Watershed: An area of land where surface water from rain or melting snow comes together to drain into another body of water.
Pollution: Substances that make land, water, or air dirty and not safe or suitable to use.
Point source pollution: Pollution that can be traced back to a single source or event, such as an oil spill.
Nonpoint source pollution: Pollution that cannot be traced back to a single point or event such as agricultural runoff
Topography: The physical features of an area, both natural and artificial.