Snow Hydrology: History of Snow Surveys
Instructor: Randy Julander
Telephone: 524-5213
WHY?? Daddy, but WHY???
As with all data collection systems, Snow Surveying was initiated to
SOLVE A PROBLEM!
This is an important concept: the reason people collect data is to solve a
specific problem! After a great database has been established - people
come and use the data for other purposes and may have a much lesser
degree of success!
But WHY??
Take the Snow Survey data base as an example. It was begun as a
method of forecasting water supply. Sites were located specifically to be
relational to streamflow. Now this does not preclude them from being
useful in other areas such as: flood forecasting, mushroom hunting or
whatever. However, flooding was not the original intent and many of
these courses are at the high and mid elevation levels - with very few at
the lower elevations which are critical to flood potential!
Is the Snow Survey snow course system used for flood forecasting?
Absolutely! Does it have systematic holes in it for that purpose?
Absolutely! It doesn't tell the whole picture with regard to flood
potential BUT: it's basically the only game in town with regard to
flooding! There is a great need for more sites at specific locations and
elevations in order to RESPOND TO THE FLOOD PROBLEM! The
water supply problem is in pretty good shape for the major basins.
*** If you use data - find out what the original purpose of the data
collection network was! Then make a determination if the data are the
right type, collected at the right places and at the right frequency for
your application.*** You will save yourself great expense, time and
frustration if you approach your data cautiously - Far too many simply
use whatever data are available with reckless abandon.***
The first recorded snow surveys were in the eastern United States by an
engineer!
In the early 1900's, Dr. James Church
was fascinated by a problem of
water rights - How high would Lake Tahoe rise in any given year? How
much water would be available for use downstream. Observing the
cyclical rise and fall of the lake's elevation synchronously with
snowmelt, he correctly deduced that knowledge of the snowpack would
lead him to the volume and timing of runoff into the lake!
The problem then became: how and where to measure snow. He
quickly ascertained that just knowing how deep the snow was at a given
point would not be sufficient data. The snow might be 10 feet deep at a
given point in time and space and several days later, with no additional
snowfall, it might be only 9 feet deep. He realized that snow depth was
not a good indicator of how much water would be released from the
snowpack. The constantly changing density of snow was the problem
and to solve that, he realized he needed to know the volume of water in
any give pack.
Dr. Church experimented and finally came up with a solution - take a
sample of the snowpack and melt it to determine exactly how much
water was contained therein.
He also quickly realized that obtaining such a sample would be difficult.
Using a shovel to isolate a column of snow was far too hard - consistent
size and shape could not be maintained between samples.
He looked at the stovepipe on his cabin and as they say "viola - history
was made". He took the pipe sections and shoved them into the
snowpack to the ground and took a sample core. This core was taken
back to the cabin and melted to determine how much water was
contained within the sample. This then was converted back to depth
(inches) of water that would have been in the pipe.
Having now ascertained how to measure snow water equivalent, the
problem of where still remained. Dr. Church realized that one single
point would hardly characterize the entire Lake Tahoe basin snowpack
over it's geographic and elevational domain. Having observed
snowpacks increase in depth with elevation, he decided that an
elevational profile would be necessary to characterize the snowpack.
What he did was to lay out a course of point to measure along a specific
transect such that every time he would take a sample in the same place.
The course was fairly long and covered elevation changes. He continued
to measure the snowpack in this way at several different locations and
within a couple of years, was producing a forecast of peak Lake Tahoe
elevation.
Dr Church soon grew very tired of dissassembling his stove every time
he wanted to take a snow sample and began taking 2 inch steel pipe with
him to do the sampling. It was at this point that graduate students from
his university classes began doing snow survey's (ha ha ha).