Lawn-watering ban to be lifted in stages, Central Iowa Water Works announces

• Central Iowa Water Works is lifting its lawn watering ban in stages, starting Tuesday.
• Odd-numbered addresses may water lawns on Tuesdays, Thursdays, and Saturdays; even-numbered addresses on Sundays, Wednesdays, and Fridays.
• The ban was implemented June 12 due to high nitrate levels in rivers exceeding federal limits after heavy spring rains.

A month after it began, a ban that has prevented 600,000 central Iowa residents from watering their lawns is being lifted in stages.

Central Iowa Water Works said Friday, July 18, that residential water users will be allowed to begin watering lawns starting Tuesday with odd-numbered addresses, which also may may water on Thursdays and Saturdays. Even-numbered addresses may water on Sundays, Wednesdays and Fridays.

“Now that we’ve lifted the restrictions, it’s very important that people follow the even-odd lawn watering schedules so we can continue to monitor demand and capacity,” said Tami Madsen, CIWW executive director.

Lawn watering for commercial customers will follow as capacity improves, and then for city, state, school and other government users.

The timing depends on water use and nitrate levels, which skyrocketed beyond the federal 10 milligrams per liter limit in the Raccoon and Des Moines rivers in the wake of heavy spring rains, prompting the ban on June 12.

Nitrate levels trending downward

Central Iowa Water Works member utilities have strained since late April to keep the nitrate levels in their water under that threshold and the agency imposed the watering ban to ensure seasonal demand wouldn’t outpace the capacity of the equipment used to remove nitrates. Lawn watering can increase overall water use by as much as 40%.

The water authority said Friday that the nitrate levels in its infiltration gallery have been consistently below 10 milligrams per liter. The gallery, a 3-mile stretch of underground pipes along the Raccoon River that collect shallow groundwater, can provide 30 million gallons daily.

More: Iowa’s largest urban area faces a water crisis. How experts say we can solve it.

The gallery water is naturally filtered through sand and gravel, and generally has lower nitrate levels, officials said.

The nitrate level in the Raccoon River also has been trending down, said Kyle Danley, chief operating officer for CIWW member Des Moines Water Works.

More: Is my water safe to drink? Do I need a water filter? What CIWW says about nitrate levels.

While nitrate concentrations may fluctuate with large rainstorms, Danley said he expects the levels in all CIWW water sources to be trending downward by early August, based on 25 years of data.

“It’s very important that customers follow the schedule and not overload the system,” Danley said, noting that demand climbs 40% with unrestricted lawn irrigation.

Agricultural fertilizer use implicated in nitrate crisis

Officials have said this year’s nitrate levels have been high in part due to drought conditions over the past few years that left nitrogen fertilizer applied to farm fields intact. Large rainstorms upstream from Des Moines have flushed out the fertilizer, which is carried through drainage tiles beneath cropland into the streams in the Des Moines and Raccoon river watersheds.

The regional authority had previously lifted some restrictions, allowing splash pads in city parks to operate and a dozen sod companies to install and water new lawns, a requirement before new homeowners can close on their mortgages.

High nitrate levels in drinking water can be harmful to pregnant mothers and cause a blood oxygen deficiency in infants under 6 months called blue baby syndrome. They also have been implicated in certain cancers.

Donnelle Eller covers agriculture, the environment and energy for the Register. Reach her at deller@registermedia.com.