The leaf water potential of two species at predawn (Ψ_max) was positively correlated with rainfall in the upstream site and tidal inundation period in the downstream site, where the salinity was higher than the upstream site. The Ψ_max was higher at a higher tidal inundation period in the downstream site, where the tidal inundation period was long compared to the upstream site. This is supported by lower turgor loss point (Ψ_tlp) and osmotic potential at full turgor (Ψ_{л 100}) of both species in the downstream site. Furthermore, Ψ_max in each species in the upstream site was higher during the warm season, when rainfall was higher, than during the cold season. However, in both seasons and species, Ψ_max was lower in the downstream site than in the upstream site. Vapour pressure deficit (VPD) has a negative impact on midday leaf water potential (Ψ_min). The Ψ_min was higher during the winter when VPD at midday was lower, and vice versa during the summer. Since VPD changes seasonally, Ψ_min also showed a clear seasonal trend. The Ψ_min in each species was significantly lower in the downstream site than in the upstream site in the warm season when water was highly lost by excessive transpiration. This could be due to limitation in water uptake owing to high salinity in the downstream site.