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44-877: The Llano River ( / ˈ l æ n oʊ / LAN -oh ) is a tributary of the Colorado River , about 105 miles (169 km) long, in Texas in the United States. It drains part of the Edwards Plateau in Texas Hill Country northwest of Austin . Two spring-fed tributaries, the North and South Llano, stretch across the otherwise arid lands of West Texas before merging just east of the small town of Junction , in Kimble County , forming

88-484: A sink , which may be a permanent lake, a dry lake , or a point where surface water is lost underground . Drainage basins are similar but not identical to hydrologic units , which are drainage areas delineated so as to nest into a multi-level hierarchical drainage system . Hydrologic units are defined to allow multiple inlets, outlets, or sinks. In a strict sense, all drainage basins are hydrologic units but not all hydrologic units are drainage basins. About 48.71% of

132-414: A watershed , though in other English-speaking places, "watershed" is used only in its original sense, that of the drainage divide line. A drainage basin's boundaries are determined by watershed delineation , a common task in environmental engineering and science. In a closed drainage basin, or endorheic basin , rather than flowing to the ocean, water converges toward the interior of the basin, known as

176-454: A drainage basin, and there are different ways to interpret that data. In the unlikely event that the gauges are many and evenly distributed over an area of uniform precipitation, using the arithmetic mean method will give good results. In the Thiessen polygon method, the drainage basin is divided into polygons with the rain gauge in the middle of each polygon assumed to be representative for

220-540: A drainage boundary is referred to as watershed delineation . Finding the area and extent of a drainage basin is an important step in many areas of science and engineering. Most of the water that discharges from the basin outlet originated as precipitation falling on the basin. A portion of the water that enters the groundwater system beneath the drainage basin may flow towards the outlet of another drainage basin because groundwater flow directions do not always match those of their overlying drainage network. Measurement of

264-624: A rate of 375,000 cfs. The flooding raised the turbidity of City of Austin 's water supply (which is sourced exclusively from the Colorado River) to untenable levels, forcing the city to issue a seven-day boil water notice By December 2018 payments under the National Flood Insurance Program had exceeded $ 22 million In the end, two people died as a result of the floods. The RM 2900 bridge in Kingsland

308-564: A single point, such as a river mouth , or flows into another body of water , such as a lake or ocean . A basin is separated from adjacent basins by a perimeter, the drainage divide , made up of a succession of elevated features, such as ridges and hills . A basin may consist of smaller basins that merge at river confluences , forming a hierarchical pattern . Other terms for a drainage basin are catchment area , catchment basin , drainage area , river basin , water basin , and impluvium . In North America, they are commonly called

352-867: Is joined by five significant tributaries : the Concho River , Pecan Bayou , the Llano River, the San Saba River and the Pedernales River. Beals Creek is also a tributary fed by arroyos such as the Sulphur Springs Draw , the Johnson Draw , and the McKenzie, Seminole, Monument, Mustang, and Midland draws. Drainage basin A drainage basin is an area of land in which all flowing surface water converges to

396-487: Is referred to as " watershed management ". In Brazil , the National Policy of Water Resources, regulated by Act n° 9.433 of 1997, establishes the drainage basin as the territorial division of Brazilian water management. When a river basin crosses at least one political border, either a border within a nation or an international boundary, it is identified as a transboundary river . Management of such basins becomes

440-614: Is the Dead Sea . Drainage basins have been historically important for determining territorial boundaries, particularly in regions where trade by water has been important. For example, the English crown gave the Hudson's Bay Company a monopoly on the fur trade in the entire Hudson Bay basin, an area called Rupert's Land . Bioregional political organization today includes agreements of states (e.g., international treaties and, within

484-713: The African Great Lakes , the interiors of Australia and the Arabian Peninsula , and parts in Mexico and the Andes . Some of these, such as the Great Basin, are not single drainage basins but collections of separate, adjacent closed basins. In endorheic bodies of water where evaporation is the primary means of water loss, the water is typically more saline than the oceans. An extreme example of this

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528-765: The Continental Divide , northern Alaska and parts of North Dakota , South Dakota , Minnesota , and Montana in the United States, the north shore of the Scandinavian peninsula in Europe, central and northern Russia, and parts of Kazakhstan and Mongolia in Asia , which totals to about 17% of the world's land. Just over 13% of the land in the world drains to the Pacific Ocean . Its basin includes much of China, eastern and southeastern Russia, Japan,

572-714: The Korean Peninsula , most of Indochina, Indonesia and Malaysia, the Philippines, all of the Pacific Islands , the northeast coast of Australia , and Canada and the United States west of the Continental Divide (including most of Alaska), as well as western Central America and South America west of the Andes. The Indian Ocean 's drainage basin also comprises about 13% of Earth's land. It drains

616-580: The Llano Estacado near Lamesa . It flows generally southeast out of the Llano Estacado and through the Texas Hill Country , then through several reservoirs including Lake J.B. Thomas , E.V. Spence Reservoir , and O.H. Ivie Lake . The river flows through several more reservoirs before reaching Austin, including Lake Buchanan , Inks Lake , Lake Lyndon B. Johnson (commonly referred to as Lake LBJ), and Lake Travis . The Llano River joins

660-582: The RM 2900 bridge in Kingsland to collapse and what used to be a two-minute drive across town became a 40-50 minute drive. The flooding was so intense that the Colorado River began to flow backwards briefly. The flood waters entered into the Colorado River and flood gates on every dam on the Texas Highland Lakes were opened. Lake Travis rose 25 feet in 24 hours and water flowed into it at

704-563: The San Saba River , near its confluence with the Colorado River. Nearly defenseless and viewed by the Comanche tribe as a territorial invasion, the mission was sacked in 1758 by about 2,000 Comanches and their allies. The Comanche were not effectively challenged on the upper Colorado River for nearly a century. The river is an important source of water for farming, cities, and electrical power production. Major man-made reservoirs on

748-694: The Colorado at Lake LBJ near Kingsland , and the Pedernales River joins at Lake Travis near Briarcliff . After passing through Austin, the Colorado River continues flowing southeast until emptying into Matagorda Bay on the Gulf of Mexico, near Matagorda . The Colorado River, which means 'red' or 'reddish' river in Spanish, was frequently confused by Spanish explorers with the Brazos River to

792-712: The Highland Lakes: Lake J. B. Thomas near Snyder , E.V. Spence Reservoir near Robert Lee , and O.H. Ivie Lake near Ballinger. Flood control and use of the Colorado River is managed by two agencies established by the Texas Legislature : the Upper Colorado River Authority and the Lower Colorado River Authority . There are 11 major reservoirs along the Colorado River. The Colorado River

836-623: The US, interstate compacts ) or other political entities in a particular drainage basin to manage the body or bodies of water into which it drains. Examples of such interstate compacts are the Great Lakes Commission and the Tahoe Regional Planning Agency . In hydrology , the drainage basin is a logical unit of focus for studying the movement of water within the hydrological cycle . The process of finding

880-406: The basin, it can form tributaries that change the structure of the land. There are three different main types, which are affected by the rocks and ground underneath. Rock that is quick to erode forms dendritic patterns, and these are seen most often. The two other types of patterns that form are trellis patterns and rectangular patterns. Rain gauge data is used to measure total precipitation over

924-430: The discharge of water from a basin may be made by a stream gauge located at the basin's outlet. Depending on the conditions of the drainage basin, as rainfall occurs some of it seeps directly into the ground. This water will either remain underground, slowly making its way downhill and eventually reaching the basin, or it will permeate deeper into the soil and consolidate into groundwater aquifers. As water flows through

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968-441: The drainage area is dependent on the soil type. Certain soil types such as sandy soils are very free-draining, and rainfall on sandy soil is likely to be absorbed by the ground. However, soils containing clay can be almost impermeable and therefore rainfall on clay soils will run off and contribute to flood volumes. After prolonged rainfall even free-draining soils can become saturated , meaning that any further rainfall will reach

1012-697: The drainage basin to the mouth, and may accumulate there, disturbing the natural mineral balance. This can cause eutrophication where plant growth is accelerated by the additional material. Because drainage basins are coherent entities in a hydrological sense, it has become common to manage water resources on the basis of individual basins. In the U.S. state of Minnesota , governmental entities that perform this function are called " watershed districts ". In New Zealand, they are called catchment boards. Comparable community groups based in Ontario, Canada, are called conservation authorities . In North America, this function

1056-857: The eastern coast of Africa, the coasts of the Red Sea and the Persian Gulf , the Indian subcontinent , Burma, and most parts of Australia . The five largest river basins (by area), from largest to smallest, are those of the Amazon (7 million km ), the Congo (4 million km ), the Nile (3.4 million km ), the Mississippi (3.22 million km ), and the Río de la Plata (3.17 million km ). The three rivers that drain

1100-598: The flow rate increased from its normal rate of 111 cubic feet per second (cfs) to 118,000 cfs. Less than a week later the remnants of Hurricane Willa rolled into the area, followed by another front, on October 16, 2018. Upwards of a foot of rain fell in Llano, Texas. The flow rate of the Llano River, in Llano, had increased from its normal rate of 150 cfs to 275,000 cfs. The river crested at 39.9 feet, its highest level in more than 80 years and just 1.5 feet below its record high of 41.5 ft, set in 1935. The high flow rate caused

1144-583: The greatest portion of western Sub-Saharan Africa , as well as Western Sahara and part of Morocco . The two major mediterranean seas of the world also flow to the Atlantic. The Caribbean Sea and Gulf of Mexico basin includes most of the U.S. interior between the Appalachian and Rocky Mountains , a small part of the Canadian provinces of Alberta and Saskatchewan , eastern Central America ,

1188-435: The ground and along rivers it can pick up nutrients , sediment , and pollutants . With the water, they are transported towards the outlet of the basin, and can affect the ecological processes along the way as well as in the receiving water body . Modern use of artificial fertilizers , containing nitrogen (as nitrates ), phosphorus , and potassium , has affected the mouths of drainage basins. The minerals are carried by

1232-781: The ground at its terminus, the area can go by several names, such playa, salt flat, dry lake , or alkali sink . The largest endorheic basins are in Central Asia , including the Caspian Sea , the Aral Sea , and numerous smaller lakes. Other endorheic regions include the Great Basin in the United States, much of the Sahara Desert , the drainage basin of the Okavango River ( Kalahari Basin ), highlands near

1276-615: The head of the Llano River proper. The Llano River runs generally east-northeast through the rolling limestone terrain of the Edwards Plateau as it flows through Kimble County and across rural Mason County , passing to the south of the town of Mason, Texas . Continuing in an easterly direction, the river carves its way through the Llano Uplift , a roughly circular geologic dome of Precambrian rock, primarily granite , located in Central Texas . Flowing through Llano County ,

1320-588: The islands of the Caribbean and the Gulf, and a small part of northern South America. The Mediterranean Sea basin, with the Black Sea , includes much of North Africa , east-central Africa (through the Nile River ), Southern , Central, and Eastern Europe , Turkey , and the coastal areas of Israel , Lebanon , and Syria . The Arctic Ocean drains most of Western Canada and Northern Canada east of

1364-514: The most water, from most to least, are the Amazon, Ganges , and Congo rivers. Endorheic basin are inland basins that do not drain to an ocean. Endorheic basins cover around 18% of the Earth's land. Some endorheic basins drain to an Endorheic lake or Inland sea . Many of these lakes are ephemeral or vary dramatically in size depending on climate and inflow. If water evaporates or infiltrates into

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1408-467: The north were true. As the legend goes, Miranda came across a cave in the side of a hill in the vicinity of the Rio de las Chanas (Llano River), and reported astounding quantities of silver to be found within. On October 9, 2018, a cold front swept through the hill country where it encountered the remnants of Hurricane Sergio . Mason County saw 10" of rain and Lake Travis saw a 3' rise. In Junction, Texas,

1452-494: The north. The European discoverer of these two neighboring rivers called the present Colorado River the Brazos de Dios , and called the present Brazos the Colorado River. The two names would later be reversed. The upper Colorado River was controlled by Comanches from the early 18th century to the late 19th century. In 1757, Spanish Texas attempted to establish an outlying Catholic mission ( Mission Santa Cruz de San Sabá ) on

1496-418: The rainfall on the area of land included in its polygon. These polygons are made by drawing lines between gauges, then making perpendicular bisectors of those lines form the polygons. The isohyetal method involves contours of equal precipitation are drawn over the gauges on a map. Calculating the area between these curves and adding up the volume of water is time-consuming. Isochrone maps can be used to show

1540-631: The responsibility of the countries sharing it. Nile Basin Initiative , OMVS for Senegal River , Mekong River Commission are a few examples of arrangements involving management of shared river basins. Management of shared drainage basins is also seen as a way to build lasting peaceful relationships among countries. The catchment is the most significant factor determining the amount or likelihood of flooding . Catchment factors are: topography , shape, size, soil type, and land use (paved or roofed areas). Catchment topography and shape determine

1584-660: The river include Lake Buchanan, Inks Lake, Lake LBJ, Lake Marble Falls , Lake Travis, Lake Austin , Town Lake now called Lady Bird Lake in Austin. Collectively, these lakes are known as the Highland Lakes . In addition to power plants operating on each of the major lakes, waters of the Colorado are used for cooling the South Texas Nuclear Project near Bay City. The Colorado River Municipal Water District owns and operates three reservoirs upstream of

1628-413: The river passes to the north of Enchanted Rock and flows through the town of Llano, Texas . Northeast of Llano, it turns sharply to the southeast, joining the Colorado from the northwest as an arm of Lake Lyndon B. Johnson , about 15 miles (24 km) southeast of Llano at Kingsland . This river is one of the few popular fly fishing destinations in the state of Texas, and contains Guadalupe bass ,

1672-461: The river rather than being absorbed by the ground. If the surface is impermeable the precipitation will create surface run-off which will lead to higher risk of flooding; if the ground is permeable, the precipitation will infiltrate the soil. Land use can contribute to the volume of water reaching the river, in a similar way to clay soils. For example, rainfall on roofs, pavements , and roads will be collected by rivers with almost no absorption into

1716-418: The speed with which the runoff reaches a river. A long thin catchment will take longer to drain than a circular catchment. Size will help determine the amount of water reaching the river, as the larger the catchment the greater the potential for flooding. It is also determined on the basis of length and width of the drainage basin. Soil type will help determine how much water reaches the river. The runoff from

1760-537: The state fish of Texas. The Llano also contains largemouth bass , Longnose gar , Spotted gar , and various sunfish . The river is also associated with the legend of the Los Almagres Mine. Translated from Spanish, almagre means red ochre. In 1756, the lieutenant-general of Texas (then still a province of New Spain ), Don Bernardo de Miranda, launched an expedition from San Fernando ( San Antonio ), to ascertain whether rumors of rich mineral deposits to

1804-415: The time taken for rain to reach the river, while catchment size, soil type, and development determine the amount of water to reach the river. Generally, topography plays a big part in how fast runoff will reach a river. Rain that falls in steep mountainous areas will reach the primary river in the drainage basin faster than flat or lightly sloping areas (e.g., > 1% gradient). Shape will contribute to

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1848-477: The time taken for runoff water within a drainage basin to reach a lake, reservoir or outlet, assuming constant and uniform effective rainfall. Drainage basins are the principal hydrologic unit considered in fluvial geomorphology . A drainage basin is the source for water and sediment that moves from higher elevation through the river system to lower elevations as they reshape the channel forms. Drainage basins are important in ecology . As water flows over

1892-673: The world's land drains to the Atlantic Ocean . In North America , surface water drains to the Atlantic via the Saint Lawrence River and Great Lakes basins, the Eastern Seaboard of the United States, the Canadian Maritimes , and most of Newfoundland and Labrador . Nearly all of South America east of the Andes also drains to the Atlantic, as does most of Western and Central Europe and

1936-515: Was rebuilt less than a year later. Colorado River (Texas) Its drainage basin and some of its usually dry tributaries extend into New Mexico . It flows generally southeast from Dawson County through Ballinger , Marble Falls , Lago Vista , Austin , Bastrop , Smithville , La Grange , Columbus , Wharton , and Bay City , before emptying into the Gulf of Mexico at Matagorda Bay . The Colorado River originates south of Lubbock , on

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