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The geography of the Antelope Valley

Location
The Antelope Valley is an approximately 2400 sqmi arid desert region located at 34.75137°N, -118.2523°W in the northern part of Los Angeles County, the southeastern portion of Kern County, and the far western edge of San Bernadino County, California. It constitutes the western tip of the Mojave Desert, lying within the foothills of the San Gabriel Mountains to the southeast, Portal Ridge and the Sierra Pelona Mountains to the southwest, and the Tehachapi Mountain Range to the northwest. The northern and eastern boundaries are not so easily defined, especially by noticeable geographic features such as mountains, but in 1911 a United States Geological Survey (USGS) Water-Supply Paper placed Rosamond "near the north margin of the valley". It also noted a region of detrital rock that stretched for about ten miles between Cottonwood Creek in the Tehachapi Mountains and Rosamond Buttes where surface runoff on the northern and eastern sides of this area possibly drained towards the northeast and the town of Mojave. On the southeastern edge of the AV another area of detritus was found to run along the San Gabriel Mountains and separate the region from Victor Valley in San Bernadino County. On the western side of this rock, the water from Little Rock Creek and Big Rock Creek was found to drain into the Antelope Valley; to the east, it was thought the water drained into the Mojave River.

The USGS thus identified the northern edge of the Antelope Valley as being along the detritus from the Tehachapi Mountains and then following the BNSF railroad which loosely parallels State Route 58 Business to the north of Rogers Dry Lake, and the eastern border of the valley as lying about six miles east of Llano, through Black Butte and towards Haystack Butte along the LA County – San Bernadino County border. A second USGS WSP published in 1929 included a map that altered the eastern border; while most recent surveys show the valley extending as far north as to actually include Mojave, as well as California City and Boron.

In a straight line, the AV is about 50 mi north of Los Angeles. Bakersfield is 60 mi northwest of the Antelope Valley, and Las Vegas, Nevada is 200 mi east of the valley. The three cities in the Antelope Valley are Lancaster and Palmdale, both in LA County, and California City in Kern County. Three of the five highest populated census-designated places in the valley are also in LA County: Lake Los Angeles, Sun Village and Quartz Hill, California; Rosamond and Mojave are in Kern County.

Topography
The Antelope Valley is a graben, the result of the surrounding mountains uplifting due to fault activity. The San Andreas Rift Zone enters the valley from the western tip at Gorman, and runs parallel to Portal Ridge and the Sierra Pelona range, forming a long, narrow basin in which lie Hughes Lake and Elizabeth Lake. The Fault Line continues through Soledad Canyon and along the foot of the San Gabriels out of the valley into San Bernadino County. The valley floor decreases gently from an elevation of around 4000 ft on the flanks of the Tehachapi Mountains, to an endorheic depression lying near the northwest corner of the valley where, at an elevation of 2300 ft, the Rogers, Buckhorn, Rich and Rosamond Dry Lakes are found. These playas are all bisected by the LA – Kern County boundary lines. Because the valley is a closed basin, all streams and rain water either sink into the ground or collect in the lower corner of the valley and evaporate. The floor of the Antelope Valley is characterized by a broad plain of undulating alluvial fans, throughout which scattered mountain peaks or buttes are found. Examples of these are Fairmont Butte, Antelope Buttes, Quartz Hill, Alpine Butte, and Piute Butte.

At 2,300 ft above sea level, the lowest elevation of the Antelope Valley is higher than most of the valleys on the other side of the mountains that surround it. The highest point of the Fremont Valley is about the same, but its lowest point is Koehn Lake at 1900 ft; the south-eastern edge of the San Joaquin Valley, which lies west of the Tehachapi Mountains, slopes upwards to 600 ft; and the San Fernando Valley, on the south side of the San Gabriels, reaches a height of 1400 ft. Victor Valley and Mojave River Valley, both east of the AV, are the exceptions at 2900 ft and 2500 ft respectively.

Hydrology
The Antelope Valley is a part of the Environmental Protection Agency's Antelope-Fremont Valleys Watershed (Hydrological code 18090206), a 3376 sqmi area that is further divided into 24 subwatersheds. There are a number of waterbodies and watercourses within the Antelope Valley, both natural and artificial, and the Antelope Valley Groundwater Basin has historically been the primary source of water for agricultural, municipal and industrial use in the valley.

Groundwater
The Antelope Valley Groundwater Basin consists of two aquifers: the principal aquifer, which is unconfined; and the deep aquifer, which is confined. The two aquifers are separated by a layer of clay between 200 and 300 feet thick. The principal aquifer is thickest in the southern area of the valley, and the deep aquifer is thickest in the northern part near the dry lakes. The possibility of the existence of a third, or middle aquifer has being studied by the USGS. The groundwater in the Antelope Valley is known to be contaminated with arsenic and other substances including fluoride, boron, lead and nitrates; however, the water quality is well within the Maximum Contaminant Levels set by the Environmental Protection Agency.

Most of the extracted groundwater is from the principal aquifer. The volume of water obtained has differed greatly since the time the valley was permanently inhabited. The USGS estimate that in the early 1900s when groundwater pumping began, around 29000 acre feet per year was pumped, and accounted for more than 90% of the water used in the valley. The figure increased to 400000 acre feet per year in the 1950s, and then decreased as farming in the area declined. The introduction of the State Water Project (SWP) in the 1970s also reduced the need for groundwater pumping, although the valley's increasing population and renewed agricultural industry soon increased the demand of water once again.

As such, groundwater is still an important source and continues to be pumped by the local water utility companies. It now accounts for anywhere between 50% and 90% of annual total water usage in the valley, depending on the yearly demand and availability of surface water. Palmdale Water District states that groundwater accounts for up to 60% of its annual water usage, and it continues to be Littlerock Creek Irrigation District's (LCID) main source of water ahead of that from Littlerock Creek and the California Aqueduct. LCID owns five wells that pump groundwater; one is suitable for irrigation only, the other four wells provide potable water (suitable for drinking).

The extended period of the pumping of groundwater has caused long-lasting issues within the Antelope Valley. For most of the first three-quarters of the 20th century, the amount of groundwater being pumped was more than that being recharged through the deep percolation of precipitation and runoff. This overdrafting has resulted in the artesian wells that were present in the late 1800s and early 1900s to stop flowing, the aquifers to compact, and the land to subside. Surveys conducted using Global positioning systems have determined that between 1930 and 1992, close to 7 ft of subsidence occurred in the Antelope Valley, mostly around Lancaster (34.74034°N, -118.11796°W and 34.74556°N, -117.97256°W). The USGS has stated that this sinking has resulted in "a loss of aquifer storage, increased flooding, cracks and fissures at land surface, and damage to man-made structures".

Reservoirs
The two main waterbodies in the Antelope Valley are reservoirs. The largest is Lake Palmdale, located about two miles south of Palmdale sandwiched between State Route 14 and the Union Pacific Railroad. It has previously been identified in literature and old USGS maps as Lake Yuna, Alpine Lake, Harold Lake, Harold Reservoir, Shoulder Lake, Palmdale Lake and Palmdale Reservoir. The area of Lake Palmdale was originally the location of a natural depression along the San Andreas Rift Zone that often filled with water. It formed as either a sag pond or rift lake due to fault activity that caused the uplift of the land to close off drainage into the depression. The development and operation of Lake Palmdale is intrinsically linked with that of Little Rock Reservoir (34.47909°N, -118.02275°W) and its primary tributary, Little Rock Creek, 7.5 mi away in the San Gabriel Mountains of the Angeles National Forest,

In the late 1880s, Nathan Cole Jr. purchased 1960 acres of land east of where Little Rock Creek enters the Antelope Valley, and with his two brothers Charles and Zack, and Charles's son Burt, developed the area for agriculture and housing. Originally called Alpine Springs, they changed its name in 1892 to the Tierra Bonita Colony and then Little Rock the following year. The Coles persuaded the land owners in the area to petition the Los Angeles County Board of Supervisors to form an irrigation district under the Wright Act of 1887. The Little Rock Creek Irrigation District (LCID) was thus formed on March 28, 1892 to cover an area of 1300 acres and use the water from Little Rock Creek.

At around the same time as the LCID was formed, so too was the private – i.e., not a Wright Irrigation district – Palmdale Irrigation Company. The Palmdale Irrigation Company, under the control of Nathan Cole Jr., dug an 8.5 mi earthen ditch between Little Rock Creek and Palmdale, and installed a headgate on the Creek to divert water via the ditch. A few years later the South Antelope Valley Irrigation District constructed a dam at Harold Lake to form a reservoir and dug a second unlined ditch, called the Palmdale Ditch, parallel to the first between the creek and the reservoir; however, the reservoir had a capacity of only 3000 acre ft, and in the winter when the surface runoff was at its greatest, the reservoir would overflow and a lose a large amount of water.

At the turn of the century following a period of drought in the late 1890s, it became clear that a dam needed to be installed on Little Rock Creek. The Palmdale Irrigation District – now Palmdale Water District (PWD) – was formed as a public district in 1918 and purchased the rights of the existing private districts, and began working with the LCID to construct a concrete dam on the creek. The Little Rock Dam was completed in June 1924 and can hold a maximum volume of 3500 acre ft. In the 1960s following Palmdale Irrigation District's contract with the State Water Project (SWP), Lake Palmdale was upgraded to hold a larger volume of water. Following the expansion, Lake Palmdale's storage capacity increased to 4129 acre ft.

Over a hundred years after it was built, the Palmdale Ditch is still used to transport water from Littlerock Reservoir to Lake Palmdale. It runs alongside the California Aqueduct but travels in the opposite direction. It was built with such accuracy that it runs downhill the entire route; gravity alone directs the flow, and pumps are not used at all.

Aqueducts
The California Aqueduct runs through the southern border of the region and is a third water supply source for the AV. It enters the valley at its westernmost edge at the mouth of Los Alamos Creek (34.83359°N, -118.71148°W) after tunneling through the Tehachapi Mountains. It then bifurcates at the Tehachapi Afterbay (34.82887°N, -118.7087°W), and from here the West Branch and East Branch split. The West Branch heads southwest towards Oso Pumping Plant (34.81026°N, -118.71954°W) and into Quail Lake, before being piped through the Sierra Pelonas into Pyramid Lake and out towards its terminus at Castaic Lake.

The East Branch navigates along the entire southern edge of the valley in a concrete ditch. From Alamo Powerplant (34.82113°N, -118.69251°W) it travels southeast along the foothills of Portal Ridge and the Sierra Pelonas before turning south into the San Andreas Rift Zone at Anaverde Valley (34.57457°N, -118.1813°W), where it passes underneath State Route 14 and runs alongside Lake Palmdale, which is fed water from the Aqueduct. The canal continues to head east along the southern border of Palmdale towards Littlerock and Pearblossom, where the Pearblossom Pumping Plant lifts the water 540 ft to the top of Ward Butte, before it descends out of the valley to Silverwood Lake near Hesperia, San Bernadino County, and its terminus at Lake Perris in Riverside County.

Three water companies in the AV have contracted to receive potable and irrigation water from the SWP until 2035: LCID, PWD and the Antelope Valley-East Kern Water Agency (AVEK). Other water districts in the area that have not contracted with the SWP purchase water from AVEK instead, such as Quartz Hill Water District, Rosamond Community Services District, and Los Angeles County Waterworks District No. 40. The Antelope Valley's maximum entitlement of SWP water is about 160000 acre feet per year.

The Los Angeles Aqueduct also passes through the Antelope Valley and serves to convey water to the City of Los Angeles from the Owens River in Inyo County.

Streams
Many of the creeks and streams that enter the valley are ephemeral. About 10 miles east of Little Rock Creek is Big Rock Creek. Amargosa Creek enters the valley from Leona Valley, and Cottonwood Creek begins in the Tehachapi Mountains.

Wetlands
Una Lake, Piute Ponds, Barrel Springs

Human development
Settlements, farming and roads

(Use Lede from above History article)

Flora and fauna
The vegetation of the Antelope Valley is limited to desert-type flora, and is in marked contrast to that found on the western side of the Tehachapis or the mountains in Los Angeles National Forest which are prevalent with oak, sycamore and willow trees, and grass-covered floor. Entering the valley from these ranges, the change in vegetation is sudden. The valley floor is covered in desert brush, while Eschscholzia californica (California poppy), Larrea tridentata (creosote bushes), Quercus berberidifolia (scrub oak), and Yucca brevifolia (Joshua trees) are the only other native flora fround in large quantities. Except for junipers, true native arboreals are rare (the Joshua tree is not really a tree as it is not woody, does not produce annual growth rings, and is closely related to agaves and lillies). The only other trees are those imported into the region by man, such as fruit trees during the late 1800s and early to mid-1900s and palm trees.

Birds

 * Western Grebe - American Ornithologists' Union Checklist # 1 - (AV migrant)
 * Eared Grebe - AOU #4 - Migrant AV
 * Pied-billed Grebe - AOU #6 - Year round resident
 * California Gull - AOU #53 - Year round (except during breeding)
 * Ring-billed Gull - AOU #54 - Resident year round (except for breeding)
 * Caspian Tern - AOU #64 - AV migrant
 * Forster's Tern - AOU #69 - AV migrant
 * Black Tern - AOU #77 - AV migrant
 * Double-crested Cormorant - AOU #120 - AV resident year round
 * Great White Pelican - AOU #125 - Uncommon in AV, also occ. @ Quail Lake
 * Common Merganser - AOL #129 - Migrant AV, also @ Quail Lake
 * Cinnamon Teal - AOU #141 - Migrant of the AV
 * Northern Shoveler - AOU #142 - Migrant AV
 * Bufflehead - AOU #153 - Migrant AV
 * Ruddy Duck - AOU #167 - Resident year round
 * Ross's Goose - AOU #170 - rare sighting
 * Canada Goose - AOU #172 - year round resident
 * Great Blue Heron - AOU #194 - year round resident
 * Great Egret = AOU #196 - Resident AV
 * Black-crowned Night Heron - AOU #202 - year round
 * Red-necked Phalarope - AOU #223 - winter uncommon, spring common, migrant of AV
 * American Avocet - AOU #225 - Spring migrant
 * Long-billed Dowitcher - AOU #232 - AV migrant
 * Least Sandpiper - AOU #242 - AV migrant
 * Dunlin - AOU #243 - Migrant AV
 * Greater Yellowlegs - AOU #254 - Migrant AV
 * Spotted Sandpiper - AOU #263 - Resident year round
 * Killdeer - AOU #273 - Resident of AV
 * Semipalmated Plover - AOU #274 - Spring visitor
 * Mourning Dove - AOU #316 - Resident year round
 * Red-tailed Hawk - AOU #337 - AV resident
 * Ferruginous Hawk - AOU #348 - Uncommon migrant
 * Barn Owl - AOU #365 - Resident AV
 * Long-eared Owl - OAU 366 - Uncommon migrant
 * Great Horned Owl - AOU #375 - AV resident
 * Lesser Nighthawk - AOU #421 - Migrant of AV
 * Western Kingbird - AOU #447 - Summer visitor
 * Black Phoebe - AOU #458 - Resident year round
 * Horned Lark - AOU #474 - AV resident
 * Rufous-sided Towhee - AOU #587 - Uncommon in AV
 * Cliff Swallow - AOU #612 - Spring migrant
 * Yellow-rumped Warbler - AOU #656 - Winter resident
 * Wilson's Warbler - AOU #687 - Spring migrant
 * Mountain Chickadee - AOU #738 - Wander in AV
 * American Robin - AOU #761 - Irregular rover in AV
 * Mountain Bluebird - AOU #768 - AV migrant
 * Mountain Bluebird - AOU #768 - AV migrant


 * Common Snipe - AOU #230 - Vagrant of the AV
 * American Kestrel - AOU @360 - Common to the AV
 * Ladder-backed Woodpecker - AOU #396 - Common in the AV
 * Downy Woodpecker - AOU #394 - Common in the AV
 * Turkey Vulture - AOU #325 - Common in AV
 * Say's Phoebe - AOU #457 - Common resident year round
 * Water Pipit - AOU #697 - Winter visitor to AV
 * Killdeer - AOU #273 - Common year round resident
 * Common Raven - AOU #486 - Year round resident
 * Northern Harrier - AOU #331 - year round resident
 * Burrowing Owl - AOU #378 - year round resident
 * Western Meadowlark - AOU #501 - year round resident
 * Prairie Falcon - AOU #355 - Endangered in the AV (Fish & Game State threatened in Los Padres National Forest)
 * California Gull - AOU #53 - common winter visitor
 * House Sparrow - year round resident
 * Dark-eyed Junco - AOU 567.1 - Winter visitor
 * Mourning Dove - AOU #316 - year round
 * Black Phoebe - AOU #458 - Resident year round
 * Sage Sparrow - AOU #574 - Uncommon resident
 * Black-tailed Gnatcatcher - AOU #752 - Vagrant of the AV
 * Ruby-crowned Kinglet - AOU #749 - winter resident
 * Horned Lark - AOU #474 - common in AV
 * Sharp-shinned Hawk - AOU #332 - uncommon AV visitor
 * White-crowned Sparrow - AOU #554 - Winter resident
 * California Quail - AOU #313 - Year round resident
 * Common Starling - AOU #493.0 - year round resident
 * Brewer's Blackbird - AOU #510 - year round resident
 * Audubon's Warbler - AOU #656 - Fall to Spring resident
 * Anna's Hummingbird - AOU #431 - year round resident
 * Common Crossbill - AOU #521 - Vagrant of AV
 * Savannah Sparrow - AOU #542 - Uncommon resident
 * Red-shafted Flicker - AOU #413 - year round resident
 * Loggerhead Shrike - AOU E622.0 - year round resident
 * Sage Thrasher - AOU #702 - Uncommon resident
 * Mockingbird - AOU #703 - year round resident
 * Le Conte's Thrasher - AOU #711 - rare resident
 * Cactus Wren - AOU #713 - year round resident
 * Cactus Wren - AOU #713 - year round resident


 * Black-throated Sparrow
 * Sage Sparrow
 * Vesper Sparrow
 * Chipping Sparrow
 * Song Sparrow
 * Lincoln's Sparrow
 * Rock Wren
 * Scott's Oriole
 * Prarie falcon
 * Shrike
 * Cactus Wren
 * Greater Roadrunner
 * Le Conte's Thrasher
 * Gnatcatcher
 * Verdin
 * Vulture
 * Pinon Jay
 * Raven
 * Ladder-backed Woodpecker
 * Rufous Hummingbird
 * Anna's Hummingbird
 * Allen's Hummingbird
 * Black-chinned Hummingbird
 * Costa's Hummingbird
 * Common Poorwill

Insects and arthropods

 * Scorpion
 * Millipede
 * Centipede
 * Dung beetle
 * Solpugid
 * Mutillid
 * Eleodes
 * Dinapate beetle
 * Tarantula
 * Black widow

Mollusks

 * Oreohelix

Lizards

 * Mojave fringe-toed lizard
 * Race-runner
 * desert spiny lizard
 * Western whiptail
 * Desert iguana
 * Zebra-tailed lizard
 * Horned lizard
 * Desert tortoise

Snakes

 * Rattlesnake
 * Gopher snake
 * King snake
 * Worm snake
 * Lyre snake
 * Western patch-nosed snake
 * Leaf-nosed snake
 * Shovel-nosed snake

Mammals

 * Mexican Free-tailed bat
 * Western mastiff bat
 * Ring-tailed cat
 * Western spotted skunk
 * Desert kit fox
 * Gray fox
 * Coyote
 * Desert lynx
 * Desert bighorn sheep
 * California mule deer
 * Pronghorn antelope
 * Black-tailed jackrabbit
 * Cottontail rabbit
 * White-footed mouse
 * Spiny pocket mouse
 * Southern grasshopper mouse
 * Westen harvest mouse
 * Merriam's kangaroo rat
 * Desert kangaroo rat
 * Kangaroo mouse
 * Desert shrew
 * Packrat
 * Pocket gopher
 * White-tailed antelope squirrel
 * Round-tailed ground squirrel
 * Striped skunk
 * Badger
 * Ring-tailed cat