My herb, vegetable and flower gardens are entirely watered with sprinklers. Here at home, that is me moving a hose and sprinkler around. In the distant garden, that is a field sprinkler system.
I have measured the water by setting cake pans at different distances from the sprinklers, measuring, and keeping track of the time.
Gary is right that different species benefit from different amounts and frequencies of irrigation. And, soil type makes a difference. The nearest weather station will help you with rainfall.
An inch of water comes close to a gallon on every square foot: 231 cubic inches in a gallon. 144 cubic inches will cover 1 square foot, 1 inch deep.
Make everything as simple as possible but not simpler. ~ Albert Einstein