Blue Mesa Dam
Blue Mesa Dam is a 390-foot-tall zoned earthfill dam on the Gunnison River in Colorado. It creates Blue Mesa Reservoir, is within Curecanti National Recreation Area just before the river enters the Black Canyon of the Gunnison; the dam is upstream of the Morrow Point Dam. Blue Mesa Dam and reservoir are part of the Bureau of Reclamation's Wayne N. Aspinall Unit of the Colorado River Storage Project, which retains the waters of the Colorado River and its tributaries for agricultural and municipal use in the American Southwest; the dam's primary purpose is hydroelectric power generation. State Highway 92 passes over the top of the dam. Blue Mesa Dam houses two turbine generators and produces an average of 264,329,000 kilowatt-hours each year; the dam stands in an area where sandstone and shale overlay pre-Cambrian granite and gneiss. It is situated at a narrows in the river valley where the Gunnison enters the upper reaches of the Black Canyon of the Gunnison; the dam has a volume of 3,080,000 cubic yards and the spillway intake structure has two radial gates.
These discharge into a concrete-lined tunnel which in turn discharges through a flip bucket into a stilling basin. The Curecanti Project was conceived in 1955 with four dams, it was approved by the Secretary of the Interior in 1959, comprising Blue Mesa Dam and Morrow Point Dam. Crystal Dam's design was unfinished and was approved in 1962. Plans for a fourth dam were dropped as uneconomical; the project was restricted to the stretch of the Gunnison above Black Canyon of the Gunnison National Monument, a 40 miles length of the river. Planned as a concrete dam, the project was changed to an earthfill design. Work on the dam started with foundation drilling and survey work. Construction of the reservoir required the relocation of US 50 and State Highway 149; this relocation was among the first work to be performed, starting in 1962 and continuing through 1964. The Sapinero Cemetery was relocated; the primary construction contract for the dam was awarded to the Tecon Corporation of Dallas, with notice to proceed on April 23, 1962.
The diversion tunnel was holed through on September 7, 1962, with excavation of the spillway tunnel completed by the April 1963. Drilling and grouting for the dam's foundation started in March 1963; the Gunnison was diverted through its tunnel on October, with excavation of the foundation to bedrock after. Placement of the dam embankments started in 1964, continuing through the year, with the dam embankment completed at the end of 1965; the diversion tunnel was closed in December and the reservoir began to fill, with final closure of the diversion tunnel on February 7, 1966. The dam project was declared complete on October 19, 1966; the powerplant project was delayed by a delivery accident to a transformer, damaged in an accident in September 1966 near Monarch Pass and had to be shipped back to its manufacturer in Sweden for repair. The powerplant was completed on February 16, 1968. Spillway modifications took place in 1984-85 to repair damage, while a uniform and cosmetic covering of riprap was applied to the dam face.
The Blue Mesa Powerplant is fed by one 16-foot diameter penstock, which supplies two turbines, as well as feeding the outlet works. The laterals feeding the Francis turbines are controlled by 156-inch butterfly valves. Initial generating capacity was 60 MW, increased in 1988 to 86.4 MW. The powerplant is located above ground at the toe of the dam, it operates as peaking plant. Blue Mesa Dam at the Bureau of Reclamation Blue Mesa Powerplant at the Bureau of Reclamation Wayne N. Aspinall Storage Unit at Curecanti National Recreation Area
Blue Mesa Reservoir
Blue Mesa Reservoir is an artificial reservoir located on the upper reaches of the Gunnison River in Gunnison County, Colorado. The largest lake located within the state, Blue Mesa Reservoir was created by the construction of Blue Mesa Dam, a 390-foot tall earthen fill dam constructed on the Gunnison by the U. S. Bureau of Reclamation in 1966 for the generation of hydroelectric power. Managed as part of the Curecanti National Recreation Area, a unit of the National Park Service, Blue Mesa Reservoir is the largest lake trout and Kokanee salmon fishery in Colorado. In 1956, the U. S. Bureau of Reclamation was given the responsibility, under the Colorado River Storage Project Act, to begin planning and construction of the Colorado River Storage Project, a series of projects in Colorado, New Mexico and Wyoming that would make possible comprehensive development of the waters of the Colorado River and its major tributaries. One of the initial projects of the CRSP, the Curecanti Unit, focused on the upper reaches of the Gunnison River, the fifth largest tributary of the Colorado River.
The centerpiece of the plans for the Gunnison was the construction of four dams on a 40-mile stretch of the river east of the National Park Service's Black Canyon of the Gunnison National Park, projects that would not only help control the amount of water flowing into the Colorado, but would create new opportunities for flood control, water storage, the generation of hydroelectric power. The first of these dams was Blue Mesa Dam, begun in 1962 30 miles west of Gunnison, 1.5 miles west of Sapinero. Finished four years the dam created Blue Mesa Reservoir, which became the primary water storage reservoir for the Curecanti Unit. Blue Mesa Dam is located on the Gunnison river 30 miles west of the city of Gunnison, near the intersection of U. S. 50 with Colorado Highway 92, which travels along the top of the dam. The reservoir extends east 20 miles and is composed of three main basins, the Iola, the Cebolla and the Sapinero, from east to west. U. S. 50 traverses the northern shore of both the Iola and Cebolla Basins before crossing the reservoir south on the Middle Bridge and continuing west to the dam.
The southern shore of the Iola Basin can be reached via Colorado Highway 149, which begins at an intersection with U. S. 50 at the Lake City Bridge 7 miles west of the city of Gunnison. While most of the recreational areas at Blue Mesa can be accessed from U. S. 50, the reservoir contains a small number of facilities on the lake's deep arms, such as Cebolla Creek and Soap Creek, which can only be reached by boat or unpaved road. While it was the Bureau of Reclamation that conceived of the plan to impound the Gunnison and constructed the Blue Mesa Dam, it was the National Park Service, tasked with developing and managing recreational facilities at Blue Mesa Reservoir and the two smaller lakes to the west; as a unit of the Curecanti National Recreation Area Blue Mesa Reservoir offers a number of recreational opportunities, including boating, boat-in, primitive camping, horseback riding, hunting. A popular lake for boating, Blue Mesa has marinas at Elk Creek and Lake Fork, near the dam, both of which can be accessed by U.
S. 50. Watercraft can be launched from the Ponderosa and Stevens Creek campgrounds, at Iola, on the reservoir's southern shore. During winter months Iola Basin is a popular spot for ice fishing. Blue Mesa contains 8 developed campgrounds; these range from the 160-site Elk Creek on the main body of the lake to smaller, more remote sites like Ponderosa and Gateview located on arms of the lake. Several of the campsites can accommodate RV's. Boaters may camp overnight in 4 free camping areas with a total of 9 individual sites. Boaters may camp on the southern shore of the Cebolla and Iola Basins, as long as campsites are not within a half-mile of any developed area, maintained public road or other boat-in/backcountry campsite. In addition to Blue Mesa Reservoir, Curecanti NRA contains two other Bureau of Reclamation projects, Morrow Point Reservoir and Crystal Reservoir. Part of the same project that created Blue Mesa, both Morrow Point and Crystal are smaller, narrower lakes, located within the Black Canyon of the Gunnison.
Though harder to access than Blue Mesa, these two lakes offer visitors unique views and challenging recreational opportunities. West of Blue Mesa and downriver from Crystal Dam is Black Canyon of the Gunnison National Park, a National Park Service unit that offers camping and views of the river and the surrounding 1900-ft. Deep canyon. North of the reservoir is the Gunnison Ranger District of the Grand Mesa and Gunnison National Forests, a unit of the U. S. Forest Service; the Gunnison Ranger District includes 30 campgrounds and a number of hiking and equestrian trails spread across 1.3 million acres. Towns near Blue Mesa include Gunnison to the east and Montrose and Delta to the west, all of which can be accessed via U. S. 50. List of largest reservoirs of Colorado Colorado River Storage Project Curecanti National Recreation Area Blue Mesa Dam Morrow Point Reservoir Crystal Reservoir Bureau Of Reclamation: Blue Mesa Dam NPS: Curecanti National Recreation Area
Morrow Point Reservoir
Morrow Point Reservoir is an 817-acre artificial reservoir on the Gunnison River in western Colorado. Located in the upper Black Canyon of the Gunnison, the lake was created in 1968 by the U. S. Bureau of Reclamation as part of a larger plan to impound the upper section of the Gunnison and create opportunities for hydroelectric power generation, water conservation, recreation. Morrow Point Reservoir is managed by the National Park Service as a unit within the Curecanti National Recreation Area, is the location of the Curecanti Needle, a striking 700 ft. granite spire on the reservoir’s southern bank whose unique shape was for decades a recognized symbol of the Denver and Rio Grande Western Railroad. Morrow Point Reservoir is part of the Wayne N. Aspinall Unit of the Colorado River Storage Project, a Bureau of Reclamation project that retains the waters of the Colorado River and its tributaries, such as the Gunnison, for agricultural and municipal use; the second of three reservoirs impounded for the Aspinall Unit, Morrow Point lies between the larger Blue Mesa Reservoir to the east and the remote Crystal Reservoir, to the west.
Morrow Point Reservoir was created by the impoundment of the Gunnison River 12 miles west of Blue Mesa Dam by Morrow Point Dam, a 486-ft. Concrete double-arch dam built by the Bureau of Reclamation. Completed in 1968, Morrow Point was the first concrete double-arch dam constructed by the Bureau. One of the most notable features of Morrow Point is the famed Curecanti Needle, a striking 700 foot tall granite spire on the reservoir’s southern shore. Located west of the mouth of Blue Creek and directly across from the mouth of Curecanti Creek, the Needle was a well-known landmark to generations of rail travelers, who passed near to the spire on the Denver & Rio Grande Western’s Black Canyon route between Gunnison and Montrose. Though difficult to access, the Needle is popular with climbers, who must either use a boat or cross the frozen lake in winter to reach the base. Morrow Point Reservoir is part of the Curecanti National Recreation Area, a National Park Service administered area charged with developing and managing recreation facilities on the three reservoirs that compose the Aspinall Unit.
Recreational opportunities at Morrow Point include boating and hiking. There are three small developed areas with lake access, the Pine Creek Trailhead, accessible via U. S. 50 1 mile west of Blue Mesa Dam, the Pioneer Point Overlook, north of the reservoir on Colorado Highway 92 5.5 miles west of Blue Mesa Dam, the Hermit’s Rest Trailhead, on Co. 92 17 miles west of Blue Mesa Dam. Pine Creek Trailhead’s 232 steps lead 180 ft. down to the water, where hand-carried craft can be launched. Once on the water, there are two developed and two primitive boat-in campsites along the north shore, two primitive sites on the south shore; the two-mile Pine Creek Trail follows an abandoned narrow-gauge railroad bed. Boat-in camping requires a Backcountry Permit, available at the Pine Creek Trailhead. Pioneer Point Overlook offers a scenic viewing area and is the trailhead for the strenuous Curecanti Creek trail, a 4-mile trail with a 900 ft. elevation change. Hikers are rewarded with stunning views of the Curecanti Needle on the south shore.
Two campsites with picnic tables, fire grates, composting toilets are located at the end of the trail. Hermit's Rest Trailhead gives access to the strenuous Hermit's Rest Trail. A 6 mile round trip with an 1800 ft. elevation change, the trail ends with lakeside picnic sites and two campsites with picnic tables, fire grates, composting toilets. List of largest reservoirs of Colorado Colorado River Storage Project Curecanti National Recreation Area Morrow Point Dam Blue Mesa Reservoir Crystal Reservoir Morrow Point Dam at the Bureau of Reclamation Wayne N. Aspinall Storage Unit at Curecanti National Recreation Area U. S. Geological Survey Geographic Names Information System: Morrow Point Reservoir U. S. Geological Survey Geographic Names Information System: Morrow Point Reservoir
John Williams Gunnison
John Williams Gunnison was an American military officer and explorer. Gunnison attended Hopkinton Academy, he graduated from West Point in 1837, second in his class of fifty cadets. His military career began as an artillery officer in Florida, where he spent a year in the campaign against the Seminoles. Due to his poor health he was reassigned to the Corps of Topographical Engineers the next year, he explored unknown areas of Florida, searching for provision routes. However, his health soon forced him out of Florida entirely. From 1841-1849 Gunnison explored the area around the Great Lakes, he surveyed the border between Wisconsin and Michigan, the western coast of Lake Michigan, the coast of Lake Erie. On May 9, 1846, he was promoted to first lieutenant. In the spring of 1849 Gunnison was assigned as second in command of the Howard Stansbury expedition to explore and survey the valley of the Great Salt Lake; that winter was heavy and the expedition was unable to leave the valley. Gunnison took the opportunity to befriend some Mormons and study the Church of Jesus Christ of Latter-day Saints.
When he returned to Washington, DC, he wrote a book titled The Mormons or Latter-Day Saints, in the Valley of the Great Salt Lake: A History of Their Rise and Progress, Peculiar Doctrines, Present Condition. Gunnison returned to the Great Lakes from 1851–1853, mapping the Green Bay area, was promoted to captain on March 3, 1853. On May 3, 1853, he received orders to take charge of an expedition to survey a route for a Pacific railroad between the 38th and 39th parallels; the surveying party left St. Louis, Missouri, in June 1853 and arrived by mid-October in Manti, Utah Territory. In Utah Territory, with Lieutenant E. G. Beckwith as assistant commander, Gunnison began the survey of a possible route, surveying areas across the Rocky Mountains via the Huerfano River, through Cochetopa Pass, by way of the present Gunnison and Green rivers to the Sevier River, his journey took him through the Tomichi Valley in Colorado, where the town of Gunnison is named in his honor. After crossing the Tomichi Valley, the survey team encountered the Black Canyon, carved by the Gunnison River, named in his honor.
The team was forced to turn south to get around the canyon. The weather was beginning to turn "cold and raw" with snow flurries, Captain Gunnison sought to speed up mapping before returning to winter quarters. At Sevier Lake, the team was divided into two detachments. On the morning of October 26, 1853, Gunnison and the eleven men in his party were attacked by a band of Pahvants. In the resulting massacre and seven of his men were killed. Several survivors of the attack alerted the other detachment of the survey team, who rode to aid Gunnison and his party. An additional survivor of the attack and the bodies of the victims were retrieved that day; the remains of the eight dead were found in a mutilated state. Killed with Gunnison were Richard H. Kern, F. Creuzfeldt, Wiliam Potter, Private Caulfield, Private Liptoote, Private Mehreens, John Bellows; the site of the massacre was added to the National Register of Historic Places in 1976. Most contemporary accounts of the massacre maintain that the Mormons warned Gunnison that his party might be in danger from local bands of Pahvant Utes.
It seems that Gunnison had entered Utah in the midst of the Walker War, a sometimes bloody conflict between the Mormons and the Ute Chief Walkara. Indeed, Lt. Beckwith wrote that the expedition found the local Mormons "all gathered into a village for mutal protection against the Utah Indians." But after the killings, rumors circulated that the Pahvants involved in the massacre were acting under the direction of Brigham Young and an alleged secret militia known as the Danites. Some claim that leaders of the Church of Jesus Christ of Latter-day Saints were concerned that the railway would increase the influx of non-Mormon settlers and non-Mormon economic concerns into the territory. However, the Utah Legislature had petitioned Congress for both a transcontinental railroad and telegraph lines to pass through the region. Indeed, when the railroad came to Utah, LDS leaders organized cadres of Mormon workers to build the railway, welcoming the income for the economically depressed community. Martha Gunnison, widow of Captain Gunnison, was one of those who maintained that the attack was planned and orchestrated by militant Mormons under the direction of Brigham Young.
Gunnison's letters to his wife throughout the expedition left her with the impression that "the Mormons were the directors of my husband's murder." She wrote to Associate Justice W. W. Drummond, the 1855 federal appointee to the Supreme Court of the Territory of Utah, she received confirmation of this belief in his response to her letter. Drummond drew this conclusion from informant and witness testimonies in several trials after the murders, he cited numerous reports by whites and natives of white attackers dressed up as Indians during the massacre. In 1854 Lieutenant Colonel Edward Steptoe was sent by the War Department to investigate the attack and determine the truth of rumors that Mormons had colluded with the Indians in the ambush; as a result of his investigation eight Ute Indians were tried for the attack. Three were convicted of manslaughter, he did not uncover evidence of Mormon involvement. Lt. Beckwith concluded that the Mormons had nothing to do with the attack and that the Pahvants acted alone.
He wrote in his official report that the "statement which has from time to time appeared in various newspapers...charging the Mormons o
A tributary or affluent is a stream or river that flows into a larger stream or main stem river or a lake. A tributary does not flow directly into a ocean. Tributaries and the main stem river drain the surrounding drainage basin of its surface water and groundwater, leading the water out into an ocean. A confluence, where two or more bodies of water meet together refers to the joining of tributaries; the opposite to a tributary is a distributary, a river or stream that branches off from and flows away from the main stream. Distributaries are most found in river deltas. "Right tributary" and "left tributary" are terms stating the orientation of the tributary relative to the flow of the main stem river. These terms are defined from the perspective of looking downstream. In the United States, where tributaries sometimes have the same name as the river into which they feed, they are called forks; these are designated by compass direction. For example, the American River receives flow from its North and South forks.
The Chicago River's North Branch has the East and Middle Fork. Forks are sometimes left. Here, the "handedness" is from the point of view of an observer facing upstream. For instance, Steer Creek has a left tributary, called Right Fork Steer Creek. Tributaries are sometimes listed starting with those nearest to the source of the river and ending with those nearest to the mouth of the river; the Strahler Stream Order examines the arrangement of tributaries in a hierarchy of first, second and higher orders, with the first-order tributary being the least in size. For example, a second-order tributary would be the result of two or more first-order tributaries combining to form the second-order tributary. Another method is to list tributaries from mouth to source, in the form of a tree structure, stored as a tree data structure. A gallery of major river basins with tributaries Estuary
New Mexico is a state in the Southwestern region of the United States of America. It is one of the Mountain States and shares the Four Corners region with Utah and Arizona. With a population around two million, New Mexico is the 36th state by population. With a total area of 121,592 sq mi, it is the fifth-largest and sixth-least densely populated of the 50 states. Due to their geographic locations and eastern New Mexico exhibit a colder, alpine climate, while western and southern New Mexico exhibit a warmer, arid climate; the economy of New Mexico is dependent on oil drilling, mineral extraction, dryland farming, cattle ranching, lumber milling, retail trade. As of 2016–2017, its total gross domestic product was $95 billion with a GDP per capita of $45,465. New Mexico's status as a tax haven yields low to moderate personal income taxes on residents and military personnel, gives tax credits and exemptions to favorable industries; because of this, its film industry contributed $1.23 billion to its overall economy.
Due to its large area and economic climate, New Mexico has a large U. S. military presence marked notably with the White Sands Missile Range. Various U. S. national security agencies base their research and testing arms in New Mexico such as the Sandia and Los Alamos National Laboratories. During the 1940s, Project Y of the Manhattan Project developed and built the country's first atomic bomb and nuclear test, Trinity. Inhabited by Native Americans for many thousands of years before European exploration, it was colonized by the Spanish in 1598 as part of the Imperial Spanish viceroyalty of New Spain. In 1563, it was named Nuevo México after the Aztec Valley of Mexico by Spanish settlers, more than 250 years before the establishment and naming of the present-day country of Mexico. After Mexican independence in 1824, New Mexico became a Mexican territory with considerable autonomy; this autonomy was threatened, however, by the centralizing tendencies of the Mexican government from the 1830s onward, with rising tensions leading to the Revolt of 1837.
At the same time, the region became more economically dependent on the United States. At the conclusion of the Mexican–American War in 1848, the United States annexed New Mexico as the U. S. New Mexico Territory, it was admitted to the Union as the 47th state on January 6, 1912. Its history has given New Mexico the highest percentage of Hispanic and Latino Americans, the second-highest percentage of Native Americans as a population proportion. New Mexico is home to part of the Navajo Nation, 19 federally recognized Pueblo communities of Puebloan peoples, three different federally recognized Apache tribes. In prehistoric times, the area was home to Ancestral Puebloans and the modern extant Comanche and Utes inhabited the state; the largest Hispanic and Latino groups represented include the Hispanos of New Mexico and Mexican Americans. The flag of New Mexico features the state's Spanish origins with the same scarlet and gold coloration as Spain's Cross of Burgundy, along with the ancient sun symbol of the Zia, a Puebloan tribe.
These indigenous, Mexican and American frontier roots are reflected in the eponymous New Mexican cuisine and the New Mexico music genre. New Mexico received its name long before the present-day nation of Mexico won independence from Spain and adopted that name in 1821. Though the name “Mexico” itself derives from Nahuatl, in that language it referred to the heartland of the Empire of the Mexicas in the Valley of Mexico far from the area of New Mexico, Spanish explorers used the term “Mexico” to name the region of New Mexico in 1563. In 1581, the Chamuscado and Rodríguez Expedition named the region north of the Rio Grande "San Felipe del Nuevo México"; the Spaniards had hoped to find wealthy indigenous Mexica cultures there similar to those of the Aztec Empire of the Valley of Mexico. The indigenous cultures of New Mexico, proved to be unrelated to the Mexicas, they were not wealthy, but the name persisted. Before statehood, the name "New Mexico" was applied to various configurations of the U.
S. territory, to a Mexican state, to a province of New Spain, all in the same general area, but of varying extensions. With a total area of 121,699 square miles, the state is the fifth-largest state of the US, larger than British Isles. New Mexico's eastern border lies along 103°W longitude with the state of Oklahoma, 2.2 miles west of 103°W longitude with Texas. On the southern border, Texas makes up the eastern two-thirds, while the Mexican states of Chihuahua and Sonora make up the western third, with Chihuahua making up about 90% of that; the western border with Arizona runs along the 109° 03'W longitude. The southwestern corner of the state is known as the Bootheel; the 37°N parallel forms the northern boundary with Colorado. The states of New Mexico, Colorado and Utah come together at the Four Corners in New Mexico's northwestern corner. New Mexico has no natural water sources
United States Geological Survey
The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, the natural hazards that threaten it; the organization has four major science disciplines, concerning biology, geography and hydrology. The USGS is a fact-finding research organization with no regulatory responsibility; the USGS is a bureau of the United States Department of the Interior. The USGS employs 8,670 people and is headquartered in Reston, Virginia; the USGS has major offices near Lakewood, Colorado, at the Denver Federal Center, Menlo Park, California. The current motto of the USGS, in use since August 1997, is "science for a changing world." The agency's previous slogan, adopted on the occasion of its hundredth anniversary, was "Earth Science in the Public Service." Since 2012, the USGS science focus is directed at six topical "Mission Areas", namely Climate and Land Use Change, Core Science Systems, Ecosystems and Minerals and Environmental Health, Natural Hazards, Water.
In December 2012, the USGS split the Energy and Minerals and Environmental Health Mission Area resulting in seven topical Mission Areas, with the two new areas being: Energy and Minerals and Environmental Health. Administratively, it is divided into six Regional Units. Other specific programs include: Earthquake Hazards Program monitors earthquake activity worldwide; the National Earthquake Information Center in Golden, Colorado on the campus of the Colorado School of Mines detects the location and magnitude of global earthquakes. The USGS runs or supports several regional monitoring networks in the United States under the umbrella of the Advanced National Seismic System; the USGS informs authorities, emergency responders, the media, the public, both domestic and worldwide, about significant earthquakes. It maintains long-term archives of earthquake data for scientific and engineering research, it conducts and supports research on long-term seismic hazards. USGS has released the UCERF California earthquake forecast.
As of 2005, the agency is working to create a National Volcano Early Warning System by improving the instrumentation monitoring the 169 volcanoes in U. S. territory and by establishing methods for measuring the relative threats posed at each site. The USGS National Geomagnetism Program monitors the magnetic field at magnetic observatories and distributes magnetometer data in real time; the USGS collaborates with Canadian and Mexican government scientists, along with the Commission for Environmental Cooperation, to produce the North American Environmental Atlas, used to depict and track environmental issues for a continental perspective. The USGS operates the streamgaging network for the United States, with over 7400 streamgages. Real-time streamflow data are available online. National Climate Change and Wildlife Science Center implements partner-driven science to improve understanding of past and present land use change, develops relevant climate and land use forecasts, identifies lands and communities that are most vulnerable to adverse impacts of change from the local to global scale.
Since 1962, the Astrogeology Research Program has been involved in global and planetary exploration and mapping. In collaboration with Stanford University, the USGS operates the USGS-Stanford Ion Microprobe Laboratory, a world-class analytical facility for U--Pb geochronology and trace element analyses of minerals and other earth materials. USGS operates a number of water related programs, notably the National Streamflow Information Program and National Water-Quality Assessment Program. USGS Water data is publicly available from their National Water Information System database; the USGS operates the National Wildlife Health Center, whose mission is "to serve the nation and its natural resources by providing sound science and technical support, to disseminate information to promote science-based decisions affecting wildlife and ecosystem health. The NWHC provides information, technical assistance, research and leadership on national and international wildlife health issues." It is the agency responsible for surveillance of H5N1 avian influenza outbreaks in the United States.
The USGS runs 17 biological research centers in the United States, including the Patuxent Wildlife Research Center. The USGS is investigating collaboration with the social networking site Twitter to allow for more rapid construction of ShakeMaps; the USGS produces several national series of topographic maps which vary in scale and extent, with some wide gaps in coverage, notably the complete absence of 1:50,000 scale topographic maps or their equivalent. The largest and best-known topographic series is the 7.5-minute, 1:24,000 scale, quadrangle, a non-metric scale unique to the United States. Each of these maps covers an area bounded by two lines of latitude and two lines of longitude spaced 7.5 minutes apart. Nearly 57,000 individual maps in this series cover the 48 contiguous states, Hawaii, U. S. territories, areas of Alaska near Anchorage and Prudhoe Bay. The area covered by each map varies with the latitude of its represented location due to convergence of the meridians. At lower latitudes, near 30° north, a 7.5-minute quadrangle contains an area of about 64 square miles.
At 49° north latitude, 49 square miles are contained within a quadrangle of that size. As a unique non-metric map scale, the 1:24,000 scale requires a separate and specialized romer scale for pl