GROUNDWATER AND SOIL MOISTURE - POTENTIAL SOURCES OF FOG IN THE NAMIB DESERT?

Fog is regarded as an eminent source of water in drylands and the comprehension of possible sources of its formation is important to make future predictions. There has been prior studies on the contribution of fog to the soil moisture and groundwater recharge. Contrariwise, no research has been conducted to comprehend the possible contribution of soil moisture and groundwater in the formation of fog. This study investigated such possibility in one of the fog-dominated drylands, the Namib Desert. The data obtained since 2013 at the sites in Namib Desert were used for the analysis. The relationship between soil temperature and volumetric water content (VWC) was used as one of the rationales to deduce the soil water-fog relationship. In addition, Hydrus 1D model was used for simulating water vapor transport from vadose zone to the soil surface using the available data. The long term data analysis illustrated general increasing trend of VWC with the increase in soil temperature in the absence of precipitation. This increasing trend implies that this might be the result of water vapor transport from the groundwater or soil moisture available at a lower depth to the soil surface. The actual surface flux obtained from simulation of the model suggests that water from the groundwater and soil moisture is transported through vadose zone to the soil surface which might contribute in the formation of fog. Considering this relationship between groundwater and soil moisture with the fog, it is predicated that climate change might induce an alarming situation in the fog water availability in the Namib Desert in the future. The available groundwater is dwindling with time in the Namib Desert and since groundwater influences the fog formation, the amount of fog in the upcoming years might be declined.