The Science of Summertime Fun June 2019

Ah, the feeling of plunging into a Texas lake, the water tingling your toes, a big smile across your face. Texas summers are the best, and creating summertime memories in our lakes, streams, springs, rivers, and coastal beaches is part of who we are as Texans. But while many of the state's water features are admired for their recreational value and scenic beauty, we can't forget that they're also key elements of our water supply and important habitats for fish and other aquatic life. Quite a bit of planning and science take place to preserve these resources and ensure they will be available for generations to come.

For example, what would a canoeing or float trip be without water? A workout, that's for sure. Water flow (or lack thereof) impacts much more than these activities, though. Instream flow studies conducted by the Texas Water Development Board (TWDB) and sister agencies provide information about the flows required to maintain a sound ecological environment in our state's rivers and streams. We measure water elevations, flow amounts, sediment sizes and amounts, and locations of various habitats. We use these data to study the flows that are required to maintain fish and mussel habitat, maintain water quality, and transport sediments that shape the river channel. The studies help inform policy aimed at balancing human and environmental water needs.

This year we completed a study of the upper Frio River with the Texas Parks and Wildlife Department (TPWD). The Frio River is one of the most beautiful and popular rivers for recreation in southwest Texas, drawing many visitors to the area every year. The portion of the study completed by our Instream Flows Team assisted the TPWD in evaluating the impact of removing sand and gravel on sediment transport and channel shape. The TPWD will use this information to better manage sand and gravel permitting on the Frio River for the benefit of Texans now and for years to come.

Although freshwater flows may start hundreds of miles away from the Gulf Coast, they ultimately affect conditions in bays and estuaries. Estuaries are formed through the mixing of freshwater and seawater and are home to unique plant and animal ecosystems that have adapted to brackish (salty) water. Estuaries support a diverse array of species that serve as the raw materials for economic activities associated with commercial and recreational fishing, hunting, and birding.

The Trinity-San Jacinto Estuary, commonly referred to as Galveston Bay, is the largest estuary in Texas and typically receives 12 million acre-feet of freshwater inflow annually from the Trinity River, San Jacinto River, and surrounding coastal basins. Although Texans who use water from those rivers in their houses and businesses may not realize it, the amount of water they use can affect this estuary.

Freshwater inflow is important to the health of an estuary for a variety of reasons, like maintaining salinity levels critical to fisheries' habitats, flushing pollutants, delivering sediments that maintain delta wetlands and shorelines, and providing nutrients that fuel biological productivity.

The TWDB's Bays and Estuaries Program monitors freshwater inflow volumes and bay conditions and also maintains bay circulation models to better understand the long-term effects of drought and flood on our coastal ecosystems. In partnership with the TPWD, the Estuary Monitoring Program collects water quality data at select locations within each estuary, which is used for these purposes.

So, next time you're chowing down on Texas Gulf Coast seafood, think about all the water conditions that had to be just right for that tasty little oyster to make it to your plate!

Lakes, another source of summertime enjoyment, have a much greater purpose than serving as expansive water playgrounds. (Just so we're clear, we appreciate that benefit, too!) Texas has 188 major reservoirs (lakes) that each hold more than 1.6 billion gallons (5,000 acre-feet) of water, giving them a leading role in ensuring that our growing population has an adequate water supply. That's really why they were built.

When lakes are enjoyed by swimmers and boaters, minuscule pieces of dirt and rock in the water swirl around and eventually sink to the lake floor. Unfortunately, this sedimentation and sedimentation that occurs naturally from run-off causes reservoirs to lose some of their water storage capacity over time. Through the Hydrographic Survey Program, the TWDB performs surveys to determine reservoir storage capacity, sedimentation levels, and rates of sedimentation, which allow planners to project future water supply availability. With population and statewide water use increasing, current estimates of reservoir capacity for water planning purposes are essential.

As we've seen throughout history, the actual amount of water stored in the reservoirs at any time varies. When this article was published (mid-June), statewide reservoir storage was at 90 percent capacity, which is relatively high for this time of year thanks to abundant spring rains across the state. Current and historical reservoir storage data are on www.waterdatafortexas.org.

As summer progresses and outdoor water sources see their annual uptick in recreational enjoyment, let's not forget all the work behind the scenes to plan for and protect this precious resource so that Texans have enough water supply—and memories—for decades to come.

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