Water, geology, climate
& soils: Sierra Nevada,
Merced River & Central
Valley connections
Geography & geology
Merced River basin
Climate & hydrology
Soils & soil formation
Roger Bales
UC Merced
Water, in all its forms, is indeed the crowning glory of the Sierra. Whether in motion
or at rest, the waters of the Sierra are a constant joy to the beholder. Above all, they
are the Sierra’s greatest contribution to human welfare.
F. Farquhar, 1965. History of the Sierra Nevada
Bierstadt, 1863-75
Contemplating the lace-like fabric of streams
outspread over the mountains, we are
reminded that everything is flowing
somewhere, animals and so called lifeless
rocks as well as water.. .
J. Muir, 1911, My First Summer in the Sierra
Bierstadt, 1863-75
The Sierra Nevada &
Central Valley
Sacramento
San Francisco
Fresno
N
0
50
miles
100
ancient seas
days of fire
& volcanoes
granite
forms
gold
deposits
days of ice
M. Hill, Geology of the Sierra Nevada, 1975
Melting of last
ice age glacier
mountains tremble, lift & tilt
Mammoth
Mountain erupts
erosive
times
present
20,000
400,000
1 million
3 million
38 million
65 million
135 million
225 million
570 million
4,500 million
The long past of the Sierra Nevada
Yosemite Valley & the days of ice
before
after
M. Hill, Geology of the Sierra Nevada, 1975
Yosemite Valley today
Douglas Alden UCSD-SIO 2005
“The Range of Light” & “Snowy Range”
Audette, Half Dome above the Merced River
Obata, Yosemite Falls
Where has all of this rock gone?
Douglas Alden UCSD-SIO 2005
Geology of the Sierra Nevada
Diverse geological activities have produced a broad suite of
rock formations in the Sierra Nevada, dominated by
granite but including many types of igneous, sedimentary
& metamorphic rocks.
Geology of the Sierra Nevada
Because the Sierra Nevada is underlain by mostly granitic
rocks, soils are thin & rocky. Although the fertility of the
soil in general over the Sierra Nevada is rather low, the
range contains some of the most productive sites for
conifers in the world.
Many individual rivers drain the western
slopes of the Sierra Nevada, flowing
eventually into San Francisco Bay
Topography of
Upper Merced
river basin
Yosemite Valley
Merced river headwaters are covered with
snow in winter & spring
Satellite
snowcover
Much of the
precipitation
falls as snow at
high elevations
% SCA
76-100
51-75
26-50
1-25
Tuolumne
Merced
May 10, 2004
Streamflow peaks during spring snowmelt
Peaks occur in late spring to early summer
Headwaters receive little summer precipitation
& are largely snow free by late summer
Streams flow year round
Merced river profile
Triple Divide
8000
6000
Yosemite Valley
4000
Merced river canyon
2000
Snelling
100
80
60
miles
40
20
0
Elevation, ft
10000
Streams enter the U-shaped Yosemite
Valley from higher V-shaped canyons
From Yosemite Valley the river drops to
El Portal & the Merced River Canyon
Merced river canyon near Briceburg
Soil formation is a result of 5 factors
–
–
–
–
–
Physical & chemical composition of the parent material
Climate
Relief, or lay of the land
Biological forces
Length of time the forces have been in operation
Soil formation along Merced river
– River & glacial erosion brought material down from the
mountains to form the agricultural soils in the San
Joaquin Valley & along the Merced river
– Glacial outwash is the main source of parent material for
the soils in the terraces & fans of the Merced river;
exception is that some Holocene alluvium is derived from
metamorphic terrane of foothills (including granitic
debris)
Sediment is transported during large floods
Soil profiles along river terraces
Terrace & fan deposits along the Merced river
range from 200 years to 3 million years in age
from Pavich et al., 1986
Older soils, Sierra foothills near Snelling
Younger soils along Merced river near Snelling
Daily temperature
Vineyard 1
Daily temperature
Vineyard 2
Temperature comparison
Daily temperature
Daily temperature
Questions?