A two-dimensional numerical model is developed to simulate the behavior of a salt gradient solar pond (SGSP) of 1 x 1 x 1 m(3). The numerical code takes into consideration double-diffusive convection in the pond, solar radiation absorption through the horizontal fluid layers, and allows an appropriate treatment of the boundary conditions at the water free surface. The transient evolution of the SGSP covers the first 5 days of July 2011 under weather conditions of Marrakesh Morocco. The study aims to investigate qualitative and quantitative thermal performances of the considered pond. In addition, a stability analysis of the intermediate non-convective zone (NCZ) of the pond is performed. Flow velocities are solved using the Lattice-Boltzmann method with the Cascaded Multi-Relaxation-Time scheme (CMRT-LBM) while both temperature and salt concentration fields are computed by the Finite Volume (FV) approach. The obtained results show that the mean temperature in the heat storage zone (HSZ) increases each day with a rate around 5 degrees C. In the absence of heat extraction, the daily amount of energy accumulated in both heat storage zone and non-convective zone increases linearly during the simulation period to reach respectively 11.3 kWh and 5.9 kWh at the end of the simulation. The present study confirms the substantial capacity of storage in the SGSP and the ability of the elaborated model to describe the erosion of the non-convective zone by predicting the motion of its limiting interfaces.