The land that carries the water you use to a water body is called a watershed. A watershed is also known as a drainage basin because it is land that allows water to drain to marshes, streams, rivers, lakes, or to groundwater.
The land that carries the water you use to a water body is called a watershed. A watershed is also known as a drainage basin because it is land that allows water to drain to marshes, streams, rivers, lakes, or to groundwater. A watershed not only carries water. It can also carry pollutants. We have to pay attention to what is going on in the watershed, and identify potential sources for pollutants that might be contributing to that watershed. Knowing the potential sources of pollutants, the different land uses and practices playing out within a watershed, gives everyone a "heads up" on what pollutants to watch for. Got a lot of agricultural land in your watershed? Expect nutrients from fertilizers. Industrial development? Expect chemicals. Residential areas? Expect nutrients, sediment, and household chemicals.
Watersheds vary in size. As the size of the watershed increases, so do the number of potential pollutant sources, and the number of competing solutions. For example, the Mississippi River watershed drains 40 percent of the entire United States.
That massive watershed can be broken down into several large watersheds, which can be broken down into smaller watersheds, scaling all the way down to areas that may be just a few square miles in size.
By narrowing the scope of a problem, it's easier to zero in on the threats to an individual water body, and to trace the sources of those threats.
Small watersheds, like a creek or stream running through your town, are just as important as bigger watersheds. In fact they are more important because acting locally helps solve the problems in your watershed and the larger watersheds it resides within.
The watershed approach allowed experts to identify the pollutant: nitrates, identify the source: farm runoff, and then work with the watershed's hydrology to come up with a solution.