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Old 03-14-2008, 07:20 AM   #1
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Default Measuring snowpack water content

While playing with the 22" of snowpack in my front yard this morning, I noticed it has changed a lot in the past week or so. The top 20" is corn snow, the bottom 2" is still ice. That got me wondering about the water content in the corn snow. There seems to be a lot of air space in the corn layer, surely not the water content that we had a few weeks ago. The pack is still frozen together enough to hold my weight, but once broken up, it just crumbles into a much smaller pile of granuals. How is snowpack water content measured, and is there a web site that publishes current measurements? Has the threat of flooding been reduced?
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Old 03-14-2008, 11:41 AM   #2
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Default flood threat remains

Any hydrologist from the USGS, Army Corps of Engineers, or US Forest Service Avalanche forecasters would be able to say how snow density and water content is measured. I believe it involves taking a core sample of the snow, and melting it down. My guess is that the core would be the same diameter as a standard rain gauge measuring tube and modified so it can be twisted into the snow, down to ground level, and pulled back out without losing any content.

It is to early too dismiss a flood threat, especially since we need to consider what's coming down from the mountains. The lakes region isn't alone in having deep snow--it's been most of VT, NH and ME.

Currently at Black Cat we have 28 inches on the ground which is incredible for mid-March.

Since we had flooding problems last year (washed out roads, high lake level, etc) I'll provide a precipitation comparison of this year and last year.

Dec. 1 - March 31 precipitation was 8.90 inches. Some of the heaviest winter rains fell when there was little or no snow on the ground; therefore it ran off. Snowpack was under 10 inches most of the winter, non-existent on many days throughout Dec., Jan., and March, and peaked at 17 inches on Feb. 14. In March it grew above 10 inches briefly, but melted back to nothing in the final few days of the month. April replenished it, and then gave the infamous nor'easter on the 16th with 2.78 inches of rain over a 3-day period. This pushed the lake level above-full and caused road washouts.

THIS YEAR.................
We have received 13.00 inches of precipitation since Dec. 1. There has been snow on the ground since Dec. 3. Snow depth has not dropped below 10 inches since December 30. Snow depth reached its max on March 1, with 43 inches, and remained above 40" until the 4th. Rainstorms have shown little or no signs of runoff, and have always had deep snow catching them.

Again, in addition to these local observations we need to consider what's yet to come our way from the mountains.
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Old 03-15-2008, 09:11 AM   #3
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Figuring the snow water equivalent is simply an exercise in determining its density - what does a certain volume of snow weigh? Light fluffy snow takes up a lot of space but doesn't weigh much. The corn snow, though it takes up less space, is generallly considerably heavier for the same volume.

This corn snow is also a sign that the pack is getting more dense and more susceptible to running off with elevated temps. and rainfall. I've attached a couple of links to track information on the current snow pack in the state. Pray (with me) for warmish days and freezing nights - the ideal cycle for melting the pack in a controlled manner.

NWS Snow Page

NHDES Snow Page
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Old 03-15-2008, 09:28 AM   #4
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Default Great links

Thanks Keeper. Interesting to see that the depth is going down while the water content is going up. Keep them rivers running high!
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