Assessment of Flood Control Capabilities for Alternative Reservoir Storage Allocations

Reservoir operation and storage allocation are important duties for agencies and water management professionals in Texas and elsewhere responsible for supplying water for municipal, industrial, and agricultural uses, hydroelectric power generation, recreation, navigation, and maintenance of instream flow for fish and wildlife, and protecting human lives and properties from flooding. Flood control capabilities for alternative reservoir storage allocations are assessed in the thesis research using the Water Rights Analysis Package (WRAP) with a daily version of the WRAP input dataset for the Trinity River Basin from the Texas Water Availability Modeling (WAM) System expanded to incorporate flood control operations. Tradeoffs between flood control and water supply in multiple-purpose reservoirs are analyzed. A system of eight multiple-purpose reservoirs operated by the United States Army Corps of Engineers (USACE) in the Trinity River Basin serves as a case study for this research. WRAP/WAM capabilities for simulating reservoir system operations for flood control were tested and improved. Frequency analyses of maximum annual storage levels were performed for both actual observed storage and storage computed by the simulation model for alternative modeling premises and reservoir operating strategies. The frequency analyses focused on determining the probability of exceeding flood control storage capacities. The Hydrologic Engineering Center (HEC) Statistical Software Package (SSP) was used to apply the log-normal and log-Pearson type III probability distribution functions. Various issues in simulating multiple-purpose reservoir systems and performing storage frequency analyses were investigated. Reallocations of storage capacity in the eight reservoirs from water supply to flood control can be implemented by raising the designated top of conservation pool. Impacts on flood control are evaluated in this study in terms of probability of overtopping the flood control pool. Impacts on water supply are quantified based on changes in reliability metrics. Alternative nine simulations are performed in WRAP for the eight Trinity River Basin Reservoirs. Three of the nine simulations are reallocation of storage capacities from flood control pool to conservation pool. Storage capacities, flood frequency analyses, and water supply reliabilities are compared and assessed for both actual observed storage capacities and simulation results