A watershed is an area which acts as a funnel, collecting water and shunting it into the ocean or into inland lakes and seas. Watersheds are also sometimes called catchment areas or drainage basins, and they are a very important part of the world's ecology. Because they cross regional and national boundaries, watershed management can be extremely challenging, especially when neighboring nations have differing views about the best way to manage the natural environment.
A watershed can be relatively small, or quite large, and in all cases, watersheds are interconnected systems. They collect rain, snow melt, springwater, and groundwater in the form of tributaries, streams, and rivers which eventually join up in a single large river or body of water. Because everything in a watershed is interconnected, small acts in one area of a watershed can have a profound impact on the entire region that the watershed covers.
Often, a watershed is visible from overhead, in the form of an extensive valley. Hills and mountains tend to make natural boundaries between watersheds, because their sloping sides act as literal funnels to divide water systems. As water passes to the sea or an inland body through the watershed, it may meander through a range of environments, from heavily forested regions to deserts, and it also frequently comes into contact with areas inhabited by humans.
One major issue in watershed management is pollution; a polluter far upstream can cause damage to a huge section of the watershed, and to the body of water the watershed eventually drains into. Many nations have strict laws about pollution which take the entirety of a watershed into account, setting a maximum pollution level which covers the entire area. Watersheds are also affected by things like logging, fishing, and harvesting of other natural resources, so before people embark upon such projects, they must demonstrate the steps they will take to protect the watershed.
Many people are involved in the study of watersheds, from a wide variety of perspectives. Biologists like to look at the diversity of animal and plant life in such areas, sometimes identifying populations which are unique to a specific watershed. Foresters and others who are interested in resource utilization look at watershed ecology to understand the potential impact of their own work, while environmental activists often focus on specific watersheds to lobby for protection for various plant and animal species.