Generation
Surface runoff can be generated either by rainfall or by the melting of snow, or glaciers.
Snow and glacier melt occur only in areas cold enough for these to form permanently. Typically snowmelt will peak in the spring and glacier melt in the summer, leading to pronounced flow maxima in rivers affected by them. The determining factor of the rate of melting of snow or glaciers is both air temperature and the duration of sunlight. In high mountain regions, streams frequently rise on sunny days and fall on cloudy ones for this reason.
In areas where there is no snow, runoff will come from rainfall. However, not all rainfall will produce runoff because storage from soils can absorb light showers. On the extremely ancient soils of Australia and Southern Africa, proteoid roots with their extremely dense networks of root hairs can absorb so much rainwater as to prevent runoff even when substantial amounts of rain fall. In these regions, even on less infertile cracking clay soils, high amounts of rainfall and potential evaporation are needed to generate any surface runoff, leading to specialised adaptations to extremely variable (usually ephemeral) streams.
Read more about this topic: Surface Runoff
Famous quotes containing the word generation:
“One of the things that is most striking about the young generation is that they never talk about their own futures, there are no futures for this generation, not any of them and so naturally they never think of them. It is very striking, they do not live in the present they just live, as well as they can, and they do not plan. It is extraordinary that whole populations have no projects for a future, none at all.”
—Gertrude Stein (1874–1946)
“There are in every generation those who shrink from the ultimate sacrifice, but there are in every generation those who make it with joy and laughter and these are the salt of the generations.”
—Patrick Henry Pearse (1879–1916)
“Could it be that those who were reared in the postwar years really were spoiled, as we used to hear? Did a child-centered generation, raised in depression and war, produce a self-centered generation that resents children and parenthood?”
—C. John Sommerville (20th century)