Whether you are moving hoses and sprinklers or you have an automatic irrigation system, it is important to understand how much water your system is delivering in a given time period. One simple method to determine this is to set out several catch cans or rain gauges over the area to be irrigated. Run the system for 20 minutes, or a known amount of time, and measure the amount collected. Take an average of the can measurements, but also make note of those that are way off the average. This will tell you that you either have a nozzle problem or a rotating head that is stuck, etc. The average measurement can be converted to inches of water per hour and you can use this information to determine how long to run your system on a particular day. As mentioned above, a lawn’s water needs change with the season, so you should change your automatic sprinkler timers to deliver the correct amount of water depending on the time of year. In the spring, for example, you may need to water enough to replace 1 inch of water every 6 days, but in the summer when the grass is using more water, you may need to water every 3-4 days. Adjusting the timer several times during the season will reduce water waste and give the grass exactly what it needs.
While the system is running, it is a good idea to look for problems with sprinkler heads such as clogged nozzles or rotating heads stuck in one position. Clogged nozzles can be cleaned by unscrewing the nozzle or may involve unscrewing a set screw and pulling out the nozzle with needle nose pliers. On some sprinkler heads, the orifice may be replaced. However, if you don’t have a repacement, be careful not to damage the orifice. Sprinker heads that do not rotate may simply need to be cleaned, but usually need to be replaced as damage to the internal gears could also be a problem. Check your system each spring, taking the time to see each sprinkler operates to its full range since sometimes a head will get stuck at one end of the arc and not the other. Also, be sure the sprinkler heads are in a vertical position so the water is being distributed as designed.
The University of Idaho publication Watering Home Lawns and Landscapes provides a more detailed discussion on soil variables as well as an in depth discussion on proper use of automated irrigation systems.
Additionally, a website devoted to lawn and tree water management has been developed by the University of Idaho. In this website you can find water calculation tools to help you determine how much water to apply based on your irrigation system test: www.uidaho.edu/extension/lawn