Catching snow is one of the most important ways to keep water on the
farm.
According to Environment Canada, only 25 percent of annual
precipitation comes in the form of snow, but it is the single most
important source for surface water used in livestock operations and
households.
Trevor Yurchak of Alberta Agriculture says the ability to “corral some
of that water can be the difference between having it next year and
hauling it.”
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Researchers at the Prairie Farm Rehabilitation Administration began a
project in Alberta in 1994 that is looking at two types of snow fences.
The eight-foot-high wooden Wyoming snow fence is built at a 15 degree
angle facing into the predominant winds. The angle discourages cattle
from rubbing against it. The other fence is the flexible plastic web
type, standing four feet high.
The vertical slat snow fence was not tested, but other studies indicate
it is somewhat less effective.
Snow fences don’t, as the name might imply, catch snow. They create a
wind pattern at ground level that interrupts airflow, causing a vacuum
and calm region on the downwind side of the fence. Snow builds up and
will eventually form a large natural barrier enveloping the fence.
To fill a dugout, place the fence close to the top of the windward
bank. This will deposit the snow inside the dugout, reducing runoff
losses and soil saturation.
While the study has found both types of fences to be effective, the
plastic fence is easier and cheaper to build and may be most effective
for low snowfall areas or to prevent thoroughfares from being blocked.
A fence’s effectiveness drops dramatically once the large snow bank
develops, with the amount of passing snow that is caught dropping to
zero from a high of 80 percent.
This makes fence height an important consideration, and means the
taller Wyoming fence may have greater potential for long-term,
higher-volume snow catching.
The plastic fences are 50 percent porous, which is recommended for snow
fences.
Wooden fences should be built by horizontally attaching two-by-six
boards six inches apart over a pressure-treated six-by-six square post
frame. To prevent plugging, the gap between the ground and the first
horizontal board should be 15 percent of the total height of the fence.
“You have to be careful how much space you give at the bottom though,”
said Ryan Davison of the PFRA.
“If you are in a very low snowfall area then you want to keep that gap
much smaller. Otherwise the snow may fail to catch.”
Davison and his team built a snow fence demonstration last winter near
Etzikom, Alta.
“Time prevented us from building the Wyoming fence. The four-foot
plastic fence was impressive though. It filled the dugout for the
colony where we built it. And it wasn’t the snowiest winter here last
year,” he said.
“Even in wet years, catching that snow won’t go to waste. It will
recharge local ground water and provide surface supplies that can be
carried over. I think we know from the past few years it can be hard to
say you’ve got too much.”
Farmers are encouraged not to wait too long to put up their fences.
“It is one of those things that farmers often leave until the last
minute or even a little after that,” Davison said.
“Pounding steel posts into frozen ground and unrolling orange plastic
fence into a gale force wind gives you the chills just thinking about
it.”
He said farmers should get the temporary fences up sooner and if
building a permanent one, they should start before the ground gets too
hard.
