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watercourse 
Natural flow of water that varies in size, depending on the ground slope and the number of tributaries.
spring
Point where underground water rises to the surface; it may be the source of a watercourse.
waterfall
Almost vertical flow of a watercourse, caused by a sudden change in the level of its bed.
lake
Body of water completely surrounded by land; it varies in size and depth.
effluent
Watercourse from a lake or glacier.
affluent
Watercourse that flows into a larger watercourse or a lake.
confluent
Point where two or more watercourses meet.
meander
Sinuosity created by a watercourse following a gentle slope.
delta
Section of the coastline where sediment builds up at the mouth of a river, divided into several arms.
sea
Vast body of saltwater at some distance inland; it is not as deep as an ocean.
floodplain
Level surface bordering a watercourse; it is subject to periodic flooding.
delta distributary
Channel that a river or stream follows near its mouth; several arms, separated by alluvial deposits, form a delta.
alluvial deposits
Sediment (mud, sand, gravel, pebbles) transported and then deposited by a watercourse.
oxbow
Meander left behind by the watercourse, forming a crescent-shaped lake.
river
Major watercourse fed by numerous smaller rivers; it empties into the sea.
plain
Vast, relatively flat expanse of land, lower than the surrounding landscape; its valleys are wide and shallow.
valley
Elongated depression shaped by a watercourse or glacier and bounded by the slopes of the surrounding land.
gorge
Deep narrow valley bounded by steep or very sheer slopes, carved out by a watercourse.
river
Natural watercourse of minor or intermediate size that empties into another watercourse.
glacier
Mass of ice resulting from the accumulation and compression of snow; it moves under its own weight.
brook
Small watercourse fed by a spring, the tributary of a river or a lake.
