Drainage basin

Diagram represents a typical small drainage basin (catchment) in Newfoundland (idealized).
The main stream drains WSW and is fed by small tributary streams, by downslope seepage of water in the soil (soil water) and bedrock (ground water), and by springs emerging in the stream bed (not shown). Tributaries drain from small ponds occupying bedrock hollows eroded by glacial ice, or depressions in glacial deposits. Wetland has developed in other depressions.

Other features are also the result of glacial action. The largest of the ponds (lake) has a long narrow shape and fairly regular outline typical of concentrated glacial erosion in a pre-glacial valley. Widespread erosion by the ice sheet eroded soil and weathered rock, exposing the bedrock in rock outcrops. Some of these are on the higher ground, near the divide; others may occur in the stream's course, creating falls or rapids. Glacial erosion on the divide created a depression now occupied by a lake which drains two ways - into the basin and into the adjacent catchment.


Legend:


Divide: the boundary between one drainage basin (catchment) and the adjacent basin.



Main stream: the stream into which all the surface water in the catchment eventually flows.



Tributary: a stream draining into a larger stream.



Fall or rapid: steepening of a steam's gradient over an outcrop of bedrock.



Downslope seepage: downslope movement of groundwater close to, or at the surface.



Ponds: small water bodies.



Lake in glacial rock-basin: a natural water body occupying a rock-basin eroded by glacial ice into bedrock.



Wetland: bog, fen, marsh; an area of poor drainage where poorly decomposed plant material accumulates to form peat.



Rock outcrop: bedrock at the surface, normally the result of glacial erosion.






Adapted and colourised by Duleepa Wijayawardhana from a diagram in The Natural Environment of Newfoundland, Past and Present. Edited by Alan G. Macpherson and Joyce Brown Macpherson (St. John's, Newfoundland: Memorial University of Newfoundland, © 1981 MUNCL) 184.


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