TxBLEND is a version of the BLEND model, developed by Dr. William Gray of Notre Dame University, which was modified by TWDB engineers for use in the shallow bays and estuaries of Texas. TxBLEND is a two-dimensional (vertically-averaged) finite-element model which solves the continuity equation, momentum equations, and the advection-diffusion equation for conservation of salt. The model uses unstructured, numerical grids based on the bathymetry of each bay. Each bay model may have one or more inflow points that correspond to natural drainages into the estuary. Model output includes time-varying depth and vertically-averaged horizontal velocity components of flow and salinity throughout the model domain. TxBLEND thus provides water velocity, surface elevation, and salinity at each node in the model grid. The model does not provide information about vertical variation within the water column, but rather provides information about horizontal variation, such as salinity zonation patterns throughout the estuary. TWDB has calibrated and validated TxBLEND models for all seven of the major estuaries in Texas including Sabine Lake, Galveston Bay, Matagorda Bay, San Antonio Bay, Aransas and Copano Bays, Corpus Christi Bay, and the Upper and Lower Laguna Madre. TWDB also has multi-bay models, such as for the bays in the Coastal Bend. TWDB has developed a series of reports documenting the calibration and validation of TxBLEND for the major estuarine systems.

Texas Water Development Board (TWDB), in partnership with the Texas General Land Office (TGLO) Oil Spill Prevention and Response effort, maintains near real-time and forecast simulations of water circulation in the major bays for use in the event that an oil spill occurs within Texas bays. For bays with heavy ship traffic, these models quickly provide information to TGLO responders on the potential path of an oil spill by predicting water current direction and speed throughout the bay. TWDB has models for Sabine Lake, Galveston Bay, Matagorda Bay, and Corpus Christi Bay and is in the process of developing a model for San Antonio Bay.