Geoscience Reference
In-Depth Information
west by the Spring Mountains and to the east by Frenchman
Mountain. Las Vegas is located about 48 km (30 mi) northwest
of Hoover Dam, which impounds Lake Mead.
The Las Vegas metropolitan area is located in the central
part of the Mojave Desert and is thus one of the hottest cities in
the United States. The average daily high temperature is >38°C
(100°F) approximately 90 days out of the year (Figure 20.6).
The record high temperature is 47°C (117°F), which occurred
in July 2005. Winter months are typically mild, with an aver-
age daily high temperature of 13°C (57°F) in January. The Las
Vegas climate is influenced strongly by the rain shadow effect
associated with the Sierra Nevada in California to the west. Av-
erage annual precipitation is only about 10 cm (4 in.), and rela-
tive humidity is usually very low. As a result, Las Vegas is one
of the sunniest cities in the country, with over 300 days of clear
skies per year.
The development of Las Vegas is directly tied to its dis-
tinctive physical geography. The Las Vegas Valley was “discov-
ered” in 1829 when a scouting party associated with a Mexican
trading caravan traveling to Los Angeles left the main trail in
search of water. While doing so, the scouts entered an unnamed
valley and found an oasis fed by numerous artesian springs. As
a result of this discovery, the site was named
Las Vegas
, which
is Spanish for “The Meadows,” and became an important place
to replenish water supplies, first for Mexican traders and later
for American explorers. The area was subsequently annexed by
the United States following the Mexican-American War in 1848
and was soon occupied by Mormon missionaries, who built a
fort near present-day downtown Las Vegas in the mid-1850s.
The fort was soon abandoned and later reoccupied in 1865 by
Octavius Gass. After constructing an irrigation system drawing
water from the springs, Gass developed a farm complex that
was about 243 hectares (600 acres) in size and renamed the area
Las Vegas Rancho
. Gass's farm became an important rest stop
for people traveling on the nearby Mormon trail from Salt Lake
City, Utah, to Los Angeles.
The population of Clark County began to grow very slowly
after Nevada became a state in 1864. A major factor in the early
growth of the area was the State Land Act of 1885, which al-
lowed homesteaders to purchase land for $1.25/acre ($309/
km²). The lure of cheap land drew many people to the area,
most of whom were farmers. As a result, agriculture dominated
the local economy until the early 1900s and was supported by
an increasingly elaborate irrigation system that drew water from
the wells. Some of this water was directed into the town proper,
and Las Vegas became firmly established as a stop for travelers
moving to and from Los Angeles and places to the east such as
Albuquerque, New Mexico.
Despite the irrigation improvements in the Las Vegas Val-
ley in the late 19th century, only about 1100 people lived in
Clark County in 1900. The first surge in population occurred af-
ter the San Pedro, Los Angeles & Salt Lake Railroad linked the
area to other places in the West in 1905. The city of Las Vegas
was founded that same year, and the population of Clark Coun-
ty grew to about 3300 in 1910. Las Vegas was subsequently
connected to Southern California by a highway in 1926, and
the population of Clark County reached about 8500 in 1930.
Approximately 60% of those residents lived in Las Vegas at
that time.
Las Vegas, NV
36° N 115° W
Elevation 618 m (2028 ft)
45
110
40
100
35
90
30
80
°C
°F
25
70
60
20
Range = 26°C (47°F)
60
15
50
10
Establishing Water Rights
The next major population surge in Clark County occurred in
the 1930s and is directly related to the establishment of the
Colorado River Compact
, which was signed in 1922 by repre-
sentatives of the seven states that lie within the Colorado River
basin. This agreement was part of an overall effort by the U.S.
federal government to draw people to the region and “reclaim”
the arid lands for economic development. The purpose of the
compact was (and remains) to sustainably allocate water to us-
ers in the basin in a fair and equitable manner by establishing a
system of
water rights
defined by law. It does so by dividing the
watershed into an upper basin (including Wyoming, Colorado,
23.5 N
Solstice
0
Equinox
Equinox
23.5 S
Solstice
Solstice
25
8
20
6
15
cm
in.
Annual precipitation = ~10 cm (4 in.)
4
10
2
5
0
0
J
F
M
A
M
J
J
A
S
O
N
D
Figure 20.6 Climograph for Las Vegas, Nevada.
Average
monthly temperatures range from mild in the winter to blis-
tering hot in the summer. Total annual precipitation is about
10 cm (~4 in.).
Water rights
Legally protected rights to take possession of
water occurring in a natural waterway and to divert that water
for beneficial purposes.
