Existing studies of sediment retention ponds (SRPs) have examined the effect of pond layout, inlet and outlet geometry and installation of baffles on the performance of the SRPs. However, the effect of a temperature difference between the pond and the inflow is a neglected phenomenon, with the buoyancy forces arising from differences in temperature potentially changing the flow in the pond. This study evaluates the effect of these temperature differences on the flow pattern and residence time in a retention pond. In this research an innovative experimental setup was used to create the temperature differentials. The results reveal that cold inflow sinks to the bottom of the pond while hot inflow remains at the surface, and in both cases the inflow moves more rapidly towards the outlet than in the isothermal case. A counter current occurred at the bottom or the surface of the pond for colder or hot influent, respectively. These thermally induced flows significantly reduced the hydraulic performance of the pond and caused severe short-circuiting. The results also show that the temperature differences in the pond decrease with time, yet small temperature differences persist with the pond remaining stratified.