Snow Water Equivalence:
Layer measurement method: Water is stored in the form of snow. The amount of H2O in the snow pack may change over time. Snow may be released to the atmosphere through sublimation. Snow may also melt and run off or be absorbed by the ground. The amount of water stored as snow is an important measure. Measuring the density of the snow pack either layer by layer or across the entire snow pack, provides an equivalent to the amount of water stored in the snow pack. For example: The weight of 100 ml of snow is compared to the weight of 100 ml of water which is equal to 100 g. This provides a water equivalent. Measurements using the 100 ml plastic container are made by pushing the container into the layer. After the container has been pressed into the layer, use a flat surface to cover the open surface while it is still in the snow layer. Remove the container and trim the ends so that the core is flush. Weigh the 100 ml snow core and container with the spring scale. Subtract the container weight from this to find the weight of the snow core in grams. Calculate snow density by dividing the weight of the snow core (g) by 100 ml (the core volume).
Making a 100 ml plastic container for snow layer sampling
Make a 100 ml plastic container. Cutting the top off a recycled pill bottles works well. Wash, pour 100 ml of water into the pill bottle, and mark the level, then cut the bottle to this size. Drill a 5 mm hole in the bottom. This allows the air to escape when taking the snow core sample. Another hole in the side near the top is used for weighing the container on the spring scale.
Remember: 1 cc H2O = 1 ml of H2O = 1gram of H2O
Example: 100 ml of H20 weighs 100 g
Calculating snow density and water equivalent for each snow layer:
Weight of container (A): _________g
Weight of snow core & container (B): _________g
Weight of snow core (W) = B - A: _________g
Volume of snow (V) = volume of container: 100 ml
Density of snow = weight or W ______g
volume V ml
Expressed as a decimal, this represents the water equivalent_______
Layer measurement method: Water is stored in the form of snow. The amount of H2O in the snow pack may change over time. Snow may be released to the atmosphere through sublimation. Snow may also melt and run off or be absorbed by the ground. The amount of water stored as snow is an important measure. Measuring the density of the snow pack either layer by layer or across the entire snow pack, provides an equivalent to the amount of water stored in the snow pack. For example: The weight of 100 ml of snow is compared to the weight of 100 ml of water which is equal to 100 g. This provides a water equivalent. Measurements using the 100 ml plastic container are made by pushing the container into the layer. After the container has been pressed into the layer, use a flat surface to cover the open surface while it is still in the snow layer. Remove the container and trim the ends so that the core is flush. Weigh the 100 ml snow core and container with the spring scale. Subtract the container weight from this to find the weight of the snow core in grams. Calculate snow density by dividing the weight of the snow core (g) by 100 ml (the core volume).
Making a 100 ml plastic container for snow layer sampling
Make a 100 ml plastic container. Cutting the top off a recycled pill bottles works well. Wash, pour 100 ml of water into the pill bottle, and mark the level, then cut the bottle to this size. Drill a 5 mm hole in the bottom. This allows the air to escape when taking the snow core sample. Another hole in the side near the top is used for weighing the container on the spring scale.
Remember: 1 cc H2O = 1 ml of H2O = 1gram of H2O
Example: 100 ml of H20 weighs 100 g
Calculating snow density and water equivalent for each snow layer:
Weight of container (A): _________g
Weight of snow core & container (B): _________g
Weight of snow core (W) = B - A: _________g
Volume of snow (V) = volume of container: 100 ml
Density of snow = weight or W ______g
volume V ml
Expressed as a decimal, this represents the water equivalent_______
Single measurement method: Another method is to use a stove pipe section to capture a cross section of the snow pack. Insert the stove pipe into the snow pack. Push a clip board under the stove pipe while it is in the snow pack. Keeping the snow captured, dump the contents into a plastic bag (i.e. garbage bag). Record the depth of the snow pack at the sample point. Calculate the volume of snow in the stove pipe. Weigh the garbage bag with snow and then subtract the weight of the bag to get the weight of the snow column. Calculate snow density by dividing the snow weight by the volume of the stovepipe sample (surface area X depth of snow). This provides a water equivalent because water density is 1 gm per ml.
Calculating snow density for the entire snow pack with a single cross section sample 1. First calculate the volume of the snow sample. Measure the diameter of the pipe (D): _______cm Calculate the radius of the pipe (r): ______cm Area of pipe (A) = π r2 = 3.14 X (radius of pipe)2 = ______cm2 Volume of sample (V) = area (A) X depth of snow: _______cm3 2. Next determine the weight and density of the snow as explained in the box above with the snow layer sampling and continue calculations to determine the water equivalent. |