The water gains kinetic energy as it falls down and loses its potential energy. Assuming no other losses, part of the kinetic energy gain of water is converted into heat , raising the temperature of water.
The water loses potential energy as it drops (you=mgh), which increases the kinetic energy and raises the temp.
As water is mixed with air on it's way down there is an evaporation that occurs. That equates to a cooling affect, like a swamp cooler. There are stories of Egyptians making ice by laying out thin pans of water in the night's arid breeze, super evaporation made ice.