An adiabatic system and method for reducing water and energy use is provided. The system comprises an adiabatic heat rejection system including a temperature sensor configured to measure the ambient wet-bulb temperature of the adiabatic system based on a measured temperature of water exiting a wetted media pad. A method for adjusting the operational parameters of the system to minimize water and energy use is provided. The method comprises the steps of determining an approximate ambient wet-bulb temperature of the adiabatic heat rejection system based on a measured temperature of water leaving the adiabatic pad, determining if a measured temperature of a process fluid stream is above a process fluid temperature setpoint, determining if the adiabatic heat rejection system is in a water conservation mode of operation or an energy savings mode of operation, and adjusting one or more operational parameters based on the mode of operation.