Santa Clara County on Wednesday became the most populous county in California to impose mandatory water restrictions, saying that the worsening drought poses a significant threat to the local groundwater supplies that provide nearly half the drinking water for 2 million residents.

On a 7-0 vote, the Santa Clara Valley Water District board declared a water shortage emergency and set a target of reducing water use 33% countywide from 2013 levels, a year the state uses as baseline. The district, a government agency based in San Jose which serves as the county’s wholesale water provider, also urged cities and private water companies who buy its water to put in place water wasting rules and other mandates, including limiting lawn watering to no more than three days a week. As in the last drought, the rules are likely to include monthly water allocations for each home beyond which financial penalties would apply.