Texas A&M University – Lake Granbury and Bosque River Assessment Final Scientific/Technical Report

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Texas Water Resources Institute

The “Texas A&M University – Lakes Granbury and Waco, and Bosque River Assessment” project was developed to address two separate water quality issues in Central Texas. Prior work in each waterbody has identified major water quality concerns and laid the ground work for the activities conducted in this project. Lake Granbury and the Bosque River both serve vital roles in the Brazos River watershed. Lake Granbury is a reservoir constructed on the main stem of the Brazos River in Hood County, Texas and provides a potable water supply for over 250,000 area residents, cooling water for a natural gas fired and a nuclear power plant, vital flood control for the city of Waco and a critical economic stimulus for the city of Granbury and surrounding areas. The Bosque River, also in the Brazos River watershed plays a vital role in Central Texas as well; it feeds Lake Waco and supplies water for 200,000 Central Texans. Lake Granbury has experienced recent toxic blooms of Prymnesium parvum (Golden algae) that have resulted in massive fish kills and concerns about general water quality. Lake Waco, a reservoir constructed on the main stem of the Bosque River, has viable P. parvum populations, but does not experience harmful blooms. Thus, comparisons between Lakes Granbury and Waco allow for comparisons of environmental conditions leading to bloom formation. Both Lake Granbury and Lake Waco are critical to this region as being primary water supplies, sources of revenue and recreational hotspots. This project addressed these water quality issues by providing critical information about the relationships between the contaminants (Golden algae and nutrients) and environmental factors in the respective watersheds. In Lakes Granbury and Waco, various plankton, nutrient and water quality samples were collected at fixed-location stations, and high-resolution spatial maps were generated using an on-board dataflow technology of various plankton and water quality parameters. Linkages between the toxic Golden algae blooms and environmental conditions were examined. In addition, a numerical model of Lake Granbury was developed and continues to be refined. Bloom forming processes were investigated with this model. In the Bosque River, elevated nutrient levels have lead to increased aquatic vegetation growth and subsequent taste and odor problems in Lake Waco. This project enlists physically based computer modeling to determine the nutrient and sediment removal capabilities of implementing recommended Best Management Practices (BMPs) throughout the watershed. Results of this project indicate areas where specific management strategies will provide the most pollutant control for the cost to implement the practice. Each project is focused on addressing specific water quality issues in a specific water body, but each will provide valuable information that can be used to correct water quality concerns in other watersheds with similar problems. Ultimately, the project will result in improved water quality for consumptive, recreational, and industrial uses and will help to sustain the economic stimulus resulting from these water bodies.