Fog as unconventional water resource: Mapping fog occurrence and fog collection potential for food security in Southern Bolivia

“Valles Cruceños” rural region, Bolivia, is characterized by intrinsic water scarcity and increasing pressure for food production by the neighboring and fast-sprawling city of Santa Cruz de la Sierra. Here, orographic fog is a phenomenon occurring all year round, representing a sustainable water source for improving farmers’ resilience to dry spells and for promoting food security and sovereignty. With the present study, we aim at a first assessment of the potential of fog collection in the area by a 1-year experimental analysis made through 1-m2 fog collectors in 10 different locations. Starting from these data, we design under safe assumption (including sensitivity analysis) a fog water irrigation system providing water for a standard theoretical field with four local crops (maize, green beans, potato, and tomato) in the dry season. The present paper represents the first study on fog collection in Bolivia, showing that, on annual basis, an average of 6.01 l/m2/d can be obtained from most productive areas, with peaks up to 8.93 l/m2/d. Moreover, to the best of our knowledge, the work represents one of the first consistent studies on the productive use of orographic fog, while a large part of the literature focuses on advection fog, mostly occurring on the Pacific Coast of South America.