The San Pedro River is a northward-flowing
stream
A stream is a continuous body of water, body of surface water Current (stream), flowing within the stream bed, bed and bank (geography), banks of a channel (geography), channel. Depending on its location or certain characteristics, a stream ...
originating about south of the international border south of
Sierra Vista, Arizona
Sierra Vista is a city in Cochise County, Arizona, United States. According to the 2020 Census, the population of the city is 45,308, and is the 27th most populous city in Arizona. The city is part of the Sierra Vista-Douglas Metropolitan Are ...
, in
Cananea Municipality
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 .
Population
The population of the municipality of Cananea was 35,892. Most of the popu ...
,
Sonora
Sonora (), officially Estado Libre y Soberano de Sonora ( en, Free and Sovereign State of Sonora), is one of the 31 states which, along with Mexico City, comprise the Administrative divisions of Mexico, Federal Entities of Mexico. The state is d ...
,
Mexico
Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...
. The river starts at the confluence of other streams (Las Nutrias and El Sauz) just east of Sauceda, Cananea. Within Arizona, the river flows north through
Cochise County
Cochise County () is a county in the southeastern corner of the U.S. state of Arizona. It is named after the Native American chief Cochise.
The population was 125,447 at the 2020 census. The county seat is Bisbee and the most populous city is ...
,
Pima County
Pima County ( ) is a county in the south central region of the U.S. state of Arizona. As of the 2020 census, the population was 1,043,433, making it Arizona's second-most populous county. The county seat is Tucson, where most of the population ...
,
Graham County, and
Pinal County
Pinal County is in the central part of the U.S. state of Arizona. According to the 2020 census, the population of the county was 425,264, making it Arizona's third-most populous county. The county seat is Florence. The county was founded in 187 ...
to its confluence with the
Gila River
The Gila River (; O'odham ima Keli Akimel or simply Akimel, Quechan: Haa Siʼil, Maricopa language: Xiil) is a tributary of the Colorado River flowing through New Mexico and Arizona in the United States. The river drains an arid watershed of n ...
, at
Winkelman, Arizona
Winkelman is a town in Gila and Pinal counties in Arizona, United States. According to the 2010 census, the population of the town was 353, all of whom lived in Gila County.
History
The community was named after Peter Winkelman, a local catt ...
. It is the last major, undammed desert river in the
American Southwest
The Southwestern United States, also known as the American Southwest or simply the Southwest, is a geographic and cultural region of the United States that generally includes Arizona, New Mexico, and adjacent portions of California, Colorado, N ...
,
and 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 almost 300 species of migrating birds.
History
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. Some Clovis sites of note are the
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.
In 1952, Ed Lehner discovered extinct mammoth bone fragments on ...
, the Murray Springs Clovis Site and the
Naco Mammoth-Kill Site
The Naco Mammoth Kill Site is an archaeological site in southeast Arizona, 1 mile northwest of Naco in Cochise County. The site was reported to the Arizona State Museum in September 1951 by Marc Navarrete, a local resident, after his father fou ...
.
The hunter-gatherer,
Cochise culture next made this area home between about 5000 to 200 BC. Followed by the more advanced
Mogollon,
Hohokam
Hohokam () was a culture in the North American Southwest in what is now part of Arizona, United States, and Sonora, Mexico. It existed between 300 and 1500 AD, with cultural precursors possibly as early as 300 BC. Archaeologists disagree about ...
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
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 (the Pimer ...
people.
The first Europeans to visit the San Pedro River may have been the parties of
Cabeza de Vaca
In Mexican cuisine, ''cabeza'' (''lit.'' 'head') is the meat from a roasted head of an animal, served as taco or burrito fillings.
Typically, the whole head is placed on a steamer or grill, and customers may ask for particular parts of the body ...
,
Fray Marcos de Niza
Marcos de Niza, OFM (or Marco da Nizza; 25 March 1558) was a Savoyard missionary and Franciscan friar from the County of Nice. He is credited with being the first European in what is now the State of Arizona in the United States. He is most kn ...
or the
Coronado Coronado may refer to:
People
* Coronado (surname)
* Francisco Vázquez de Coronado (1510–1554), Spanish explorer often referred to simply as "Coronado"
* Coronado Chávez (1807–1881), President of Honduras from 1845 to 1847
Places United ...
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." The Jesuit priest
Eusebio Kino
Eusebio Francisco Kino ( it, Eusebio Francesco Chini, es, Eusebio Francisco Kino; 10 August 1645 – 15 March 1711), often referred to as Father Kino, was a Tyrolean Jesuit, missionary, geographer, explorer, cartographer and astronomer born i ...
visited the villages along the San Pedro and
Babocomari River
The Babocomari River is a major tributary of the upper San Pedro River (Arizona), San Pedro River in southeastern Arizona. The river begins in the Sonoita Basin near the community of Elgin, Arizona, and flows eastward for approximately before me ...
s in 1692 and soon after introduced the first livestock to this area (assuming Coronado's livestock did not survive/breed).
It is widely believed that by 1762
Apache
The Apache () are a group of culturally related Native American tribes in the Southwestern United States, which include the Chiricahua, Jicarilla, Lipan, Mescalero, Mimbreño, Ndendahe (Bedonkohe or Mogollon and Nednhi or Carrizaleño an ...
depredation drove the Sobaipuri and Spanish out of the San Pedro Valley which then remained largely uninhabited until the early 1800s. This, however, is not true as a recent study has shown. 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.
Early American exploration of the San Pedro River, like most rivers in western North America, was driven by the pursuit of
beaver
Beavers are large, semiaquatic rodents in the genus ''Castor'' native to the temperate Northern Hemisphere. There are two extant species: the North American beaver (''Castor canadensis'') and the Eurasian beaver (''C. fiber''). Beavers ar ...
pelts.
James Ohio Pattie
James Ohio Pattie (c. 1804Hafen (1966), p. 232 – c. 1850) was an American frontiersman and author from Kentucky. Between 1824 and 1830, Pattie took part in a series of fur trapping and trading expeditions, traveling through the American West a ...
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.
[ 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.
The ]Mormon Battalion
The Mormon Battalion was the only religious unit in United States military history in federal service, recruited solely from one religious body and having a religious title as the unit designation. The volunteers served from July 1846 to July ...
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. Mormon
Mormons are a religious and cultural group related to Mormonism, the principal branch of the Latter Day Saint movement started by Joseph Smith in upstate New York during the 1820s. After Smith's death in 1844, the movement split into several ...
settlers later returned to this area in 1877 to found a settlement that became St. David
Saint David ( cy, Dewi Sant; la, Davidus; ) was a Welsh bishop of Mynyw (now St Davids) during the 6th century. He is the patron saint of Wales. David was a native of Wales, and tradition has preserved a relatively large amount of detail ab ...
, and logged the Huachuca Mountains
The Huachuca Mountains are part of the Sierra Vista Ranger District of the Coronado National Forest in Cochise County in southeastern Arizona, approximately south-southeast of Tucson and southwest of the city of Sierra Vista. Included in this ar ...
to provide lumber for building Fort Huachuca
Fort Huachuca is a United States Army installation, established on 3 March 1877 as Camp Huachuca. The garrison is now under the command of the United States Army Installation Management Command. It is in Cochise County in southeast Arizona, appr ...
and Tombstone.
In the 19th century the river was a meandering stream with fluvial marshlands, riparian forest, ''Sporobolus
''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 (), meaning "seed", and the root of () "to throw", referring to the dispersion of ...
'' grasslands and extensive beaver
Beavers are large, semiaquatic rodents in the genus ''Castor'' native to the temperate Northern Hemisphere. There are two extant species: the North American beaver (''Castor canadensis'') and the Eurasian beaver (''C. fiber''). Beavers ar ...
ponds. As the region experienced a rapid climate warming and drying, (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. 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." The beaver were finally extirpated by 1920s dynamiting of the beaver dams from soldiers from Fort Huachuca
Fort Huachuca is a United States Army installation, established on 3 March 1877 as Camp Huachuca. The garrison is now under the command of the United States Army Installation Management Command. It is in Cochise County in southeast Arizona, appr ...
to prevent malaria. By the mid-20th century the once perennial river only flowed during the rainy season and beaver, fluvial marshlands and Sporobolus grasslands were uncommon. Physician naturalist Edgar Alexander Mearns
Edgar Alexander Mearns (September 11, 1856 – November 1, 1916) was an American surgeon, ornithologist and field naturalist. He was a founder of the American Ornithologists' Union.
Life
Mearns was born in n Highland Falls, New York to Al ...
' 1907 ''Mammals of the Mexican boundary of the United States'' reported beaver
Beavers are large, semiaquatic rodents in the genus ''Castor'' native to the temperate Northern Hemisphere. There are two extant species: the North American beaver (''Castor canadensis'') and the Eurasian beaver (''C. fiber''). Beavers ar ...
(''Castor canadensis'') on the San Pedro River and the Babocomari River. 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.
Ecology
The San Pedro River is the central corridor of the Madrean Archipelago of "Sky Islands
Sky islands are isolated mountains surrounded by radically different lowland environments. The term originally referred to those found on the Mexican Plateau, and has extended to similarly isolated high-elevation forests. The isolation has s ...
", high mountains with unique ecosystems different from the ecology of the Sonoran desert "seas" that surround it.
More than 300 species of birds
Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...
nest in by the river or use this corridor as they migrate between South
South is one of the cardinal directions or Points of the compass, compass points. The direction is the opposite of north and is perpendicular to both east and west.
Etymology
The word ''south'' comes from Old English ''sūþ'', from earlier Pro ...
, Central
Central is an adjective usually referring to being in the center of some place or (mathematical) object.
Central may also refer to:
Directions and generalised locations
* Central Africa, a region in the centre of Africa continent, also known as ...
and North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
. This includes the yellow-billed cuckoo
The yellow-billed cuckoo (''Coccyzus americanus'') is a cuckoo. Common folk-names for this bird in the southern United States are rain crow and storm crow. These likely refer to the bird's habit of calling on hot days, often presaging rain or th ...
(''Coccyzus americanus''). The area provides for more than 80 species of mammals, including jaguar
The jaguar (''Panthera onca'') is a large cat species and the only living member of the genus '' Panthera'' native to the Americas. With a body length of up to and a weight of up to , it is the largest cat species in the Americas and the th ...
(''Panthera onca''), coatimundi (''Nasua narica''), beaver
Beavers are large, semiaquatic rodents in the genus ''Castor'' native to the temperate Northern Hemisphere. There are two extant species: the North American beaver (''Castor canadensis'') and the Eurasian beaver (''C. fiber''). Beavers ar ...
(''Castor canadensis frontador''), 20 species of bat
Bats are mammals of the order Chiroptera.''cheir'', "hand" and πτερόν''pteron'', "wing". With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most bi ...
s and several types of rodents. There are also over 65 species of reptiles and amphibians, among them Sonoran tiger salamander ('' Ambystoma mavortium stebbinsi'') and western barking frog ('' Eleutherodactylus augusti''). Some notable fish species native to the river are the endangered Gila chub
The Gila chub (''Gila intermedia'') is a species of ray-finned fish in the family Cyprinidae.
It is found in Mexico and the United States. The Gila chub is closely related to the roundtail chub.Rinne, J.N. 1969. ''Cyprinid fishes of the genus G ...
(''Gila intermedia''), both the longfin
The longfins, also known as roundheads or spiny basslets, are a family, Plesiopidae, which were formerly placed in the order Perciformes but are now regarded as being ''incertae sedis'' in the subseries Ovalentaria in the clade Percomorpha. They ...
and speckled dace
The speckled dace (''Rhinichthys osculus''), also known as the spotted dace and the carpita pinta, is a member of the minnow family. It is found in temperate freshwater in North America, from Sonora, Mexico to British Columbia, Canada.
Canada is ...
, Sonora sucker
The Sonora Sucker (Gila Sucker), ''Catostomus insignis'', is a medium-sized catostomid
The Catostomidae are the suckers of the order Cypriniformes, with about 78 species in this family of freshwater fishes. The Catostomidae are almost exclu ...
and desert sucker
The desert sucker or Gila Mountain sucker (''Catostomus clarkii''), is a freshwater species of ray-finned fish in the sucker family, endemic to the Great Basin and the Colorado River Basin in the United States. It inhabits rapids and fast-flowi ...
, and the roundtail chub
The roundtail chub (''Gila robusta'') is a cyprinid fish in the genus '' Gila'', of southwestern North America. It is native to the Colorado River drainage basin, including the Gila River and other tributaries, and in several other rivers. It i ...
. The flora includes Fremont cottonwood
''Populus fremontii'', commonly known as Frémont's cottonwood, is a cottonwood (and thus a poplar) native to riparian zones of the Southwestern United States and northern through central Mexico. It is one of three species in ''Populus'' sect. ...
(''Populus fremontii''), Goodding willow (''Salix gooddingii''), velvet mesquite
''Prosopis velutina'', commonly known as velvet mesquite, is a small to medium-sized tree. It is a legume adapted to a dry, desert climate. Though considered to be a noxious weed in states outside its natural range, it plays a vital role in the ...
trees, and the Huachuca water umbel (''Lilaeopsis schaffneriana spp. recurva''), Federally listed as endangered.[
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
The San Pedro Riparian National Conservation Area (San Pedro Riparian NCA; SPRNCA) contains nearly of public land in Cochise County, Arizona, between the international border with Mexico and St. David, Arizona. The riparian area, where some of ...
(SPRNCA) was established in 1988 to protect some forty miles of the upper San Pedro valley. The Nature Conservancy
The Nature Conservancy (TNC) is a global environmental organization headquartered in Arlington, Virginia. it works via affiliates or branches in 79 countries and territories, as well as across every state in the US.
Founded in 1951, The Natu ...
also owns several preserves in the watershed, including the San Pedro River Preserve
The San Pedro River Preserve is a Nature Conservancy preserve in Dudleyville, Arizona.
The Preserve comprises of deeded land along the San Pedro River acquired for the protection of southwestern willow flycatcher
The willow flycatcher ('' ...
, 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
A ciénega (also spelled ciénaga) is a wetland system unique to the American Southwest. Ciénagas are alkaline, freshwater, spongy, wet meadows with shallow-gradient, permanently saturated soils in otherwise arid landscapes that often occupy ...
, 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.
With large portions of the river dry much of the year, Bureau of Land Management
The Bureau of Land Management (BLM) is an agency within the United States Department of the Interior responsible for administering federal lands. Headquartered in Washington DC, and with oversight over , it governs one eighth of the country's la ...
(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.[ 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. Fredlake reasoned that ]beaver dam
A beaver dam or beaver impoundment is a dam built by beavers to create a pond which protects against predators such as coyotes, wolves and bears, and holds their food during winter. These structures modify the natural environment in such a way t ...
s 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 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. 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.[ A short video reviews the use of re-introduced beaver to restore the river. In the upper river, re-introduced beavers have created willow and pool habitat which has extended the range of the endangered ]Southwestern willow flycatcher
The willow flycatcher (''Empidonax traillii'') is a small insect-eating, neotropical migrant bird of the tyrant flycatcher family. There are four subspecies of the willow flycatcher currently recognized, all of which breed in North America (inc ...
(''Empidonax trailii extimus'') with the southernmost verifiable nest recorded there in 2005.
Watershed
The San Pedro drains an area of approximately in Cochise, Graham, Pima, and Pinal Counties. Its course traverses deep sedimentary basins flanked by the Huachuca
''Echinopsis pachanoi'' (syn. ''Trichocereus pachanoi'')—known as San Pedro cactus—is a fast-growing columnar cactus native to the Andes Mountains at in altitude. It is found in Argentina, Bolivia, Colombia, Chile, Ecuador and Peru, and ...
, Mule
The mule is a domestic equine hybrid between a donkey and a horse. It is the offspring of a male donkey (a jack) and a female horse (a mare). The horse and the donkey are different species, with different numbers of chromosomes; of the two pos ...
, Whetstone, Dragoon
Dragoons were originally a class of mounted infantry, who used horses for mobility, but dismounted to fight on foot. From the early 17th century onward, dragoons were increasingly also employed as conventional cavalry and trained for combat w ...
, Rincon, Little Rincon, Winchester
Winchester is a City status in the United Kingdom, cathedral city in Hampshire, England. The city lies at the heart of the wider City of Winchester, a local government Districts of England, district, at the western end of the South Downs Nation ...
, Galiuro, Tortilla
A tortilla (, ) is a thin, circular unleavened flatbread originally made from maize hominy meal, and now also from wheat flour. The Aztecs and other Nahuatl speakers called tortillas ''tlaxcalli'' (). First made by the indigenous peoples of Me ...
, and Santa Catalina Mountains
The Santa Catalina Mountains, commonly referred to as the Catalina Mountains or the Catalinas, are north and northeast of Tucson in Arizona, United States, on Tucson's north perimeter. The mountain range is the most prominent in the Tucson area, w ...
. 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. 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
Aravaipa Creek is a 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 ...
, each have extensive bedrock-lined stretches. Historically the San Pedro has been divided into upper and lower reaches at the Narrows.[
On May 27, 2011, a U.S. District judge ruled that Fort Huachaca's plan to pump of groundwater without mitigation plans to replenish the San Pedro River flows failed to protect the endangered ]Southwestern willow flycatcher
The willow flycatcher (''Empidonax traillii'') is a small insect-eating, neotropical migrant bird of the tyrant flycatcher family. There are four subspecies of the willow flycatcher currently recognized, all of which breed in North America (inc ...
(''Empidonax traillii'') and the Huachuca water umbel so they could recover from their imperiled status. The ruling was in response to a second lawsuit brought by the Center for Biological Diversity
The Center for Biological Diversity is a nonprofit membership organization known for its work protecting endangered species through legal action, scientific petitions, creative media and grassroots activism. It was founded in 1989 by Kieran Suckl ...
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.[
]
Geology, paleontology
The San Pedro Valley
The San Pedro Valley of western Cochise County, Arizona, is a , mostly north–south valley, trending northwesterly. The San Pedro River drains from the state of Sonora, Mexico, through Benson, Arizona, and the southeast of the Rincon Mountains. ...
is a site for Holocene
The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togethe ...
mammal fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
s because of the riparian
A riparian zone or riparian area is the interface between land and a river or stream. Riparian is also the proper nomenclature for one of the terrestrial biomes of the Earth. Plant habitats and communities along the river margins and banks ar ...
environment.
In recent decades, the Arizona Geological Society
The Arizona Geological Society (AGS) is a non-profit scientific organization founded in 1948 whose purpose is to promote and encourage interest in the science of geology and in the geology of the State of Arizona. The Society holds monthly meetin ...
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
A floodplain or flood plain or bottomlands is an area of land adjacent to a river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge.Goudi ...
study focused on the Holocene floodplain alluvium
Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Alluv ...
and its history, over a stretch of the river to understand subground waterflow resources.[ Document repository for report map files]
/ref>
Picture gallery
Pipevine Swallowtail Butterfly San Pedro House River Sierra Vista AZ 2018-08-29 09-12-25 (48038782687).jpg, Pipevine Swallowtail Butterfly
Pipevine Swallowtail San Pedro House & River Sierra Vista AZ 2019-07-25 10-25-48 (48441573357).jpg, Pipevine Swallowtail Butterfly
Pipilo chlorurus -Arizona, USA-8.jpg, Green-tailed towhee (''Pipilo chlorurus'')
Vireo bellii -Arizona, USA-8.jpg, Bell's vireo(''Vireo bellii'')
River san pedro - panoramio.jpg
San Pedro - panoramio (3).jpg
San Pedro - panoramio (4).jpg
San pedro - panoramio.jpg
San Pedro House & River Sierra Vista AZ 2018-08-10 09-07-46 (29447176047).jpg
San Pedro Riparian NCA 2.jpg
San Pedro Riparian NCA 3.jpg
San Pedro River Fairbank Arizona 2014.JPG
San Pedro RNCA - Fairbanks AZ 2018-07-21 12-04-57 (41979141630).jpg
San Pedro Snowy Sunrise (46299374315).jpg
See also
*San Pedro Riparian National Conservation Area
The San Pedro Riparian National Conservation Area (San Pedro Riparian NCA; SPRNCA) contains nearly of public land in Cochise County, Arizona, between the international border with Mexico and St. David, Arizona. The riparian area, where some of ...
*List of Arizona rivers
List of rivers in Arizona (U.S. state), sorted by name.
By drainage basin
This list is arranged by drainage basin, with respective tributaries indented under each larger stream's name.
Colorado River
*Colorado River—(downstream-to-upstr ...
*List of tributaries of the Colorado River
The principal tributaries of the Colorado River of North America are the Gila River, the San Juan River, the Green River, and the Gunnison River.
Tributary tree
The following is a tree demonstrating the points at which the major and minor trib ...
From Desert to Sky Islands
References
External links
This page explores many features of the valley
Aviatlas: Birding along San Pedro
Geology, groundwater, paleontology
* ttp://arizonageology.blogspot.com/2009/08/geology-of-san-pedro-river-aravaipa.html Anti-development, (Bypass-route)
{{authority control
Rivers of Arizona
Rivers of Sonora
International rivers of North America
Rivers of Cochise County, Arizona
Rivers of Graham County, Arizona
Rivers of Pima County, Arizona
Rivers of Pinal County, Arizona
San Pedro Valley (Arizona)
Tributaries of the Gila River