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48-522: Voters in 1986 approved a quarter cent sales tax to fund construction of regional flood control facilities. The first project began in 1988. As of June 2013, a total of $ 1.7 bill was spent on flood control, including construction of 90 detention basins and approximately 581 miles of channels and underground storm drains. To date, 51 square miles have been removed from federally identified FEMA flood zones, saving residents millions of dollars per year in flood insurance premiums. The Regional Flood Control District

96-484: 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

144-414: 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

192-458: A direct connection with the water cycle . It has increased evaporation yet decreased precipitation, runoff, groundwater, and soil moisture. This has altered surface water levels. Climate change also enhances the existing challenges we face in water quality. The quality of surface water is based on the chemical inputs from the surrounding elements such as the air and the nearby landscape. When these elements are polluted due to human activity, it alters

240-454: 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

288-540: 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

336-663: A network of approximately 500 stream gages collecting real time data from all across the state. This then contributes to the 8,000 stream gage stations that are overseen by the USGS national stream gage record. This in turn has provided to date records and documents of water data over the years. Management teams that oversee the distribution of water are then able to make decisions of adequate water supply to sectors. These include municipal, industrial, agricultural, renewable energy (hydropower), and storage in reservoirs. Due to climate change , sea ice and glaciers are melting, contributing to

384-410: 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

432-559: Is also used for irrigation, wastewater treatment , livestock , industrial uses, hydropower , and recreation. For USGS water-use reports, surface water is considered freshwater when it contains less than 1,000 milligrams per liter (mg/L) of dissolved solids. There are three major types of surface water. Permanent (perennial) surface waters are present year round, and includes lakes , rivers and wetlands ( marshes and swamps ). Semi-permanent (ephemeral) surface water refers to bodies of water that are only present at certain times of

480-494: Is caused by over-pumping. Aquifers near river systems that are over-pumped have been known to deplete surface water sources as well. Research supporting this has been found in numerous water budgets for a multitude of cities. Response times for an aquifer are long (Young & Bredehoeft 1972). However, a total ban on ground water usage during water recessions would allow surface water to retain better levels required for sustainable aquatic life . By reducing ground water pumping,

528-631: Is more than 75 percent complete with the Master Plan. Another 31 detention basins are planned, along with 226 miles of conveyance. The District's website , provides citizens information about the District and the progress of flood control in Clark County. The site also gives current rainfall information on approximately 189 locations throughout the county. The District produces a 30-minute television news program six times per year that updates

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576-487: 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

624-614: 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

672-498: Is the forcing of surface water sourced from rivers and streams to produce energy. Surface water can be measured as annual runoff. This includes the amount of rain and snowmelt drainage left after the uptake of nature, evaporation from land, and transpiration from vegetation. In areas such as California , the California Water Science Center records the flow of surface water and annual runoff by utilizing

720-713: 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

768-828: 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,

816-714: 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

864-502: The National Weather Service . This system collects hydrometeorological data primarily for the purpose of detecting situations which could cause flooding. Drainage basin A drainage basin is an area of land in which all flowing surface water converges to 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

912-404: The groundwater . A drainage basin is an area of land where all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. Surface water Surface water is water located on top of land , forming terrestrial (surrounding by land on all sides) waterbodies , and may also be referred to as blue water , opposed to

960-455: The seawater and waterbodies like the ocean . The vast majority of surface water is produced by precipitation . As the climate warms in the spring, snowmelt runs off towards nearby streams and rivers contributing towards a large portion of human drinking water . Levels of surface water lessen as a result of evaporation as well as water moving into the ground becoming ground-water . Alongside being used for drinking water, surface water

1008-623: 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

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1056-406: 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

1104-528: The basins and near the channels and washes . The detention basins operated by the district vary in size from 10 to 50 acres (4.0 to 20.2 ha) and are up to 50 feet (15 m) deep. Given the topography of the area, some areas may not be fixable. One example being the Flamingo Wash where the channel overflows into the Imperial Palace parking garage during flash flooding events. With

1152-436: The chemistry of the water. Surface and groundwater are two separate entities, so they must be regarded as such. However, there is an ever-increasing need for management of the two as they are part of an interrelated system that is paramount when the demand for water exceeds the available supply (Fetter 464). Depletion of surface and ground water sources for public consumption (including industrial, commercial, and residential)

1200-552: The community about the progress of flood control and provides information about flash flood safety. The program airs about 40 times per month on Cox Cable channels 2 and 4, as well as on stations in Laughlin and Mesquite. Since Las Vegas is located in a basin with a single outlet, the Las Vegas Wash , all rain runoff drains to the east side of the basin where it will eventually be deposited into Lake Mead . Rainfall in

1248-430: 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

1296-441: 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

1344-697: 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

1392-857: 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

1440-583: 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 ,

1488-435: 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

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1536-781: 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

1584-639: 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

1632-514: 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

1680-521: The northwest part of the city of Las Vegas for two hours in August 2003, causing some hail damage and considerable water damage. Heavy localized flooding occurred, with property damage reaching into the hundreds of thousands of dollars. In February 2005, the southwest part of the Vegas Valley was hard hit by flooding from the mountain rainfall runoff. Higher than average precipitation that same winter

1728-418: 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

1776-461: The rapid growth occurring in the valley, the plan and finances have not been able to keep up. As a result, developers are deciding to build in areas not yet protected by detention basins or other control measures. This is causing many new home buyers to deal with damage or severe runoff on local streets which are used as flood channels when other facilities are not available. Heavy rainfall can cause localized flash flooding . A thunderstorm hit

1824-631: 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

1872-675: The rise in sea levels. As a result, salt water from the ocean is beginning to infiltrate our freshwater aquifers contaminating water used for urban and agricultural services. It is also affecting surrounding ecosystems as it places stress on the wildlife inhabiting those areas. It was recorded by the NOAA in the years 2012 to 2016, ice sheets in Greenland and the Antarctic reduced by 247 billion tons per year. This number will continue to increase as global warming persists. Climate change has

1920-461: 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

1968-418: 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

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2016-474: The surrounding mountain ranges, can cause flooding in the area as water flows off the mountains onto the valley floor. The area is also subject to localized weather events. It is possible for an area to receive heavy rainfall in a short time, while nearby areas as close as one or two miles (2-3 km) away receive little or no rain. Additional history about past flood events is available as well as some historical rainfall data . The increase of hardscape as

2064-415: 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

2112-477: 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

2160-519: The valley has developed has contributed to an increase of runoff over time. To help alleviate the damage caused by flooding, the Clark County Regional Flood Control District has spent millions of dollars to build detention basins and concrete drainage channels throughout the area. The belief is that these structures will control the flow of water when there is storm runoff and reduce flooding in areas below

2208-673: 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

2256-408: The year including seasonally dry channels such as creeks , lagoons and waterholes . Human-made surface water is water that can be continued by infrastructures that humans have assembled. This would be dammed artificial lakes , canals and artificial ponds (e.g. garden ponds ) or swamps. The surface water held by dams can be used for renewable energy in the form of hydropower. Hydropower

2304-629: Was responsible for significant damage in Mesquite and Overton which, as of that point in time, had not received much attention since their populations were so much smaller than the Las Vegas valley area. In addition to building and maintaining flood control projects, the District also operates a Flood Threat Recognition System of ALERT rain and stream gage , with the cooperation of the United States Geological Survey and

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