What Is a Watershed?

What is a Watershed? A watershed is an area or ridge of land that separates waters flowing to different rivers, basins, or seas. It is separated from other watersheds by highpoints such as hills or slopes. It doesn’t just have water, but it also includes the entire land area that drains into it. Rainfall and snow melt flow into streams, rivers, wetlands, lakes and eventually the ocean. The water may also travel through the soil to become groundwater. Everyone lives in a watershed and we will always be a part of a watershed, no matter where you live. Pollution anywhere within the watershed can affect all water bodies located downstream. Watersheds provide many with our drinking water supply. And forested areas also play an important role in the health of watersheds. Plant cover and leaf litter absorb moisture and help maintain soil structure, while root masses keep soil permeable and stable so moisture can move into it for storage. This is good because it allows water to be filtered and release slowly into the stream system.

What is Stream Order? Stream order is a measure of the relative size of streams. The stream order hierarchy was officially proposed in 1952 by Arthur Newell Strahler, a geosciences professor at Columbia University in New York City. Strahler outlined the order of streams as a way to define the size of perennial (a stream with water in its bed continuously throughout the year.) and recurring (a stream with water in its bed only for only half of the year) streams. The sizes to classify a stream range from a first order stream all the way to a 12th order stream, the largest. A stream order is important to geographers, geologists, hydrologists and other scientists because it gives them an idea of the size and strength of specific waterways within stream networks. First through third order streams are called headwater streams and constitute any waterways in the upper reaches of the watershed. It’s estimated that over 80% of the world’s...