West Gulf River Forecasting Center (WGRFC) Trinity River Reservoir Model Calibration

The National Weather Service (NWS) West Gulf River Forecast Center (WGRFC) implemented Advanced Hydrologic Prediction Services (AHPS) in the Trinity River basin during 2004. Hydrologic modeling in the Trinity is complicated by a number of water supply reservoirs as well as eight U.S. Army Corps of Engineers (USACE) flood control reservoirs that result in significant regulation in the basin.

WGRFC Flood Category of Highest Forecast River Stage

Additionally, RTi performed calibration of the Sacramento Soil Moisture Accounting (SAC-SMA) model for 16 headwater basins and 20 local areas for incorporation into the forecast system for the Neches, Sabine, and Lavaca-Navidad Rivers in Texas. LAG/K routing model calibration was also performed on 20 river reaches within these basins. RTi calibrated a total of 12 reservoir operations models for the Trinity River Basin so that they adequately simulate normal and flood control operations based on hydrologic model inputs. The USACE flood control reservoirs are operated as a system to control floods at a series of control points on the mainstem and tributaries to the Trinity River. Special treatment of these reservoirs was required to reflect interaction between the reservoirs.

RTi’s approach to the development, calibration, and implementation of the reservoir models included an initial analysis of the system, its operational procedures, and associated historical data, followed by consultation with WGRFC staff to outline an appropriate overall design that would be consistent with the constraints of an operational forecast office. Prior to detailed calibration of the individual reservoirs, RTi developed an initial system model to test the design.

Lavon Lake Dam

A more complete calibration of each reservoir within the system model followed, concluding with the presentation of model results and implementation assistance to WGRFC. The SAC–SMA model was calibrated as the rainfall-runoff model for each sub-basin. Following the assignment of initial model parameters based on physiographic data and review of previous models, the sensitive SAC-SMA parameters were identified and adjusted based on visual and statistical comparison with historic data. Similarly, LAG/K models were developed based on comparisons with available instantaneous discharge.

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