By Dennis McKernan, CID, CGIA, CLIA, IA Instructor
For most landscape and irrigation contractors in mid to northern climates, the season is upon us — it’s “pedal to the metal” time!
In the midst of getting new people trained, starting new jobs, becoming familiar with new equipment, it is easy to lose sight of some key concepts regarding irrigation maintenance and proper scheduling. Forgetting some of these key water-conserving concepts allows mistakes to be made during installation or maintenance of our systems. These mistakes come back to haunt us later in the summer in the form of increased water or maintenance costs, or as reduced profits on new installations. Some key concepts that allow us to “keep our eyes on the prize” are as follows:
1. Adjust for optimum performance at the season’s start-up
Adjusting this arc early in the year will save water.
Photos by Dennis McKernanWhen irrigation systems first get started up each spring, it is always a good idea to check each sprinkler’s performance. The system operating pressure should be close to design pressure. When doing the spring check-up, make sure you check operating pressures — under “lifelike” conditions. If the normal static pressure is 55 psi when a residential irrigation system turns on at night, then you need to make sure you do your system check when the static water pressure from the house is close to 55 psi. Performing a system check at 10:30am, when the city’s water main pressure is only 45 psi due to high water consumption, will definitely affect your system’s performance. The system runs just fine, but when tested at below-normal pressures, it appears to be running poorly. Make sure you do your spring tests under lifelike pressures.
It is advantageous to check a sprinkler’s radius of throw and angles of coverage at the beginning of the season. Forgetting to do so can lead to water being applied that does not irrigate the desired plant materials. This water is costly to the homeowner, and is wasted in the sense that a plant does not take it up. I’m sure many of you have seen sprinklers whose arc of coverage extended beyond the planted area — onto sidewalks, boulevards and roadways. Ensuring proper coverage early in the year reduces water consumption and saves money for the homeowner or homeowners’ association. It is also during a coverage check that you can spot clogged nozzles or riser seals that have deteriorated and are now leaking during operation. You can see what the sprinkler is actually doing — and you probably will not get another chance to see the head operating again all season. If you have to go back to check a sprinkler’s performance later in the year, it is usually because there is now a problem in the landscape related to the sprinkler’s performance (i.e., plant materials that have died due to lack of water, large dry spots in the turf because of poor performance, etc.). The initial system check-up can save maintenance costs from escalating later in the year.
2. Use base irrigation schedules
A proper “base” irrigation schedule is a basic irrigation schedule that takes into account several factors for irrigating a landscape. It should take into account the plant material to be irrigated and its inherent water needs. Base schedules should be calculated for each individual “hydrozone” (a group of plants that have similar water requirements). A base schedule should take into account local weather patterns and any microclimate factors that could affect plant water needs. A base irrigation schedule takes into account the depth of the rootzone, the type of soil, the water-holding capacity of the soil and its infiltration rate, etc. A proper irrigation schedule is a science-based calculation that tells you how much water a particular zone needs. Once a base schedule is developed for each zone or station, it should be entered into the controller and act as the basic or “default” management schedule.
3. “Optimize” your irrigation schedules
This irrigation schedule keeps the roadway clean!Optimum irrigation schedules take into account things like rapid weather changes, compacted soils in some locations, or heavy thatch levels. An “optimized” schedule is one that has been tweaked to take into account something unique to that particular zone or system. Although measuring soil compaction and soil infiltration rates is costly and time consuming, it affords a much higher level of scheduling accuracy. Setting a base schedule and then just leaving it is like having a Ferrari and just going to the grocery store in it — it never gets out of second gear. An “optimized” schedule is custom tailored to each zone, and is adjusted daily if possible. “Optimizing” irrigation schedules allows you to minutely adjust water delivered through the irrigation system to perfectly mirror the plants’ water needs in your landscape. As the weather changes day to day, so does the irrigation schedule.
4. Embrace new irrigation technology
Very few areas of life today are becoming simpler and easier as time goes by. But new irrigation technology, particularly controllers, continues to get easier and simpler in operation than ever before. There really is little or no point in “optimizing” base schedules if we are still using older electro-mechanical controllers. New-generation controllers greatly aid in water-conserving efforts by offering much more flexible scheduling options and, truth be told, are significantly cheaper to buy and install than to fix outdated controllers. New irrigation nozzles have better distribution uniformity characteristics than older standard nozzles. Newer irrigation valves deal with dirty water conditions better than older valves have, and now give us the option of regulating pressure at the valve for the whole zone. Newer irrigation technology makes our life easier while we save water use.
These tips should help you stay focused on making your irrigation year less problematic and more profitable.
Dennis McKernan, CID, CGIA, CLIA, is an irrigation designer and consultant, based in Olds, Alberta, Canada. He is a regional authorized instructor for the Irrigation Association and can be reached at firstname.lastname@example.org