<p>Sandy soils, with inherently low water retention and poor hydraulic properties, present significant challenges for sustainable agriculture, particularly in water-limited conditions. This study investigates the impact of biochar, sludge, and compost amendments on the soil hydraulic properties and water balance of a sandy soil. A 441-day lysimeter experiment evaluated six treatments: biochar (A), sludge (B), compost (C), biochar + sludge (D), biochar + compost (E), and biochar + sludge + compost (F). Results showed that combined treatments outperformed single amendments, with treatment F (biochar + sludge + compost) exhibiting the most pronounced improvements in soil water dynamics. This treatment reduced cumulative drainage by over 40% relative to individual amendments and exhibited higher average soil water content and more stable water storage across seasonal fluctuations. Biochar addition enhanced soil porosity and water-holding capacity, while compost and sludge improved retention through organic matter input and fine particle contributions. Treatments containing biochar reduced drainage and increased actual evaporation, indicating improved soil water retention and availability. Saturated hydraulic conductivity, field capacity, and plant available water were closely correlated with observed drainage behavior, confirming the functional relevance of these soil hydraulic indicators. Statistical analyses, including one-way ANOVA and Tukey’s HSD, supported the significance of treatment differences in drainage and actual evaporation. Overall, the study demonstrates that integrating biochar, compost, and sludge can synergistically enhance water retention, reduce drainage, and stabilize soil water contents in sandy soils. These findings offer practical insights for improving water use efficiency and resilience in arid and semi-arid agroecosystems.</p>