Since its inauguration, in 1993, the horizontal weir crest of the Olympic fountain in Lausanne has suffered from differential settlings leading to a difference in level of more than 30 mm. The settling involves a visible non-uniform discharge distribution along the weir crest. In order to maintain the aesthetics, the discharge has to be increased leading to a high-energy consumption. To reduce the energy consumption, a rehabilitation of the weir crest is needed. A series of numerical simulations are run using the solver FLOW-3D. The obtained results are validated with a circular round crest shape as found in the literature. The numerical and experimental results of the flow behaviour are in good agreement. Two different rehabilitation measures have been proposed. The proposition to install a Plexiglas plate