Faced with as little as three months' supply of drinking water on hand, the city of Willits declared the maximum possible emergency level this week and instituted sharp limits on residents and businesses.

The restrictions limit households to just 150 gallons per day and require businesses to cut water use by at least 35 percent from the same time last year. Violators could face up to 30 days in jail and a fine of up to $1,000.

The city normally monitors water use monthly, but it has the capability of reading the meters more often. City Manager Adrienne Moore said the city has the ability to shut off service to customers using more than the allotment.

"We can do that," she said, "but that's not what we hope to have to do."

Instead, Moore said, staff hopes to encourage violators to come into voluntary compliance. In many cases, violations are inadvertent or are the result of leaks or inefficient fixtures and can be remedied easily.

The city already has identified the heaviest commercial and residential users and plans to focus attention on those accounts, so minor violations by smaller users probably will not draw a sharp rebuke.

Willits is supplied by two small reservoirs holding up to 1,250 acre-feet, or about 407 million gallons. But coming out of a record dry year in the region, the driest in more than a century, the reservoir is down to just 360 acre-feet, only about 260 acre-feet of which are usable for drinking water, Moore said.

Water systems throughout the area are facing similarly dry reservoirs, and many have instituted voluntary conservation campaigns, including those in Sonoma and Marin counties that rely on Sonoma County Water Agency reservoirs.

On Tuesday, Mendocino County supervisors declared a drought emergency, becoming the first county in the state to do so, and the Willits City Council imposed its restrictions Wednesday, making it the first water system in the region to institute strict mandatory limits.

City staff warned in early December that the reservoirs had only about 100 days of supply left. Residents quickly embraced voluntary conservation that cut water use by about 40 percent, Moore said. Because of that enthusiastic conservation, and because of a small trickle of water entering the reservoir from ground springs, engineers say that the city still has about 100 days' supply.

One concern for the city is the presence of "grow houses," or indoor marijuana farms, which can draw enormous amounts of water. Those operations are likely to draw the attention of city inspectors.

"It's the elephant in the room," Moore said.

Police Chief Gerry Gonzalez said he did not know how many grow houses there might be in the city, but if inspectors uncover them, "we will look at that on a case-by-case basis to see if they comply with the Compassionate Use Act," the 1996 ballot initiative that legalized marijuana for medical purposes.

The city has about 5,000 residents. The water system serves 2,014 residential accounts and 390 commercial ones. A few of those accounts are outside city limits, but Mendocino County inspectors and law enforcement have agreed to help monitor the activity of those users, Moore said.

The city has relatively few easy ways to get more water should the drought persist into the summer. Moore said the City Council is studying the possibility of converting two wells normally used for landscape irrigation to drinking water. That would require modifying the city's pipe network and renting a portable drinking water treatment system.

It's not clear yet how expensive such a system would be, but it is likely to cost at least $800,000. The wells could stretch the city's supply for an extra two months or so, Moore said.

The city is also negotiating with private well owners to draw water for public use, but that raises a host of technical and legal issues, and no deals have been hashed out as yet. The city also has considered drilling new wells on public property.

In the longer term, the city is studying how to use more treated wastewater from the sewage plant for irrigation and other nondrinking uses, which would take some pressure off of the drinking water supply. That, however, is likely to be expensive and time-consuming, so it is of little use in solving the immediate water emergency.

This year's drought also will add urgency to long-term planning to use the 80-acre lake at Wente Scout Reservation, a Boy Scout camp in the hills east of Willits, as an emergency backup water source. That idea, however, would require an extensive permitting process and an expensive pipeline.

The City Council is expected to meet again next week in special session to discuss the backup well plan. In the meantime, the city is asking residents to report excessive uses of water by calling City Hall at 459-4601.

(You can reach Staff Writer Sean Scully at 521-5313 or sean.scully@pressdemocrat.com. On Twitter @BeerCountry.)