Gov. Gavin Newsom’s call for all Californians to reduce their water use by 15 percent amid a severe drought across most of the state won’t be met with the same urgency in San Diego County as elsewhere because of a decades-old effort to diversify water supplies here and because of a new court order.

Last month, the U.S. Supreme Court unanimously declined a legal challenge by Imperial Valley farmers that had the potential to threaten the San Diego County Water Authority’s access to Colorado River supplies. This is why San Diego County is being asked to conserve but is not one of 50 counties in the state subject to Newsom’s stricter drought decrees.