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
There was "minor improvement" in California drought conditions over the past week. But as long-term drought persists throughout the west, and storage levels drop, water supply is a worry.
(AP) — The House has waded into a long-running California water war. Lawmakers have endorsed a Republican plan to shift more water to San Joaquin Valley farmers and cut the flow for threatened fish and growers in another part of the state.
The U.S. Drought Center says the past week brought "widespread improvements" in drought conditions in northern California and Nevada.
California's energy grid manager says supply should be adequate for the summer, despite potential natural gas shortages in Southern California.
California water regulators will allow cities and water agencies to set their own conservation targets based on water supply.