Here are some tips for “water harvesting” on the move.
1 - If climbing or hiking across a snowfield, keep your water bottle easily accessible. Frequently add handfuls of snow to your water, without stopping. On a warm, sunny day, this snow will melt or form a drinkable slush — bring a straw and some Gatorade powder for a poor-man’s Slurpee. (One more reason not to use a water bladder - you can't easily refill like this.)
When you grab or cut snow chunks to add to your water bottle, collect from the bottom edge of a snowfield or serac. This snow is heavily saturated with percolation and will add more water than the same snow volume gathered from lighter, fluffier snow.
2) Water running down a rock face face in a broad, yet shallow, curtain can be hard to collect. Here’s 2 tricks.
A - Carry a small length of aquarium tubing type hose; buy it any a decent hardware store or aquarium shop. Use it as a flexible straw to suck up water that you can't reach. (This is especially handy in desert areas, where water may be just a tiny trickle.)
B - Remove your jacket and long-sleeved shirt, and then spread and flatten your hand across the rock, giving the wet slab a chest-level “high-five.” The water will collect on your fingers and run down to your elbow in a stream; fill your bottle from this drippage point. (This last tip and image are from Climbing magazine.)