That would be bad for the cactus because the cactus needs the water to live. Some cacti have waxy coatings on their stems, so that water will run down the stem to the roots. Cacti can absorb water from fog in the air, since it does not rain very much in the desert. Most cacti have long roots which can spread out close to the surface so they can absorb a lot of water on the occasions when it rains.