Snow Water Equivalent
Updated: Dec 22, 2020
Does all snow hold the same amount of water?
Properties & Changes in Properties of Matter
Water on Earth
Tools & Materials
3-5 same size containers (Talenti jars, jam jars, plastic cups, etc…)
1 cup measuring cup
Labels (tape, dry erase marker, etc..)
To Do & Notice
1. Make a claim. Do you think all snow holds the same amount of water? Why or why not?
2. Test your claim.
Collect snow samples.
Go outside into the snow with the measuring cup, spoon and containers.
Scoop one cup of snow (do not pack or smoosh into the cup) and level off.
Transfer snow into one of the containers with the spoon, label where you collected snow and set aside.
Repeat this same process in different parts of your yard and continue until all of your containers are filled.
Ideas for snow collection:
On the side of your driveway
Where snow has been thrown from a shovel (perhaps off a deck or walkway)
Under a tree
On the deck
On the ground
Caution: be careful and mindful of icicles that may fall and potential for snow shedding off the roof.
3. Once you have all of your snow samples, bring them inside to melt. Place by the fireplace, heater or melt in the microwave.
Caution: If using a microwave, be sure your containers are microwave safe. Also, melt in short time increments of 10-20 seconds. Be careful to remove snow samples from the microwave as soon as they have changed from solid to liquid. Don’t let the samples get hot.
4. Analyze the evidence.
Once all of your snow samples have melted, observe. Is the volume of water the same in every container? What does this mean? What does this tell us about water content in the snow?
5. Draw a conclusion.
Does all snow hold the same amount of water? What influences the water content in the snow?
6. Share your findings.
Take a photo of your containers with melted snow or create a short video explaining your results. Share your results on social media and tag us @sweptahoe on Instagram and/or to @swep4 on Facebook. Be sure to hashtag and follow #SWEPsnippets. If you cannot post directly yourself, send SWEP your faceplant photos (Jenna@4swep.org).
What’s Going On?
What is Snow Water Equivalent?
Snow Water Equivalent (SWE) is a common snowpack measurement. It is the amount of water contained within the snowpack. It can be thought of as the depth of water that would theoretically result if you melted the entire snowpack instantaneously. Or in simpler terms: Snow water equivalent is the depth of water that would cover the ground if the snow cover was in a liquid state.
Why is SWE important?
Our snowpack acts as a reservoir, holding our water until the spring. Knowing how much water is held in the snowpack can help prepare us for spring runoff conditions, farming and irrigation, lake and river levels, wildlife management, recreation options and overall water supply forecasting.
Why wouldn’t scientists just use snow depth to get this information?
Snow Depth can vary greatly from hour to hour, due to settlement and compaction, but the amount of water contained within the snow remains consistent.
Where do Snow Scientists measure SWE?
SnoTel sites are observational sites sprinkled throughout the western United States that measure snowpack depth and SWE. These sites transmit data hourly for use by hydrologists, water managers, recreationists, and the public. Visit this site to see an interactive map of all the SnoTel sites. Can you find the SnoTel site closest to you? Have you ever come across a SnoTel site when adventuring through the woods?
How do these sites measure SWE?
In the words of the USDA, “All SNOTEL sites have snow pillows, a large bladder filled with antifreeze and water, to measure the snow water equivalent of the snowpack. Snow pillows have plumbing which runs into the SNOTEL shelter allowing for displacement of the fluid as snow accumulates in the winter. A specially calibrated sensor inside the shelter converts the pressure into inches of water. As such, snow pillows are actually measuring the weight of the water in the snowpack through the winter. A typical SNOTEL site also has a Snow Depth sensor which allows users to also know the depth of snow that has accumulated on the pillow.”
Videos that helps explain SWE:
Did you know mountains can create snow? Learn how in this video.
Why is freshwater important? Watch this video.
Thanks to our great partners at Winter Wildland Alliance's SnowSchool for the inspiration!!! And thank you to Tahoe Cross Country Ski Education Association for partnering with us for this lesson!