Drip systems need to run for several hours to give a thorough soaking. Mini-sprinklers and microsprayers have become very popular, because they're flexible and easier than sprinklers to install and repair. They put out water about twice as fast as drip systems, so they usually need to run for a few hours once a week. Lawn sprinkler systems vary greatly in how much water they apply, but it's easy to measure an inch of water using tuna cans or cake pans. To avoid wasting water, it's important to measure how long your system takes to get that inch of water twice a week.
Sprinklers placed on the end of a hose also vary greatly, with respect to how much area is covered.
A little spot sprinkler may cover only a 20-foot circle, putting out an inch of water in only 25 minutes, and probably running off as it does. If you have a water meter, it's not hard to learn how much water you use. Your city may have experts who can help reduce your water use, and nursery professionals can calculate how much water would be optimal for your landscape.