I've done quite a bit of desert hiking over the years here in Southern California, and follow a few personal rules:

First, I try to plan a hike into an area with reliable water sources. You say your trip is in a place with "no water." Plan carefully and ask questions of local rangers; you might be surprised to find there are springs and seeps available. If not, look for alternative routes. A caveat: make sure to carry enough water to hike out early should your spring be found dry. I've had to bail out on more than one occasion when my formally reliable water source was found dry.

Second, if there is no reliable water, I limit my hikes to out and back two-day treks. Trying to lug twenty-plus pounds of water for a three-day trip is too much for me and, I suspect, for most people. Carry at least a gallon per person per day, and drink it. I used to carry gallon water jugs until I had one spring a leak. Now I carry several of those 1 1/2 liter Arrowhead bottles.

Third, I plan dry meals that don't need to be rehydrated; save the water for drinking.

Fourth, again, drink your water. By all means don't allow your scouts to ration. Make sure they stay hydrated. Many a person have been found debilitated or even dead from dehydration in the desert back country with a half-full water bottle next to them.

Also, make sure your scouts wear wide-brimmed hats and loose fitting clothes and long-sleeved shirts. Hike early in the day or late in the evening. Or plan the hike for a full moon and hike at night. Find shade during the heat of the day. The cooler the scout the less perspiration and the less chance of dehydration.