- total annual snowfall is only one factor
determining the contribution of snow to a water budget
- snow is first stored for days to months
before participating in the hydrological cycle and therefore, the
important considerations are
- the spatial distribution of snow fall,
especially in terms of altitude
- in the Himalayan Karakoram
(Pakistan), the altitudinal zone of maximum snowfall is 13,000 to
17,000 feet asl; catastrophic flooding and most of the annual
erosion occurs during 20% of the year when thawing temperatures
occur at these elevations
- in contrast, snowmelt in regions of
low relief (plains) is simultaneous over large areas and thus of
relatively short duration
- depth of the snowpack during the melt
season
- this depends on snowfall over the
winter and on the duration of the snowcover (number of days that
the ground is snow covered)
- the periodic ablation of the
snowpack over the winter seriously limits the snow cover during
the period of conssitently higher temperatures, i.e., when
ice is leaving the ground, rivers and lakes and thus snowmelt
runoff can be stored
- in the continental interior, the
onset and waning of the winter snow cover occurs with advance and
retreat of colder air, and thus a regional snowline, with latitude
and elevation (annual analogue of the advance and retreat of a
continental glacier)
- the rate of melt
- the rate and degree of temperature
increase above 0o, determines the rate of snowmelt
relative to the capacity of the watershed to accommodate the snow
meltwater
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