Due to its historical and strategic significance, the Mequinenza dam has a vital importance within the Spanish hydrographic system. From its early stages in the 1960s, it is endowed with a complex and complete auscultation system which at one time detected some remanent displacements, the cause of which was attributed to the swelling (expansion induced by water absorption) of the dam concrete. The works carried out during the 1970s were efficient in controlling the movements, but the diagnosis given includes several questionable aspects. The diagnosis has been recently reformulated and a new proposal has been put forward, explaining the displacements produced more consistently [1]. This paper introduces a numerical analysis based on the 2D finite elements method (FEM), which includes joint elements with no thickness in order to represent the formation and growth of cracking, the results from which support the new proposal regarding the behavior of this dam.