Field areas

A unique feature of the Southern Sierra CZO is our extensive measurement program along an elevation transect that extends from oak grassland, through mixed-conifer forest, to the red-fir transition. This transect extends from the rain-dominated central valley, through the snow-dominated higher elevations of the Sierra Nevada. The most well-instrumented set of headwater catchments is in the Providence Creek drainage, located at the rain-snow transition elevation of 1700-2000 meters in mixed-conifer forest. An additional instrumented catchment is the snow-dominated Wolverton basin, in Sequoia National Park.

© Southern Sierra Critical Zone Observatory


Providence Creek headwater catchments

4.6 km2, 1660-2117 m elevation, 8 °C, 1200 mm/yr

The primary Southern Sierra CZO research area is the Providence Creek headwaters, located on the North Fork of the Kings River. The Providence Creek headwaters area varies in elevation from 1660 to 2115 meters. This 4.6 square kilometer catchment is designated as P300. Nested within the P300 catchment are three subcatchments, designated as P301, P303 and P304.

Providence Creek Subcatchment P301

0.992 km2, 1790-2117 m elevation,

P301 Meadows

Critical Zone Tree 1

0.0001 km2,

Providence Creek Subcatchment P303

1.323 km2, 1731-2025 m elevation,

Providence Creek Subcatchment P304

0.487 km2, 1768-1983 m elevation,

Flux Towers Transect

Transect area: 568 km2, 405-2700 m elevation,

The Southern Sierra CZO operates eddy co-variance flux towers installed at four different locations varying from 405-2700 meters.

405 m Flux Tower, San Joaquin Experimental Range

513 mm/yr

1160 m Flux Tower, Soaproot Saddle

805 mm/yr

2015 m Flux Tower, Providence Creek subcatchment P301

1015 mm/yr

2700 m Flux Tower, Short Hair Creek

1078 mm/yr

Wolverton Basin

8 km2, 2230-2700 m elevation,

The Southern Sierra CZO conducts additional research in the Wolverton basin, located at an elevation of 2230-2700 meters, in Sequoia National Park.

Other instrumented sites

Three additional sets of instrumented sites are available in the Southern Sierra for comparative research: these include the Kings River Experimental Watershed (KREW) project, sites in the Sierra Nevada Adaptive Management Project (SNAMP), and the America River Observatory.

Other instrumented Sierra Nevada sites


The Kings River Experimental Watersheds (KREW) is a research program of the U.S. Forest Service, Pacific Southwest Research Station. KREW consists of two sets of 4 ~1-km2 headwater catchments, plus 2 larger catchments that encompass three headwater catchments each.  See the KREW overview map here. The Southern Sierra CZO is co-located with KREW.

Other instrumented sites

Two additional pairs of instrumented headwater catchments are available for comparative research. One pair lies just north of the main CZO site, in the Sierra National Forest, just south of Yosemite National Park. The second pair lies in the American River basin. There is also an east-west transect of instrumented sites in Yosemite National Park, along Tioga Pass Road.

American River Observatory

Based on wireless-sensor measurement technology developed at the CZO, a basin-scale (> 2000 km2) observatory is under development in the American River basin. Twenty groups of wireless sensors similar to that in P301 are being deployed to make representative measurements of snow properties and soil moisture across the landscape.

The Sierra Nevada

California's Sierra Nevada (snowy mountain range) extends 600 km north to south and about 80 km east to west. To the east lies the Basin and Range Province, and to the east the Great Central Valley. It is drained by over 20 rivers, and supplies over 60% of the water consumed by California's cities and agriculture. Precipitation ranges from over 2 m in the north to under 1 m in the south, with strong east-west elevation gradients in precipitation. Topographically, the Sierra Nevada is an asymmetric mountain range with a long, gentle west slope and a short, steep east escarpment that culminates in the crest of the Sierra Nevada.

The modern Sierra Nevada is quite young in geologic terms, since the all of uplift that has created it has occurred in the last 10 million years. By the end of Cretaceous time, about 65 million years ago, after the granitic core of the range had been exposed, the area had a low relief in comparison with the mountains of today. Then, about 25 million years ago, this lowland area began to be uplifted and tilted toward the southwest. The oldest rocks in the Sierra Nevada are quite a bit older and distinctly different from the granitic rocks. A number of peaks in the eastern Sierra are capped by "roof pendants", metamorphosed sedimentary rocks that were originally deposited in shallow seas off west coast of North America. A larger belt of metamorphic rocks present in the western foothills of the Sierra Nevada became important as the Mother Lode, responsible for much of the gold discovered in the Sierras.

There is a strong elevation zonation of vegetation in the Sierra Nevada. Rising above agricultural lands of the Central Valley, grasslands merge into the oak woodlands that cover the western foothills. The main tree species include deciduous and live oaks, gray or foothill pines, and California buckeyes. Chaparral shrubs, such as Ceanothus, and grasses form the understory. The mixed conifer forest extends from 600 m in the north and 1500 m in the south up through 2100-2700 m. Main tree species in this zone include ponderosa and jeffry pine, incense cedar, white fir, sugar pine and black oak. Above this is a transition to a lodgepole-red fir forest, with a subalpine zone at the highest elevations.


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