Numerical Modeling of Recovery of Moisture from the Unsaturated Zone: A Feasibility Study

Numerical modeling of the recovery of moisture by injecting warm air in the unsaturated zone in a 100 m × 100 m plot of agricultural land in Kuwait, a country located in an arid environment, was conducted to provide "proof of concept" of the technique. If technically and economically feasible, it will be a potential additional source of water that could be exploited for farming activities and other uses. The COMSOL software was used to develop the model and, based on the results of the scenario runs, the effects of different hydraulic and operational parameters, including that of well spacing, on moisture recovery were assessed. In general, the results suggested that the recovery should increase with the increase in the hydraulic conductivity of the unsaturated zone, the amount of heat input, and the pressure differential between the unsaturated zone and the well head. Within the period examined (0 to 11 days), the recovery decreases with the increase in the soil moisture content, possibly due to the fall in relative permeability to moisture-rich air with the increased water contents in the pore spaces, although the effects may change over a longer period as water contents decrease with moisture recovery. The moisture recovery from the unsaturated zone through the injection of warm air appears to be a feasible proposition from this study that should be demonstrated through a pilot scale experiment in the field.