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On the Trinity River, unnaturally high baseflows in summer are released from Lewiston Dam to provide adult Chinook cold water for holding in deep pools until spawning in Fall. The high releases often meet this objective but generate turbulence that prevents thermal stratification in pools that could provide juvenile salmon access to a spatially and temporally wider range of temperatures to maximize growth. To understand how Lewiston Dam releases may be lowered in summer to stratify pools, the first step was to develop a one-dimensional (1D) HEC-RAS hydraulic and temperature model to make 15-minute predictions of water temperature in the restoration reach. The need for the 1D model is to predict inlet temperatures at unobserved discharges for pools the meet the depth criteria (>2 m) for holding spring Chinook. The 1D HEC-RAS hydraulic model was developed using over 900 cross sections cut from bathymetry measured in 2022 and calibrated by adjusting Manning’s roughness coefficients to closely predict water surface elevations measured by jet boat in two events that year. Upstream boundary conditions were Lewiston Dam releases and temperatures with inflows and temperatures from major tributaries with downstream stage from a measured stage-rating curve. The temperature modelling used a full energy budget approach and was calibrated to water temperatures measured at 12 pools in 2021 and at two U.S. Geological Survey gages by adjusting short-wave solar radiation and air temperatures in meteorological inputs to the model. Model performance was strong in predicting observed temperatures in 15-minute increments, as root mean square error, mean error, and mean absolute error were less than 1 oC. The calibrated hydraulic and temperature models at 100, 200, 300, 450, 600, 850, and 1000 cfs releases from Lewiston Dam added to observed tributary inflows. Results closely predicted daily and seasonal water temperatures variations that are expected with increases in discharge and distance from Lewiston Dam. The model also closely predicted the observed number of days that water temperatures were within targeted ranges for juvenile Chinook rearing in June and July 2021 near the downstream end of the model domain.