Colorado River Delta

The Colorado River Delta is the region where the Colorado River flows into the Gulf of California (also known as the Sea of Cortez). The delta is part of a larger geologic region called the Salton Trough.[2] Historically, the interaction of the river's flow and the ocean's tide created a dynamic environment, supporting freshwater, brackish, and saltwater species. Within the delta region, the river split into multiple braided channels and formed complex estuary and terrestrial ecosystems. Use of water upstream and the accompanying reduction of fresh water flow has resulted in loss of most of the wetlands of the area, as well as drastic changes to the aquatic ecosystems. However, a scheme is currently in place which aims to rejuvenate the wetlands by releasing a pulse of water down the river delta.[3]

Designations
Official nameHumedales del Delta del Río Colorado
Designated20 March 1996
Reference no.814[1]
ColoradoRiverDelta ISS009-E-09839
Colorado River Delta as seen from space (2004); Isla Montague is the large island in the center.

Natural history

Until the early 20th century, the Colorado River ran free from its headwaters in the Rocky Mountains of Colorado southwest into Mexico, where it flowed into the Gulf of California. Significant quantities of nourishing silt from throughout the Colorado River Basin were carried downstream, creating the vast Colorado River Delta.

Prior to the construction of major dams along its route, the Colorado River fed one of the largest desert estuaries in the world. Spread across the northernmost end of the Gulf of California, the Colorado River delta's vast riparian, freshwater, brackish, and tidal wetlands once covered 7,810 km² (1,930,000 acres) and supported a large population of plant, bird, aquatic, and terrestrial life. Because most of the river's flow reached the delta at that time, its freshwater, silt, and nutrients helped create and sustain a complex system of estuarial wetlands that provided feeding and nesting grounds for birds, and spawning habitat for fish and marine mammals. In contrast to the surrounding Sonoran Desert, the Colorado River delta's abundance was striking.

Human history

Early history

Early explorers reported jaguars, beavers, deer, and coyotes in the delta, in addition to the abundance of waterfowl, fish, and other marine and estuary organisms (Spamer, 1990; {Aldo Leopold, 1948}). Early explorers also encountered local people known as the Cucapá, or the people of the river. The Cucapá are descendants of the Yuman-speaking Native Indigenous peoples of the Americas and have inhabited the delta for nearly a thousand years. Spanish explorer Hernando de Alarcón made the first recorded contact with the Cucapá in 1540 and reported seeing many thousands. The Cucapá used the delta floodplain extensively, for harvesting Palmer's saltgrass (Distichlis palmeri), a wild grain which grows in salty soil; and for cultivating maize (corn), beans, and squash.

On the map the Delta was bisected by the river, but in fact the river was nowhere and everywhere, for he could not decide which of a hundred green lagoons offered the most pleasant and least speedy path to the Gulf.

— Aldo Leopold, from A Sand County Almanac, describing the Colorado River Delta as it existed in 1922

After dam construction

Today, conditions in the delta have changed. Like other desert river deltas, such as the Nile Delta and the Indus River Delta, the Colorado River delta has been greatly altered by human activity. Decades of dam construction and water diversions in the United States and Mexico has reduced the delta to a remnant system of small wetlands and brackish mudflats.[4] As reservoirs filled behind dams and captured floodwaters, freshwater could no longer reach the delta.

The construction of Hoover Dam in the 1930s marked the beginning of the modern era for the Colorado River Delta. For six years, as Lake Mead filled behind the dam, virtually no freshwater reached the delta. Even spring flooding was captured. This ecologically devastating event was repeated from 1963 to 1981 as Lake Powell filled behind the Glen Canyon Dam. With these reservoirs now filled, the dams are used to regulate flow so that water can be reliably apportioned among the users of the Colorado River Compact, and its use maximized. Most flood flows can be contained, regulated, and added to the river's capacity to sustain the Western United States' urban centers and agriculture. Floodwaters are released only when the Bureau of Reclamation, the agency managing the dams, predicts flows that exceed the system's capacity for use and storage.

The loss of freshwater flows to the delta over the twentieth century has reduced delta wetlands to about 5 percent of their original extent, and non-native species have compromised the ecological health of much of what remains. Stress on ecosystems has allowed invasive plants to out-compete native species along Colorado River riparian areas. Native forests of cottonwood and willow have yielded to sand and mudflats dominated by the nonnative tamarisk (also known as salt cedar), arrowweed, and iodinebush, a transformation that has decreased the habitat value of the riparian forest (Briggs and Cornelius, 1997).

High flows in 1980s

Full reservoir conditions coupled with a series of flood events throughout the 1980s and early 1990s resulted in flood releases that reached the delta. These flows reestablished an active floodplain and revegetated many areas of the floodplain within irrigation and flood control levels, and helped to reestablish riparian forests.

Ecology

The delta supports a variety of wildlife, including several threatened and endangered species. Mexico's Environmental Regulations on Endangered Species lists the following endangered species found in the terrestrial and aquatic regions of the delta (Diario Officiel, 1994):

  • the desert pupfish, also listed as an endangered species in the U.S., the largest remaining population anywhere is in La Ciénega de Santa Clara
  • the Yuma rail, also listed as endangered in the U.S.
  • the bobcat
  • the vaquita porpoise, the world's smallest marine cetacean, listed as a species of special concern by the U.S. Marine Mammal Commission. There are thought to be 12 vaquita left in the world.[5]
  • the totoaba, now virtually extinct, a steel-blue fish that grows up to 2 m (7 ft) and 136 kg (300 pounds), and once supported a commercial fishery that closed in 1975 (Postel et al., n.d.).
  • the Colorado delta clam, once an extremely abundant species and important in the trophic dynamics of the ecosystem.

Although not extensively studied, the delta's significance for migratory birds is indisputable, as it is the principal freshwater marsh in the region. A total of 358 bird species have been documented in the Colorado River Delta and upper Gulf of California region. From these, two are listed as endangered, six as threatened, and sixteen are under special protection in Mexico. Two wintering species and five breeding species have been locally extirpated, including the southwestern willow flycatcher, the Fulvous whistling duck, and the sandhill crane.

Biosphere reserve

The Gulf of California lies within the jurisdictional boundaries of Mexico and its states of Baja California and Sonora. In 1974, the Mexican government designated portions of the upper Gulf and lower Colorado River Delta as a reserve zone.

The United Nations Educational, Scientific and Cultural Organisation (UNESCO) designated over 12,000 km² (3 million acres) of Upper Gulf of California and Colorado River Delta Biosphere Reserve as a Biosphere Nature reserve in June 1993. Within this 12,000 km² (3 million acres), over 4,000 km² (1 million acres) nearest the Colorado River Delta are designated as the Reserve "core area", with the remaining 8,000 km² (2 million acres) of open water and shoreline designated as a "buffer area".[6]

UNESCO considers areas for designation as Biosphere Reserves only after the nation in which the site is located submits a nomination. Once designated, Biosphere Reserves remain under the sovereign jurisdiction of the countries where they are located. Federal Mexican governmental agencies with administrative authority over the Biosphere Reserve include the National Commission of Protected Natural Areas (CONANP) and the Secretary of the Environment, Natural Resources and Fisheries (SEMARNAP) .

In addition to designation as a Biosphere Reserve, 2500 km² (618,000 acres) within Colorado River Delta (Humedales del Delta del Río Colorado) are designated as a Ramsar Wetland under the U.N. Convention on Wetlands. Ramsar Wetlands are wetlands of international importance in terms of their ecology, botany, zoology, limnology or hydrology. The U.N. designation is considered following a nomination by the nation in which the site is located.

View

The Salton Trough region from orbit
The region from orbit.[7]

References

  1. ^ "Humedales del Delta del Río Colorado". Ramsar Sites Information Service. Retrieved 25 April 2018.
  2. ^ David A. Alles, ed., "Geology of the Salton Trough", Western Washington University, Edited May 28, 2005.
  3. ^ Water, wildlife surge back into once-parched Colorado River delta
  4. ^ Clifford, Frank (September 21, 2007), "A trickle of water might save estuary", Los Angeles Times
  5. ^ "Only 12 vaquita porpoises remain, watchdog group reports". news.mongabay.com. Retrieved 10 April 2018.
  6. ^ "Archived copy". Archived from the original on 2012-04-08. Retrieved 2010-07-04.CS1 maint: Archived copy as title (link) . accessed 7/4/2010
  7. ^ Salton Trough July 29, 2013

External links

Coordinates: 31°44′N 114°40′W / 31.74°N 114.66°W

Alto Golfo de California Biosphere Reserve

Alto Golfo de California Biosphere Reserve is a UNESCO Biosphere Reserve located in the state of Sonora in extreme northwestern Mexico. The 1,652,110 hectares (6,378.8 sq mi) reserve comprises the El Pinacate y Gran Desierto reserve and the Bahia Adair on the Gulf of California border. Geological volcanic formations with craters, dunes, oasis and beaches, and the diversity of plant associations determine its special landscape. The reserve was established in 1993 by the President of Mexico as Reserva de la Biosfera del Alto Golfo de California y Delta del Río Colorado (Upper Gulf of California and Colorado River Delta Biosphere Reserve) and extended in 1995.As of 1990, 129,516 inhabitants live in the transition and buffer areas in ejidos or communal properties, primarily engaged in agriculture, forestry, mineral extractions and cattle raising located mainly in the coastal areas. One of the most important economic activities in the transition areas is the existence of international enterprises (maquiladoras), in San Luis Río Colorado, which engage 5,880 people living in the urban villages.The reserve is managed by the Municipality of Mexicali in the State of Baja California and the Municipalities of Puerto Peñasco and San Luis Río Colorado in the State of Sonora.

Chenier

A chenier or chénier is a sandy or shelly beach ridge that is part of a strand plain, called a “chenier plain,” consisting of cheniers separated by intervening mud-flat deposits with marsh and swamp vegetation. Cheniers are typically 1 to 6 m high, tens of km long, hundreds of metres wide, and often wooded. Chenier plains can be tens of km wide. Cheniers and associated chenier plains are associated with shorelines characterized by generally low wave energy, low gradient, muddy shorelines, and abundant sediment supply. The name is derived from the French word for wood, “chêne,” meaning oak, which grows on chenier ridges within southwest Louisiana.

Colorado I (sternwheeler)

Colorado, was a stern-wheel paddle-steamer, the third steamboat on the Colorado River, and first stern-wheel steamboat put on that river, in December 1855.

The Colorado was a 120 foot long, stern-wheel steamboat, built for the George A. Johnson & Company in San Francisco by John G. North a well known builder of steamboats in California. It was equipped with an 80-horsepower steam engine capable of carrying up to 70 tons of cargo while drawing only 2 feet of water. North subsequently disassembled and shipped in sections by sea to the estuary of the Colorado River. There North unloaded, reassembled and launched in it in December, 1855 under the command of Captain Isaac Polhamus. More powerful than Johnson's first steamboat, the side-wheeler General Jesup, it made faster runs between the estuary and Fort Yuma with larger cargoes against strong currents in the river. As a stern-wheeler it was narrower, with a lesser draft, so was better equipped to avoid or pass over sandbars and through the narrower sloughs that sometimes occurred on the ever-changing course of the old Colorado River Delta. Besides running cargoes between Fort Yuma from the estuary, it was used with the General Jesup to carry supplies and soldiers up river during the 1858-59 Mohave War and for the establishment of Fort Mohave. The steamboats were engaged to carry the troops and supplies up river for at $500 per day.At the end of its service life the first Colorado's hull was dismantled in April, 1862. Its engine and boiler was removed and used to equip the new, larger stern-wheeler Colorado that was built and launched under the guns of Fort Yuma, in Arizona City, for fear of an attack by Confederate raiders.

Coyote Mountains

The Coyote Mountains are a small mountain range in San Diego and Imperial Counties in southern California. The Coyotes form a narrow ESE trending 2 mi (3.2 km) wide range with a length of about 12 mi (19 km). The southeast end turns and forms a 2 mi (3.2 km) north trending "hook". The highest point is Carrizo Mountain on the northeast end with an elevation of 2,408 feet (734 m). Mine Peak at the northwest end of the range has an elevation of 1,850 ft (560 m). Coyote Wash along I-8 along the southeast margin of the range is 100 to 300 feet in elevation. Plaster City lies in the Yuha Desert about 5.5 mi (8.9 km) east of the east end of the range.To the southeast lie the Jacumba Mountains and the Volcanic Hills. To the north and northeast lie the Carrizo Badlands, the Carrizo Valley and the Fish Creek Mountains. The west end of the range is within the Anza-Borrego Desert State Park and the east end is within the Carrizo Naval Gunnery Range. The international border lies approximately 11 mi (18 km) south of the southeast margin of the range.The range consists of sand dunes left over from the ancient inland Sea of Cortez. Seismic activity has raised these. Much of the terrain is still loose dirt, interspersed with sandstone and occasional quartz veins. A dirt road leads towards the mountains, starting off State Highway 2 (S2), also known as the Imperial Highway, not far from the desert community of Ocotillo.

There are no marked trails and the footing is treacherous, made up of loose sand, dirt and crumbled shards of sandstone. Most slopes have no vegetation, but there is occasional mesquite and ocotillo, with coastal cholla at lower elevations. The local fauna includes jackrabbits and sparrows.

There are a few ancient sand dunes that have been fossilized and hollowed out by winds, producing wind caves. Marine fossils such as sand dollars and snails can be found, but it is illegal to remove any fossils. In 1994, the United States Congress designated 18,631 acres (75 km2) as a U.S. Wilderness Area, the Coyote Mountains Wilderness (California).

Cucapá Beer

Cerveceria de Baja California (founded in 2002), is located in the City of Mexicali, and is one of a handful of Mexican microbrews. The product they brew is Cucapá Beer. This name comes from the Cocopah (Cucapá in Spanish), one of the five Indian tribes that live in the Mexicali Valley. The Cucapá tribe was the first settlers of the region and their love for water and nature took them to live in the Colorado River delta.

The tradition of nature, the water of the river, the geographical location and the initiative of being the first people to explore the region is what makes Cerveza Cucapá as unique as the Cucapá tribe's ancestors.

Gore Island (Baja California)

Gore Island, or Isla Gore, is an island in the Colorado River Delta within the state of Baja California, Mexico. It lies between two dis-tributary channels east of the main channel of the Colorado River and Montague Island that flow southeastward into the Gulf of California, southeast of the mainland of Baja California Peninsula.

Hardy River

The Hardy River (Spanish: Río Hardy) is a 26-kilometer (16 mi)-long Mexican river formed by residual agricultural waters from the Mexicali Valley and running into the Colorado River. The river is believed to have been an ancient channel of the Colorado. In the 19th century, an Englishman lieutenant named R.W.H.Hardy explored the Colorado River Delta, and noted that the main channel of the Colorado followed this course. Later in the 1880s, sea captains noted that the main channel of the Colorado had moved east, and this old channel became known as Hardy's Colorado.

In much earlier times, the Colorado River periodically flowed north into the Salton Sink, forming a large lake called Lake Cahuilla. Eventually, Lake Cahuilla would fill to about 30' above sea level, at which point the lake would overflow its banks near Cerro Prieto and flow south to the Gulf of California. During those times, the Rio Hardy would serve as the overflow channel for Lake Cahuilla.

Heintzelman's Point

Heintzelman's Point, a sharp bend in the Colorado River, 47 miles from the mouth of the Colorado River at the top of the influence of the tide in the estuary of the Colorado River Delta during the 19th century, in Sonora, Mexico.

James Turnbull (steamboat captain)

James Turnbull was the first steamboat captain on the Colorado River. His voyages supplying the Army at Fort Yuma demonstrated that the river was navigable by steamboats.

After obtaining a contract to supply the fort, James Turnbull sailed with supplies and the disassembled Uncle Sam, a 65-foot long side-wheel paddle steamer tug, to the Colorado River Delta, in the schooner Capacity. There he had the vessel re-assembled at a landing in the delta in two months. Turnbull then successfully brought supplies up the Colorado River 120 miles in 15 days from the Colorado River Delta to Fort Yuma, where he arrived December 3, 1852. He then took some passengers from the fort up the river for a few miles as a celebration of the success before returning to bring up more supplies.Equipped with only a 20-horsepower engine, the Uncle Sam could only carry 35 tons of supplies, It made trips for four more months up and down the river to finish carrying the supplies from the Capacity to the fort reducing its time for a round trip to 12 days. Negligence caused it to sink at its dock below Fort Yuma, and was then washed away before it could be raised, in the spring flood of May 1853. Turnbull who meanwhile had returned to the Delta from San Francisco with another cargo and a more powerful engine for the Uncle Sam. Finding it lost he returned for a new hull, while the army sent wagons to recover the cargo from the delta. However Turnbull disappeared from San Francisco, leaving creditors unpaid. Turnbull later turned up in Mazatlan, Mexico, where he ran a small steamboat for many years and attempted to promote the building of a canal. However Turnbull had shown the worth of steamboats to solve Fort Yuma's supply problem and to successfully navigate the Colorado River, an example that was soon followed by George Alonzo Johnson.

Lake Cahuilla

Lake Cahuilla (also known as Lake LeConte and Blake Sea) was a prehistoric lake in California and northern Mexico. Located in the Coachella and Imperial Valleys, it covered surface areas of 5,700 square kilometres (2,200 sq mi) to a height of 12 metres (39 ft) above sea level during the Holocene. During earlier stages of the Pleistocene, the lake reached even higher levels, up to 31–52 metres (102–171 ft) above sea level. During the Holocene most of the water came from the Colorado River with little contribution from local runoff; in the Pleistocene local runoff was higher and it is possible that Lake Cahuilla was supported solely from local water sources during the Wisconsin glaciation. The lake overflowed close to Cerro Prieto into the Rio Hardy, eventually draining into the Gulf of California.

The lake formed several times during the Holocene, when water from the Colorado River was diverted into the Salton Trough. This tectonic depression forms the northern basin of the Gulf of California, but it was separated from the sea proper by the growth of the Colorado River Delta. Such changes in river courses may have been caused by earthquakes among the numerous faults that cross the region, such as the San Andreas Fault. Conversely, it is possible that the weight of the water itself triggered earthquakes. During its existence, Lake Cahuilla formed strandlines and various beach deposits such as gravel bars and travertine deposits.

The lake existed in several stages over the last 2,000 years, periodically drying and refilling and eventually disappearing sometime after 1580. Between 1905–1907, due to an engineering accident, the Salton Sea formed in parts of the lower basin of Lake Cahuilla. Were it not for human intervention, the sea might have grown to the size of prehistoric Lake Cahuilla. Today the former lake bed forms the fertile regions of the Imperial and Coachella Valleys.

The Algodones Dunes were formed from sand deposited by Lake Cahuilla, which was transported by wind toward the area. During its existence, the lake supported a rich biota with fish, bivalves and vegetation on its shorelines. These resources supported human populations on its shores, as evidenced by a number of archeological sites and mythological references to the lake in the traditions of the Cahuilla. The lake may have had profound effects on population genetics and language history of the surrounding regions.

List of regions of Arizona

This is a list of regions of Arizona, in the USA.

Lower Colorado River Valley

The Lower Colorado River Valley ("LCRV") is the river region of the lower Colorado River of the southwestern United States in North America that rises in the Rocky Mountains and has its outlet at the Colorado River Delta in the northern Gulf of California in northwestern Mexico, between the states of Baja California and Sonora. This north–south stretch of the Colorado River forms the border between the U.S. states of California/Arizona and Nevada/Arizona, and between the Mexican states of Baja California/Sonora.

It is commonly defined as the region from below Hoover Dam and Lake Mead to its outlet at the northern Gulf of California (Sea of Cortez); it includes the Colorado River proper, canyons, the valley, mountain ranges with wilderness areas, and the floodplain and associated riparian environments. It is home to recreation activities from the river, the lakes created by dams, agriculture, and the home of various cities, communities, and towns along the river, or associated with the valley region. Five Indian reservations are located in the LCRV: the Chemehuevi, Fort Mojave and Colorado River Indian Reservations; at Yuma are the Quechan and Cocopah reservations.

Matagorda Bay

Matagorda Bay ( (listen)) is a large Gulf of Mexico estuary bay on the Texas coast, lying in Calhoun and Matagorda counties and located approximately 80 miles (130 km) northeast of Corpus Christi, 143 miles (230 km) east-southeast of San Antonio, 108 miles (174 km) south-southwest of Houston, and 167 miles (269 km) south-southeast of Austin. It is separated from the Gulf of Mexico by Matagorda Peninsula and serves as the mouth of numerous streams, most notably the Lavaca and Colorado Rivers. The Texas seaport of Port Lavaca is located on the system's northwestern extension of Lavaca Bay. The city of Palacios is found on northeastern extension of Tres Palacios Bay, and Port O'Connor is located on the southwestern tip of the main bay's shore. The ghost town of Indianola, which was a major port before it was destroyed by two hurricanes in the late 19th Century, is also found on the bay.

The bay's shore, especially near the Colorado River delta, provides a habitat for a wide variety of wildlife. The wildlife serves as a basis for the birding and fishing tourism, and is an essential component of the production of seafood, specifically shrimp and blue crab, which are the specialties of the area. The fertile land near the bay is ideal for farming, especially for the propagation of rice.

Montague Island (Baja California)

Montague Island, known in Spanish as Isla Montague, is an island at the mouth of the Colorado River in the municipality of Mexicali, Baja California, Mexico, and is part of the Colorado River Delta and part of a broader region called the Salton Trough. It is about 32 km (20 mi) in length along its longest axis.The Colorado River Delta region experiences some of the highest tidal ranges in the world, up to 10 metres (33 ft), and at the highest tides, Montague Island is completely inundated. Although the islands in the delta have changed much over time, a map of the region shows Montague Island in 1873. The island is uninhabited, as the climate is very hot, arid and the area occasionally floods. The nearest inhabited town is El Golfo de Santa Clara.

Port Isabel Slough

Port Isabel Slough was a deep slough in the Colorado River Delta near the mouth of the Colorado River during the 19th century, within the state of Sonora, Mexico.

Robinson's Landing

Robinson's Landing was a location in Baja California, Mexico. It lay on the west bank of the Colorado River northwest of the north tip of Montague Island in the Colorado River Delta, 10 miles above the mouth of the river on the Gulf of California. Named for David C. Robinson, it was the place where cargo was unloaded in the river from seagoing craft on to flatbottomed steamboats and carried up to Fort Yuma and points further north on the river from 1852 onward. Joseph C. Ives, described it as it was in 1858, in his 1861 Report upon the Colorado river of the West The river here was subject to a severe tidal bore that formed in the estuary about Montague Island and propagated upstream and could on occasion swamp barges, boats and ships. By 1865, a better location was found, ships offloaded their cargos on the east bank of the river at Port Isabel, Sonora, northeast of Montague Island. 17 miles from Robinson's landing and 57 miles below Port Famine.

Sea urchins of the Gulf of California

The sea urchins of the Gulf of California live between the coasts of the Baja California Peninsula to the west and mainland state of Sonora, Mexico to the east. The northern boundary is the lateral band of land with the remains of the Colorado River Delta, and the southern is the Pacific Ocean.

The Gulf of California is known for its high diversity and endemism of biota. One type of marine animal that can be found in this region is the sea urchin (class echinoidea, in the phylum echinodermata). One echinoid, Mellita granti, is a sea urchin endemic to the Gulf of California.

Topock Marsh

The Topock Marsh is one of the larger birdwatching sites found in the Lower Colorado River Valley, found from south of Hoover Dam to the Colorado River Delta in Mohave County, Arizona. This public land is managed by the US Fish and Wildlife Service, and available to the public for recreational purposes.

Uncle Sam (1852 sidewheeler)

Uncle Sam, was a side-wheel paddle steamer and the first steamboat on the Colorado River in 1852.

In November 1852, Uncle Sam, a 65-foot (20 m) long side-wheel paddle steamer was brought by the schooner Capacity from San Francisco to the Colorado River Delta by the next contractor to supply Fort Yuma, Captain James Turnbull. It had been built in June 1852 in San Francisco by Domingo Marcucci and disassembled for shipment. It was assembled and launched in the estuary, 30 miles (48 km) above the mouth of the Colorado River. Equipped with only a 20-horsepower (15 kW) engine, Uncle Sam could only carry 35 tons of supplies, taking 15 days to make the first 120-mile (190 km) trip.

Uncle Sam made many trips up and down the river for four months to finish carrying all the supplies for the fort, improving its time up river to 12 days. Negligence caused it to sink at its dock below Fort Yuma, and was then washed away and lost before it could be raised, in the spring flood of 1853. Turnbull who meanwhile had returned to the Delta from San Francisco with another cargo and a more powerful engine for the Uncle Sam. He returned to San Francisco, for a new hull, while the army sent wagons to recover the cargo from the delta again. However, Turnbull in financial difficulty, disappeared from the city leaving creditors unpaid. Nevertheless, Turnbull had shown the worth of steamboats to solve Fort Yuma's supply problem.

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