Application of Indicators of Hydrologic Alteration to Ecological Hydrology in Trinity and Brazos River Basins

As the demand for water resources has been increasing all around the world, intense water appropriation has led to alterations of flow regimes over time. Changes in environmental flows have impaired beneficial functions of ecosystems. Thus, the protection of environmental instream flows to maintain healthy ecosystems has become more and more critical. The Texas Commission on Environmental Quality (TCEQ) has established environmental flow standards through a process established by the Texas Legislature in its 2007 Senate Bill 3 (SB3). The SB3 has expedited the process of developing methodologies and tools to analyze and quantify alterations in environmental flows. Furthermore, with the experts’ participation, the establishment of SB3 has helped lawmakers to improve regulations, laws, and water management practices. This thesis applies the Indicators of Hydrologic Alteration (IHA) software and the TCEQ Water Availability Modeling (WAM) System allied with Hydrologic Engineering Center Data Storage System (HEC-DSS) to analyze and quantify flow conditions at 13 gaging stations in the Trinity River Basin and 20 gaging stations in the Brazos River Basins. The thesis focuses on three types of flows: observed flow, WAM naturalized flow, and WAM simulated regulated flow. The thesis explores long-term alterations in different types of flow characteristics in research areas, develops meaningful frequency metrics, and evaluates capabilities of different methodologies. The results reveal the differences and similarities of alterations in long-term flow characteristics in Trinity and Brazos River Basins. In addition, this thesis proves that the application of IHA is meaningful. Also, the use of the WAM System is fundamental in this thesis