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:
“The world is never the same as it was.... And that’s as it should be. Every generation has the obligation to make the preceding generation irrelevant. It happens in little ways: no longer knowing the names of bands or even recognizing their sounds of music; no longer implicitly understanding life’s rules: wearing plaid Bermuda shorts to the grocery and not giving it another thought.”
—Jim Shahin (20th century)
“Never before has a generation of parents faced such awesome competition with the mass media for their children’s attention. While parents tout the virtues of premarital virginity, drug-free living, nonviolent resolution of social conflict, or character over physical appearance, their values are daily challenged by television soaps, rock music lyrics, tabloid headlines, and movie scenes extolling the importance of physical appearance and conformity.”
—Marianne E. Neifert (20th century)
“One generation plants the trees under which another takes its ease.”
—Chinese proverb.