The mandatory reduction includes residents and businesses. Commercial water customers are required to reduce irrigation by 30 percent for landscaping. It also bans the washing of cars or boats without a nozzle, and prohibits the washing of outdoor surfaces unless necessary for health and safety.
Roseville says outdoor irrigation accounts for more than half of a typical home's water use, and says reducing that is the quickest way to reach the 20 percent goal.
The city gets most of its water from Folsom Lake, which is extremely low due to the drought. Earlier this year, the city turned on its groundwater wells in order to conserve water from the lake, but turned them off this month after more rain and snow fell in Northern California. The city of Sacramento has also implemented a mandatory 20 percent reduction.
While Roseville is calling the reduction "mandatory," water customers will not be hit with a surcharge or penalty if they do not meet that target.
Roseville, the largest city in Placer County, operates its own utility, which serves most of the 127,000 residents. Officials backtracked on a February proposal that would have used surcharges to compel reductions
Water conservationists criticized Roseville's approach, saying that without an enforcement or penalty structure, customers were unlikely to heed the call. But city leaders expect that education and outreach will translate into cutbacks.
The Associated Press contributed to this report.
California Communities Respond To Drought
California lawmakers heard testimony about the dire state of the fishing industry on the West Coast.
There was a slight reduction in the percentage of drought in California over the past week. But the U.S. Drought Monitor says it will take time to ease the state's historic four-year drought.
A new study says California's four-year drought has reduced hydroelectricity generation, resulting in higher electricity costs to ratepayers and increased greenhouse gas pollution.
Legislation introduced in the California state Assembly would create the Lower American River Conservancy to improve, protect, preserve and possibly expand the 5,000-acre American River Parkway.
January brought above-average rainfall and snow to much of California, partly due to El Niño. But forecasters say the ocean warming condition is "taking a break" for the next week or longer.