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 (or drainage basin) is the geographic. area from which water in a particular stream, lake. or estuary originates (Figure 2). All lands in the. watershed drain toward the stream, lake or bay. and contribute pollutants to these waters.