Applying ½ inch of water to clay soil will moisten it to a root depth of about 6 inches.
You can determine how long it takes to apply ½ inch of water by setting out several cans, running your sprinklers, and measuring the time it takes to fill them to ½ inch. It’s really quite simple, just be sure to use can with straight sides, not tapered. They can be any diameter – used food cans work perfect. Put several out and you may be surprised how inconsistently your sprinkler are delivering water.