In the desert, water is life, and your pack is likely to be quite heavy with it. Water weighs eight pounds per gallon. Since you'll need at least a gallon a day in the warm months, more at the height of summer, planning a backpacking trip in the desert revolves around the quantity of water that you can reasonably carry and the likelihood of finding additional sources along your route. Always carry enough water that if the spring or intermittent stream at your proposed campsite is dry, you can make it back out. Don't count on water being available just because the map shows a spring. You can probably trust people who have actually been there – so long as they were there yesterday, not the week or month before. Even in that case, bring along some extra water.
In an emergency, your map, your eyes and your trowel are your best bets for finding water. Examine the map not only for springs and streams, but also for man-made structures like wells, cattle tanks and windmills. As you hike, look for bright green vegetation. There may be a seep or spring nearby. Keep an eye out for cottonwoods, sycamores and seep willows growing in dry stream beds. They too may mean water is close at hand. If you find damp sand, dig down with your trowel. You may find water further down, or you may be able to wait until the depression fills up. Search out places in canyons where flash-flood waters have scoured away the sand and gravel, exposing bedrock. Shallow depressions in the bedrock, called tinajas, may have trapped pools of rainwater. If you're hiking the ridges in hilly terrain, examine the canyon floors below you for the bright flash of sunlight reflecting in a water-filled pothole. Lava and limestone are porous rocks that often contain springs. A cave in a limestone cliff or a place where lava abuts a sandstone cliff may contain a seep or a spring. Look for the dark stains and green moss that mark seeps in sandstone cliffs. In the high desert in the winter months, examine the shady north sides of cliffs where the sun never shines. Lingering snow patches may provide a source of water. Whatever the source, an easily cleaned water filter will not only remove whatever critters may exist, but also the inevitable sand and silt.