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
The long past of the Sierra Nevada Mammoth Mountain erupts Melting of last ice age glacier 4,500 million 570 million 225 million 135 million 65 million 38 million 3 million 1 million 400,000 20,000 present ancient seas granite forms gold deposits erosive times days of fire & volcanoes days of ice mountains tremble, lift & tilt M. Hill, Geology of the Sierra Nevada, 1975
Yosemite Valley & the days of ice before after M. Hill, Geology of the Sierra Nevada, 1975
Douglas Alden UCSD-SIO 2005 Yosemite Valley today
The Range of Light & Snowy Range Audette, Half Dome above the Merced River Obata, Yosemite Falls
Douglas Alden UCSD-SIO 2005 Where has all of this rock gone?
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
Yosemite Valley Topography of Upper Merced river basin
Merced river headwaters are covered with snow in winter & spring
Much of the precipitation falls as snow at high elevations Tuolumne Satellite snowcover % SCA 76-100 51-75 26-50 1-25 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 10000 Snelling Merced river canyon Yosemite Valley 8000 6000 4000 2000 Elevation, ft 100 80 60 40 20 0 miles
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?