What is a watershed?
Everyone lives in a watershed
A watershed is an area of land that drains into a body of water, such as a lake, river, or stream. This includes water flowing along the earth’s surface or beneath the surface as groundwater.
Watersheds can be as small as the water flowing to your neighborhood pond, and as large as 31 states!
Iowa’s Watersheds
Iowa’s two great border rivers – the Mississippi and the Missouri – capture all the flowing water in Iowa before themselves merging near St. Louis, Missouri. Small watersheds in Iowa (HUC-8), make up bigger watersheds (HUC-6), eventually forming the Mississippi River watershed. In Iowa water quality programs, we usually refer to HUC-8.
Click to view each watershed map:
Mississippi River Basin
HUC-8 watersheds
HUC-6 watersheds
The Mississippi Watershed
4th Largest in the World
The Mississippi River drains an area of about 3.2 million square kilometers (1.2 million square miles) including all or parts of 31 states and two Canadian provinces, about 40% of the continental United States. The Amazon for comparison drains about 7.1 million square kilometers (2.7 million square miles). Learn more.
Important Migratory Flyaway
The Mississippi River valley–along with its rich diversity of habitats–provides birds with those important resources. Forty percent of the nation’s migratory waterfowl use the river corridor during their spring and fall migration. Sixty percent of all North American birds (326 species) use the Mississippi River Basin as their migratory flyway. Learn more.
Home to 260 Species of Fish
At least 260 species of fish, 25% of all fish species in North America, live in the Mississippi River. At least 145 species of amphibians and reptiles inhabit the Upper Mississippi River environs. Learn more.
Watershed Challenges and Solutions
Challenges
Water is a powerful force
Flowing surface water–often called runoff–picks up many things in its path such as:
- Litter in your grocery parking lot
- Spilled oil in your driveway
- Construction dirt in your new neighborhood
Water in Iowa often encounters nutrient rich soil, carrying the nutrients and silt downstream. Nutrients that make it to the Mississippi River from Iowa and other states impact the Gulf of Mexico. This has created the well-known Gulf Dead Zone (a.k.a. Hypoxia Zone), an area where excess nutrients have diminished water oxygen levels, meaning normal levels of marine life cannot be sustained.
Solutions
Watershed Approach
Focusing on critical watersheds – those with the highest needs or with the greatest potential for downstream impact – is an effective way of improving water quality.
Pillars of this approach include:
- Strong partnerships for decision-making and implementation
- A strategic geographic focus
- Science based practices like those outlined in the Iowa NRS (cover crops, wetlands, prairie, etc.)
Do you know which watershed you live in?
Find out here by typing in your address! Remember, the bigger the number, the smaller the watershed. In Iowa water quality programs, we usually refer to HUC-8.