The Sacramento Bee reported Thursday that the San Juan Water District board of directors approved the move this week.
The district serves more than 265,000 people in the Sacramento suburbs, including the communities of Citrus Heights, Orangevale and Folsom.
Most of its water comes from Folsom Reservoir, which the newspaper says has shrunk perilously low amid one of the driest winters in California history.
District General Manager Shauna Lorance says the call for conservation is not mandatory, but it could become so next month if the area doesn't get rain soon.
The district also is extending a request for a 20 percent cut in all water use that has been in place for months.
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.
The U.S. Drought Monitor says, other than a slight reduction in exceptional drought in the northern Sierra, it needs more time to assess impacts of the recent moisture on California's long-term drought.
California regulators have made modest adjustments to water conservation requirements for cities.
The second measurement this winter of snowpack in the Sierra Nevada was 130 percent of average. State water officials say the snowpack will help reservoir recovery.
California's water conservation rate dropped to 18 percent in December. But water regulators say the state continues to meet its long term goals.