Residents in northern Pinellas County will have to cut back on sprinkler usage as the drought afflicting the Tampa Bay region worsens, the county’s utilities department announced Thursday.

Customers of the county’s reclaimed water supply who live north of Curlew Road are now allowed to use the water only one day a week, down from the usual three days a week during the spring dry season. For addresses ending in the numbers 0, 2, 4, 6 or 8, that day is Saturday; all others are allowed to water on Wednesday. Watering is not allowed from 8 a.m. to 4 p.m.

A combination of low rainfall and increased demand has used up the reclaimed water in storage, according to a county news release. Almost all of Pinellas moved last week into what the U.S. Drought Monitor deems an extreme drought, the county’s worst in more than a decade.

Rainfall in the county this year was down more than 6½ inches from normal through March this year, according to the National Integrated Drought Information System, making it the fifth-driest first quarter for the county in the past 129 years.

In the past three years, Pinellas County recorded anywhere from just more than 2 inches of rain to nearly 6 for the month of April. So far this April, the county has received 0.29 inches of rain.

The reclaimed water system will be shut down for the other five days a week it’s not in use, the county said. Restrictions will stay in place “until seasonal rainfall resumes,” according to the release. Fines for violating water restrictions start at $193 and may be doubled for subsequent offenses.

A county spokesperson said nearly 9,400 customers are affected by the new restrictions. She said pay and hours for county employees in the water department will not be affected.

Contact Jack Evans at jevans@tampabay.com. Follow @JackHEvans.