The Great Basin section is a physiographic area which extends into the Colorado River

Colorado River

The Colorado River , is a river in the Southwestern United States and northwestern Mexico, approximately long, draining a part of the arid regions on the western slope of the Rocky Mountains. The watershed of the Colorado River covers in parts of seven U.S. states and two Mexican states...

 watershed on the southeast (including the Las Vegas metropolitan area

Las Vegas metropolitan area

The Las Vegas Valley is the heart of the Las Vegas-Paradise, NV MSA also known as the Las Vegas–Paradise–Henderson MSA which includes all of Clark County, Nevada, and is a metropolitan area in the southern part of the U.S. state of Nevada. The Valley is defined by the Las Vegas Valley landform, a ...

 and northwest corner of Arizona

Arizona

Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...

), as well as into the watersheds of the Klamath River

Klamath River

The Klamath River is an American river that flows southwest through Oregon and northern California, cutting through the Cascade Range to empty into the Pacific Ocean. The river drains an extensive watershed of almost that stretches from the high desert country of the Great Basin to the temperate...

 (northwest) and Sacramento River

Sacramento River

The Sacramento River is an important watercourse of Northern and Central California in the United States. The largest river in California, it rises on the eastern slopes of the Klamath Mountains, and after a journey south of over , empties into Suisun Bay, an arm of the San Francisco Bay, and...

 (west). The largest section of the Basin and Range Province was originally defined as two sections in 1917 (the northwest was the Oregon lakes section).

The Great Basin section's northern border in Nevada is a portion of the Great Basin Divide

Great Basin Divide

The Great Basin Divide is the western continental divide that separates the Great Basin from the Pacific Ocean watershed. The water divide is the perimeter of the largest set of contiguous endorheic watersheds of North America, including six entire USGS watershed subregions...

, the southern border extends into the Mojave Desert

Mojave Desert

The Mojave Desert occupies a significant portion of southeastern California and smaller parts of central California, southern Nevada, southwestern Utah and northwestern Arizona, in the United States...

, and the western border is primarily the Sierra escarpment. Small portions of the section extend into the Northern Basin and Range (ecoregion)

Northern Basin and Range (ecoregion)

The Northern Basin and Range ecoregion is a Level III ecoregion designated by the United States Environmental Protection Agency in the U.S. states of Oregon, Idaho, Nevada, Utah, and California. It contains dissected lava plains, rolling hills, alluvial fans, valleys, and scattered mountain ranges...

 and the Sonoran Desert

Sonoran Desert

The Sonoran Desert is a North American desert which straddles part of the United States-Mexico border and covers large parts of the U.S. states of Arizona and California and the northwest Mexican states of Sonora, Baja California, and Baja California Sur. It is one of the largest and hottest...

Level III EPA ecoregions.