dr. maddock: there are certain processes that can only be described mathematically. from soil to air. water enters a tree through its root system, moves through xylem tissue -- the very thin straws lining the inside of the tree -- before evaporating into the atmosphere through its leaves. dr. maddock: some of the trees in the riparian system can use quite an astounding amount of water. it's been estimated that under, say, perfect conditions, a healthy cottonwood can take up as much as 90 gallons per day of water, which is about the same as half of a normal household here in the sohwt. t we're taing aba irly substantial amount of water that's being transpired by the trees. one of the things that had been suggested at e time was perhaps one way to save water in the river is to cut down all the trees along it. the problem is, is when you do that, regular evaporation takes over and you can end up actually losing more water with regular evaporation than you would from transpiration from the trees. there were several studies done by the bureau of reclamation and one by the