What is A Watershed?
A watershed is all the land that drains to a particular body of water. Think of a watershed as similar to a bathtub. No matter where you dump water in a bathtub, it will eventually flow out of the bathtub drain. Similarly, no matter where rain falls in a watershed, it will eventually flow into the watershed's namesake river or lake. The hills around a watershed and the forces of gravity direct water to the largest river or lake in that area. The Zumbro Watershed Partnership works in the Zumbro River Watershed
in southeastern Minnesota.
Knowing your watershed matters because any pollution on the land can eventually lead to pollution in the watershed's rivers or lakes. In addition, changing land use practices can change how much water flows in to area streams, rivers, and lakes, and how quickly that water moves, possibly leading to increased erosion, sedimentation (dirty water), chemical pollution, and in some instances, floods.
Over the past 100 years, humans in the Zumbro River Watershed have been changing the landscape from one that absorbed and soaked up rainfall (5 percent runoff), to one that transports water quickly to nearby streams and rivers (65 percent runoff). Water-absorbing landscapes like tallgrass prairie, forests, and wetlands are increasingly rare with 90 percent loss of wetland acres and 95 percent lost of prairie acres in Minnesota. At the same time, water-draining landscapes like corn and soybean fields, cities, and suburbs are increasingly common. This may explain why river gauges at Zumbro Falls, Minnesota have registered a 41 percent increase in river flow volume in the Zumbro River between 1910 and 1983. Now almost 30 years later, with fewer livestock farms, more cornfields, and growing cities in the watershed, the Zumbro River could easily be doubling it's historical flow, leading to increased erosion, sedimentation, and downstream flooding.
The Water Moving from the uplands to the lowlands in a portion of a model watershed. Notice how above-ground waterways funnel water to the dominant river in the watershed. Source U.S. EPA