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Water School

Archive by category: HydrologyReturn

What is the water cycle?

The water cycle is the continuous process of water moving from Earth's oceans, atmosphere and land. This cycle does not move in a particular order but in many different variations because different variables impact it like, topography, temperature and location.      Through precipitation, water condenses, forming a liquid and falling to the Earth as rain, snow, hail or fog. Once on the ground, water either remains in its liquid state, freezes, becoming ice or evaporates, or be...
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How is the flow of the river measured?

The rate of the river flow is measured in cubic feet per second (cfs), which is the measure of the volume of water passing any given point in a river in one second. One cubic foot of water is about the size of a beachball. These levels are measured by the United States Geological Survey (USGS) along the course of the waterflow at different points, or subsections, along a marked line. A river will typically be measured approximately 25 to 30 times at regularly spaced locations. USGS gage loc...
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What is an acre-foot?

An acre-foot is commonly used to measure water volume. It is the amount of water needed to cover one acre (43,560 square feet) with one foot of water. One acre-foot is equal to 325,851 gallons of water, enough to cover a football field with a foot of water.Measuring acre footage is an important way to calculate the volume of large water resources, like irrigation sources, reservoirs, sewers, canals, and human-made lakes, such as Possum Kingdom Lake, which is located in Palo Pinto, Jack, Young, ...
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What is a drought?

A drought is generally considered to be a prolonged period of less-than-normal precipitation such that the lack of water causes below-average streamflow or lake levels, lowered soil moisture, crop damage, or economic losses.  Droughts are globally the second-most costly weather event behind hurricanes, according to National Geographic. In Texas, during the 2011 drought, an estimated $7.62 billion was lost by farmers and ranchers, according to Texas AgriLife. Not only are droughts one o...
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What is a flood plain?

A floodplain is any ordinarily dry land area susceptible to inundation by water. This area is usually low, flat, and next to a stream or other body of water. Living on a floodplain can be especially dangerous in the circumstance that flooding does occur. There is always some risk for those on a floodplain, whether it’s people, businesses, or agriculture. Some floodplains are clearly defined by natural features, by infrastructure made by people, or not clearly outlined.Some floodplains are ...
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What is "firm" water?

Firm water is a supply term referring to the specific amount necessary to fully supply an area with water during a repeat of the most severe drought within the historical record.
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What is the National Flood Insurance Program?

The National Flood Insurance Program is a federal insurance program under which flood-prone areas are identified and flood insurance is made available to residents of participating communities that agree to adopt and enforce floodplain management ordinances to reduce future flood damage.  For additional information and qualification requirements, click here.
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What is constant level?

Constant level is a term given to the practice of maintaining a body of water at a specific elevation.  No natural body of water has a constant level.  While some fluctuate more than others, all-natural bodies of water change on a daily basis, some rapidly during floods.Few man-made reservoirs have the ability to be maintained at a constant level as evaporation, drought, water use and/or flooding affect elevation levels. 
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What is cubic foot per second?

The measurement cubic foot per second (cfs or ft3/s) is the rate of water movement representing a volume of 1 cubic foot passing a given point during 1 second.  This measurement is equivalent to approximately 7.48 gallons per second or 448.8 gallons per minute.
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What is bankfull stage?

Bank-full stage is an established river stage at a given location along a river that represents the maximum safe water level that will not overflow the river banks or cause any significant damage within the river reach.
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What is the USGS?

The United States Geological Survey (USGS) is a federal scientific agency that works in biology, geography, geology and hydrology. USGS is the nation’s primary civilian mapping agency. The agency also monitors streams and other bodies of water across the country for flow and depth. Among its other activities, USGS also monitors earthquakes and volcanic activity.The USGS web site may be found by clicking here.
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What is pH?

A measure of water’s alkalinity or acidity is called pH. Water with a pH of 7 is neutral; lower pH levels indicate increasing acidity and higher pH levels indicate increasingly basic solutions.
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What is datum?

Datum is the basis for relating a river's stage to mean sea level. (datum + stage = elevation in feet above mean sea level)
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What is a gaging station?

A gaging station is a site on a stream, lake, reservoir or other body of water where observations and hydrologic data such as gage height and stream discharge are obtained.
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Why are there so many man-made lakes in Texas?

Natural lakes have been a rare commodity in Texas. In fact, the state had only one natural lake, Caddo Lake in East Texas, that was formed by a log jam.  A permanent dam was installed at the lake in the early 20th century.A large number of the state’s remaining lakes were made in response to the occasional propensity of Texas’ usually tranquil rivers to flood during heavy rains.Texas’ early history is filled with accounts of devastating floods causing loss of human life an...
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What is mean sea level?

Mean sea level is the average height of the ocean’s surface, between high and low tide. It is used as a standard in reckoning land and other elevations such as lake levels. A lake’s conservation pool will be measured as a certain number of feet above mean sea level.
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I’ve heard that reservoirs have a “lifetime.” What does that mean?

Texas streams and rivers are in constant motion and the waters they pour into our reservoirs carry with them a continuous but varying amount of sediment.When the water is slowed or stopped as it runs into a reservoir or by a dam, the sediment drops to the bottom. This sediment builds up year after year and at some point, fills the reservoir to a point it can no longer continue to serve its purpose in flood control or water supply. Without expensive dredging, this would be the end of the res...
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What is yield?

Yield refers to the amount of water produced by a water treatment process or the quantity of water that can be collected for a given use from surface or groundwater sources. The yield may vary depending on the proposed use, the development plan, location of the water source, and economic considerations.
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What is a flood pool?

A flood pool is a specified area within a flood control lake and the surrounding land that may only be inundated during periods of flooding. This allows the flow of waters to be regulated and released in a safe manner.
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What is a 100-year flood?

A 100-year flood is a flood event that it has a 1 percent chance of happening in any given year. The term “100-year” is a measure of a flood’s size, not how often it occurs. Although statistically unlikely, several 100-year floods can occur within the same year or a few short years. It is also called the base flood.
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What is a drought of record?

A drought of record is the worst recorded drought since compilation of meteorologic and hydrologic data began.  In terms of severity and duration, the devastating drought of the 1950s is considered the drought of record for many areas in the Brazos River basin. This drought lasted a decade in many places and covered much of the nation, including all of Texas.  In 2008-2009, some parts of the state recorded a new drought of record.
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What is Xeriscape?

Xeriscaping [zeer-i-skey-ping] is a form of landscaping that uses native plants and those adapted to survive in areas with periods of low precipitation.  Using this technique can help conserve water or deal with periods of drought. Xeriscaping is becoming a more popular landscaping option because it’s environmentally friendly and saves the homeowner money by reducing watering costs and puts less strain on water resources.Drought-friendly plants also are a great option for households t...
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The information provided on this site is intended as background on water within the Brazos River basin. There should be no expectation that this information is all encompassing, complete or in any way examines every aspect of this very complex natural resource.

If you have questions about a post or would like additional information, please contact us or call 888-922-6272.

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