A thick thatch layer restricts the movement of water into the soil. Gradually increase your mowing height to allow your lawn to develop a deeper root system. Keep your lawn mower blades sharp. Sharp blades make cleaner cuts which helps the grass blades recover sooner and causes less water loss than cuts from dull blades. Control weeds with a good broadleaf weed killer.
Weeds use water that is otherwise available for more desirable plants.
Apply soil additives to help absorb water uniformly and to prevent dry spots. Apply a thick layer of mulch to all of your beds to maintain even temperatures and soil moisture. Extend the number of days between irrigations to the longest possible interval. When irrigating, water slowly and soak the area deeply, you may have to cycle irrigation time to prevent run off. Get rid of any plants that are growing poorly.