Do you live in a region of the world that is blessed (or maybe not so blessed) with snowfall during the winter months? If so, you probably have a strong opinion on whether this weather is welcomed or unwarranted. Even as an environmental scientist, it can be easy to forget that the water we splash around in all summer is the same stuff that buries us in cold darkness each winter. The amount of solid water that lays upon the frozen ground like blankets in the cold season directly impacts the water levels of the lakes, rivers, and streams we enjoy as the earth warms in spring. Lets take some time to look at how snowfall impacts our local and global water supply and what different types of winters may mean for the seasons to come.
Personally, I get to experience Wisconsin winters in the Upper Midwest region of the United States where our average snowfall is 40 to 50 inches per year. Our snow arrives between the months of November and April and it is a glorious, terrible experience. Why are all of the beautiful things on earth also slightly dangerous? It is that allure, my friends, that keeps us on our toes.
In my research for this post I realized how insanely difficult it is to actually calculate “average snowfall in inches” of a region. These types of estimations are more easily done for individual cities. Because the United States is so large and full of diverse ecosystems there are not numbers that exist to describe this average. Follow this link for an interesting list of average snowfall per state or to reference the area where you live.
How do we measure snowfall in a given area?
This meteorologist and author’s description talks about the history of measuring snow fall and reliability (or lack there-of) of the data. Recorded data from the 1900’s cannot be fairly compared with our measurements of today because each city or organization or person collected the information differently. On top of that, each snow storm and physical components of wet versus dry snow and confounding factors like blowing winds make this a difficult and fascinating concept to study.
The final factor in understanding how snow becomes groundwater is- how much water actually results from an inch of snow? Referencing the same meteorologist, “a simple 10-to-1 snow-to-liquid ratio was often used to estimate the snowfall (i.e., 1” of melted precipitation = 10” of snow). As it turns out, the average ratio for the contiguous U.S. is roughly 12:1 or 13:1, and that ratio can vary greatly from place to place and storm to storm, even within a single storm.” In my area, this would translate to around four inches of water that will seep into the ground in spring. This was much less than I had thought and left me questioning how a warmer winter may affect ground water levels. Our aquifers depend on rain and snow to replenish the water that we take our to serve our homes and communities.
What happens to Snow as Groundwater
According to the Environmental Protection Agency (EPA) website, snowmelt can account for up to 75% of the water supply in areas like the Western United States that rely on melt water from the mountains. Some interesting facts…
- Since 1930, total snowfall has decreased overall with 57% of the observed weather stations reporting fewer inches of snow.
- The average decrease across all weather stations was approximately 0.2% less snow per year.
- With climate change, we are receiving more precipitation in the form of rain, not snow. Almost 80% of the weather stations reported more rain occurrences in proportion to snow events.
Climate change has created more variation and unpredictability in these weather events. Big rain and snow events are shifting geographically in response to changes in evaporation and seasonal storms. The image below is a visual representation of areas around large bodies of water like the Great Lakes are experiencing more snow than before where the western region is receiving less. This can be a difficult topic to talk about because as you can see, the argument goes both ways- there are areas where winter events seem stronger and areas where warming is more obviously taking place. It is very important to look at the big picture when it comes to climate and data trends to see change as it is happening over time and over a larger space than just your backyard.
Consequences of Depleting Ground Water Supply
Evaporation of snow on warm winter days, moisture of the soil below, changing weather patterns and more have a tremendous impact on how much water reaches our underground aquifers. Snow accumulation is a large component of the overall cycling of our water supply- especially in areas prone to drought or dependent on large amounts of mountain runoff. Depending on your area, it may seem like the amount of water actually provided by the winter snow will not significantly add up. Remember how we said to pay attention to the big picture? The snow and rain you receive where you live drains into a much, much larger watershed shared by many other communities.
Watersheds are areas of land defined by ridges that contain specific water features and drainage ways.
If your watershed is not receiving the amount it needs to supply what the local communities are using from it, there is no way to get more from another. The image above shows where these watersheds boundaries exist in the United States. Our water usage is only increasing as more homes are built and drought conditions threaten our crops or God forbid singe our perfectly green golf courses, but the water going into the land is dwindling.
While we have absolutely no say in the amount of snow or rain we experience each year, we as humans are able to be mindful of these changes and make choices that reflect a healthier future. The general trend has shown less water, fewer snowfalls, drier watersheds, and emptier aquifers. Small choices and awareness in the now will help mitigate consequences of the future.
