Tool (IST) is a guide calculated to replenish the soil moisture lost during the previous week. It is not a forecast; if unseasonably hot or wet weather is expected, please adjust if needed for your garden. The IST is updated daily during the irrigation season. The IST provides a recommended irrigation schedule for different types of plants and irrigation emission devices. Your irrigation system may differ from the assumptions used to create the schedule; adjust the times accordingly.
How to Use the Irrigation Scheduling Tool – The IST provides everything you need to program a conventional irrigation controller for the changing weather patterns through the year. If you have a smart controller it will make these adjustments for you. Find the plant and irrigation type that most closely resembles your system. Use the suggested watering schedules as a starting point and then adjust as needed. Every system and every landscape is unique and therefore may need more or less than what is suggested. Start with the recommended watering times and then adjust as necessary.
Option 1 – Program your controller for July and use the watering index to adjust your controller each week using the
seasonal adjustment feature on your controller.
Option 2 – Use the schedules published to adjust your controller throughout the irrigation season.
How to Program Your Irrigation Controller – Here are the basic parameters that most conventional controllers have in common:
Stations refer to irrigation valves or zones. Different controllers have different numbers of stations ranging from 1 for a hose-bib controller, to many for large commercial models.
Programs are individual schedules on your controller that are used to group stations with similar watering requirements together, e.g. program A for lawn, program B for shrubs and perennials, and program C for trees. Most residential controllers have 3-4 programs. Be careful to ensure that each station only has start times on one program.
Start time is the time of day that each program will begin. Start times should be programmed to ensure that watering is completed before 9 a.m., or begins after 7 p.m. This helps to avoid evaporation from soil and leaf surfaces.
Cycles per day is the number of times a zone will cycle on a day that it is programmed to irrigate. Most controllers provide multiple start times for each program to help reduce runoff by splitting the total daily run time into shorter periods. Provide 30-60 minutes between start times to allow water to infiltrate into the soil.
Run time is the length of time for each zone that the controller will run for each program start time, e.g. a run time of 5 mins with 3 cycles per day will run for a total of 15 mins.
Days per week is the number of days in each week that watering is recommended. Total weekly run time is the product of run time, cycles per day, and days per week, e.g. a run time of 5 mins per day with 3 cycles per day operated 2 days per week will result in a total weekly run time of 30 mins.
Cycle and soak is another way to achieve multiple run times that some controllers have where the cycle time and soak period are specified.
Seasonal adjustment is a percentage adjustment that changes all of the run times in the controller. July is typically the hottest month of the year and would be programmed to 100%, whereas other months typically require less water. Seasonal adjustment is also referred to as the Watering Index. The Watering Index is a guide to help people adjust watering schedules for irrigation controllers that include a water budget adjustment feature.
Plant Type – Different plants have different water requirements. The categories used in the IST are based on those provided by the Water Use Classification of Landscape Species (WUCOLS), a program of the California Department of Water Resources and the University of California Cooperative Extension.
- Low water use plants use 10-30% of the water needed by cool season turf grass. Low water use plants include many California native and Mediterranean plants that are adapted to a summer-dry climate. Identifying characteristics include small leathery leaves, waxy or hairy leaves, and grey foliage. Succulents are also generally low water use.
- Moderate water use plants use 40-60% of the water needed by cool season turf grass. Moderate water use plants include many traditional landscape plants such as Maples, Camellias, and Hydrangeas.
- High water use plants need 80-100% of the water needed by cool season turfgrass. High water use plants include cool season turfgrass, many annuals, tropical plants, and vegetable gardens. High water use plants often have large soft leaves and/or large flowers.
Drip irrigation is the most common way to apply water to all kinds of plants including trees, shrubs, perennials, and even lawns.
- Drip emitters that are either inserted directly into distribution tubing or attached to ¼” spaghetti tubing. Drip emitters are used to apply water near to the root zone of each plant.
- Inline drip where emitters are embedded inside the tubing at regular spacing. Inline drip is used to apply water to the entire root zone of a group of plants, typically using a gridded layout.
- Micro-sprays put out a fine spray of water, and typically emit water at a faster rate than other drip irrigation.
Overhead spray is the most common way to apply water to lawns.
- Multi-stream rotating sprinklers apply rotating streams “fingers” of water. They offer the most uniform coverage and apply water more slowly than traditional fixed spray sprinklers, which results in less runoff. The larger water droplets that they put out are less prone to wind drift.
- Fixed spray sprinklers apply a fan of water. They typically apply water much more quickly than it can be absorbed by most soils, which often results in water waste due to runoff. They are also prone to misting when used with high water pressure.
- Rotors apply a single stream of water and are commonly used for covering large areas, such as sports fields and parks.