Studies have shown that most turf grasses used on the Central Coast transpire (use) about one-third of an inch of water per day during the summer months. If you live right on the coast (fog belt), water use will be slightly less, and if you reside at Lake Lopez or Garey/Sisquoc, your lawn is using about one-half inch of water per day. If you wish to keep your lawn green and growing, you need to adjust the watering time and frequency to supply adequate water to maintain the grass.
Some homeowners will say “My sprinkler system supplies that amount and still there are dry areas!” My reply is – even the best engineered sprinkler system will not apply the same amount of water to all parts of your lawn. Also the system does not take into account variations in soil composition in the yard. Therefore, to keep the turfgrass green, you must set the sprinkling time and frequency so the driest place in the yard gets adequate water. Setting the water schedule so the driest areas stay green will mean that some areas will be slightly overwatered. If some overwatering is not acceptable, then the dry areas will need to be given supplemental manual watering with a hose and sprinkle.
A second option is to convert your yard to a Mediterranean landscape (winter wet, summer dry). Plants used in this landscape will be species that can tolerate the dry Central Coast summers with no or very little supplemental summer watering.