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Nikki Ingram, P.E. - Project Engineer, Tyler Water Utilities

Lake Tyler is a critical asset for the City of Tyler. Its primary function is that it serves as a water supply reservoir that provides high-quality drinking water to the community. It also promotes outdoor recreational activities like boating, fishing, and swimming. It does provide passive flood mitigation in that it collects all the stormwater runoff in the surrounding areas. 

We’re primarily interested in the sedimentation build-up trends and then the current capacity of the lake. When the boats go through the lake, the waves can create erosion along the shoreline. Also, when we get that runoff, the runoff does contain sedimentation that will build up in the lake over time.

A bathymetric survey is essentially the underwater equivalent of a topographic map. It uses sonar equipment to measure the depth and shape of the lakebed. And then, we take these measurements, and they help us analyze the sedimentation build-up around the lake and then how much the volume and capacity of the lake has changed since it was first constructed. And we are currently working with the Texas Water Development Board to conduct a new bathymetric survey.

Josh Duty – Hydrologist, Texas Water Development Board

So, for the Lake Tyler contract, we're doing a volumetric and sedimentation survey where we're going to be using a single-beam multifrequency sonar. The sonar is equipped with a 200 kilohertz, a 50 kilohertz, and a 12 kilohertz transducer. And all three of those transducers record data simultaneously as we collect data. And then, we'll go back and review that data. And then, we'll come back and do part two, which is the sedimentation survey where we collect sediment cores.

Before we leave the office, we have to create a lake boundary to input into the survey software. We create that lake boundary using historical topographic maps, aerial photographs, also using Lidar data. And then, once we delineate our reservoir boundary, we create our transect files or what we also call plan survey lines. And then, we come out on good weather week; come out, launch the boat. We'll calibrate our equipment. We'll collect speed of sound measurements. And then, we'll survey on those plan survey lines throughout the reservoir until we get done.

So, we typically could finish a reservoir this size anywhere between 5 to 8 days depending on weather, boat traffic, the number of docks we have to drive around, any underwater obstacles, standing timber. 

These volumetric and sedimentation surveys are important for the city to do. And they can make really good management decisions on what they need to do here for their citizens.

Nikki Ingram, P.E. - Project Engineer, Tyler Water Utilities

The Texas Water Development Board has taken a proactive approach in helping the City of Tyler look at this bathymetric survey and look at the sedimentation build-up and volume and capacity of Lake Tyler. And then, in the end, this will help us in looking at our long-term future and what kind of infrastructure improvements we need to make around the lake. We're very thankful for the Texas Water Development Board and helping us like they do help all the communities around Texas.