Posting Snow Observations
Snowfall is a critical input to our water resources. Cold, winter storms can bring significant snowfall amounts to many higher elevation areas across Arizona. Snow will typically melt slowly into the spring, infiltrating deep into soils for vegetation to use into the hot spring months and also running off to provide baseflows for perennial streams. Your snowfall observations will help characterize complex patterns of snow depth and water content important for monitoring Arizona's water resources. Making snow observations is more complicated than simple rainfall measurements. This guide will help you decide what type of snow observations you may want to make and additional equipment you may need. (If you are really interested in the science behind snow and collecting snow observations, check out the The Snow Booklet by Dr. Nolan Doesken the Colorado State Climatologist. You can order a copy here.)
There are two basic types of snow observations: snow depth and snow water equivalent. Snow depth is as simple as it sounds, but can vary depending on the period for which you are reporting (e.g. new accumulation in 24 hours vs. depth of snow on ground at any time). Snow water equivalent is the liquid water content of melted snow that has accumulated in your gauge (Tru-Chek, wedge gauges will only work for very small snowfall amounts, < 2 inches. See other gauge options below). This requires you to bring new snow that has accumulated in your gauge inside to melt and then report the depth of water in the gauge.
There are several ways you can make and report snow observations for Rainlog.org. The simplest being a measure of snow depth in your backyard to collecting daily snow water equivalent measurements. Check out the following methods:
Method 1, Snow water equivalent
Measuring the
liquid water content of snow is also done as a 24-hour
observation at the standard 7 a.m. reporting time.
This measurement requires that you bring your gauge
with new accumulations of snow inside to melt.
Report the melted snowfall amount as the total
precipitation and mark the observation as 'snow' in
the data quality section. Replace your gauge as soon as
possible. [Equipment Note: The wedge shaped, Tru-Chek gauge
is not ideal for measuring large snowfall amounts (>2 inches).
If you live in an especially snowy area and are interested in
measuring snow water equivalent, consider purchasing a rain
gauge with a larger opening. A simple, cylinder gauge with a
large 4" opening can be found at
Forestry Suppliers Inc.
or
CSP Outdoors
.
This gauge has a funnel that can be removed for
collecting snowfall. Snow in the outer cylinder can
be melted and measured directly with the inner
graduated cylinder].
Method 2, Daily snow depth reading
Use a yardstick to
measure snow depth at a representative location on your
property. A representative location should be free of
overhanging trees and away from buildings. The measurement
point should also be free of drifting snow and represent
the average level of snow accumulation for the area. Take
several measurements and report the average depth, if
the snow accumulation of snow is irregular (e.g. drifting
with bare spots). Try to make your measurements in the
same location or locations each time. This measurement
will track additional snow amounts storms as well as
melting during warm periods.
Method 3, New accumulation of snow in 24-hrs
This measurement uses a similar approach to Method 2,
but requires an additional piece of equipment, a
snow board. A snow board is a simple, wood board that
can be used as a floating measuring surface for daily
observations. You can make a snow board by purchasing an
inexpensive piece of ply wood at a lumber yard or hardware
store. The board only needs to be a 2x2 foot surface area.
You can have your board cut to this dimension or sometimes
purchase pre-cut board sizes with this dimension. Using your
board for daily snowfall measurements is simple. If you are
starting with bare ground, place your snow board on the ground
and mark its location with a wooden stake or flag that is tall
enough to stick up above the snow. After a snow event, make your
7 a.m. observation by measuring the snow depth on the board.
Report this depth as the 24-hour snowfall accumulation. Dig
out your snow board and place it on top of the newly fallen
snow nearby. Replace the stake or flag to mark the new location
of the board. The next morning, measure the depth of snow that
has accumulated on top of the board. Clean off the board and
repeat these steps each day to report new 24 hour
accumulations of snow.
At a minimum, please consider reporting snow observations using Methods 1 and 2. This information is very helpful in characterizing snow depth amounts after storm events and into the spring when water resource management decisions are made.
On the other hand, observations made with methods 1 and 3 provide useful information on the ratio of snow depth to water in a snowpack.
Many thanks for your interest and participation in Rainlog.org and may your winter be snowy!
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