The rainforest provides water to the Earth's atmosphere through the process of evapotranspiration. Evapotranspiration is the combination of evaporation water turning from liquid to vapor on the surface of vegetation and transpiration or the release of water from the stomata of leaves of plants to keep cool, or plant sweating. This moisture is released into the atmosphere, and collected in clouds. These clouds then move across the globe, releasing water as they go. affecting precipitation and water resources worldwide.

These maps from Nasa show how rainforests distribute water around the globe. The measurements were collected by the MODIS sensors on NASA's Terra and Aqua satellites.

Some of the biggest contributors of this moisture are the rivers and lakes within the rainforest. In fact, many of the largest rivers in the world are found in tropical rainforests. The Amazon River, in South America, is the largest river in the world and accounts for one-fifth of the world's total river flow.

In Africa, the Congo River (also known as the Zaire River), is the deepest river in the world. Although it is significantly shorter than the Amazon, the Congo measures over 750 feet deep. Waterfalls overflow in the rivers and run from the rivers to the tributaries transferring minerals and nutrients and nourishing plant life.

These rivers and lakes are habitats teeming with water dwelling species, almost as many different species as their surrounding rainforests. In addition to being thriving habitats, these rivers and lakes provide food for the native people and act as means of transportation and communication. For many of the villages, these are the only ways of getting to and from major cities. Towns and villagers rely on these rivers to meet their daily needs.