What is a watershed?

A Watershed is an area of land that allows water to flow over or under its surface into a particular body of water. The boundaries of a watershed are determined by the guiding contours of the land surrounding that stream, river, lake, or bay. Because precipitation must flow somewhere, all land areas are a part of a watershed. 

Our rivers and streams intertwine with all living things. Those waters lead to one great ocean. What lies in our water, in our soil, and in our air affects us now and in the future. 

Soil and other contaminants can impact a watershed

Iowa has deep, productive soil. The organic matter in the soil acts like a sponge to hold water. Rain and snowmelt on bare ground carries that loose soil into the waterway. Soil particles accumulating as sediment in a water body can reduce dissolved oxygen levels and suffocate organisms and reduce sunlight needed by aquatic life. Sediment often carries pollutants such as phosphorus, a nutrient in fertilizer. These nutrients cause excessive growth of algae and aquatic plants, deplete the oxygen level of water and degrade water quality. 

The added soil can increase the turbidity (how clear or how cloudy the water is). Turbid water interferes with sunlight reaching aquatic plants for photosynthesis and fish respiration. The best place for soil to be is NOT in the water. 

Mussels benefit the water

Freshwater mussels are important to river structure, stream ecology, and biodiversity. Mussel beds provide a firm, natural structure where the river bottom would otherwise be a shifting mixture of sand, silt, and clay. With only one muscular foot, their mobility is somewhat confined. It is not easy for mussels to escape disturbances, like droughts, floods, dredging, or contaminants. They become a stable micro-habitat and home to many different species, all of which contribute to a river ecosystem.

Mussels quietly sit in the water and never utter a sound. They were an important food source for Native Americans, especially in the winter months, and still are for animals like fish, turtles, mink, otters, and raccoons. Mussels filter algae and other microscopic organisms from the water providing much needed cleaning services. What they don’t digest is spit back out as mucous plugs – a tasty meal for nearby fish. They also make a positive impact on the ecosystem by filtering large volumes of water and reducing suspended particles and contaminate loads.

An Iowa example

DSM river watershedThe Des Moines River watershed and its placement within the Mississippi River watershed allows opportunity for all of us to become more aware of our global and local environment and how our watershed connection affects all things. For example, migratory birds rely on a healthy land base and clean water in both nesting and wintering habitat. Iowa ranks 50th as the most-altered U.S. state. Habitat loss, habitat fragmentation, habitat quality and the concerns of our water threaten the quality of our life, as well as the quality of our wildlife. 

Explore your local watershed with Aquatic WILD “Watershed!” activity for middle school / high school students!

Extend the activity for your students by having them research local water issues near them! Search for water quality issues, drinking water issues, algal blooms, fish kills. Ask them to determine what happened within the watershed to cause problems. What solutions did they consider?

Other MS / HS Aquatic WILD Activities that Correlate

  • Where Does Water Run
  • What’s in the Water?
  • How Wet is our Planet?

For elementary students, try this: Take the class outside your school and help your children look for signs of where the water flows when it rains. Ask them to predict where the water goes. Take pictures of any signs of erosion in and around your yard. During the next rain shower, go outside again to verify or disprove the class prediction about where the water flows. Brainstorm about ways to minimize erosion on your property. Explore with your class where the water goes downstream and if there is a relationship between the water drainage on the property and where water drains in your neighborhood or community. Discuss the term ‘watershed’ (the area that drains into a particular river or lake).

Marion County Park watershed is outlined in red. The watershed is approximately 320 acres.











Links for more learning:

Cross-reference to these Aquatic WILD units: