Drainage Basins: Watershed Drainage System Quiz

A divide, such as a mountain ridge or a high hill, acts like the peak of a roof. Rain falling on one side flows into one river system, while rain on the other side flows elsewhere.

No matter where you stand, you are in a watershed. Even if there is no river nearby, the rain that falls on that spot will eventually flow toward a specific stream, lake, or ocean.

When the ground is saturated or covered in hard surfaces like pavement, gravity pulls the excess water downhill as runoff, which eventually enters the drainage system.

Watersheds are defined by the shape of the land. Water follows gravity, meaning elevation changes dictate exactly where a basin begins and ends.

Just as small streams flow into large rivers, small sub-watersheds flow into larger ones. For example, a creek's watershed is nested inside the much larger Mississippi River watershed.

Cities are full of impermeable surfaces like concrete. These prevent water from soaking into the ground, causing more runoff to enter the drainage system much faster than it would in a forest.

This term is used interchangeably with watershed. It describes the entire catchment area where all water converges at a single point.

Everything done on the land affects the water. Pollutants on a street in the upper part of a watershed will eventually flow down to the river at the bottom.

The vegetation along a stream bank slows down runoff and traps sediments and pollutants, keeping the water in the drainage system cleaner.

Because topographic maps show elevation using contour lines, you can find the high ridges (divides) to trace the perimeter of a watershed.

Infiltration is the opposite of runoff. It allows the watershed to store water underground, which slowly feeds streams even during dry weather.

The outlet is the lowest point where all the water from the basin finally exits. This could be a river mouth meeting the sea or a stream entering a lake.

Headwaters are the roots of the drainage tree. They are the small, often steep streams where the watershed first begins to collect water.

Without gravity, water wouldn't flow from high divides to low outlets. Gravity ensures that the drainage system always moves water toward the lowest possible point.

The Continental Divide in the United States is a famous example that separates water flowing toward the Atlantic Ocean from water flowing toward the Pacific.