Wildlife Resort to Water Catchments

Water and time, a suitable note to sound for this end-of-the-year edition of the Arizona Water Resource newsletter, are separate and distinct, yet at some level water and time strike a common chord. For example, rivers often represent the passing of time, with both water and time flowing relentlessly onward. In at least one particular instance, however, the association of water and time is more direct: water clocks.

Water clocks were among the earliest timekeepers not relying on the tracking of celestial bodies. An early bowl-shaped version is seen at right. The bowl when placed in a container of water slowly fills at a constant rate from a hole in the bottom of the vessel. Markings on the inside surface measured the passage of “hours” as the water level reached them. These clocks were handy to determine hours in the dark of night but may also have been used in daytime.

Also shown is a more sophisticated water clock designed in 245 BC by Ctesibius, a Roman living in Alexandria. Water drips at a constant rate from the higher container to the lower container. The rising water level in the lower container causes a float, which is attached to a notched stick, to rise. As the stick rises, the notches turn a gear that moves the hand to point to the time.