Boise-area irrigation shutoffs loom amid drought. How to save your lawn and plants
With irrigation districts shutting off water early this year — Sept. 15 for many — Treasure Valley residents should prepare for a late summer with little or no irrigation water available.
For Mike Smith, a Southwest Boise resident whose Muir Woods subdivision is in the Nampa and Meridian Irrigation District, the shutoffs are a concern.
“It is unusual,” Smith said by phone Friday. “A lot of folks in the southwest part of Boise have irrigation water, and the shutoffs are normally around Oct. 7 or 8.”
Smith said some of the residents in his subdivision are wondering whether they should switch to city water during September so they can continue watering their lawns and landscaping.
There are 66 irrigation-district organizations, including private and public, throughout Ada and Canyon counties. The districts distribute nondrinkable irrigation water to farms and homeowners, including at least 50 subdivisions in five irrigation districts maintained by the Boise Project Board of Control, a management agency.
Drinking water is provided mostly by city water departments, though Boise residents get water from Suez, a private company. Residents who do not receive irrigation water use city water to irrigate their yards. City water is much costlier than irrigation water.
The irrigation districts distribute water to the homes in their districts through the Valley’s canals, laterals and drains. A lateral is a ditch that moves irrigation water to water-control structures, such as small dams, along the water route. A drain removes surface water from an area and stores it below. The Boise Project Board of Control says there are 1,500 miles of these waterways in Ada and Canyon counties. The board’s five districts supply water to 224,000 acres.
The irrigation districts have infrastructure like pipes and pumps that help deliver pressurized irrigation water to your property, so water sprays out when you turn on your sprinklers.
Many of the irrigation districts in the valley expect to shut off water on Sept. 15. That could change if the area gets more rain. The Pioneer Irrigation District originally was going to shut off water on Sept. 7, but later decided to extend service an extra week.
The shutoffs are happening nearly a month earlier than usual because of the small snowpack last winter, drought conditions this summer and lower-than-normal reservoirs.
Still, for many residents, the shutoffs could mean browning grass and shrubs. That is why local landscaping experts are telling people to be strategic about how they water.
The Idaho Statesman sought advice for home irrigators’ lawns and landscapes from Jos Zamzow, co-CEO of Zamzows, a group of lawn, garden and pet stores; and Cody Swander, Nampa’s parks superintendent.
Lawns, do you have to water them? If so, how often?
It depends, Zamzow said.
“People who have been watering improperly all summer long are going to struggle,” Zamzow said. “If you water frequently, the roots are going to be shallow. They are going to dry out without water on the surface.”
If you have been watering less frequently but for longer periods, Zamzow said, the roots are going to be deeper. So when mid-September rolls around and there is less water, those roots can go deeper to find water. Shallow-rooted grass will likely brown and die.
Swander said if you water less frequently and deeply, your grass is more likely to bounce back in the springtime when the water comes back on.
The cooler temperatures in August helped grass and helped people conserve water, Zamzow said. He said during cooler temperatures he advises people to provide 1 inch of water each week. When it jumps to 100 degrees, the water need rises.
“We are hoping it won’t be 100 in September,” Zamzow said.
Swander recommended that people watch the weather and fiddle with their water-timing systems throughout the summer.
“Earlier this month we needed 1.62 inches of water,” Swander said. “That is dropping down with the cooler temperatures.”
How will lawns fare if we have a hot September?
Usually, Zamzow said, people have pressurized irrigation on until October. With an early shutoff, if temperatures warm up, the valley could see browning grass.
“It is conceivable that some lawns would die completely if we had a real dry September,” he said. “We just have our fingers crossed that it is not hot and we get some moisture.”
When does grass go dormant? How can you tell?
Lawns start going dormant in October, Zamzow said, meaning the grass goes brown and tries to conserve water and nutrients. This usually happens in the winter but can happen in the summer if grass isn’t watered.
If your grass goes for a long period with no water, the lawn can go from dormant to dead.
Zamzow said that could happen to a lawn that goes without water from Sept. 15 to later in the fall.
Should people switch to city water from September to October?
Smith’s neighbors have wondered whether it would be worthwhile to apply city water to their lawns during September to keep their lawns from dying. Zamzow says yes.
“Based on a typical September weather-wise, it would be too long to go without any water from now until later fall when we typically get some rain,” he said in a text message.
But people who switch over to city water should use it sparingly — just enough to keep grass from dying completely. If the temperatures stay the same, he said giving grass a good drink once per week should be enough.
“It may not be beautiful perfect green, but it won’t die,” he said.
Trees, shrubs, gardens: Will they survive September?
Swander gave similar advice for watering trees: Water infrequently and for long periods.
“Most older trees with an expansive root system are going to survive a drought,” Swander said.
He recommended trimming shrubs, especially those that produce annual flowers.
Zamzow recommended buying mulch for any flowers or shrubs in garden beds.
“That mulch will hold that water in,” Zamzow said. “Mulch is key. And the long, deep watering.”
Garden vegetables don’t do well in drought, Zamzow said. He recommended putting mulch around some plants, but said people should plan to “be in full harvest mode in September” anyway.
Four additional tips
1. Swander said he has been trying to educate people about Idaho’s complex water system. “We only have what Mother Nature gives us,” he said. “It is an education thing. We are going to learn, as our valley grows, that people will need to watch their water output. Mess with your clocks. You can easily be watering too much.”
2. People who live in subdivisions that have homeowner’s associations, Swander said, should talk to the landscape workers about watering too much or changing the timing up as the summer goes along.
3. Zamzow said people should cut their grass a little higher than usual. The longer blades will help the grass deal with water stress, he said.
4. To find out what irrigation district you may be in and when your water could be shut off, consult the map on the Idaho Department of Water Resources website at idwr.idaho.gov/water-rights/irrigation-organizations.
Rachel Spacek covers western Ada and eastern Canyon counties. Have a story suggestion or a question? Email Spacek at rspacek@idahostatesman.com.
This story was originally published August 28, 2021 at 4:00 AM with the headline "Boise-area irrigation shutoffs loom amid drought. How to save your lawn and plants."
