Mandatory water rationing that prohibits residents from watering their lawns more than twice a week began on Saturday.

The Roy Water Conservancy Subdistrict established a strict schedule and said residents would be required to comply. Those who don't risk losing their flow of untreated, non-culinary water, officials say."We're just trying to help conserve the water for next year to ensure there's a carry-over," said General Manager Roy Watts. "I think next year will be all right. But I wouldn't want to drain the bank account this year and find out we need money next year."

Watts said the district won't allow its customers to use any secondary, untreated water on Sundays. Residents must stick to the following plan for the rest of the season:

-Customers north of the Davis County line to the south side of 52nd South can water on Mondays and Thursdays.

-Customers on the north side of 52nd South to the south side of 44th South can water on Tuesdays and Fridays.

-Customers on the north side of 44th South to the district's northern boundary or any other user to the north can water on Wednesdays and Saturdays.

People also are banned from irrigating their yards with culinary, indoor water. Roy City is also asking that people use water only on the same days they are allowed to use the subdistrict's water, said Noel Padden, interim city manager.

The city can't turn off drinking water, but the subdistrict plans to shut off the secondary water of anyone who doesn't follow the new rationing schedule, Watts said.

The subdistrict early this summer asked its customers to voluntarily conserve water the subdistrict gets from Davis and Weber Counties Canal Co.

But recently the canal company decided to halve the amount of water flowing through its system to ensure this year's stores last until Oct. 1, Watts said.

Farmers will be irrigating row crops such as beans through September. They'll be able to do that even though only half the usual amounts are flowing through the canal, said Floyd Bahem, general manager of the canal company.

Davis and Weber supplies Echo and East Canyon reservoir water to farmers in Sunset, Clinton, West Point, Clearfield, Layton, Kaysville and Syracuse.

Most residents and irrigation farmers in northern Utah depend on water stored in reservoirs. But the past two years have been drier than normal, drawing down stores.

The Weber Basin Water Conservancy District and Pineview Water Systems, two other main suppliers of secondary water, are not planning on rationing this summer, spokesmen said.

Willard Bay contains 98,475 acre feet of water. That's about 20,000 acre feet lower than this time last August and about 4,000 acre feet lower than in 1977, a drought year.