<p>In conventional engineering practice, seepage and slope stability analyses are often conducted using a deterministic approach, where soil properties are assumed to be constant. However, this simplistic assumption fails to account for the inherent uncertainties associated with the material and the models used to analyze it. Incorporating the stochastic nature of soil properties, rather than relying solely on deterministic values, can provide a more accurate representation of the system's behavior and lead to more informed decision-making. Also, the stability of earth dams is a critical concern, as the failure of such structures can have catastrophic consequences. This study aims to provide a comprehensive understanding of the factors that influence the overall stability and performance of earth dams, focusing on the role of the clay core location. For this research, Seydon Dam in Iran has been analyzed by slide Rocscience software. The findings indicate that relocating the clay core from the upstream to the downstream side of the dam decreases both the flow through the dam and the safety factor, as well as the reliability of the downstream slope under static and quasi-static conditions. Also, the results of the analysis of spatial variation show that the correlation length in different directions has a great impact on the reliability of the slope.</p>