Reports

The Puget Lowland Ecoregion covers an area of approximately 18,009 km² (6,953 mi²) within northwestern Washington (fig. 1) (Omernik, 1987; U.S. Environmental Protection Agency, 1997). The ecoregion is located between the Coast Range Ecoregion to the west, which includes the Olympic Mountains, and the North Cascades and the Cascades Ecoregions to the east, which include the Cascade Range...

This chapter has been modified from original material published in Raumann and Soulard (2007), entitled “Land-cover trends of the Sierra Nevada Ecoregion, 1973–2000” (U.S. Geological Survey Scientific Investigations Report 2007–5011). The Sierra Nevada Ecoregion covers approximately 53,413 km² (20,623 mi²) with the majority of the area (98 percent) in California and the remainder in...

Located in south-central Idaho, the Snake River Basin Ecoregion spans 66,063 km2 (25,507 mi2) of mostly sagebrushsteppe (Artemisia tridentata) with some areas of saltbushgreasewood (Atriplex spp. and Sarcobatus spp.) and barren lava fields (fig. 1) (Omernik, 1987; U.S. Environmental Protection Agency, 1997). The Snake River is the dominant hydrographic feature extending the full length...

The Sonoran Basin and Range Ecoregion covers approximately 116,364 km2 (44,928 mi2) of desert landscape in southeastern California and southwestern Arizona (fig. 1) (Omernik, 1987; U.S. Environmental Protection Agency, 1997). This ecoregion is bounded on the west by the Southern and Central California Chaparral and Oak Woodlands and the Southern California Mountains Ecoregions; on the...

The Southern and Central California Chaparral and Oak Woodlands Ecoregion, which covers approximately 102,110 km2 (39,425 mi2), is characterized by a Mediterranean climate with cool, moist winters and hot, dry summers (Omernik, 1987; U.S. Environmental Protection Agency, 1997). Natural vegetation includes chaparral (for example, manzanita, Arctostaphylos spp.) and oak (Quercus spp.)...

This chapter has been modified from original material published in Soulard and others (2007), entitled “Land-cover trends of the Southern California Mountains ecoregion” (U.S. Geological Survey Scientific Investigations Report 2007–5235). The Southern California Mountains Ecoregion (Omernik, 1987; U.S. Environmental Protection Agency, 1997) encompasses approximately 17,871 km² (6,900 mi²...

The Southern Rockies Ecoregion is a high-elevation mountainous ecoregion that covers approximately 138,854 km2 (53,612 mi2), including much of central Colorado and parts of southern Wyoming and northern New Mexico (fig. 1) (Omernik, 1987; U.S. Environmental Protection Agency, 1997). It abuts six other ecoregions: the Wyoming Basin and Colorado Plateaus Ecoregions on the north and west...

The Wasatch and Uinta Mountains Ecoregion covers approximately 44,176 km2 (17, 057 mi2) (fig. 1) (Omernik, 1987; U.S. Environmental Protection Agency, 1997). With the exception of a small part of the ecoregion extending into southern Wyoming and southern Idaho, the vast majority of the ecoregion is located along the eastern mountain ranges of Utah. The ecoregion is situated between the...

The Willamette Valley Ecoregion (as defined by Omernik, 1987; U.S. Environmental Protection Agency, 1997) covers approximately 14,458 km² (5,582 mi2), making it one of the smallest ecoregions in the conterminous United States. The long, alluvial Willamette Valley, which stretches north to south more than 193 km and ranges from 32 to 64 km wide, is nestled between the sedimentary and...

The Wyoming Basin Ecoregion (Omernik 1987; U.S. Environmental Protection Agency, 1999) covers approximately 128,914 km2 (49,774 mi2) in Wyoming and parts of northwestern Colorado, northeastern Utah, southeastern Idaho, and southern Montana (fig. 1). The ecoregion is bounded on the east by the Northwestern Great Plains Ecoregion; on the south and east by the Southern Rockies Ecoregion; on...

The U.S. Geological Survey (USGS), in cooperation with the U.S. Department of Defense Task Force for Business and Stability Operations, prepared databases for mineral-resource target areas in Afghanistan. The purpose of the databases is to (1) provide useful data to ground-survey crews for use in performing detailed assessments of the areas and (2) provide useful information to private...

The Elkhorn-Loup Model (ELM) was begun in 2006 to understand the effect of various groundwater-management scenarios on surface-water resources. During phase one of the ELM study, a lack of subsurface geological information was identified as a data gap. Test holes drilled to the base of the aquifer in the ELM study area are spaced as much as 25 miles apart, especially in areas of the...