Natural streamflow cycles and effects on water supply reliability

Abstract

The Texas Natural Resource Conservation Commission, its partner agencies, and contractors are conducting a statewide Water Availability Modeling (WAM) Project pursuant to Senate Bill 1 enacted by the Texas Legislature in 1997. Climate change is not explicitly considered in the WAM Project. The main objective of this thesis is to assess the significance of potential impacts of climate change trends and cycles in the Texas WAM. The study focuses on the Brazos River Basin that constitutes one of the principal river basins within the state of Texas. Climate change impacts on naturalized streamflows are addressed, and a 98-year, 1900 to 1997, period of analysis is used throughout the study. Statistical analyses of naturalized streamflows at selected gauging stations in the Brazos River Basin are implemented in order to detect long-term or step-wise trends and cycles. An attempt to explain the behavior of specific cycles is also made by correlating them to the past ENSO events that have occurred during the last century. Results of these statistical analyses are further used to establish the validity of the WAM Project under climate change. This particular objective is realized by the assessment of impacts of climate change and cycles on water supply reliabilities, based on using the WRAP model, which represents the river/reservoir management model of the WAM Project. A conditional reliability version of the WRAP model is also being used to address specific problems related to short-term water supply reliabilities conditioned upon current reservoir storage contents.