A two-dimensional hydrodynamic model is used to simulate the flow field and the concentration distribution of a conservative tracer in shallow basins. A series of numerical test are performed to evaluate different numerical schemes and problems which arise for the use of the Second Moment Method (SMM) in diffusion dominated flows are reported. The results of the basin simulations are compared with experimental data. The model predicts the location and the size of the dead zones, bypassing, recirculation, and local concentrations within the basin. The positioning of the inlet and outlet, and the presence of baffles are important parameters for the location and size of dead zones. The model gives results which are in agreement with the experimental data. The results show that the hydrodynamic model is quite powerful in terms of predicting correctly the residence time distribution for ponds of various dimensions and shapes.

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