> Warm rain on isothermic snow banks is a partial explanation
> for the Christmas floods on the Eel in '64. This condition
> has the potential to put a hydrograph right over all previous
> scales;
(Are you all bored with all this hydrology? Should we stop
now?)
Well this rain on snow thing is overrated. It's all about
energy.
The energy required to turn one gram of ice (at 0 degrees C,
just ready to melt) to water is 80 calories. The energy given
up by a gram of water as it cools one degree C is 1 calorie.
Thus, lets just say that we had 20-degree C rain (room
temperature, very warm rain) falling on snow. As it cooled
to 0 degrees C, each gram of rain would give up 20 calories to
melt snow, enough to melt 1/4 gram. Thus, the rain would
supplement itself by 25%. Not a sufficient explanation for
extreme events. (It is a sufficient explanation of why its so
damned hard to defrost a freezer.)
(The heat released by a gram of water vapor as it condenses is
540 calories. A real bomb. That's the powerhouse that drives
storms.)
I think the real impact of snow is twofold. First, water
tends to run efficiently on its surface or channels within it
and thus get to streams _quickly_ (increasing peak flows) and
without too much infiltration. Second, the soil below
isothermal snow should be saturated and unable to take up much
additional water.
Disclaimer--I'm an engineer, not a hydrologyist.
Ben
-- -------------------------------------------------- -- Ben Harding blh@hydrosphere.com -- -- Hydrosphere Resource Consultants -- -- Hydrosphere Data Products -- -- 1002 Walnut, Suite 200 -- -- Boulder CO 80302 -- -- -- -- 303-443-7839 voice 303-442-0616 fax -- -- -- -- Publishing Natural Resources Data on CD ROM -- -- Consultants in Natural Resources Planning -- -------------------------------------------------- ==================================================================== To subscribe, send email to majordomo@songbird.com, with "subscribe gcboaters" as the only line in the message body. To unsubscribe send "unsubscribe gcboaters". For further information send "info gcboaters", or see http://www.songbird.com/gcboaters ====================================================================