Hydraulic redistribution (HR) is the process of passive water movement from deeper relatively moist soil to shallower dry soil layers using plant root systems as a conduit. Recent studies suggest that savanna trees in semi-arid areas can increase understorey plant production. We hypothesized that one of the mechanisms to explain the facilitation between shrubs (Guiera senegalensis;Piliostigma reticulatum ) and annual food crops in Sahelian systems is HR. Although soil water potential (Ψsoil) at the 20 cm depth declined significantly during the dry season, passive water release from shrub roots revealed diel changes in Ψsoil of approximately 0.2 to 0.5 MPa, resulting in rewetting of the drier upper soil layers overnight. Shrubs exhibited significant leaf water stress with eventual stomatal closure after midday and rehydration ceasing before midnight. This suggests a strategy for making economical use of scarce water reserves that may contribute to these shrubs' competitive success in these ecosystems. Neighboring annual crops exhibited stomatal closure before shrubs and recuperated after their shrub counterparts. Sap flow measurements on both tap and lateral shrub roots indicated daily reversals in the direction of flow. During the peak of the dry season, both positive (toward shrub) and negative (toward soil) flows were observed in lateral shrub roots with sap flow in the small lateral root frequently negative at night and rapidly becoming positive soon after sunrise. Flow in the larger descending root remained positive at this time. The negative sap flow at night in the superficial root and the periodic positive flow in the descending taproot are also indicative of redistribution. HR thus appears to be an important mechanism for drought stress avoidance and a mechanism to maintain plant physiological functions. This unique phenomenon could promote greater plant growth with practical implications for nutrient cycling and landscape water balance in fragile ecosystems.