Residents around Northern California have made a significant effort to reduce their water use by nearly 20 percent since the start of the drought, according to the Regional Water Authority.Compared to the past two years, people who live in Sacramento, Placer, El Dorado and Yolo counties have cut back on water use by more than 18 percent, officials said.How much water is being used by California cities?The RWA passed a resolution on Jan. 9 urging residents to reduce their water use by 20 percent or more, and soon after, Gov. Jerry Brown declared a statewide emergency in response to California's drought.Inside California's drought: 40 haunting photos"Clearly, residents have heard the call to conserve and have taken action," said RWA Executive Director John Woodling in a released statement. "They absolutely deserve to be commended."How much water does it take to produce common foods?Some water providers have offered incentives for those who reduce their water use, including rebates to replace water-inefficient appliances."It will be critical for everyone to continue conserving water, especially as temperatures peak this summer," said Amy Talbot, RWA water efficiency program manager. "With hot, dry weather ahead, the temptation to ramp up outdoor watering will be intense."The RWA is also encouraging people to cut back on water use in their yards by limiting landscape watering to two days per week, adjusting sprinklers and even plant water-efficient grasses and plants.