A line separating the surface water runoff on opposite slopes. The watershed is taken into account when determining the catchment area necessary for the design of a fish farm.

A watershed is a conditional topographic line on the earth's surface that divides the catchment areas (basins) of two or more rivers, lakes, seas or oceans, and directs the runoff of precipitation along two opposite slopes. The area around the watershed line is called the catchment area. In different directions from the watershed there are slopes and slopes in the relief of the earth's surface. In mountainous areas, watersheds usually run along the ridges, and in plains, along the hills or even in the lowlands. On the plains, the watershed is usually indistinct in relief and becomes a flat watershed (or watershed area) in which the direction of flow may be variable. Sometimes a watershed (or elevation) is also called a divide. The main dividing line of a continent, separating the basins of different oceans or outlining large drainage-free areas, is called the continental divide. The line dividing the basins of the Pacific (rivers flowing into the Pacific and Indian Oceans) and Atlantic (rivers flowing into the Atlantic and Arctic Oceans) slopes is called the Earth's major watershed. There are surface watersheds and underground watersheds. The groundwater divide is a conditional line that separates groundwater flows moving in different directions.