Water School

A reservoir may be a pond, lake, or constructed basin, either naturally made or made by people, used for the storage, regulation, and control of water.

Releases are made for several reasons including water supply for users near the lake and downstream, to pass through water released from another system reservoir, or to refill storage in a downstream reservoir.  For a look at current lake levels, click here.

Beneficial use represents the amount of water necessary when reasonable intelligence and diligence are used for a stated purpose authorized by a water rights permit. Such uses include watering crops, municipal, mining, and industrial use.Beneficial use results in a gain or benefit to the user and society, which is consistent with state law. Most states recognize the following uses as beneficial: domestic and municipal, industrial, irrigation, mining, hydroelectric power, navigation, stock r...

Water supply refers to the amount of water stored and available for consumption by municipalities, agriculture and industry.

Salinity or chloride concentration, refers to the amount of salt dissolved or contained in water. The higher the salinity, the less useful the water is for human consumption, agriculture and other uses.The Brazos River particularly in the upper part of the watershed, contains a high amount of salinity due to a naturally occurring underground salt deposits located northwest of Abilene.  As a result, surface water in some areas of the Brazos River must be treated to remove the amount of salt befor...

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...

While the process may vary for each location, here’s a general outline of how a reservoir goes from idea to reality.Once a need for water in an area is established, a site for the reservoir must be chosen. Several factors go into this decision, including nearness to a source of demand, a feeder supply of water (such as a river or creek), the geological suitability of the area and engineering constraints. Other factors considered could include impact on the environment, the local population...

The great majority of our lakes (reservoirs) in Texas were built to help tame the state’s rivers and streams, which from time to time would swell beyond their banks and cause devastating floods. Such was the case with the Brazos River. History books record numerous destructive floods took place in the Brazos basin before a series of dams were built along its length to create reservoirs to hold periodic flood waters.

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.

Periodically, officials conduct surveys of reservoirs within the Brazos River basin to determine each lake’s volume. As part of that work, survey crews determine each lake’s depth (in feet). Do not confuse this measurement with lake level, however.A reservoir’s depth is the distance from the bottom to the top of the conservation pool, the point where the lake is considered full. The lake level is the number of feet the surface is above mean sea level.Surveys use a combinat...

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...

To overdraft a reservoir, aquifer or basin is to withdraw water out faster than the water can be replenished by rain, runoff or percolation.  Overdraft may also refer to an use of the permitted yield of a reservoir.

The conservation pool of a reservoir is a specified amount of water dedicated to water storage. This water is to be used to meet water needs, including municipal, domestic, agricultural, industrial, and recreational.

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.

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.

Evaporation is the process in the water cycle in which liquid water becomes water vapor.

This doctrine has its roots in the 1800s, when Texas officials determined riparian doctrine did not address the needs of more arid parts of the state. Since the late 19th century, land acquired from the state has used prior-appropriation doctrine instead of riparian when considering water rights.Under this approach, water rights are based on seniority.  In other words, one’s water rights are based on the date one applied for the right, with older claimants having seniority. However, those pre-e...

Water rights in Texas are complicated.  They date back to Spanish colonial law, but also include influences from English common law, a history of state legislation as well as judicial decisions. Water rights in Texas are further complicated because ground and surface water rights are approached differently. Generally, water rights law determine who can use water, how much may be used and for what purpose.

Different laws for surface water use have led to conflicting claims over time. In 1967, the Texas Legislature directed a predecessor of the Texas Commission on Environmental Quality to settle claims. The agency looked at all claims and issued certificates of adjudication for those they approved. Each was assigned a priority date that determined the claimant’s seniority for water rights.

The Texas Water Code provides for water permitting in a “first in time; first in right” basis.  This practice establishes a place in line for water users with the earliest permits being guaranteed priority to take water over those with more “junior” permits.  This date is important as it determines who priority to divert and use water first.

Senior rights have an earlier priority date and claimants who hold them have a higher priority to divert water from a stream or water body than those with more junior rights. However, in times of scarcity, when there is not enough water to meet demand in a basin, those who need water for domestic and livestock use have first right to water, regardless of one’s priority date.After domestic and livestock needs are met, those with senior water rights can insist diversions by those with junior wate...

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.

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.

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...

Water is an essential part of the electrical generating process at steam-electric power plants. The plants generate heat, either through the burning of fossil fuels, or in the case of a nuclear plant, through a nuclear reaction. Water is pumped into the area and turned to steam by the heat. That steam builds pressure, which turns the turbines that generate electricity.  After passing through the turbines, the spent steam must be cooled to remove the remaining heat from the process.  Water from t...

A hydroelectric plant uses energy provided by the weight of water to rotate turbines that generate electricity.  Considered renewable energy, hydroelectric plants are located at dams and utilize water stored in the reservoir.  Once the stored water is passed through the turbines to generate electricity, it is allowed to continue downstream.