Ancient Hydraulic Structures: Initial Findings on the Engineering Behind the Network of Channels and Ponds in the Incan Sanctuary of Pachacamac in Peru

The Sanctuary of Pachacamac is considered to be one of the most important sanctuaries of the Incan Empire, and it is located in the coast of Peru, approximately 20 km south of Lima. The Sanctuary consists of several precincts, such as the Temple of the Sun or Pilgrims’ Square, as well as network of channels and ponds. Though these hydraulic structures were discovered several years ago, no hydraulic engineering study has been conducted, to date, about their functionality and the purpose for which they were built. In this paper, we discuss our initial findings about the purpose for their construction as well as their functionality. The geometry of the channels was obtained using LiDAR as well as drone photogrammetry, whereas the geometry of the ponds was obtained using LiDAR and discrete GPS points. The geometry was then used to developed 3 computational models: HEC-RAS (1-D), TELEMAC-2D (2-D) and OpenFOAM (3-D). The 1-D model was used to study the overall functionality of the system and it is concluded that the network of channels and ponds was built for water distribution purposes, rather than for ceremonial purposes. The 2-D model was used to study potential for erosion throughout the whole network and it is concluded that the network was built taking this criterion into account. Finally, the 3-D model was used to study in detail the local hydrodynamics of areas with high potential for erosion. It is concluded that the channels included several large roughness elements to lower the potential for erosion in areas prone to it.