I'm very familiar with your predicament, since much of my home paddling territory, Baja's Sea of Cortez, gets less than six inches of rain per year. For a ten- or twelve-day trip, I'll often load 100 pounds of water in the boat before anything else goes in. So I've long searched for an alternative.

	Jonathan Hanson Jonathan Hanson Jonathan Hanson is a writer whose lifelong appreciation of nature shows up frequently in his work. Meet Jonathan Previous Answers

The ultimate irony of paddling desert coastlines is that you're floating on billions of gallons of water that you can't drink. There are ways of removing the dissolved salts from ocean water, but unfortunately no one has invented a magic pill that you can just drop in your canteen.

The most sophisticated desalination system is a reverse osmosis pump, such as those made by Recovery Engineering (612-541-1313) under their PUR brand name. A reverse osmosis pump removes dissolved salts by forcing the water through an extremely fine filter at exceedingly high pressure (around 800 psi). PUR makes electrically driven reverse-osmosis systems for large yachts that can produce hundreds of gallons of fresh water per day. For kayakers who need a manually operated system, however, the choices are reduced to two: the PUR Survivor 06 and the Survivor 35.

The 06 is a very compact unit, not much bigger than a couple of VCR tapes, that weighs 2.5 pounds. It's also relatively affordable at about $600 U.S. Unfortunately, the physics of the reverse osmosis process means that less than ten percent of the water pumped through the system emerges as fresh water; the rest is utilized in a loop to build and maintain the requisite pressure and is ultimately lost through a waste valve. The upshot is that the Survivor 06, with steady pumping, will produce about one quart of fresh water per hour of pumping. If you figure a gallon per day as your intake, that means if you rely on the 06 as your primary water source you'll be sitting and pumping for four hours a day. Trust me, no scenery in the world will keep you from getting seriously bored at that rate.

At about a gallon per hour, the Survivor 35 has a much higher output than the 06, which makes it significantly more practical. However, the 35 is more expensive ($1,400 or so), and is a big and bloody awkward thing to store in a kayak (nearly two feet long and with a big handle and lots of tubing). Nevertheless, it does work; furthermore, both the 06 and the 35 seem to be as reliable as bricks — I've never heard of either one failing.

There is another way to make fresh water from salt, and that's to distill your own. I've made very efficient stills using a pot with a lid that can be clamped down (an old pressure cooker works fine), plus several feet of 1/4" copper tubing. Make sure there is a fitting in the lid of the pot to attach the tubing. Bring the pot of water to a boil and run the tubing in a series of loops to another pot. This will result in a slow, but steady drip of fresh water into the empty pot. You can increase the efficiency of the system by running the tubing through another container of water (or a tidal pool), which will help cool and condense the steam. The distilling method is slow, but the advantage is you can be doing other things while it's working. It is also fiendishly wasteful of fuel, so it's not worth considering unless you're in an area with plentiful natural fuel.

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