An inch of water per week

1 inch per week watering

Seattle was recently on one of the driest streaks in decades. Not a drop of rain for 50 straight days, though just one day shy of the record 51 dry days set in 1951.

For gardeners and homeowners, a dry spell means plants and lawns may need a little extra TLC this summer. Even plants that are well-established and drought-tolerant still may need a bit of a drink to help them get through the extra dry spell. We earlier blogged about how to care for lawns during dry weather. When you water your lawn and landscapes, do it in the early morning to avoid losing water to evaporation. It’s better to water deeply (about one inch per week) than to water too often, too little. Deep watering is better for plant health than frequent shallow watering. Why? Light applications of water promote lush growth but shallow grass roots. Shallow-rooted turf grass undergo more stress in dry conditions.

So, how much is an inch of water a week? Experts say this amounts to roughly six gallons per square yard per week. One crude but easy way to figure out how long you need to water to get one inch a week: scatter five empty tuna cans or other containers throughout your lawn. Turn on your sprinkler system and let it run for 30 minutes. Measure the depth of water in those cans, add the amounts together and divide by 5 (or the number of cans you end up using). You’ll end up with the average amount of water you get when you have the sprinkler on for 30 minutes. Once you know the depth of wet soil, you can calculate how long you need to run your sprinkler.

Installing a smart controller on your sprinkler system is an even better way to control the amount of water your lawn or landscape beds need.

The EPA provides a good tipsheet with other tips on saving water for outdoor use, which we’ve summarized below.

1. Know how much water your landscape actually needs before you set your sprinkler. Your local utility can offer recommendations for how much water certain plants need in your region and best times to water. Generally, it’s best to water lawns and landscapes in the early morning and late evening because significant amounts of water can be lost due to evaporation during the heat of the day.

2. Look for the label: If your system uses a clock timer, consider upgrading to a WaterSense labeled controller. WaterSense labeled irrigation controllers act like a thermostat for your lawn, using local weather data to determine when and how much to water, reducing waste and improving plant health.

3. Tune up your system: Inspect irrigation systems and check for leaks and broken or clogged sprinkler heads. Fix sprinkler heads that are broken or spraying on the sidewalk, street, or driveway.

4. Play zone defense: When planting, assign areas of your landscape different hydrozones depending on sun/shade exposure, soil and plant types, and type of sprinklers, then adjust your irrigation system or watering schedule based on those zones’ specific needs. This helps you avoid overwatering some areas or underwatering others.