Death due to disease is called death by natural causes. There are four main types of disease: pathogenic disease, deficiency disease, hereditary disease, and physiological disease. Diseases can also be classified as communicable and non-communicable disease.
A watershed is the area of land where all of the water that falls in it and drains off of it goes to a common outlet.
A watershed includes not only the land within its boundaries but also the surface water of lakes, streams and wetlands as well as the groundwater moving beneath the surface. Watersheds vary from the largest river basins to just a few acres in size. Watersheds are natural systems that link the land and water resources and the living organisms, including people, within its boundaries. How we live on the land affects the quality and quantity of water resources within the watershed.