Seepage through soil is among the most prominent hydraulic phenomena threatening the safety of engineering structures such as earth dams, foundations, retaining walls, and deep excavations. Geotechnical engineering stands out as the scientific field concerned with understanding the movement of water within soil and analyzing it quantitatively, ensuring design efficiency and the long-term sustainability of the structure. Seepage occurs when water flows through the voids between soil particles under the influence of a difference in hydraulic head between two points. The amount of flow depends on the soil's permeability and hydraulic gradient according to Darcy's law, and its danger increases in coarse soils and at water exit zones at the upstream face of a structure or at the bottom of an excavation. The geotechnical engineer's role includes carrying out site investigations, determining the sequence of soil layers and the groundwater level, measuring the coefficient of permeability in the laboratory and in the field, and then analyzing seepage using flow nets or numerical modeling with the finite element method and software such as SEEP/W, in order to estimate the seepage discharge and the distribution of water pressures before construction. Seepage affects the stability of structures by raising pore water pressure and reducing effective stress and the soil's shear strength, generating uplift forces beneath foundations, and causing piping when the hydraulic gradient exceeds its critical value, so that particles are washed away and channels form and widen until the structure fails. It also leads to heave at the bottom of excavations and weakens slopes and the bodies of earth dams. To limit these risks, design relies on several measures, including cutoff walls and sheet piles to lengthen the seepage path, clay cores to reduce permeability, filters and drains to discharge water while preventing particle migration, pressure-relief wells, and foundation grouting. In addition, piezometers are installed and discharge is monitored during operation. Understanding and controlling seepage is essential for the safety and durability of hydraulic and structural works, particularly in Iraq, where groundwater levels are high and soluble gypsiferous soils are widespread. This underscores the importance of comprehensive geotechnical studies that balance hydraulic performance, structural stability, and economic feasibility. Lecturer Farah Hameed Abd Al-Khudhr (M.Sc.) Master's in Civil Engineering – Water Resources, University of Babylon