SAN FRANCISCO (AP) — San Francisco officials have declared a water shortage emergency and are asking customers in four counties to voluntarily reduce water use by 10% due to California’s drought.

The request Tuesday took effect immediately and applies to all 2.7 million customers of the San Francisco Public Utilities Commission in San Francisco, Alameda, Santa Clara and San Mateo counties.

Customers who don’t meet the goal will see a surcharge of up to 5% on their bills starting April 1. Last summer, Gov. Gavin Newsom asked all Californians to voluntarily reduce water use by 15%, but data shows few people are doing that.