Elephants being hindgut fermenters* are dependent on water for digestion. Unlike a ruminant who ferments food in the first stomach and then regurgitates to carry on with the process of digestion, elephants complete this action in the 3 chamber called the cecum. Fermentation in herbivores is crucial as it breaks down tough substances in the plants such as lignin and cellulose. With these broken down effectively a herbivore obtains enough nutrition to sustain energy levels and size.
*Hindgut fermentation is a digestive process seen in monogastric herbivores, animals with a simple, single-chambered stomach.