Mammoth Lakes, Ca. — The majestic beauty of California’s Sierra Nevada never fails to impress. But the mountain range, which stretches hundreds of miles, is much more than a stunning vista. It’s a linchpin that helps make living in an arid state possible.

That’s because one of California’s most important water supplies is melted snow. Each spring and summer, the Sierra sends runoff down its slopes that recharges rivers and reservoirs, allowing crops to be irrigated and drinking glasses to be filled.

Knowing with precision how much snow has accumulated is crucial for farmers and water managers.

That’s where a mapping project at NASA’s Jet Propulsion Laboratory known as the Airborne Snow Observatory comes in. Using measurements gathered by specialized instruments on a plane, scientists have been able to gain an unprecedented understanding of the amount of water present in the Sierra’s snow.

This year, after California’s very wet winter, the totals have been remarkably big.

Using the NASA data, we compared this year’s snowpack with that of 2015, when the state was in the grip of drought (which, at least officially, is still ongoing). In the interactive maps below, the white areas had a meter, or 3.3 feet, or more of snow on the ground in March.

High in the mountains, this year’s snow blankets the ground in layers tens of feet deep in many places. In 2015, almost none of this area had snow that thick:

At the lower elevations around the Hetch Hetchy reservoir, which collects most of the melting snow runoff in this area and supplies water to millions, there was almost no snow to speak of in 2015. This year, the snowpack reached down to within a few hundred feet of the reservoir’s edge:

These maps show parts of the Tuolumne Basin, which in late February was blanketed by 1.2 million acre-feet of snow-water equivalent, or the amount of water that would result if the snow were instantly melted.

That’s about 10 times the amount as the same time in 2015, said…