If you live in or visit the mountains, you can look at the snow-covered hills as nature’s water towers. As that snow melts, it could provide 75 percent or more of the area’s freshwater each year.

That’s true far downstream from the mountains too, and even in snowy flat areas. Around the world, snow provides 50 percent of our total annual freshwater supply.

And it does more than that: snow reflects sunlight, keeping areas cooler and making it possible for snow to accumulate.

Snow protects against erosion, slowly melting and deeply recharging the soil with water–preventing it from leaving the area as runoff.

Melting snow gradually fills streams, which slowly fill rivers, providing a steady supply of freshwater that can last through summer.

Warmer winters are disrupting this process though.

So-called ‘dry snow droughts’—as we’ve seen in California’s Sierra Nevada—sometimes with just 5 percent of normal snowfall, have led to water shortages for the region’s growing cities.

Warm snow droughts, where precipitation falls as rain—as we’ve seen in the Pacific Northwest—melt the snowpack early, causing heavy streamflow and even floods in winter and early spring, again depriving communities and agriculture of water later in the year.

So, whether you’re a ski bum or someone who works in the billion-dollar winter recreation industry, a fisherman or a farmer, or just a city dweller who drinks water, we should all hope for cold, snowy winters.