As you walk north towards the Moon Pyramid you cross a small bridge that spans a verdant streambed. This little stream is the remains of one of the most audacious engineering feats Teotihuacános ever attempted: the re-channeling of local streams into a new river that ran through the city on the new master grid pattern they imposed on the entire city after AD 200.
Water must have been a constant concern for people living in the city. Heavy summer rains led to flooding while five-month-long annual winter droughts turned the region into near desert. Farmers depended on irrigation for regular, abundant harvests but annual variations in rainfall must have led to frequent poor crops and famine.
The Apartment Compounds had sub-floor drains for removing rain water and archaeologists suspect that these drains ultimately entered into Rio San Juan. The river probably dried up during the rainless winter season when deep wells in the Apartment Compounds provided household water for daily use.
Written by Richard A. Diehl