Over the last several months, I am constantly being asked about Lake Sam Rayburn’s water levels. People want to know why so much water was released following Hurricane Ike. Other people want to verify rumors, such as the lake being lowered to aid in construction of the Cassells-Boykin pavilion and the new fish hatchery. At conservation pool Sam Rayburn’s water level is 164.4 feet above sea level. On January 5th as I write this article the lake level is 157.9 feet above sea level or approximately 6.5 feet below pool. The lowest recorded lake level was in 1996 (150.8 feet above sea level or 13.6 feet below pool). With all that being said leave it there – the best way to think about lake level is what is “normal” or average for each month of the year.

Based on historical water levels, Sam Rayburn fluctuates on a fairly predictable pattern (6-7 feet every year).  Typically, water levels are highest in mid-March (average is 166 feet) and lowest in mid-October (159 feet).  The “normal” lake level for January is about 162 feet above sea level, so right now the lake is only about 3 feet lower than normal for this time of year. I recently met with the U.S. Army Corps of Engineers (USACE) (controlling authority for Sam Rayburn). Hopefully, this article will help inform folks of the factors that affect the lake water levels.

First, let’s dispel some rumors – the lake level HAS NOT been intentionally lowered to aid in any construction projects, including that of the Cassells-Boykin pavilion nor the new fish hatchery. The Lower Neches Valley Authority (LNVA) has water rights down to 149 feet above sea level for Lake Sam Rayburn. LNVA supplies water for irrigation and drinking water supplies for people living in Tyler, Hardin, Liberty, Chambers, and Jefferson counties below Sam Rayburn. Hurricane Ike slammed onto the Texas coast on September 13th, 2008, causing a massive tidal surge. This tidal surge overtopped the salt water barrier that LNVA had installed to help prevent salt water intrusion into its water supplies. Remember LNVA is responsible for supplying fresh water for drinking, irrigation, and for livestock. The USACE began releasing water at full capacity beginning on September 16th through September 19th to help flush out the salt water that had inundated the fresh water supplies in the Lower Neches River. Beginning on September 20th through October 2nd water releases from Lake Sam Rayburn were cut back to 6 hours a day. At the time releases began on September 16th the lake level was 159.6 feet.  On October 2nd the level had dropped 1.3 feet down to 158.3 feet above sea level. Between October 11th and November 16th there was no water released from the dam. Currently the USACE is running one single turbine releasing water 5 hours a day with no operations during the weekend. This is being done to satisfy their power generation requirements and to maintain some water in the Angelina River and Neches River.

Another factor that affects water level is evaporation loss. This is when water simply evaporates into the atmosphere and subsequently produces rain somewhere. There are several factors that affect evaporation rates for a lake. Primarily season, temperature (both air and water), wave action, depth, and size of a lake affect evaporation rates. The USACE measures evaporation losses daily for Sam Rayburn. To give an example of how much water can be “lost” to the atmosphere in one day from Lake Sam Rayburn I’ll walk you through a real example from 2008. On August 25th, 2008 a half of an inch of the lake’s surface level evaporated. Sam Rayburn is roughly 110,000 acres, with a half inch being 0.042 feet at the lake’s size this equates to about 4,620 acre-feet of water that evaporated on a single day in August. An acre-foot is 325,800 gallons of water so multiply that by the 4,620 acre-feet of water that was “lost” and you come up with over a billion gallons of water that simply evaporated from Lake Sam Rayburn on one sunny afternoon this past August. It boggles the mind, but simply put even in the absence of water being released from the dam the lake will drop over time with no rain. Rain is complicated because an inch of rain does not mean the lake comes up an inch. Even though for the last year we had about average rainfall, it came in spurts and down pours. Again we need to think in terms of “normal” and for us that means steady and consistent rain where most often the ground is already wet enough that it becomes saturated pretty easily. With ground saturation we then get runoff that feeds the Angelina River and the creeks that in turn feed the lake. This year we did not have “normal” rainfall, therefore the lake level is also down because evaporation loss exceeded what normally runs into it.

As always, if you have any questions concerning this article or have any other fishery questions please don’t hesitate to contact me at This e-mail address is being protected from spambots. You need JavaScript enabled to view it or call me at 409-384-9572. Good Luck and Good Fishing!

Dan Ashe is a fisheries biologist with Texas Parks and Wildlife Department. He has worked out of the Jasper, Texas field office since 2005 helping to manage east Texas reservoirs including Sam Rayburn and Toledo Bend. Dan has also worked as fisheries biologist in Puerto Rico, California, and Alaska but now calls Texas home.