Water School

Why do lake levels fluctuate?

Despite a common misconception, there are very few “constant level lakes,” and none operated by the Brazos River Authority.  A constant level lake is one that is artificially managed to remain at a specific level essentially by using another source of water to replenish losses due to evaporation, etc.

Several factors can affect a lake’s level and only some are within human control. The chief factor that is not controllable is the impact of climate.  Evaporation is a constant, natural part of the water cycle that causes the liquid form of water to change into gas or vapor and move into the atmosphere reducing the amount of  water in a lake.

During periods when outdoor temperatures rise, the rate of evaporation increases. During periods of drought the effect is even more dramatic.

As temperatures rise, increased demand by residents, agriculture, cities, industry, power plants and others on water stored can also draw down a lake’s level.  This impact is exacerbated during periods of extended drought.

Though it can be frustrating for those who live near Texas lakes or turn to them for recreation, dropping lake levels during a drought are also a sign that a reservoir is successfully meeting one of its basic obligations: supplying water to thirsty Texans during a time of need.




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.