Three-Dimensional Hydrodynamic and Sediment-Transport Modeling of a Shallow Urban Lake in the Brazilian Amazon

A three-dimensional numerical model was developed using Delft3D-Flow to simulate temperature dynamics, flow circulation, and sediment transport in Água Preta Lake, a shallow urban lake in the Brazilian Amazon. The simulation incorporated meteorological and physical data—including water inflows, temperature, bathymetry, and bed roughness—collected through in situ campaigns and meteorological stations. It was calibrated using a temperature time series (RMSE = 0.27 °C; MAE = 0.87 °C; R2 = 0.79; ρ = 0.89), and validated with two flow velocity measurements (RMSE = 0.009–0.012 m/s; ρ = 0.1–0.5) and with 19 temperature profiles over 4 months (RMSE = 0.08–0.93 °C; MAE = 0.12–2.04 °C; R2 = 0.00–0.99; ρ = −0.29–0.99). Due to its shallowness, the lake does not develop thermal stratification, with a maximum vertical temperature difference of only 2 °C. The lake is fed by high-discharge inflows that significantly affect internal circulation and promote resuspension. This may increase turbidity and possibly alter ecological dynamics, favoring eutrophication processes. Additionally, the simulation showed sediment accumulation rate of 27,780 m3/year; if continuous, this indicates complete siltation in about 318 years. These results emphasize the importance of ongoing monitoring, effective management of anthropogenic pressures, and restoration efforts, to prevent further degradation of these systems.