We aimed at evaluating morpho-physiological responses of Populus euphratica to flooding with fresh and saline water to assess its potential for conservation of lowland areas prone to suffer soil waterlogging. One-year-old cuttings were subjected to five treatments, including control, and flooding at increasing salinity concentrations (0, 50, 100, and 150 mM NaCl) for 90 days. Plant survival and growth, leaf gas exchange, leaf water potential, and concentration of Na+, K+, Ca2 +, Mg2 + in leaves were assessed. Flooding with saline water of 100 or 150 mM NaCl compromised plant survival. Plant death was preceded by strong reductions in photosynthesis, stomatal conductance and leaf water potential, increments in leaf Na+ concentration, and restricted adventitious rooting. By contrast, flooding with fresh or slightly saline water (50 mM NaCl) did not endanger survival although it reduced final plant biomass (65–68%). Cuttings flooded with fresh or slightly saline water showed profuse development of adventitious roots and hypertrophied lenticels in stems as typical adaptive responses to hypoxia, and despite having smaller-sized leaves, these were able to continue photosynthesizing at levels of 40–50% of their controls even after 90 days of flooding. So, P. euphratica appears as a promising candidate species to be included in conservation programs for riparian areas experiencing long-term flooding with fresh or slightly saline water of up to 50 mM NaCl.