W/r/t water in the desert, not all guides are created equal. Steve Allen lists large, medium, and small spring and potholes. The descriptors do not necessarily refer to size, but to longevity. In my experience, Allen's beta is very accurate. Mike Kelsey, on the other hand, often only hikes a route once before he writes it up, and leaves it to the reader to discren the details that might affect the water situation.
National park backcountry offices maintain reasonably accurate data on seasonal water sources (Grand Canyon comes to mind), that are usually pretty safe as the NPS tends to be conservative.
As you get to know an area, you'll learn what rock layers produce springs, when those springs flow, what rock layers and types of canyons tend to form potholes that hold water, and so forth. It takes time.
In the end, carry enough water to make it back to the last known source.
This all contrasts to Montana, where in the spring and summer there is water everywhere, and I rarely carry more than a half liter at a time.