San Pedro River (Arizona)

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San Pedro River
Rio San Pedro, [1] Beaver River [2]
San Pedro RCNA.jpg
Fall colors, San Pedro RNCA
Countries Mexico, United States
States Sonora, Arizona
 - left Babocomari River
 - right Aravaipa Creek
Source The Sierra Manzanal Mountains in northern Sonora
 - location North of Cananea, Mexico, Mexico
 - elevation 4,460 ft (1,359 m)
 - coordinates 31°12′04″N110°12′28″W / 31.20111°N 110.20778°W / 31.20111; -110.20778   [1]
Mouth Confluence with the Gila River
 - location Winkelman, Arizona, Pinal County , United States
 - elevation 1,919 ft (585 m)
 - coordinates 32°59′04″N110°47′01″W / 32.98444°N 110.78361°W / 32.98444; -110.78361 Coordinates: 32°59′04″N110°47′01″W / 32.98444°N 110.78361°W / 32.98444; -110.78361   [1]
Map of the Gila River watershed including the San Pedro river Gilarivermap.png
Map of the Gila River watershed including the San Pedro river
The San Pedro River near Palominas, Arizona. San Pedro River Palominas Arizona 2014.jpeg
The San Pedro River near Palominas, Arizona.
A typical river flow following the monsoon rains. This photo was taken August 16, 2005 at the Charleston Road bridge, several miles west of Tombstone, Arizona. Estimated depth at this location is 5 feet. River-1.jpg
A typical river flow following the monsoon rains. This photo was taken August 16, 2005 at the Charleston Road bridge, several miles west of Tombstone, Arizona. Estimated depth at this location is 5 feet.

The San Pedro River is a northward-flowing stream originating about 10 miles (16 km) south of the international border south of Sierra Vista, Arizona, in Cananea Municipality, Sonora, Mexico. The river starts at the confluence of other streams (Las Nutrias and El Sauz) just east of Sauceda, Cananea. [3] Within Arizona, the river flows 140 miles (230 km) north through Cochise County, Pima County, Graham County, and Pinal County to its confluence with the Gila River, at Winkelman, Arizona. It is the last major, free-flowing undammed river in the American Southwest, [4] it is of major ecological importance as it hosts two-thirds of the avian diversity in the United States, including 100 species of breeding birds and 300 species of migrating birds. [5]

Stream A body of surface water flowing down a channel

A stream is a body of water with surface water flowing within the bed and banks of a channel. The stream encompasses surface and groundwater fluxes that respond to geological, geomorphological, hydrological and biotic controls.

Sierra Vista, Arizona City in Arizona, United States

Sierra Vista is a city in Cochise County, Arizona, United States. As of the 2010 census the population of the city was 43,888. The city is part of the Sierra Vista-Douglas Metropolitan Area, with a 2010 population of 131,346. Fort Huachuca, a U.S. Army post, is located in the northwest part of the city.

Cananea Municipality Municipality in Sonora, Mexico

Cananea is a municipality in the northern portion of the Mexican state of Sonora, on the U.S. border. Its municipal seat is the city of Cananea, located at 30°58′55″N110°18′02″W.



The first people to enter the San Pedro Valley were the Clovis people who hunted mammoth here from 10,000 years ago. The San Pedro Valley has the highest concentration of Clovis sites in North America. [6] Some Clovis sites of note are the Lehner Mammoth-Kill Site, the Murray Springs Clovis Site and the Naco Mammoth-Kill Site.

Lehner Mammoth-Kill Site

The Lehner Mammoth-Kill Site is a location in southern Arizona that is significant for its association with evidence that mammoths were killed here by Paleo-Indians 9000 years BCE.

The hunter-gatherer, Cochise Culture next made this area home between about 5000 to 200 BC. Followed by the more advanced Mogollon, Hohokam and Salado cultures who built permanent homes and engaged in agriculture here. By the time the first Europeans arrived these cultures had disappeared and the San Pedro River was home to the Sobaipuri people.

Mogollon culture ethnic group

Mogollon culture is an archaeological culture of Native American peoples from Southern New Mexico and Arizona, Northern Sonora and Chihuahua, and Western Texas, a region known as Oasisamerica.

Salado culture

Salado culture, or Salado Horizon, was a human culture of the Tonto Basin in southeastern Arizona from approximately 1150 CE through the 15th century.

The Sobaipuri were one of many indigenous groups occupying Sonora and what is now Arizona at the time Europeans first entered the American Southwest. They were a Piman or O'odham group who occupied southern Arizona and northern Sonora in the 15th-19th centuries. They were a subgroup of the O'odham or Pima, surviving members of which include the residents of San Xavier del Bac which is now part of the Tohono O'odham Nation and the Akimel O'odham.

The first Europeans to visit the San Pedro River may have been the parties of Cabeza de Vaca, Fray Marcos de Niza or the Coronado expedition, and while no archeological evidence as yet exists of the passing of these groups, it has been fairly firmly established that the upper San Pedro was a widely recognized and utilized leg of the "Cibola Trail." [7] The Jesuit priest Eusebio Kino visited the villages along the San Pedro and Babocomari Rivers in 1692 and soon after introduced the first livestock to this area (if we assume that Coronado's livestock did not survive/breed). [8]

Francisco Vázquez de Coronado Spanish explorer of the American southwest

Francisco Vázquez de Coronado y Luján was a Spanish conquistador and explorer who led a large expedition from Mexico to present-day Kansas through parts of the southwestern United States between 1540 and 1542. Vázquez de Coronado had hoped to reach the Cities of Cíbola, often referred to now as the mythical Seven Cities of Gold, which is a term not invented until American gold-rush days in the 1800s. His expedition marked the first European sightings of the Grand Canyon and the Colorado River, among other landmarks. His name is often Anglicized as "Vasquez de Coronado".

Eusebio Kino Italian Jesuit missionary

Eusebio Francisco Kino was a Jesuit, missionary, geographer, explorer, cartographer and astronomer born in the Territory of the Bishopric of Trent, then part of the Holy Roman Empire. For the last 24 years of his life he worked in the region then known as the Pimería Alta, modern-day Sonora in Mexico and southern Arizona in the United States. He explored the region and worked with the indigenous Native American population, including primarily the Tohono O'Odham, Sobaipuri and other Upper Piman groups. He proved that the Baja California Peninsula is not an island by leading an overland expedition there. By the time of his death he had established 24 missions and visitas.

Babocomari River river in the United States of America

The Babocomari River is a major tributary of the upper San Pedro River in southeastern Arizona. The river begins in the Sonoita Basin near the community of Elgin, Arizona, and flows eastward for approximately 25 miles (40 km) before merging with the San Pedro, just south of the Fairbank Historic Townsite in the San Pedro Riparian National Conservation Area. The Babocomari drains an area of about 310 square miles (800 km2), including the northern Huachuca Mountains, the northwestern Canelo Hills, and the southern Mustang Mountains, and is one of three drainages of the Sonoita Basin, the other two being Sonoita Creek and Cienega Creek. Vegetation consists of riparian trees along the main channel and small marshy grasslands.

It is widely believed that by 1762 Apache depredation drove the Sobaipuri and Spanish out of the San Pedro Valley which then remained largely uninhabited until the early 1800s. [9] This, however, is not true as a recent study has shown. [10] In fact, documents state that not all the Sobaipuri left and in the 1780s Sobaipuri were noted still living along the river. Archaeology has confirmed additional Sobaipuri settlements along the middle San Pedro not mentioned in the documentary record throughout the 1800s.

The Apache are a group of culturally related Native American tribes in the Southwestern United States, which include the Chiricahua, Jicarilla, Lipan, Mescalero, Salinero, Plains and Western Apache. Distant cousins of the Apache are the Navajo, with which they share the Southern Athabaskan languages. There are Apache communities in Oklahoma, Texas, and reservations in Arizona and New Mexico. Apache people have moved throughout the United States and elsewhere, including urban centers. The Apache Nations are politically autonomous, speak several different languages and have distinct cultures.

Early American exploration of the San Pedro River, like most rivers in western North America, was driven by the pursuit of beaver pelts. James Ohio Pattie and his father led a party of fur trappers down the Gila River and then down the San Pedro River in 1826 which was so successful that he called the San Pedro the Beaver River. [2] The party was attacked by Apache Indians (probably the Aravaipa Band) at "Battle Hill" (probably Modern-day Malpais Hill) where they subsequently stashed and lost over 200 beaver pelts. [11] In the 19th century the river was a meandering stream with fluvial marshlands, riparian forest, Sporobolus grasslands and extensive beaver ponds. As the region experienced a rapid climate warming and drying, [12] (coincident with beaver removal and large-scale cattle introduction; correlation not directly established) the river down-cut and then widened in a process of arroyo formation observed on many rivers in the Southwest. [13] In 1895, J. A. Allen described a mammal collection from southeastern Arizona, "On the headwaters of the San Pedro, in Sonora, a colony of a dozen or more had their lodges up to 1893, when a trapper nearly exterminated them. All the streams in the White Mountains have beaver dams in them, although most of the animals have been trapped." [14] The beaver were finally extirpated by 1920s dynamiting of the beaver dams from soldiers from Fort Huachuca to prevent malaria.(citation?) By the mid-20th century the once perennial river only flowed during the rainy season and beaver, fluvial marshlands and Sporobolus grasslands were uncommon. [13] [15] Physician naturalist Edgar Alexander Mearns' 1907 Mammals of the Mexican boundary of the United States reported beaver (Castor canadensis) on the San Pedro River and the Babocomari River. [16] Mearns claimed that the San Pedro River beaver represented a new subspecies Castor canadensis frondator or "Sonora beaver" that ranged from Mexico up to Wyoming and Montana. [17]

North American beaver species of mammal

The North American beaver is one of two extant beaver species. It is native to North America and introduced to Patagonia in South America and some European countries. In the United States and Canada, the species is often referred to simply as "beaver", though this causes some confusion because another distantly related rodent, Aplodontia rufa, is often called the "mountain beaver". Other vernacular names, including American beaver and Canadian beaver, distinguish this species from the other extant beaver species, Castor fiber, which is native to Eurasia. The North American beaver is an official animal symbol of Canada and is the official state mammal of Oregon.

James Ohio Pattie was an American frontiersman and author from Kentucky. In 1831, Pattie collaborated with Timothy Flint to publish The Personal Narrative of James O. Pattie of Kentucky, which described his travels through what is now the Western United States and Mexico.

<i>Sporobolus</i> genus of plants

Sporobolus is a nearly cosmopolitan genus of plants in the grass family. The name Sporobolus means "seed-thrower", and is derived from Ancient Greek word σπόρος (spóros), meaning "seed", and the root of βάλλειν (bállein) "to throw", referring to the dispersion of seeds. Members of the genus are usually called dropseeds or sacaton grasses. They are typical prairie and savanna plants, occurring in other types of open habitat in warmer climates. At least one species is threatened with extinction, and another is extinct.


The San Pedro River is the central corridor of the Madrean Archipelago of "Sky Islands", high mountains with unique ecosystems different from the ecology of the Sonoran desert "seas" that surround it. [18]

More than 300 species of birds, 200 species of butterflies and 20 species of bats use this corridor as they migrate between South, Central and North America, including the imperiled yellow-billed cuckoo (Coccyzus americanus). More than 80 species of mammals, including jaguar (Panthera onca), coatimundi (Nasua narica), bats, beaver (Castor canadensis frontador), mountain lion, and many rodents; more than 65 species of reptiles and amphibians, including Sonoran tiger salamander ( Ambystoma mavortium stebbinsi) and western barking frog ( Eleutherodactylus augusti ). Remaining native fish species include the Gila chub (Gila intermedia) which is proposed for federal listing as endangered, and the longfin dace, desert sucker, roundtail chub, Sonora sucker, and speckled dace. The flora includes Fremont cottonwood (Populus fremontii), Goodding willow (Salix gracilistyla), velvet mesquite, sacaton, and the Federally endangered Huachuca water umbel (Lilaeopsis schaffneriana spp. recurva). [5]

In recent decades, rapid growth and population increases in southern Arizona has caused concern with this river. Several non-profit organizations have risen in recent years to raise awareness of this problem. The San Pedro Riparian National Conservation Area (SPRNCA) was established in 1988 to protect some forty miles of the upper San Pedro valley. [19] The Nature Conservancy also owns several preserves in the watershed, including the San Pedro River Preserve, Aravaipa Canyon Preserve, Muleshoe Ranch Preserve, Ramsey Canyon Preserve, and most recently, Rancho Los Fresnos. Rancho Los Fresnos, near the river's source, is the largest ciénega, an isolated desert spring or marsh, remaining in the San Pedro River watershed. Its protection is important as 99% of the ciénegas in the Southwest have been drained and destroyed. [20]

With large portions of the river dry much of the year, Bureau of Land Management (BLM) wildlife biologist Mark Fredlake proposed restoring beaver to the watershed to retain water flows into the dry season and to support re-growth of the historic riparian vegetation. [15] Riparian habitat covers only 1% of the Southwest but supports 50% of breeding bird species and is vital as a food source for migrating avifauna. [21] Fredlake reasoned that beaver dams would raise the water table, allowing groundwater to recharge the river's flow in the dry season. From 1999 to 2002, 19 beavers were released into the SPRNCA, a 40-mile (64 km) stretch of the river, in Cochise County. By 2006 there were more than 30 dams. The beavers also dispersed widely and rapidly. One beaver migrated to Aravaipa Canyon, more than 100 rivermiles away; another to the river's terminus at the Gila River, earning itself the moniker “the surfing beaver”; and others up into Mexico, building several dams along the river’s upper tributaries. The program was successful with measurable increases in bird diversity and formation of deep pools and lasting flows. [22] In 2008, flooding destroyed all the beaver dams and this was followed by a long drought. However, as in historic times the beaver seems well adapted to the San Pedro River, and the 2009 dam count is back above 30 with a current population between 30 and 120 beavers. [15] A short video reviews the use of re-introduced beaver to restore the river. [23] In the upper river, re-introduced beavers have created willow and pool habitat which has extended the range of the endangered Southwestern willow flycatcher (Empidonax trailii extimus) with the southernmost verifiable nest recorded there in 2005. [24]


The San Pedro drains an area of approximately 4,720 square miles (12,200 km2) in Cochise, Graham, Pima, and Pinal Counties. Its course traverses deep sedimentary basins flanked by the Huachuca, Mule, Whetstone, Dragoon, Rincon, Little Rincon, Winchester, Galiuro, Tortilla, and Santa Catalina Mountains. The San Pedro is fed by numerous tributaries, which in general, drain relatively short and steep catchments oriented more or less perpendicular to the mainstem. [25] For most of its length the San Pedro flows over sedimentary basin fill deposits, although it is bound by bedrock at the Tombstone Hills at Charleston and near Fairbank, “the Narrows” south of Cascabel, near Redington, and again at Dudleyville (Heindl, 1952). Two major tributaries, Babocomari River and Aravaipa Creek, each have extensive bedrock-lined stretches. Historically the San Pedro has been divided into upper and lower reaches at the Narrows. [26]

On May 27, 2011, a U.S. District judge ruled that Fort Huachaca's plan to pump 6,100 acre feet (7,500,000 m3) of groundwater without mitigation plans to replenish the San Pedro River flows failed to protect the endangered Southwestern willow flycatcher (Empidonax traillii) and the Huachuca water umbel so they could recover from their imperiled status. [27] The ruling was in response to a second lawsuit brought by the Center for Biological Diversity and the Maricopa Audubon Society. In 2002, in response to an earlier suit filed by the center, another judge tossed out an earlier Wildlife Service biological opinion that the water pumping could be mitigated. [4]

Mormon Battalion

The Mormon Battalion marched through the river valley in 1846, and the only battle the battalion fought in their journey to California occurred near the river. The battalion's presence had aroused curiosity among a number of wild cattle, and the bulls of these herds damaged wagons and injured mules. In response, the men shot dozens of the charging bulls. [28] Mormon settlers later returned to this area in 1877 to found a settlement that became St. David, and logged the Huachuca Mountains to provide lumber for building Fort Huachuca and Tombstone. [29]

Geology, paleontology

The San Pedro Valley is a site for Holocene mammal fossils because of the riparian environment.

In recent decades, the Arizona Geological Society has focused on the region, as well as researchers. Development pressures, recreation, and groundwater harvesting have led to recent concerns of protecting the region. A recent floodplain study focused on the Holocene floodplain alluvium and its history, over a 125-mile (201 km) stretch of the river to understand subground waterflow resources. [26]

See also

Related Research Articles

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Spanish missions in the Sonoran Desert

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Huachuca Mountains

The Huachuca Mountain range is part of the Sierra Vista Ranger District of the Coronado National Forest. The Huachuca Mountains are located in Cochise County, Arizona approximately 70 miles (110 km) south-southeast of Tucson and southwest of the city of Sierra Vista, Arizona. Included in this area is the highest peak in the Huachucas, Miller Peak, and the region of the Huachucas known as Canelo Hills in eastern Santa Cruz County. The mountains range in elevation from 3,934 feet (1,199 m) at the base to 9,466 feet (2,885 m) at the top of Miller Peak. The second highest peak in this range is Carr Peak, elevation 9,200 feet (2,804 m). The Huachuca Mountain area is owned principally by the USDA Forest Service (41%), the U.S. Army (20%), and private land (32%). Sierra Vista is the main population center.

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San Pedro Riparian National Conservation Area

The San Pedro Riparian National Conservation Area contains nearly 57,000 acres (23,000 ha) of public land in Cochise County, Arizona, between the international border with Mexico and St. David, Arizona. The riparian area, where some 40 miles (64 km) of the upper San Pedro River meanders, was designated by Congress as a Riparian National Conservation Area on November 18, 1988.

Aravaipa Creek river in the United States of America

Aravaipa Creek is a major drainage between three mountain ranges in southwest Graham County, Arizona --- the Galiuro Mountains, the Santa Teresa Mountains and the Pinaleno Mountains. These mountains are part of the high altitude Madrean Sky Islands located in southern Arizona and New Mexico in the United States, and northern Sonora and Chihuahua states in Mexico.

Little Rincon Mountains

The Little Rincon Mountains are a small range of mountains, lying to the east of the Rincon Mountains, at Tucson, of eastern Pima County, Arizona. The range is located in northwest Cochise County and is part of the western border of the San Pedro River and Valley, the major valley and river of western Cochise County. The river is northward flowing to meet the Gila River; its headwaters are south of the US-Mexico border in northern Sonora. A small part of the Little Rincon range's southwest lies in Pima County.


  1. 1 2 3 U.S. Geological Survey Geographic Names Information System: San Pedro River
  2. 1 2 David J. Weber (2005). The Taos Trappers: The Fur Trade in the Far Southwest, 1540-1846. Norman, Oklahoma: University of Oklahoma Press. p. 96. ISBN   978-0-8061-1702-7 . Retrieved May 31, 2010.
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  24. Johnson, Glenn E., and van Riper III, Charles (2014). Effects of reintroduced beaver (Castor canadensis) on riparian bird community structure along the upper San Pedro River, southeastern Arizona and northern Sonora, Mexico (PDF). U.S. Geological Survey. Retrieved 2015-01-23.
  25. Huckleberry G, Lite SJ, Katz GL, Pearthree P (2009). Stromberg JS, Tellman B, eds. Fluvial Geomorphology in Ecology and Conservation of the San Pedro River. Tucson,Arizona: University of Arizona Press.
  26. 1 2 Joseph P. Cook; et al. (2009). Mapping of Holocene River Alluvium along the San Pedro River, Aravaipa Creek, and Babocomari River, Southeastern Arizona (PDF) (Report). Arizona Geological Society . Retrieved 2015-01-01. Document repository for report map files
  27. "Court Rejects Fort Huachuca's Groundwater Pumping Plan". Center for Biological Diversity. Retrieved September 3, 2017.
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Geology, groundwater, paleontology