SOIL AND WATER CONSERVATION DISTRICT
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What Is A Watershed?
A watershed is the land area that drains to a waterbody. That landscape affects the waterbody's flow, water levels, water quality, and natural diversity. In both the real and figurative sense, a lake or river, a wetland, a floodplain, a farm, a city and even human beings, are a reflection of their watershed and its health. Everyone has a stake in how water is used within watersheds.
Watersheds occur at multiple scales ranging from the largest river basins, such as the Mississippi River, to the watersheds of small streams or lakes that may measure only a few acres in size. A small watershed that nests inside of a larger watershed is sometimes referred to as a "sub-watershed." Because watershed are defined by natural hydrology, they represent the most logical basis for managing water resources. The resource becomes the focal point to consider overall conditions in an area and the factors affecting those conditions.
The U.S. Geological survey has developed a national hierarchical framework for identifying watersheds of different geographical scales. Each scale, or level, is designated using the hydrologic unit code (HUC) system. At the national level, this system involves an eight-digit code that identifies several levels of classification. Iowa has 56 HUC-8 watersheds that range from 390 to 1,945 square miles in size. Within these HUC 8 watersheds are 420 smaller HUC 111 basins ranging from 62.5 to 390.6 square miles in size. Within the HUC 11's at the local level where most watershed projects are organized, there are 1,400 HUC 14-sized subwatersheds that range from 15.6 to 62.5 square miles.
So, what watershed are you in? A good start for identification is if you cross some of the larger streams in the district, you might see signs with the name of the stream. That name would be the watershed name. The district has contributed funds to a project to sign these streams. There are multiple partners involved.
But not all streams are signed or even named. Potentially, if you open a water hydrant at the top of a hill, you have now created a small (very small) watershed. You name it! Just remember, everyone lives in a watershed and everything you do to the landscape affects that watershed.