ARCHIVED CONTENT: In December 2020, the CZO program was succeeded by the Critical Zone Collaborative Network (CZ Net) ×

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Researching Earth's outermost layer

The Southern Sierra Critical Zone Observatory (SSCZO) is an Earth-systems research program investigating the living layer of Earth where water, soil, rock, air, and biota interact to form landscapes and support ecosystems. Hydrologists, geomorphologists, soil scientists, and ecologists from University of California campuses, University of Wyoming, and other institutions collaborate to improve our understanding of water and nutrient cycling, weathering processes, and forest function in the Sierra Nevada.
>> Learn more about the critical zone >>

Interdisciplinary research and ongoing monitoring at our intensively studied sites allows us to research this thin skin of the Earth at spatial scales ranging from bacteria to batholith and water droplet to watershed, and temporal scales from minutes to millenia. Coordinated, linked activities enable us to explain and predict the properties and processes southern Sierra landscapes and ecosystems, including water cycle responses to drough, fire, tree mortality, changing climate, and other disturbances to the landscape.
>> Explore our research >>

Our Critical Zone Observatory's field areas are located in the headwaters of the Kings River on the western slope of the southern Sierra Nevada, on federal lands including Sierra National Forest, San Joaquin Experimental Range, and Sequioa National Park. Sites span a range of elevation from 400 m to over 2100 m above sea level. As elevation increases, vegetation, temperature, and dominant precipitation phase also change.
>> View our field areas >>


Critical for sustaining societies and ecosystems of today and tomorrow

Advancing our knowledge of the critical zone and Sierra Nevada headwaters and forests—California’s largest water tower—is vital to California and beyond. The critical zone is where water flows, soils form, food grows, and ecosystems thrive; and it is facing increasing pressure from changing population, climate, and land use. We engage with research communities, stakeholders, students, educators, and public audiences in order to increase understanding and awareness of the critical zone, and share findings from our Observatory about these sensitive mountain regions.
>> Learn about our outreach >>


A platform of research, infrastructure, models, and data for the critical zone science community

We and nine other Critical Zone Observatories (CZOs) in the U.S. Critical Zone Observatory Network funded by the National Science Foundation, as well as several other international CZOs, strive to rapidly advance Earth-systems knowledge through our open sites, datasets, and other resources for researchers.


Investigators, students, collaborators, and other research site users conduct research on a variety of topics spanning several disciplines, at multiple spatial and temporal scales:

  • hydrology
  • geochemistry
  • pedology
  • geomorphology
  • ecology
  • geophysics

>>Explore more research


Hundreds of instruments are installed and maintained at SSCZO, many continuously logging measurements through a wireless sensor network:

  • covariant eddy flux towers
  • meteorological stations
  • soil matric potential senors
  • sap flow meters
  • peizometers and wells
  • snow depth sensors

>>Explore more infrastructure


Data from instruments and other measurements are available for research analysis and modeling. Our data catalog:

  • covers a range of research disciplines
  • contains thousands of entries from several sites
  • provides opportunities for cross-czo comparison

>>Explore more data


SSCZO continues to develop and expand conceptual and numerical models of the critical zone covering:

  • drivers of critical zone development
  • ecohydrological processes
  • changes in properties and processes with space and time

>>Explore more models














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Problems with this form? Please email Michelle Gilmore.

Archive of older updates and announcements: 2014-01-24  ||  2014-01-31  ||  2014-02-03  ||  2014-02-08  ||  2014-02-27  ||  2014-03-24  ||  2014-04-07  ||  2014-05-20a  ||  2014-05-20b  ||  2014-06-17  ||  2014-07-01  ||  2014-07-08  ||  2014-07-18  ||  2014-08-26  ||  2014-09-02 ||  2014-11-06  ||  2014-12-04  ||  2015-01-21  ||  2015-01-22  ||  2015-02-13  ||  2015-02-17  ||  2015-03-18  ||  2015-04-15  ||

The following are links to a local document archive at the Southern Sierra CZO

Document archive: Public || Background || Internal || Other presentations || Forms

Annual Reports (pdf): 2008 || 2009 || 2010 || 2011 || 2012 || Final for 2007-2012 grant || 2013 || 2014 + Addendum || 2015 + Additional Reporting + Figures || 2016

Work plan: 2008 || 2010 || 2014 Management Plan (including Work plan)


© Southern Sierra Critical Zone Observatory

Warm sunlit morning at SJER this past winter. 


SSCZO - Instruments

Hundreds of instruments and sensors have been deployed in the primary SSCZO research site of the Providence Creek watershed as well as in Wolverton basin.  Additional SSCZO flux towers and instruments have also been installed at the San Joaquin Experimental Range, Soaproot Saddle, and Short Hair Creek.

Explore more photos of the intstuments and sensors used by SSCZO.

Southern Sierra CZO

Established 2007

"We investigate the critical zone across a mountainous elevation gradient, focusing on water balance, nutrient cycling, and weathering processes."

Science Questions:

  • How do regolith, or weathered bedrock, properties and soil formation processes vary over 10-­m to 100-­km scales?
  • How do physics, chemistry, and biology interact to influence critical­ zone function over instantaneous to decadal timescales?
  • How quickly do regolith properties change in response to longer-term climactic and shorter-term biologic processes?
  • How do regolith development and properties control, limit or regulate the effects of climate change and forest management, or of hydrologic, biogeochemical and ecologic disturbances?
  • What measurements of the critical zone can best advance knowledge of the critical zone, using cutting edge technology and a range of spatial and temporal scales?

SSCZO is based in the southwestern Sierra Nevada with sites ranging from oak savannah to subalpine forest, crossing the rain-snow transition zone.

Research at these sites focuses on water, nutrient, and soil fluxes; and landscape and climate changes cross space and time.