The present invention relates to systems and methods for dehumidifying air by establishing humidity gradients in one or more dehumidification units. Water vapor from relatively humid atmospheric air entering the dehumidification units is extracted by the dehumidification units without substantial condensation into low pressure water vapor vacuum volumes. The water vapor is extracted through water vapor permeable membranes of the dehumidification units into the low pressure water vapor vacuum volumes. The air exiting the dehumidification units is less humid than the air entering the dehumidification units. The low pressure water vapor extracted from the air is compressed to a slightly higher pressure, condensed, and removed from the system at ambient conditions. In addition, each of the dehumidification units may be associated with one or more evaporative cooling units through which the air will be directed, with the evaporative cooling units being upstream and/or downstream of the dehumidification units.