Examine individual changes

[ 0 => '{{Refimprove|date=October 2012}} ', 1 => '[[Image:ColoradoRiverDelta ISS009-E-09839.jpg|thumb|300px|Colorado River Delta as seen from space (2004); [[Isla Montague]] is the large island in the center.]]', 2 => '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 Sink|Salton Trough]].<ref>[http://www.institute.redlands.edu/salton/Downloads/Docs/PhysicalGeography/20050528_Alles_GeologySaltonTrough.pdf David A. Alles, ed., "Geology of the Salton Trough", Western Washington University, Edited May 28, 2005.]</ref> Historically, the interaction of the river’s flow and the ocean’s tide created a dynamic environment, supporting freshwater, [[Brackish water|brackish]], and saltwater species. Within the [[river delta|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.<ref>http://www.latimes.com/nation/la-na-ff-delta-pulse-20140328,0,2209717.story#axzz2xIBMboEh</ref>', 3 => false, 4 => '==Natural history==', 5 => '{{unreferenced section|date = October 2014}}', 6 => '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.', 7 => false, 8 => 'Prior to the construction of major [[dam]]s 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 [[River delta|delta’s]] vast [[riparian]], freshwater, brackish, and [[tidal]] [[wetlands]] once covered 7,810&nbsp;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 [[Spawn (biology)|spawn]]ing habitat for fish and marine mammals. In contrast to the surrounding [[Sonoran Desert]], the Colorado River delta’s abundance was striking.', 9 => false, 10 => '==Human history==', 11 => false, 12 => '===Early history===', 13 => 'Early explorers reported [[jaguar]]s, [[beaver]]s, [[deer]], and [[coyote]]s 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 [[Cocopa|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, a wild grain, and for cultivating [[maize]] (corn), [[beans]], and [[Squash (fruit)|squash]].', 14 => false, 15 => '<blockquote>''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.''<br>', 16 => ':--[[Aldo Leopold]], from ''[[A Sand County Almanac]]'', describing the Colorado River Delta as it existed in 1922</blockquote>', 17 => false, 18 => '===After dam construction===', 19 => 'Today, conditions in the delta have changed. Like other desert river deltas, such as the [[Nile Delta]] and the [[Indus River]], the Colorado River delta has been greatly altered by human activity. Decades of [[dam]] construction and water diversions in the United States has reduced the delta to a remnant system of small wetlands and brackish mudflats.<ref name="latimes">{{citation | last=Clifford | first=Frank | title=A trickle of water might save estuary | newspaper=Los Angeles Times | volume= | issue= | pages=', 20 => ' | date=September 21, 2007 | url=http://www.latimes.com/news/printedition/california/la-me-delta17sep17,1,5768653.story?coll=la-headlines-pe-california&ctrack=6&cset=true}}</ref> As reservoirs filled behind dams and captured floodwaters, freshwater could no longer reach the delta.', 21 => false, 22 => '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.', 23 => false, 24 => '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 nonnative species have compromised the ecological health of much of what remains. Stress on ecosystems has allowed [[invasive plant]]s to out compete native species along Colorado River riparian areas. Native forests of [[Populus sect. Aegiros|cottonwood]] and [[willow]] have yielded to sand and mudflats dominated by the nonnative [[Tamarix|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).', 25 => false, 26 => '===High flows in 1980s===', 27 => '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.', 28 => false, 29 => '==Ecology==', 30 => '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):', 31 => false, 32 => '*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]]', 33 => '*the [[Ridgway's rail|Yuma rail]], also listed as endangered in the U.S.', 34 => '*the [[bobcat]]', 35 => '*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 less than 250 vaquita left in the world.', 36 => '*the [[totoaba]], now virtually extinct, a steel-blue fish that grows up to 2&nbsp;m (7&nbsp;ft) and 136&nbsp;kg (300 pounds), and once supported a commercial fishery that closed in 1975 (Postel et al., n.d.).', 37 => '* the [[Colorado delta clam]], once an extremely abundant species and important in the [[trophic dynamics]] of the ecosystem.', 38 => false, 39 => 'Although not extensively studied, the delta’s significance for [[Bird migration|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]].', 40 => false, 41 => '==Biosphere reserve==', 42 => 'The [[Gulf of California]] lies within the jurisdictional boundaries of Mexico and its [[Mexican states|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.', 43 => false, 44 => 'The [[United Nations Educational, Scientific and Cultural Organisation]] (UNESCO) designated over 12,000&nbsp;km² (3 million acres) of [http://www.cedointercultural.org/uppergulf.htm Upper Gulf of California and Colorado River Delta Biosphere Reserve] as a [[Biosphere]] [[Nature reserve]] in June 1993. Within this 12,000&nbsp;km² (3 million acres), over 4,000&nbsp;km² (1 million acres) nearest the Colorado River Delta are designated as the Reserve “core area”, with the remaining 8,000&nbsp;km² (2 million acres) of open water and shoreline designated as a “buffer area”.<ref>http://www.cedointercultural.org/uppergulf.htm . accessed 7/4/2010</ref>', 45 => false, 46 => 'UNESCO considers areas for designation as [[Biosphere Reserve]]s 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]]) .', 47 => false, 48 => 'In addition to designation as a Biosphere Reserve, 2500&nbsp;km² (618,000 acres) within Colorado River Delta (Humedales del Delta del Río Colorado) are designated as a [[List of Ramsar wetlands of international importance|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.', 49 => false, 50 => '==View==', 51 => '[[File:The Salton Trough region from orbit.jpg|thumb|left|800px|The region from orbit.<ref>[http://earthobservatory.nasa.gov/IOTD/view.php?id=81711 Salton Trough July 29, 2013]</ref>]]', 52 => '{{clear}}', 53 => false, 54 => '==References==<!-- BiolConserv141:113. -->', 55 => '{{reflist}}', 56 => false, 57 => '==External links==', 58 => '*Official '''[http://www.cedointercultural.org/uppergulf.htm Upper Gulf of California and Colorado River Delta Biosphere Reserve website]'''', 59 => '*[http://www.conanp.gob.mx/anp/consulta/subzoni230204.pdf Map of the Biosphere Reserve (in español)]', 60 => '*[http://www.environmentaldefense.org/documents/425_Delta.pdf A Delta Once More: Restoring Riparian and Wetland Habitat in the Colorado River Delta]', 61 => '*[http://www.ibwc.state.gov/html/colorado_river.html International Boundary and Water Commission Site on Colorado River Operations]', 62 => '*[http://www.ibwc.state.gov/Files/Minutes/Min306.pdf IBWC Minute 306 (Conceptual Framework for U.S. - Mx Studies for Future Recommendations Concerning the Riparian and Estuarine Ecology of the Limitrophe Section of the Colorado River and its Associated Delta.)]', 63 => '*[http://www.ibwc.state.gov/FAO/CRDS0901/EnglishSymposium.pdf Proceedings of IBWC Colorado River Delta Symposium]', 64 => '*[http://geo.arizona.edu/rcncrd/ Colorado River Delta Research Coordination Network]', 65 => false, 66 => '{{coord|31.74|N|114.66|W|display=title}}', 67 => false, 68 => '{{-}}', 69 => '{{Colorado River system}}', 70 => false, 71 => '[[Category:Colorado River]]', 72 => '[[Category:Landforms of Baja California]]', 73 => '[[Category:Landforms of Sonora]]', 74 => '[[Category:River deltas]]', 75 => '[[Category:River deltas of the United States]]', 76 => '[[Category:Gulf of California]]', 77 => '[[Category:Lower Colorado River Valley]]', 78 => '[[Category:Wetlands of Mexico]]', 79 => '[[Category:Flooded grasslands and savannas]]', 80 => '[[Category:Ecoregions of Mexico]]', 81 => '[[Category:Ramsar sites in Mexico]]', 82 => '[[Category:Landforms of Mexico]]', 83 => '[[Category:Natural history of the Lower Colorado River Valley]]', 84 => '[[Category:Sonoran Desert]]', 85 => '[[Category:World Heritage Sites in Mexico]]', 86 => '[[Category:Biosphere reserves of Mexico]]', 87 => false, 88 => '[[es:Delta del río Colorado (México)]]' ]