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Physical Conditions
One of the unique features of the UARP is the range in elevation of the
different project facilities. The uppermost facility, Rubicon Reservoir,
lies at an elevation of 6,545 feet, while the lowermost facility, White
Rock Powerhouse, is at 995 feet.
The landscape and topography of the UARP area reflects this change in elevation. The large expanses of exposed granite rock, common in the upper elevations, are the result of glaciers pushing volcanic rock layers away to expose the underlying granite. Former valley glaciers also moved many miles down the west slope of the mountains, carving out the steep-walled river valleys characteristic of the range.The cutting action of streams has continued the process, deepening the canyons of the Rubicon River, Silver Creek, and the South Fork American River. Canyon wall vertical drop is as much as 1,000 feet in some places and as steep as 100 percent, rendering some of the river canyons nearly inaccessible.
California’s Mediterranean type climate creates warm, dry summers
and cold, wet winters. Average annual precipitation varies from 40 to
70 inches, with more than 90 percent of this precipitation occurring from
October through April. Mainly falling as snow in the higher elevations,
a snow pack of 5 to 10 feet is common above 6,500 feet from December to
May.
The water quality within the UARP drainages is very good. Representative of west slope Sierra Nevada conditions, project area streams are typically clear, cold streams that are naturally highly oxygenated, are low in dissolved ions and nutrients, and exhibit low instream plant or algal growth.
Biological Resources
Biological resources within the UARP are as varied as the elevations
and types of ecosystems in which they are found. At the mid-elevation
range (1,500 to 5,000 feet), a wide variety of plant and animal resources
can be observed. Amphibian, reptile and fish species such as California
newt, foothill yellow-legged frog, alligator lizard, garter snake, western
rattlesnake, rainbow trout and brown trout may be found. Bird and mammal
species include red-breasted merganser, mountain quail, mourning dove,
Stellar’s jay, western bluebird, mountain chickadee, warblers, squirrels,
skunk, chipmunk, grey squirrel, coyote, mule deer, black bear and mountain
lion. Typical trees include ponderosa pine, sugar pine, white fir, black
oak and incense cedar.
In the higher elevation range (above 5,000 feet) the ecosystem is less
diversified, as can be vegetation. White fir, Jeffrey pine, western juniper,
red fir and lodgepole pine are dominant trees, with huckleberry oak the
dominant shrub. Granite outcrops are commonplace, with very little vegetation
found in some areas. Some animal species that may be found include mule
deer, marmot, coyote, fox and black bear.
With few exceptions, the high mountain lakes and streams above 6,000 feet were historically fishless -dominated instead by amphibians, insects and small aquatic invertebrates, such as fresh-water shrimp. It has been only within the last few decades that fish were introduced in the higher elevation lakes. One aquatic species of particular interest to biologists is the mountain yellow-legged frog, a highly aquatic frog that lives in lakes, meadow streams and isolated ponds that may be found in gently sloping terrain.
Species of Special Concern
Within the Eldorado National Forest, nine
federally listed species (designated as either threatened or endangered)
likely exist, including the American bald eagle, California red-legged
frog, the valley elderberry longhorn beetle and Layne’s butterweed.
An additional 29 species designated by the Forest Service as sensitive
species are thought to inhabit the forest, including the California spotted
owl, northern goshawk, pine marten, foothill and mountain yellow-legged
frog and hardhead fish.
Over the years, SMUD has worked to protect special-status
species. For example, SMUD has cooperated in protecting a bald eagle pair
that has nested at Union Valley Reservoir for the past several years.
Forest Service biologists and SMUD project managers have worked together
to ensure successful fledging of offspring, and will continue to do so
as long as the pair nests at the reservoir.
Reference
www.r5.fs.fed.us Forest Service Region 5 covering El Dorado County.
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