The correct answer is option 4, that is, watershed.
Watershed refers to the area of land, which channels snowmelt and rainfall to the streams, creeks, and rivers, and finally to the points of outflow, like the bays, reservoirs, and the ocean.
The size of a watershed, also known as a catchment or a drainage basin is illustrated on many scales, considered to as its hydrological unit codes, on the basis of its geography, which is most relevant to its particular region. A watershed can be small, like as a single county or modest as an inland lake.
