A lot of great information on this thread - maybe the best I've seen in a long time. Since none of us are geologists, I'll put my $.02 out there. The previous posts have said pretty much anything I can add, but I'd describe it like this:
Arizona has rocky, pourous soil, from the mountains to the desert. When Spring rains fall and snow is melting at the higher elevations, the water always drains to the lowest point, and does it quickly. On tall flats surrounded by rocky cliff areas, the water seeps out of the cliffs, onto the flatter areas. In the rolling hills, it obviosly flows through the sandy bottoms that make our landscape, but is soaking in as it passes through.
I'm no geologist, but I've seen what the soil looks like here compared to the narrows and slot canyons in Utah. The Escalante Staircase is perfect example of what our desert lands would look like without soil. There is a hard sandstone or granite base under most of AZ, and the water is squirting through the top layers of dirt and rock, like a sponge under pressure. All that water has to go somewhere, and it either soaks downward or flows on top of the ground West and South as fast as gravity will take it. When a lot of water has soaked in, the water tables start pushing it back out to the top, through the lower sandy or broken rock that it origanally seeped in through.
So, from a hunting perspectivet, like others have suggested, when you find a sandy draw with old cottonwoods, you know the water is only a few feet under the surface. It may look like a dry creekbed, but where the water has to take a sharp angle underground, it pools and gives those big trees something to live on. More likely than not, there will be pools of standing water where those cottonwoods grow - and they are easy to spot year 'round. Green in the Spring and Summer, colored during the Fall, and brown in winter months.
Seeps, from what I've seen, are usually found around cliff areas, and are easy to spot by the moss or other lush vegetation in an otherwise dry area. These are the spots where water takes its sweet time filtering through tens of meters of limestone or grantite drop-by-drop. To me, these spots are golden because when he cattle ponds have dried up and the sandy washes are dry on the surface, they still produce drinkable water. It's because the water coming out of a hard granite seep probably landed on the ground above a couple of years ago - and has taken that long to finally drain out.
In a tough drought year, the creek bottoms will be dry, the cattle tanks will look like an alligator's back, but a rocky seep will still be draining the excess of years past.
Just my ramblings on the subject