This shot was taken approximately 1 hour after sunset local time (Melbourne, Florida). The foreground lighting is from street lamps around the boat ramp. The brighter, whiter lighting on the right is from the light for the flag across the little inlet. The horizon glow is quite exaggerated due to the 25 seconds this exposure lasted. I have a picture, taken with my phone, that shows the lake as basically pitch black darkness, so I assume the glow is a combination of the remnants of the sunset and the city of Orlando 50 miles west.