Flathead catfish
The flathead catfish called by several names including mudcat or shovelhead cat, is a large species of North American freshwater catfish. It is the only species of the genus Pylodictis. Ranging from the lower Great Lakes region to northern Mexico, they have been introduced and are an invasive species in some areas; the closest living relative of the flathead is the widemouth blindcat, Satan eurystomus. The Flathead catfish is known as Yellow cat, Mud cat, Shovelhead cat, Johnnie cat, Goujon and Opelousas; the fish is called Pied cat and Mississippi cat. Flatheads grow to a length of 155 cm and may weigh up to 56 kg, making it the second-largest North American catfish; the average length is about 25-46 in. Their maximum recorded lifespan is 24 years. Males are mature from 16 cm and 4 years of age, while females mature from 18 cm and 5 years of age, but may mature as late as 10 years; the world angling record flathead catfish was caught May 14, 1998, from Elk City Reservoir and weighed 123 lb 9 oz, however a record from 1982 shows that the flathead catfish would be North Americas longest species of catfish, after a specimen pulled from the Arkansas river that measured 175 cm and weighed 63.45 kg.
Their native range includes a broad area west of the Appalachian Mountains encompassing large rivers of the Mississippi and Ohio basins. The range extends as far north as Canada, as far west as Texas, south to the Gulf of Mexico including northeastern Mexico. Flatheads cannot live in full-strength seawater, but they can survive 10 ppt for a while and thrive up to about 5 ppt. Flatheads prefer live prey, they are voracious carnivores and feed on other fish, annelid worms, crustaceans. Spawning occurs in late June and early July, the nests are made in areas with submerged logs and other debris; the males, which build the nests and tirelessly defend and fan the clutch. The size of the clutch varies proportionately to the size of the female; the fry frequent shallow areas with rocky and sandy substrates, where they feed on insects and worms such as annelids and polychaetes. Young flatheads are cannibalistic, which has precluded their presence in aquaculture. Inhabiting deep pools and large, slow-moving rivers, flathead catfish are popular among anglers.
Their size make the flatheads effective subjects of public aquaria. Sport fishing for flathead catfish using either rod and reel, limb lines, or bare hands can be an exciting pastime. Anglers target this species in a variety of waterways, including small rivers, large rivers, reservoirs. A common element of flathead catfish location is submerged wood cover such as logs and rootwads which collect at bends in rivers. A good flathead spot also includes deep water compared to the rest of a particular section of river, a moderate amount of current, access to plentiful baitfish such as river herring, carp, panfish, or suckers. Anglers targeting large flathead catfish use stout tackle such as medium-heavy or heavy action rods from 6–10 ft in length with large line-capacity reels and line ranging from 20–80 pounds-force test breaking strength. Large live baits are preferred such as river herring, sunfish, carp, goldfish and bullheads ranging from 5–12 in in length. List of fish common names Froese and Pauly, eds..
"Pylodictis olivaris" in FishBase. December 2011 version. "Pylodictis olivaris". Integrated Taxonomic Information System. Retrieved 30 January 2006. Species Profile- Flathead Catfish, National Invasive Species Information Center, United States National Agricultural Library. Lists general information and resources for Flathead Catfish
Sonoran Desert
The Sonoran Desert is a North American desert which covers large parts of the Southwestern United States in Arizona and California and of Northwestern Mexico in Sonora, Baja California, Baja California Sur. It is the hottest desert in Mexico, it has an area of 260,000 square kilometers. The western portion of the United States–Mexico border passes through the Sonoran Desert. In phytogeography, the Sonoran Desert is within the Sonoran Floristic Province of the Madrean Region in southwestern North America, part of the Holarctic Kingdom of the northern Western Hemisphere; the desert contains a variety of unique and endemic plants and animals, such as the saguaro and organ pipe cactus. The Sonoran desert wraps around the northern end of the Gulf of California, from Baja California Sur, north through much of Baja California, excluding the central northwest mountains and Pacific west coast, through southeastern California and southwestern and southern Arizona to western and central parts of Sonora.
It is bounded on the west by the Peninsular Ranges, which separate it from the California chaparral and woodlands and Baja California Desert ecoregions of the Pacific slope. To the north in California and northwest Arizona, the Sonoran Desert transitions to the colder-winter, higher-elevation Mojave, Great Basin, Colorado Plateau deserts. To the east and southeast, the deserts transition to the coniferous Arizona Mountains forests and Sierra Madre and Sierra Madre Occidental pine–oak forests at higher elevations. To the south the Sonoran–Sinaloan transition subtropical dry forest is the transition zone from the Sonoran Desert to the tropical dry forests of the Mexican state of Sinaloa; the desert's sub-regions include the Colorado Desert of southeastern California. In the 1957 publication Vegetation of the Sonoran Desert, Forrest Shreve divided the Sonoran Desert into seven regions according to characteristic vegetation: Lower Colorado Valley, Arizona Upland, Plains of Sonora, Foothills of Sonora, Central Gulf Coast, Vizcaíno Region, Magdalena Region.
Many ecologists now consider Shreve's Vizcaíno and Magdalena regions, which lie on the western side of the Baja California Peninsula, to be a separate ecoregion, the Baja California Desert. Within the southern Sonoran Desert in Mexico is found the Gran Desierto de Altar, with the Reserva de la Biosfera el Pinacate y Gran Desierto de Altar, extending 2,000 square kilometers of desert and mountainous regions; the Pinacate National Park includes the only active erg dune region in North America. The nearest city to the Reserva de la Biosfera el Pinacate y Gran Desierto de Altar is Puerto Peñasco in the state of Sonora, Mexico. Sub-regionsSonoran Desert sub-regions include: Colorado Desert Gran Desierto de Altar Lechuguilla Desert Tonopah Desert Yuha Desert Yuma Desert The Sonoran Desert includes 60 mammal species, 350 bird species, 20 amphibian species, over 100 reptile species, 30 native fish species, over 1000 native bee species, more than 2,000 native plant species; the Sonoran Desert area southeast of Tucson and near the Mexican border is vital habitat for the only population of jaguars living within the United States.
The Colorado River Delta was once an ecological hotspot within the Sonoran desert, fueled by the flow of fresh water through the Colorado river in this otherwise dry area, but the delta has been reduced in extent due to the damming and use of the river upstream. Many plants not only thrive in the harsh conditions of the Sonoran Desert. Many have evolved to have specialized adaptations to the desert climate; the Sonoran Desert's biseasonal rainfall pattern results in more plant species than any other desert in the world. The Sonoran Desert includes plant genera and species from the agave family, palm family, cactus family, legume family, numerous others; the Sonoran is the only place in the world. Cholla, hedgehog, prickly pear, nightblooming cereus, organ pipe are other taxa of cacti found here. Cactus provides food and homes to many desert mammals and birds, with showy flowers in reds, pinks and whites, blooming most from late March through June, depending on the species and seasonal temperatures.
Creosote bush and bur sage dominate valley floors. Indigo bush and Mormon tea are other shrubs. Wildflowers of the Sonoran Desert include desert sand verbena, desert sunflower, evening primroses. Ascending from the valley up bajadas, various subtrees such as velvet mesquite, palo verde, desert ironwood, desert willow, crucifixion thorn are common, as well as multi-stemmed ocotillo. Shrubs found at higher elevations include whitethorn acacia, fairy duster, jojoba. In the desert subdivisions found on Baja California, cardon cactus, elephant tree, boojum tree occur; the California fan palm is found in the Colorado Desert section of the Sonoran Desert, the only native palm in California, among many other introduced Arecac
Colorado Desert
California's Colorado Desert is a part of the larger Sonoran Desert. It encompasses 7 million acres, including the irrigated Coachella and Imperial valleys, it is home to fauna. The Colorado Desert is a subdivision of the larger Sonoran Desert encompassing 7 million acres; the desert encompasses Imperial County and includes parts of San Diego County, Riverside County, a small part of San Bernardino County. Most of the Colorado Desert lies at a low elevation, below 1,000 feet, with the lowest point of the desert floor at 275 feet below sea level, at the Salton Sea. Although the highest peaks of the Peninsular Ranges reach elevations of nearly 10,000 feet, most of the region's mountains do not exceed 3,000 feet. In this region, the geology is dominated by the transition of the tectonic plate boundary from rift to fault; the southernmost strands of the San Andreas Fault connect to the northernmost extensions of the East Pacific Rise. The region is subject to earthquakes, the crust is being stretched, which will result in a sinking of the terrain over time.
The Colorado Desert's climate distinguishes it from other deserts. The region experiences greater summer daytime temperatures than higher-elevation deserts and never experiences frost. In addition, the Colorado Desert experiences two rainy seasons per year toward the southern portion of the region; the west coast Peninsular Ranges, or other west ranges, of Southern California–northern Baja California, block most eastern Pacific coastal air and rains, producing an arid climate. Other short or longer-term weather events can move in from the Gulf of California to the south, are active in the summer monsoons; these include remnants of Pacific hurricanes, storms from the southern tropical jetstream, the northern intertropical convergence zone. The region's terrestrial habitats include creosote bush scrub. Higher elevations are dominated by pinyon pine and California juniper, with areas of manzanita and Coulter pine. In addition to hardy perennials, more than half of the desert's plant species are herbaceous annuals, appropriately timed winter rains produce abundant early spring wildflowers.
In the southern portion of the region, the additional moisture supplied by summer rainfall fosters the germination of summer annual plants and supports smoketree and palo verde trees. Common desert wildlife include mule deer, desert kangaroo rat, cactus mouse, black-tailed jackrabbit, Gambel's quail, red-diamond rattlesnake. Among sensitive species are flat-tailed horned lizard, Coachella Valley fringe-toed lizard, desert tortoise, prairie falcon, Andrews' dune scarab beetle, peninsular bighorn sheep, California leaf-nosed bat; the best place to spot wildlife is at the wetland refuges along the Colorado River, Cibola National Wildlife Refuge and Imperial National Wildlife Refuge. In the Colorado Desert's arid environment and wetland habitats are limited in extent but are critically important to wildlife. Runoff from seasonal rains and groundwater springs forms desert arroyos, desert fan palm oases, freshwater marshes, brine lakes, desert washes and perennial streams, desert riparian vegetation communities dominated by cottonwood and non-native tamarisk.
Two of the region's most significant aquatic systems are the Colorado River. While most desert wildlife depend on aquatic habitats as water sources, a number of species, such as the arroyo toad, desert pupfish, Yuma rail, southwestern willow flycatcher, are restricted to these habitats. In some places, summer rains produce short-lived seasonal pools that host uncommon species like Couch's spadefoot toad. Desert fan palm oases are rare, they occur only where permanent water sources are available, such as at springs or along fault lines, where groundwater is forced to the surface by the movement of hard impermeable rock, can be found in the San Jacinto, Santa Rosa, Little San Bernardino mountains, in the canyons of Anza-Borrego Desert State Park, along the San Andreas Fault in the Coachella Valley. The only palm native to California, Washingtonia filifera, grows at the oases; some sub-regions of the Colorado Desert contain endemic flora. Along the Lower Colorado River Valley, in-flow side canyons, flatlands, or low-to-higher level elevations, at least three such flora occur: Hesperocallis undulata, Nolina bigelovii, Peucephyllum schottii.
Joshua Tree National Park Imperial NWR Sonny Bono Salton Sea NWR Indio Hills Palms Anza-Borrego Desert State Park Ocotillo Wells State Vehicular Recreation Area Picacho State Recreation Area Heber Dunes State Vehicular Recreation Area Salton Sea State Recreation Area The Colorado Desert is one of the least-populous regions in California, but human activities have had substantial impacts on the region's habitats and wildlife. Many unique communities aquatic and dune systems, are limited in distribution and separated by vast expanses of inhospitable, arid desert terrain. Limited human disturbances can have markedly deleterious effects on the endemic and sensitive species supported by these unique regional systems; some of the greatest human-caused effects on the region have resulted from the water diversions and flood control measures along the Colorado River. These measures have altered the region's hydrology by redistributing the region's water supp
Lake Havasu City, Arizona
Lake Havasu City is a city in Mohave County, United States. According to 2010 census, the population of the city was 52,527 people, it is served by Lake Havasu City Airport. Lake Havasu City is geographically isolated from the other cities in Mohave County and is the southernmost community of the Las Vegas–Henderson, NV–AZ combined statistical area; the community first started as an Army Air Corps rest camp, called "Site Six". During World War II on the shores of Lake Havasu. In 1958, American businessman Robert P. McCulloch purchased 3,353 acres of property on the east side of the lake along Pittsburgh Point, the peninsula that would be transformed into "the Island". After four years of planning, McCulloch Properties acquired another 13,000 acres of federal land in the surrounding area. Lake Havasu City was established on September 30, 1963, by a resolution of the Mohave County Board of Supervisors as the Lake Havasu Irrigation and Drainage District, making it a legal entity; the city was incorporated in 1978.
London Bridge crosses a narrow channel. Hoping to attract tourists and prospective buyers of residential lots, McCulloch bought it for US$2.5 million from the City of London when the bridge was replaced in 1968. The bridge was disassembled on contract with Sundt Construction, Tucson and the marked stones were shipped to Lake Havasu City and reassembled by Sundt for another US$7 million; the construction took three years to complete. McCulloch gave an acre of land to London; when Lake Havasu City wanted to use this land for a visitors' center, it leased it back for a quit rent of a Hopi Kachina figure. Since its inauguration on October 5, 1971, London Bridge has become the second-largest tourist attraction in Arizona, after the Grand Canyon. In 2017, a panel of experts partnering with USA Today's 10Best.com chose London Bridge as one of 20 initial nominees for Best Arizona Attraction. 10Best.com readers voted London Bridge as a top 5 favorite. Lake Havasu City is an active event destination for a wide range of people.
During spring months, the community is joined by university students for spring break. In 1995, Lake Havasu City was featured during MTV's Spring Break coverage. For boaters, March to September are the prime months on Lake Havasu; the city is home to the International World Jet Ski Final Races, multiple professional fishing tournaments, custom boat regattas, the Western Winter Blast pyrotechnics convention, Havasu 95 Speedway, the Chilln-n-Swilln Beer Festival annual charity event, the Havasu Triathlon, the Havasu Balloon Festival & Fair. During the winter months, the community is joined by retirees from colder regions of the country and Canada. During this period, multiple events are held on McCulloch Boulevard. During the second weekend of February, McCulloch Boulevard is home to Winterfest, an annual event which draws thousands of visitors and residents for two days of food, activities and products from over 200 vendors from across the United States. Lake Havasu City is located at 34°29′24″N 114°18′32″W.
According to the United States Census Bureau, the city has a total area of 43.1 square miles, of which, 43.0 square miles of it is land and 0.04 square miles of it is water. The only surface access to Lake Havasu City is by road via Arizona State Route 95, which meets Interstate 40 to the north of the city and Interstate 10 to the south. C. V. Wood, who designed Disneyland, was hired by Robert McCulloch to lay out Lake Havasu's unique road system. In the early stages of development of the city, McCulloch Properties operated a fleet of secondhand airliners such as the Lockheed Constellation and the Lockheed L-188 Electra to fly prospective property purchasers to the area from California and elsewhere in the USA. Lake Havasu City does not have a public transit system. Lake Havasu Shuttle provides transportation to Las Vegas and Laughlin, Nevada. Havasu Landing Resort and Casino provides a ferry to California. Lake Havasu City has a hot desert climate. In the winter months, daytime highs range from 60 °F to 70 °F.
Lows in winter average between 40 °F to 50 °F. The city has hot summers, with highs remaining between 100 °F and 115 °F. Highs are known to exceed 120 °F during the summer months. Overnight low temperatures stay between 80 °F to 90 °F for the months of August; the highest overnight low temperature recorded in Lake Havasu City was 98 °F on July 22, 2003. Mean annual precipitation is 3.84 inches. The annual mean temperature is 74.6 °F. Lake Havasu City holds the all-time record high temperature in Arizona history with 128 °F recorded on June 29, 1994; this temperature is the highest for a town or city in the Western Hemisphere. On December 31, 2014, snow fell on Lake Havasu City; as of the census of 2000, there were 41,938 people, 17,911 households, 12,716 families residing in the city. The population density was 974.4 people per square mile. There were 23,018 housing units at an average density of 534.8 per square mile. The racial makeup of the city was 94.35% White, 0.31% Black or African American, 0.69% Native American, 0.58% Asian, 0.10% Pacific Islander, 2.51% from other races, 1.46% from two or more races.
7.86% of the population were Hispanic or Latino of any race. There were 17,911 households out of which 22.5% had children under the age of 18 living with them, 59.4% were married couples living together, 7.7% had a female householder with
Carp
Carp are various species of oily freshwater fish from the family Cyprinidae, a large group of fish native to Europe and Asia. The cypriniformes are traditionally grouped with the Characiformes and Gymnotiformes to create the superorder Ostariophysi, since these groups share some common features; these features include being found predominantly in fresh water and possessing Weberian ossicles, an anatomical structure derived from the first five anterior-most vertebrae, their corresponding ribs and neural crests. The third anterior-most pair of ribs is in contact with the extension of the labyrinth and the posterior with the swim bladder; the function is poorly understood, but this structure is presumed to take part in the transmission of vibrations from the swim bladder to the labyrinth and in the perception of sound, which would explain why the Ostariophysi have such a great capacity for hearing. Most cypriniformes have scales and teeth on the inferior pharyngeal bones which may be modified in relation to the diet.
Tribolodon is the only cyprinid genus. Several species return to fresh water to spawn. All of the other cypriniformes have a wide geographical range; some consider all cyprinid fishes carp, the family Cyprinidae itself is known as the carp family. In colloquial use, carp refers only to several larger cyprinid species such as Cyprinus carpio, Carassius carassius, Ctenopharyngodon idella, Hypophthalmichthys molitrix, Hypophthalmichthys nobilis. Carp have long been an important food fish to humans. Several species such as the various goldfish breeds and the domesticated common carp variety known as koi have been popular ornamental fishes; as a result, carp have been introduced to various locations, though with mixed results. Several species of carp are listed as invasive species by the U. S. Department of Agriculture, worldwide, large sums of money are spent on carp control. At least some species of carp are able to survive for months with no oxygen by metabolizing glycogen to form lactic acid, converted into ethanol and carbon dioxide.
The ethanol diffuses into the surrounding water through the gills. In 1653 Izaak Walton wrote in The Compleat Angler, "The Carp is the queen of rivers. Carp are variable in terms of angling value. In Europe when not fished for food, they are eagerly sought by anglers, being considered prized coarse fish that are difficult to hook; the UK has a thriving carp angling market. It is the fastest growing angling market in the UK, has spawned a number of specialised carp angling publications such as Carpology, Advanced carp fishing and Total Carp, informative carp angling web sites, such as Carpfishing UK. In the United States, carp are classified as a rough fish, as well as damaging to naturalized exotic species, but with sporting qualities. Carp have long suffered from a poor reputation in the United States as undesirable for angling or for the table since they are an invasive species out-competing more desirable local game fish. Nonetheless, many states' departments of natural resources are beginning to view the carp as an angling fish instead of a maligned pest.
Groups such as Wild Carp Companies, American Carp Society, the Carp Anglers Group promote the sport and work with fisheries departments to organize events to introduce and expose others to the unique opportunity the carp offers freshwater anglers. Various species of carp have been domesticated and reared as food fish across Europe and Asia for thousands of years; these various species appear to have been domesticated independently, as the various domesticated carp species are native to different parts of Eurasia. Aquaculture has been pursued in China for at least 2,400 years. A tract by Fan Li in the fifth century BC details many of the ways carp were raised in ponds; the common carp, Cyprinus carpio, is from Central Europe. Several carp species were domesticated in East Asia. Carp that are from South Asia, for example catla and mrigal, are known as Indian carp, their hardiness and adaptability have allowed domesticated species to be propagated all around the world. Although the carp was an important aquatic food item, as more fish species have become available for the table, the importance of carp culture in Western Europe has become less important.
Demand has declined due to the appearance of more desirable table fish such as trout and salmon through intensive farming, environmental constraints. However, fish production in ponds is still a major form of aquaculture in Central and Eastern Europe, including the Russian Federation, where most of the production comes from low or intermediate-intensity ponds. In Asia, the farming of carp continues to surpass the total amount of farmed fish volume of intensively sea-farmed species, such as salmon and tuna. Selective breeding programs for the common carp include improvement in growth and resistance to disease. Experiments carried out in the USSR used crossings of broodstocks to increase genetic diversity, selected the species for traits such as growth rate, exterior traits and viability, and/or adaptation to environmental conditions such as variations in temperature. Selected carp for fast growth and tolerance to cold, the Ropsha carp; the results showed a 30 to 77.4% improvement of cold tolerance, but did not provide any data for growth
Dam
A dam is a barrier that stops or restricts the flow of water or underground streams. Reservoirs created by dams not only suppress floods but provide water for activities such as irrigation, human consumption, industrial use and navigability. Hydropower is used in conjunction with dams to generate electricity. A dam can be used to collect water or for storage of water which can be evenly distributed between locations. Dams serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions; the earliest known dam is the Jawa Dam in Jordan, dating to 3,000 BC. The word dam can be traced back to Middle English, before that, from Middle Dutch, as seen in the names of many old cities; the first known appearance of dam occurs in 1165. However, there is one village, mentioned in 1120; the word seems to be related to the Greek word taphos, meaning "grave" or "grave hill". So the word should be understood as "dike from dug out earth".
The names of more than 40 places from the Middle Dutch era such as Amsterdam and Rotterdam bear testimony to the use of the word in Middle Dutch at that time. Early dam building took place in the Middle East. Dams were used to control the water level, for Mesopotamia's weather affected the Tigris and Euphrates rivers; the earliest known dam is the Jawa Dam in Jordan, 100 kilometres northeast of the capital Amman. This gravity dam featured an 9-metre-high and 1 m-wide stone wall, supported by a 50 m-wide earth rampart; the structure is dated to 3000 BC. The Ancient Egyptian Sadd-el-Kafara Dam at Wadi Al-Garawi, located about 25 km south of Cairo, was 102 m long at its base and 87 m wide; the structure was built around 2800 or 2600 BC as a diversion dam for flood control, but was destroyed by heavy rain during construction or shortly afterwards. During the Twelfth Dynasty in the 19th century BC, the Pharaohs Senosert III, Amenemhat III and Amenemhat IV dug a canal 16 km long linking the Fayum Depression to the Nile in Middle Egypt.
Two dams called Ha-Uar running east-west were built to retain water during the annual flood and release it to surrounding lands. The lake called "Mer-wer" or Lake Moeris is known today as Birket Qarun. By the mid-late third millennium BC, an intricate water-management system within Dholavira in modern-day India was built; the system included 16 reservoirs and various channels for collecting water and storing it. One of the engineering wonders of the ancient world was the Great Dam of Marib in Yemen. Initiated somewhere between 1750 and 1700 BC, it was made of packed earth – triangular in cross section, 580 m in length and 4 m high – running between two groups of rocks on either side, to which it was linked by substantial stonework. Repairs were carried out during various periods, most important around 750 BC, 250 years the dam height was increased to 7 m. After the end of the Kingdom of Saba, the dam fell under the control of the Ḥimyarites who undertook further improvements, creating a structure 14 m high, with five spillway channels, two masonry-reinforced sluices, a settling pond, a 1,000 m canal to a distribution tank.
These extensive works were not finalized until 325 AD and allowed the irrigation of 25,000 acres. Eflatun Pınar is a Hittite spring temple near Konya, Turkey, it is thought to be from the time of the Hittite empire between the 15th and 13th century BC. The Kallanai is constructed of unhewn stone, over 300 m long, 4.5 m high and 20 m wide, across the main stream of the Kaveri river in Tamil Nadu, South India. The basic structure dates to the 2nd century AD and is considered one of the oldest water-diversion or water-regulator structures in the world, still in use; the purpose of the dam was to divert the waters of the Kaveri across the fertile delta region for irrigation via canals. Du Jiang Yan is the oldest surviving irrigation system in China that included a dam that directed waterflow, it was finished in 251 BC. A large earthen dam, made by Sunshu Ao, the prime minister of Chu, flooded a valley in modern-day northern Anhui province that created an enormous irrigation reservoir, a reservoir, still present today.
Roman dam construction was characterized by "the Romans' ability to plan and organize engineering construction on a grand scale." Roman planners introduced the then-novel concept of large reservoir dams which could secure a permanent water supply for urban settlements over the dry season. Their pioneering use of water-proof hydraulic mortar and Roman concrete allowed for much larger dam structures than built, such as the Lake Homs Dam the largest water barrier to that date, the Harbaqa Dam, both in Roman Syria; the highest Roman dam was the Subiaco Dam near Rome. Roman engineers made routine use of ancient standard designs like embankment dams and masonry gravity dams. Apart from that, they displayed a high degree of inventiveness, introducing most of the other basic dam designs, unknown until then; these include arch-gravity dams, arch dams, buttress dams and multiple arch buttress dams, all of which were known and employed by the 2nd century AD. Roman workforces were the first to build dam bridges, such as the Bridge of Valerian in Iran
