How to check sprinkler output?

Q:  How do I measure how much water my sprinklers are putting down each time I water?

A:  Unless you know how much water in inches you are applying with each irrigation cycle, it is difficult to determine the effectiveness of your watering schedule.  An easy method to measure how you’re doing is to gather up some empty tuna  or cat food cans, (any shallow container with straight sides will do), and place them in various locations where you water with overhead irrigation.  After a 30 minute cycle (chosen for easy math), use a ruler to measure, in inches, how much water was collected in the container.  For example, if it was .5 inches (again, chosen for easy math) you will need to water 4 times during the week, for 30 minutes each time, to replace 2” of water loss.  Compare the results in each container and each location throughout the landscape to determine if your sprinkler heads are delivering the same amount of water per head in all zones.   Some heads may be worn out and need replacement.

Drip irrigation can be trickier.  Most systems are using 1 gallon per hour drippers.  Which means a drip system with 1 gph drippers needs to run for 1 full hour to deliver just one gallon of water per dripper.  Will that be enough for a newly planted, 10’ tall shade tree?  Nope.  Larger plants will require multiple drippers per plant to provide enough water, deeply enough to keep the plant happy.  It’s important to know how many gallons per hour your drippers are delivering.  They are usually color coded based on rate of delivery.  Check out the previous question and answer to determine frequency.  

When all else fails, let the plant tell you what it needs just by observing its behavior.  Wilting is one way the plant will let you know it needs water.  However, that isn’t fool proof.  Some plants like hydrangea, squash and cucumbers will wilt in the middle of the day because the direct sun is causing them to lose more water that they can physically pick up through the roots even though there may be plenty of moisture in the soil.   This is a protection mechanism the plant uses to reduce the leaf exposure to the sun and reduce water loss. In this situation the plant leaves will bounce back to normal as evening approaches and temperatures cool.  No extra watering is needed & may in fact harm the plant’s roots. If the plant doesn’t bounce back and the soil is dry, a long, slow soak of water will be required for the plant to recover.  Repeated episodes of dry wilt will lead to plant damage.  Try to time your next watering a day earlier, before the soil has dried to that extreme.

Keith Funk is handling our Q & A this year. You may have visited one of Keith’s Denver area gardens on a tour or know him from his years at Echter’s and now at Nick’s Garden Center. For 30 years he’s been heard every Saturday morning from 7-9 with fellow Wise Guy, Jim Borland, on the Garden Wise Radio Show on Legends 810AM.