A drainage basin is an area of land where all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, the drainage divide, made up of a succession of elevated features, such as ridges and hills. A basin may consist of smaller basins that merge at river confluences, forming a hierarchical pattern.
Other terms for a drainage basin are catchment area, catchment basin, drainage area, river basin, water basin, and impluvium. In North America, they are commonly called a watershed, though in other English-speaking places, "watershed" is used only in its original sense, that of a drainage divide.
In a closed drainage basin, or endorheic basin, the water converges to a single point inside the basin, known as a sink, which may be a permanent lake, a dry lake, or a point where surface water is lost underground.
Drainage basins are similar but not identical to hydrologic units, which are drainage areas delineated so as to nest into a multi-level hierarchical drainage system. Hydrologic units are defined to allow multiple inlets, outlets, or sinks. In a strict sense, all drainage basins are hydrologic units but not all hydrologic units are drainage basins.
Efficient management is strongly correlated to the proper protection perimeter definition around springs and proactive regulation of land uses over the spring's catchment area ("impluvium").
In order to preserve the long-term stability and purity of natural mineral water, bottlers have put in place "protection policies" for the impluviums (or catchment areas) of their sources. The catchment area is the territory on which the part of precipitated rainwater (and/or snowmelt) that infiltrates the subsoil feeds the mineral aquifer and thus contributes to the renewal of the resource. In other words, a precipitated drop on the impluvium territory may join the mineral aquifer; ...
The non-karstic impluvium comprises all elements of the ground surface and soils that are poorly permeable, on a part of which water is running while also infiltrating on another minor part. This superficial impluvium, if it exists, constitutes the first level of organisation of the drainage system of the karstic basin.