Water School

The level of water in all lakes fluctuates, raising during years of higher amounts of rainfall and snowmelt and falling during periods of drought. The Environmental Protection Agency has been measuring the fluctuations of the Great Lakes, the largest natural lakes in the United States, since the 1860s. Similarly, water levels in reservoirs, human-made lakes, fluctuate because of evaporation, a lack of rainfall, water supply use, and water flow requirements. Levels tend to be relatively lower in ...

Possum Kingdom Lake, located on the main stem of the Brazos River northwest of Fort Worth, was the first water supply reservoir constructed in the Brazos River basin. Located in Young, Palo Pinto, Stephens, and Jack counties, the construction of the Morris Sheppard Dam was begun in 1938 and completed in 1941 with the aid of the Works Progress Administration Program.Possum Kingdom Lake covers an area of 16,716 acres with 219 miles of shoreline. The reservoir holds approximately 556,340 ...

DeCordova Bend Dam and Lake Granbury were constructed by the Brazos River Authority and are maintained and operated by the BRA as a source of water supply.Construction of the project began in December 1966 and was completed in September 1969. The reservoir provides 129,011 acre-feet of storage capacity for conservation of flood and storm waters to meet requirements of municipalities, industries, agriculture and mining.  The reservoir has a permitted yield of 64,712 acre feet. ...

Lake Limestone, located on the upper Navasota River in Limestone, Robertson and Leon counties, is a water supply reservoir built by the Brazos River Authority in 1978. Construction of the reservoir was made possible through the sale of water to Texas Electric Utilities to be used by their lignite-burning electric plants in the area.  To view a copy of the Lake Limestone state permit, click here.Water from the reservoir is supplied for similar use at a NRG steam-electric plant just...

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. 

Allens Creek Reservoir is a planned water storage lake permitted for construction on Allens Creek, a tributary of the Brazos River, in Austin County. The permit to build the lake was originally issued to Houston Lighting and Power (Reliant Energy) in 1974 by the Texas Natural Resource Conservation Commission, now known as the Texas Commission on Environmental Quality (TCEQ).The reservoir was originally to have served as a cooling lake for a nuclear power plant. When Reliant Energy abandoned plan...

The height above mean sea level that water in a reservoir has reached. Brazos River Authority and U.S. Army Corps of Engineers lakes are actually reservoirs, or parts of the Brazos River basin impounded by dams. (A free-flowing river is measured in stages, that is, by depth from the river bed to the surface.)

There are a number of factors that may affect water clarity.  The chief factor in the clarity of lakes and rivers in Texas is sediment. The more sediment in a stream or body of water, the cloudier it appears. This factor can vary depending on geography and climate. Some areas naturally have more sediment drawn from the surrounding land, particularly agricultural areas, where soil is often broken up and exposed. Water tends to be cloudier during rainier seasons when runoff carries topsoil and oth...

A watershed is the land area or topographic region that drains into a particular stream, river, or lake. This land feature can be identified by tracing a line on a map along the highest elevations between two areas.Large watersheds may contain hundreds or thousands of smaller subwatersheds that drain into the river or other waterbody. The Brazos River watershed encompasses more than 42,000 square miles and includes many smaller streams and rivers with their own smaller watersheds.

A reservoir may be a pond, lake or basin, either natural or man-made, 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.

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...

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...

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.