Dew, fog, and rain as supplementary sources of water in south-western Morocco

One full year of dew, fog and rain collection measurements data were collected during 2007–2008 of in the dryland area of Mirleft, Morocco, for use as alternative or supplemental sources of water. Four passive dew condensers and a passive fog net collector were used, each with 1 m2 surfaces. Meteorological data were collected in parallel. During the observation period, 178 dew events (18.85 mm), 31 rain events (48.65 mm) and 7 significant fog episodes (1.41 mm) occurred, corresponding to almost 40% of the yearly rain contribution (48.7 mm, 31 events). Chemical and biological analyses were carried out. Dew and rain pH were neutral (close to 7) and the total mineralization was considerable (dew: 560 mg/L; rain: 230 mg/L). Ca2+, K+, SO42− and NO3− were of continental origin; Cl−, Na+ and Mg2+ were of sea origin. The ions concentration agrees with the World Health Organization recommendations for potable water. The biological analysis shows harmless vegetal spores and little contamination by animal/human bacteria. A cost analysis shows that, with little investment, the population of the arid and semi-arid coastal areas of south-western north Africa could make dew water a useful supplementary alternative water resource.