An evaporative cooling system comprising: an evaporative cooler liquid-to-air membrane energy exchanger (LAMEE) disposed within a scavenger air plenum that is configured to channel a scavenger air stream, the evaporative cooler LAMEE configured to receive a scavenger air supply stream through an air inlet and to discharge a scavenger air exhaust stream through an air outlet, the evaporative cooler LAMEE further configured to receive an evaporative cooling fluid through a fluid inlet and to evaporatively cool the cooling fluid by allowing the cooling fluid to evaporate into the scavenger air stream; a cooling fluid circuit that is configured to circulate the cooling fluid between the evaporative cooling LAMEE and a first liquid-to-air heat exchanger (LAHE), the first LAHE disposed within a process air plenum that is configured to channel a process air stream, the first LAHE configured to receive the cooling fluid from the evaporative cooler LAMEE and to allow the cooling fluid to absorb heat from the process air stream to cool the process air stream; characterized in that an air-to-air heat exchanger (AAHE) is disposed within the scavenger air plenum downstream of the evaporative cooler LAMEE in a direction of flow of the scavenger air stream, the AAHE configured to receive the scavenger air exhaust stream and to allow the scavenger air exhaust stream to absorb heat from at least one of the process air stream upstream of the first LAHE in a direction of flow of the process air stream or the scavenger air supply stream upstream of the evaporative cooler LAMEE to cool the process air stream or the scavenger air supply stream, respectively, and wherein the evaporative cooler LAMEE is configured to direct the cooling fluid and the scavenger air stream through separate channels divided by membrane separation layers, the membrane separation layers including a semi-permeable membrane thereon. an evaporative cooler liquid-to-air membrane energy exchanger (LAMEE) disposed within a scavenger air plenum that is configured to channel a scavenger air stream, the evaporative cooler LAMEE configured to receive a scavenger air supply stream through an air inlet and to discharge a scavenger air exhaust stream through an air outlet, the evaporative cooler LAMEE further configured to receive an evaporative cooling fluid through a fluid inlet and to evaporatively cool the cooling fluid by allowing the cooling fluid to evaporate into the scavenger air stream; a cooling fluid circuit that is configured to circulate the cooling fluid between the evaporative cooling LAMEE and a first liquid-to-air heat exchanger (LAHE), the first LAHE disposed within a process air plenum that is configured to channel a process air stream, the first LAHE configured to receive the cooling fluid from the evaporative cooler LAMEE and to allow the cooling fluid to absorb heat from the process air stream to cool the process air stream; characterized in that an air-to-air heat exchanger (AAHE) is disposed within the scavenger air plenum downstream of the evaporative cooler LAMEE in a direction of flow of the scavenger air stream, the AAHE configured to receive the scavenger air exhaust stream and to allow the scavenger air exhaust stream to absorb heat from at least one of the process air stream upstream of the first LAHE in a direction of flow of the process air stream or the scavenger air supply stream upstream of the evaporative cooler LAMEE to cool the process air stream or the scavenger air supply stream, respectively, and wherein the evaporative cooler LAMEE is configured to direct the cooling fluid and the scavenger air stream through separate channels divided by membrane separation layers, the membrane separation layers including a semi-permeable membrane thereon. <EOS>