What is a watershed?

The augmented reality sandbox in the Dickinson County Nature Center has been a hit since it was installed.

The exhibit talks about watersheds and how water moves through the landscape, but do you really understand what a watershed is? Let's answer some questions about watersheds.

What is a watershed?

A watershed is an area of land that drains into a lake, river or other body of water. Watersheds are separated from one another by higher parts of the landscape such as a ridges, hills and mountains.

How does water move through the watersheds in the Iowa Great Lakes?

In the map from the Iowa State University GIS Facility, the yellow and orange borders show the watershed area that feeds each lake.

Subterranean --- underground --- springs help provide water to West Lake Okoboji. All Iowa Great Lakes are also filled by precipitation as well as water flowing from the Iowa Great Lakes watershed. Water flows through the entire Iowa Great Lakes system, from Big Spirit Lake through the spillway into East Lake Okoboji. West and East Lake Okoboji flow into Upper Gar, then Lake Minnewashta and finally into Lower Gar before emptying into Milford Creek.

How does precipitation add water to watersheds?

Learning about watersheds begins with the water cycle, because the flow of water is a neverending cycle.

Once rainwater runs off into rivers and other bodies of water and combines with groundwater, energy from the sun evaporates the water into the air. Atmospheric winds move that water vapor around until it combines to form clouds. In those clouds, the water vapor cools and condenses into liquid water. When that water gets heavy enough, it falls to the earth, producing precipitation such as rain or snow.

Then the cycle starts all over again.

How does what is on the land affect the watershed?

How land is used can affect water quality in a watershed. We've all seen algae blooms on lakes and streams from excess nutrients or massive scale fish kills from water contamination.

In suburban areas, precipitation that falls on hard surfaces such as parking lots, buildings, roads and driveways will run off directly into the sewer system and then into bodies of water, carrying with it oil, fertilizer, sediments, bacteria and pesticides.

Development in urban areas also affects water quality as vegetation is removed and the surface topography changes, altering natural drainage networks.

Precipitation in rural areas often runs off from crop fields and stockyards directly into streams and rivers, carrying with it fertilizer, pesticide, large amounts of soil and livestock waste.

Erosion can also harm water quality as loose stream and lake banks begin to leech soil into the water, sometimes even completely filling in a stream or riverbed.