Experiment. Stand there and spray as long as you think you need to. Then go run your fingers through the "wet" soil. I'd be surprised if you find it isn't dry 1/4" down. You can design your garden with "irrigation ditches" that go plant to plant, lay the hose at one end and let it run on low flow until all the plants in that "ditch" have been watered, let the "ditch" fill up and soak into the ground then move the hose to the next one. If you want to go whole hog you can set up a drip system that will water each plant individually. More work and it gets kind of expensive. More often used for patio plants or plantings near a house.
Some years we have rain often enough that I don't have to water the garden except for when I first put out the seeds/plants. Then there was last year, pretty much no rain all summer and I did have to water. I don't water the grass. Just too much of it and who knows how the well would keep up with demand. On the up side, I didn't spend much on gas or time for the riding mower.
The mulch isn't there to absorb and hold water but to keep the soil from drying out so fast. I've been using old small hay rolls the prior owners took out to the edge of the woods when they listed the place instead of leaving them in the barn. I think I there were 5 or 6. Still have 2 out there I can bring back.
Chipmunks, like most wild animals have all day to look for food. If you think about it, they eat, sleep. That is what they do. Well and procreate a bit.