In your planning stages for a trip how do you determine where you will have a reliable water source? I have an especially hard time with this in the desert where a lot of water sources flow only after it has rained.

Guidebooks or rangers or previous trip reports from reliable people.

Guidebooks +1

If you're going to a very dry climate, do a lot of research on where the more prominent drainages, streams, pools, and other water sources are. Find out how reliable they are during "average" rainfall, and go from there. For example, don't trust a source if during an average year it's only 50% reliable, and the rainfall for the year is well below average. Unless, however, you get very recent confirmation from trip reports that the source has water.

Is it possible to cache water along your route?

Edited by T.L. on 05/12/2010 20:02:38 MDT.

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.

Edited by DaveC on 05/12/2010 23:58:26 MDT.

When planning our recent Western Atlas traverse ,see our recent trip report, we knew we would have to descend off the ridge at least 300m altitude every camp to get water for the 5 days on the ridge. unless there was snow to melt. It might have been much more than that, making the route impossible. Luckily in good weather the snowy side of the ridge is nearly all visible from near Marrakesh. We could confirm that there were still occasional snow patches before we committed.