We have a little history lesson today that this old colorized post card has sparked.

Not many Zonians have ever heard of the Rio Grande River before.  I don't mean the Rio Grand between Mexico and the United States.  The Rio Grande was a small river that originally ran through the jungle behind Contractors Hill and formed a small valley from Paraiso to the La Boca mud flats.  The Rio Grande River Valley is one of the reasons the 11 miles from La Boca to Paraiso was selected for the Canal axis.  To control the Rio Grande's flow and to provide drinking water for the Pacific towns, including Panama City it was damed.  An old steel bridge that was part of the original Panama Railroad served as the base of the dam.  The Rio Grande Reservoir provided drinking water for many years until Miraflores Lake, the Cut and Gatun Lake were formed.  The Miraflores filtration plant then took water from them. (See photo and article below for more information).

Going Strong at 1OO-Plus

      SOMETHING NEW has been added to a structure which has under­gone a number of changes and served a variety of purposes on the Isthmus for more than 100 years.
      The structure involved was built originally as a bridge for the Panama Railroad, on its original route across the Isthmus. Later, it was modified to serve as a dam to impound water of the Rio Grande near Contractors Hill, while the top of it was used to carry vehicular traffic, rather than the relocated railway.
       For many years, the water impounded behind the dam was the principal source of supply for the Pacific side of the Isthmus, including Panama City. With the reservoir no longer being used to impound water for treatment by the Zone's Pacific side purification and filtration plant, a hole 5 feet in diameter recently was made through the bottom of the dam to permit the water to escape.
       The limited size of the hole in the dam, coupled with the volume of water which at times collects upstream from it, causes considerable turbulence and potentially destructive force in the water being discharged, so a stilling basin designed to dissipate the turbulence and force of the flow has been built just below the dam.
       The project is part of a flood control system for the Rio Grande drainage area. It is associated with a recently constructed culvert under the relocated section of Borinquen Highway and with the concrete spillway just south of Contractors Hill through which the river enters the Canal.
       By dissipating the force of the water flowing through the stream during periods of heavy rainfall, the dam and stilling basin permit the gradual discharge of the water without detriment to downstream structures or to ship traffic in the Canal.

Photo and article from Panama Canal Review - September 1, 1961

As adventurous youth, we used to explore this old structure many times.  Remember "the slide" just before Contractors Hill?  Well that was the culvert mentioned above. As far as I know all of it is still there and always will be.  I used to go bottle hunting across the bridge and up into the jungle behind the old reservoir basin.  There was an old settlement there in the construction days....and you guessed it.  The town was called Rio Grande.  Rio Grande can be found on most of the old Canal maps.

Another piece of our forgotten Canal Zone history.