Environmental Flow Standards in Water Availability Modeling
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The Texas Commission on Environmental Quality (TCEQ) has established environmental flow standards in seven river systems through a process defined by the Texas Legislature in its 2007 Senate Bill 3 (SB3). The environmental flow standards have been incorporated in the state’s water right permitting system with a priority date that corresponds to the date when the flow recommendations were received by the TCEQ. Therefore, all the environmental flow standards in the different systems are junior to the water rights previously granted in the state. This thesis first presents a comprehensive literature review of environmental flow standards and an explanation of the process that led to the implementation of environmental flow standards in Texas. Moreover, a comparative assessment regarding the structure of the environmental flow standards is presented to reveal the differences between the river systems defined by TCEQ. Additionally, this thesis presents a research study that used frequency analyses and Water Rights Analysis Package capabilities to evaluate the attainment of environmental flow standards and the impacts of the standards on unappropriated flows. This assessment revealed that none of the standards are met 100% of the time due to the priority system that regulates surface water in the state. This system protects old water rights in the state, so environmental flow standards only affect water availability of future water rights. Because of this, this study included frequency analyses for unappropriated flows considering two scenarios for each system: (a) without including SB3 standards and (b) including SB3 standards. These analyses revealed that attainment of environmental flow and water availability depends on the geographical location.
Cristancho, Camilo Andres (2017). Environmental Flow Standards in Water Availability Modeling. Master's thesis, Texas A & M University. Available electronically from