Add compost to your soil to improve its water holding capacity. Check for and repair leaky hose connections and sprinkler valves.
Small leaks can be very wasteful.
Ask your nursery person about low water using turf and raise your lawnmower cutting height. Longer grass blades help shade each other and cut down on evaporation. Preserve existing trees. Established plants are often adapted to low water conditions. Water trees and shrubs, which have deep root systems, longer and less frequently than shallow-rooted plants which require smaller amounts of water, more often.