Effects of Water-level Reductions on Littoral Habitat and Recreational Access in Brazos River Reservoirs, Texas

Reservoirs provide recreational opportunities along with water supplies, flood control, and hydroelectricity. Although recreational values are often considered in water management plans, reservoir regulators often lack data to evaluate the impacts of operations on fish habitat and recreational access. We partnered with the Brazos River Authority (BRA) and used reservoir bathymetry and side-imaging sonar data to investigate the effects of reservoir water-level changes on littoral habitat characteristics and boat access in 11 BRA reservoirs. Littoral area, coarse substrate, and submerged aquatic vegetation generally declined with decreasing water level. Availability of large woody debris in the littoral zone was stable as water levels declined. The magnitude of these responses varied among reservoirs, likely due to differences in reservoir morphology. Effects of water-level reductions on boat access were also reservoir specific: complete loss of access occurred with 2 m of water loss in some reservoirs while in others all access remained useable even if water levels declined up to 5m. Categorizing the magnitude of these responses aided in identifying reservoirs most sensitive to water level change. These data facilitated our ability to work proactively with the BRA to incorporate fishery considerations into water management planning and prioritize future habitat and access enhancement efforts.

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