A drought response Level 4 is triggered upon declaration by the Mayor, and resolution of the City Council, that a water shortage emergency exists pursuant to California Water Code Section 350, and upon a declaration that a demand reduction of greater than 40% is required in order to have maximum supplies available to meet demands.

At a Level 4 response, all landscape irrigaton is stopped except for hand held watering of trees and shrubs two days a week; the maintenance of landscaping necessary for fire protection and erosion control; the watering of livestock; water for public works projects and actively irrigated environmental mitigation projects; and irrigaton necessary for the maintenance of plant materials that are rare or essential to the well being of rare animals. The maintenance of parks and playing fields and golf course greens is also allowed under a two-day-a-week schedule, as previously provided in Level 3.