The ancient city of Machu Picchu uses a water source of natural springs that are located on the north slope of the mountain of Machu Picchu . The ancient Incan engineers created a very sophisticated collection system to carry the spring water to the city.
What is incredible is that the system remains functional to this day. A canal carries the water from the first spring to the city center.
The canal is 749 m long, varying in width between 10 and 12 cm and depth between 10 and 16 cm, and stone lined. A cross section of the canal can be seen below in The average slope of the canal is about 3 percent and gravity flow is relied upon for delivering the water to the city.
The design capacity of the canal to be 300 L/min while the typical yield from the primary spring is 25 to 150 L/min The ancient Incan engineers planned the canal well to be able to accommodate varying flow rates over time. The canal first enters the city in the agricultural sector and then into the urban center where it starts flowing through the system of fountains. The canal has a fairly steady slope on its way into the city.
The infrastructure of Machu Picchu was designed to maintain the purity of the domestic water supply by directing the agricultural and urban stormwater discharges away from the domestic water canal. Drainage of excess water was crucial at Machu Picchu due to the location of the city.
There is a threat of mudslides due to excess or extreme rainfall events. The agricultural terraces are one of the most recognizable and visual characteristics of the ancient city. These terraces not only maximize the available land for farming, but they help to protect against erosion. The subsurface of the terraces reveals a very well-planned drainage system with stones at the bottom, then gravel, sandy material, and finally the topsoil.
The above schematics shows a basic schematic of the terrace layers. This layering effect provides strength for the terraces and ensures that water drains at an appropriate rate. The agricultural terraces are also sloped slightly which will direct the runoff into drainage channels that lead to a main drain that carries the water out of the city safely.
The city incorporated many drainage holes into the walls and structures of the city, and many drainage channels into stairways, walkways, and buildings that carry runoff to the main drain.
The Incans also built channels that collected water from the roofs of their buildings to be able to protect the building foundations and structures. Two collecting locations for excess spilling water are located above urban sector to keep runoff out of the main domestic water source.
The very extensive drainage system at Machu Picchu is one of the reasons why the ancient city is still in very good condition and works to this day. The Incans built the city for longevity and it definitely shows.