The amount of water that most people in Southern California waste in incorrectly watering their lawns and landscapes is immense. We water too often, not deep enough (sometime too deep), and inefficiently. This subject can not be covered adequately in a short article so we will cover it with many. The placement of the right type of sprinklers is important to get Irrigation Uniformity. There are many efficient sprinklers on the market and many old types that are very inefficient.
Old Brass pop up heads (right) are not efficient; they spout out large amounts of water just to pop up and distribute the water inefficiently, they don't pop up high enough to clear most types of grass and often get stuck up and mowed off.
Old style impact heads (left) are also inefficient because they shoot out bulk water and distribute it by impacting the stream of water and knocking it down. The water goes everywhere, there is also a lot of mist and evaporation. These sprinklers are not easily fitted to compensate for different configurations. The same sprinkler head set to water a quarter circle will put out the same water in ¼ of the area as a full head will put out in an area 4 times as big. Thus, the area with the quarter circle will get 4 times the amount of water as the area with the full head.