Overwatering due to poor irrigation system management is a major culprit of water waste, and offers the largest potential for conservation. A minimum of each quarter as the seasons change, homeowners should reprogram their irrigation controller to optimize water run time and frequency schedule to avoid watering too much or too little. They can also hire a certified water manager (CWM) to audit the landscape and expertly program the irrigation timer
Know your soil:
The type of soil you have and the type of irrigation system you use will help determine how often and how long you should water. Depending on your location, you may have clay, sand, silt, loam or a combination of these. Heavy soils such as clay have very tiny pore spaces and take in water very slowly so water runoff is more likely. Sandy soils have large pore spaces which allow water to penetrate quickly but don't retain water, so you may need to water more often
Assess the terrain:
The steeper the terrain, the greater the potential for water runoff. To avoid runoff, have an irrigation system with a low precipitation rate and/or to set short run times
Ensure your irrigation system is property "zoned" based on exposure to sunlight, wind and other elements. For example, you would not want to water sunny and shady zones at the same time, for the same frequency and length of time, because the water needs greatly differ in these two areas
Adding a 2 inch layer of groundcover mulch to planter beds is a good way to conserve water. Doing this will lower the temperature of the soil and dramatically reduce evaporation. You will also get the added benefits of weed control, erosion control and adding organic matter to the soil.
Those homes with mature plants and trees, which have a fully developed root system, can be watered less frequently and in some instances only a few times a year or not at all. So, as your landscaping ages, your watering schedule should be decreasing in kind.
Understand water needs:
Know what's planted in your yard, and if your flowers, plants and trees require high, moderate or low water so that you can set your irrigation system accordingly. Try to plant items together in zones with similar watering needs rather than mixing and matching high and low water use plants in the same area
Find and fix problems:
Each month check, or have your landscape maintenance company check, the condition of your irrigation system throughout the property so that problems such as leaks, overspray, broken heads and/or pipes, incorrect water pressure, etc. may be rectified
Become drought tolerant:
If your current landscape requires a lot of water, consider changing the plantings to Mediterranean and native plants. This will allow you to water less often and still have a beautiful garden.
There are many online resources to help homeowners conserve. For example, the San Diego County Water Authority offers a free, online residential Landscape Watering Calculator that can help homeowners avoid over-watering their property.