River Flow. Source: Thundershead
Rivers always flow downhill. A stream, or a river, is formed whenever water moves downhill from one place to another. This means that most rivers begin high up in the mountains, where snow from the winter, or ancient glaciers, is melting. On their way down to the sea, they collect water from rain, and from other streams. Rivers also rise up from springs. Where groundwater seeps up onto the surface, it may form a lake or pool or it may start running downhill right away. This is the source of the river. In lower places where there are no mountain peaks covered with snow, rivers often begin this way.

The amount of flow in rivers affects many issues of water quality and quantity together - for example, pollutant concentration, water temperature, aquatic habitat, and recreational uses.

Read more: Precipitation

Read Local: Water Flow in My Watershed

Adapted from Stream Biology and Ecology website in association with Washington University.