"This study evaluates the efficacy of various downstream drainage configurations in mitigating seepage within earth dams, utilizing extensive numerical simulations via the SEEP/W module. Model validity was established through rigorous benchmarking against existing experimental and computational literature, confirming high consistency. Parametric analysis identifies horizontal drain length as the dominant factor in seepage reduction, whereas drain thickness exhibits minimal influence. Specifically, an optimal horizontal drain length-to-dam width ratio (L/B) of 0.34 was determined to maximize performance. In contrast, variations in toe drain angle yielded negligible improvements. Furthermore, inclined chimney drains demonstrated superior hydraulic efficiency compared to vertical arrangements. Beyond specific geometric findings, the research advocates for site-specific design protocols, noting that soil permeability, hydraulic gradients, and dam geometry critically influence seepage behavior, thereby limiting the utility of generalized standards. The study concludes by recommending future inquiries into combined drainage systems and long-term performance under varying environmental conditions. Ultimately, this work validates SEEP/W as a robust tool for optimizing dam safety and sustainability through tailored drainage design."