In the context of global warming and reduction in fresh water availability is presented a study of the evolution of dew, rain and evapotranspiration in the NW of Africa. The time periods are concerned with the years 2005-2020, using existing data, and years 2020-2100, using the low and high emissions representative concentration pathway scenarios RCP 2.6/8.5 from the Cordex database. A continuous decrease in rain precipitation is observed, on order of -14 mm/decade for the more credible scenario RCP 8.5. The amplitude is maximum on the coast and on the foothills of Atlas. A clear decrease in dew yields is also observed along a NW/SE axis, strongly correlated with a corresponding decrease in relative humidity (up to 7%). Chemical dew and rain data in the representative site of Mirleft correspond to the major cations Na+ > Ca2+ > Mg2+ > K+, similar to a local spring water. Concentrations in rain are about two times less than in dew water. Ionic concentrations are compatible with WHO standards. The seasonal variations of the ionic concentrations in dew and rain follow a volume dilution dependence. The expected diminution in dew and rain volumes according to the RCPs 2.6 and 8.5 should increase the dew and rain ionic concentrations in the future.