Our directory of things of interest

Sierra Nevada snowpack shrinks

Deficit in the total volume of water contained within the Tuolumne River Basin snowpack from this time in 2014 to now. The deeper the red color, the greater the volume of water lost Deficit in the total volume of water contained within the Tuolumne River Basin snowpack from this time in 2014 to now. The deeper the red color, the greater the volume of water lost NASA/JPL Caltech
30 Apr
As California’s record drought continues, snowpack in the Sierra Nevada shrinks

The snowpack in the Tuolumne River Basin in the Sierra Nevada, California contains 40 per cent less water than it did at its highest level in 2014.

NASA data indicates that the water in the snowpack amounts to 74,000 acre-feet or 24billion gallons. At its high-point two years ago, the snowpack covered 179,000 acre-feet. The agency has been using airborne monitoring to check on the snowpack for the last three years.

Tuolumne feeds the irrigation districts and the Hetch Hetchy Regional Water System, which serves San Francisco and nearby settlements. Snowfall accounts for 70 per cent of California’s annual precipitation in normal years, with the ice melting in spring and early summer.

The new research will allow water authorities to provide almost real-time information about how much water will flow from the mountains during California’s ongoing drought.

earth20150401ab-fullSpatial distribution of the total volume of water in the snowpack across the Tuolumne River Basin on 25 March, 2015 (bottom) and 7 April, 2014 (top) as measured by NASA’s Airborne Snow Observatory. (Image: NASA/JPL-Caltech)

‘A mountain’s snowpack is like a giant TV screen, where each pixel in the image varies but blends together with the others to make up a picture,’ says Tom Painter from NASA’s Jet Propulsion Laboratory.

‘For the past century, we’ve estimated mountain snowpack by looking at just a few pixels of the screen – that is, a few sparse ground measurements in each watershed basin. During an intense drought like this one, most of the pixels on the screen are blank – that is, they’re snow-free,’ he adds.

Before the surveys began, the California Department of Water Resources used manual surveys to map snow courses using data from electronic sensors planted in the ground called snow pillows. These are accurate, but sparsely distributed.

Related items

Geographical Week

Get the best of Geographical delivered straight to your inbox every Friday.

Subscribe Today

Adventure Canada


Aberystwyth University University of Greenwich The University of Winchester




Travel the Unknown


Like longer reads? Try our in-depth dossiers that provide a comprehensive view of each topic

  • National Clean Air Day
    For National Clean Air Day, Geographical brings together stories about air pollution and the kind of solutions needed to tackle it ...
    The Air That We Breathe
    Cities the world over are struggling to improve air quality as scandals surrounding diesel car emissions come to light and the huge health costs of po...
    Diabetes: The World at Risk
    Diabetes is often thought of as a ‘western’ problem, one linked to the developed world’s overindulgence in fatty foods and chronic lack of physi...
    The Nuclear Power Struggle
    The UK appears to be embracing nuclear, a huge U-turn on government policy from just two years ago. Yet this seems to be going against the grain globa...
    Hung out to dry
    Wetlands are vital storehouses of biodiversity and important bulwarks against the effects of climate change, while also providing livelihoods for mill...


NEVER MISS A STORY - Follow Geographical on Social

Want to stay up to date with breaking Geographical stories? Join the thousands following us on Twitter, Facebook and Instagram and stay informed about the world.

More articles in PLACES...


IPCC Cities and Climate Change Conference: Alberta host dresses non-renewable…


Increased carbon dioxide is affecting freshwater ecosystems


The latest laser scanning technology reveals new insights into the…


Deforestation is having an unexpected effect in the Amazon: fewer…


The iconic Douglas fir tree, familiar to fans of the…


Rocky Mountain forests are not regenerating after wildfires


Cape Town is edging closer to ‘Day Zero’, the long-feared…


Ongoing restoration projects are breathing new life into Florida’s Everglades


Despite protests, an experimental pedestrianisation system is proving to be…


National Archives map historian, Rose Mitchell, highlights some of the…


An expedition into the Jordanian desert is helping teachers and…


Trivia fans take note, Mount Hope in the British Antarctic…


An enormous hydropower development in Ethiopia is expected to put…


From nuclear warnings to whether your favourite band will ‘make…


New maps of global reptile distribution reveal significant gaps in…


Indigenous conservation schemes in Peru can be more effective than…


How are the EU member nations faring in the fight…


Violence against women violates human rights, and the lack of…


Deadly heat waves could become more frequent in cities thanks…


These 13 poignant infographics are in the running for the…