 Why does Evans give up his drinking water?
Evans was a prospector, and like all prospectors, a sort of jackknife geologist, selenologist, rather. This boiling lowered the temperature, and the condenser demonstrated its efficiency by quickly freezing the water in the tank. Evans sealed the turbine from the rest of the steam system by closing the shut-off valves. Morning to him had no meaning at all, but he thought in the strictest sense that it would be morning on the Moon for another week. It was used mostly, from sun-up to sun-down, to supplement the nuclear power plant. After the sun rose, Evans returned to the lava cave that he had been exploring when the meteor hit. All of these needed water to form, and their existence on the Moon puzzled him for a while.
 Using the water is the only way for his transportation to work
 Using the water is the only way for his transportation to work  He knows he will be able to find more soon in one of the caves  He knows his rescuers will come find him and bring water  He knows he does not have enough to survive so he uses it to save his equipment