Water, geology, climate & soils: Sierra Nevada, Merced River & Central Valley connections
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
050100 miles The long past of the Sierra Nevada 135 million 4,500 million 20,000 65 million 38 million 570 million 400,000 225 million 3 million present 1 million
ancient seas days of fire & volcanoes granite forms gold days of ice deposits erosive times mountains tremble, lift & tilt Mammoth Melting of last ice age glacier
M. Hill, Geology of the Sierra Nevada, 1975 Mountain erupts 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”
Obata, Yosemite Falls Audette, Half Dome above the Merced River
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 Tuolumne 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
8000
6000 Yosemite Valley 4000 Elevation, ft Merced river canyon Snelling 2000
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