Surveys help Texas address sedimentation in state reservoirs April 2015

Texans are anything but strangers to the Texas lakes we rush to during spring break or summer vacation. But while people swim, wade, fish, and ski, minuscule pieces of dirt and rock in the water swirl around us and eventually sink to the lake floor. While these sediments do little to disturb our enjoyment of the water, they create problems for the water supply collected in our state's reservoirs.

Sedimentation is the term used to describe what happens when these bits of rock and dirt settle to the bottom of the lake. Sedimentation occurs in reservoirs as soon as they are built and begin to capture and store water. In Texas, this means sedimentation has been taking place for many years. Unfortunately, sedimentation causes reservoirs to lose some of their capacity over time. Since more than half of the available surface water in Texas is stored in reservoirs, it is critical to identify sedimentation's impact on the capacity of this water supply source.

In 1991, the Texas Water Development Board (TWDB) started the Hydrographic Survey Program that provides current data on reservoir capacities through different types of surveys. Reservoir owners contract with the TWDB for these surveys, and the information the TWDB gathers, such as storage capacity, sedimentation levels, and rates of sedimentation, is important to the owners and to regional water planning groups. The planning groups use the information to estimate projected water supply availability.

The TWDB's Hydrographic Survey Program produces maps detailing sediment thickness and reservoir depths, contours, and elevation through its volumetric, sedimentation, and multi-beam surveys. Since 1992, the TWDB has completed 147 hydrographic surveys on 104 unique reservoirs. This includes 81 of the 109 water supply reservoirs monitored in the TWDB's monthly Water Conditions Report.

Now more than ever, as the population and water use increase in Texas, we must conserve and account for every drop of water. The legislature, regional water planning groups, and citizens from all corners of the state are working hard to develop sustainable and affordable water supply solutions. However, reliable data on all water resources, such as our reservoirs, is necessary to make sound planning decisions.

The TWDB's Hydrographic Survey Program makes the information from its surveys available to the public on its website. To learn more about the program or to get your reservoir surveyed, please contact Jason Kemp or call (512) 463-2456.

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