A watershed is an area of land which all the rivers and streams drain into a larger body of water, like a larger river, lake, or ocean. It is important to make sure we take care of our land, so our watersheds are not polluted. Whatever is spilled on the land may eventually end up in the water. Salmon need a healthy watershed in order to thrive. Some of the things necessary for a healthy stream a salmon can live in are the correct temperature, cover, food, oxygen, substrate, access, flow, and clarity. It is hard to have some of these if the water is polluted.