The topographic land area that contributes flow to a river/ lake/wetland as defined by a particular point of reference. Sometime referred to as a catchment area. Large drainage basins, like the area that drains into the Mississippi River contain thousands of smaller drainage basins. Also called a “watershed.” The area contributing water to a particular reference point in a aquifer system is known as a phreatic catchment. Because of geologic structure, topographic and phreatic catchment areas may not exactly coincide, especially when small areas are considered.