An evaporative cooler, including one or more media, distributes water from a source of water to each media through a constant flow valve. A distribution unit at each media includes a pair of spray bars for spraying water through two rows of uniformly spaced apertures disposed in each spray bar. A spray bar channel associated with each spray bar distributes the streams of water impinging thereupon from one row of apertures to the underlying media in specific locations. A distribution cap associated with each spray bar distributes streams of water impinging thereupon to the front and back edges of the underlying media. The water dripping from the media is drained. A fan or other air moving device draws air through the media to obtain cooled air resulting from evaporation of water flowing downwardly along the media. A microprocessor controller, responsive to any of one or more sensors for sensing the temperature of the air flowing into and out of the media, the relative humidity of the air flowing into and out of the media, the pressure differential between the upstream and downstream sides of the media, the temperature of the water flowing to the spray bars, the fan speed, and the pressure differential between the downstream side of the media and the downstream side of the fan, controls the flow of water and the fan speed.