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 is the area of land that drains into a body of water. The watershed also includes the creeks and other water bodies in the area. The quality of a water source depends greatly upon the watershed. The contaminants in a watershed will end up in the surface water body. This is the reason that watershed management is important.