Ingenious Pre-Incan Hydrologic System Could Stabilize Modern Water Supply in Peru
The coastal region of Peru has one of the world’s least reliable water supplies, which dwindles dramatically during its dry season, meaning Lima especially struggles to supply water to its growing population. However, scientists believe that an existing Pre-Incan water flow system engineered just for this problem could help Peru to better manage its water. They believe that this system, which is 1400 years old, used in conjunction with modern methods, could help to create a stable and sustainable water supply for cities such as Lima.
World’s most unstable water conditions
The availability of water is a major concern for the coastal districts of Peru, which is the location of the country’s capital, Lima. home to twelve million people. This area relies on surface water, such as rivers. Phys. Org quotes Dr. Wouter Buytaert, of the Imperial College London, who states that the people of the region “live with one of the world's most unstable water situations.” During the wet season, there is too much water and in the dry season, there is simply not enough. Furthermore, there are concerns that there is not enough to meet the growing demands of cities such as Lima and that climate change could make the situation even worse.
Panoramic view of the community of Huamantanga in the central Andes, where the pre-Inca infiltration system is located. The city of Lima would be located downstream in the horizon background. Credits: Junior Gil-Ríos, CONDESAN, 2014.
Pre-Incan water system
In order to find a solution to this problem, hydrological experts from Imperial College, London, partnered with researchers from the Regional Initiative for Hydrological Monitoring of Andean Ecosystems in South America. They have turned to Peru’s ancient past and one of its indigenous communities for answers. For centuries Pre-Incan people have developed systems to ensure that they have water during the dry season.
A diversion canal as part of the pre-Inca infiltration system during the wet season. Canals like this divert water during the wet season to zones of high permeability. Water is stored in the soils and becomes available during the dry season. Image: Musuq Briceño, CONDESAN, 2012.
Over several seasons, researchers studied an ancient hydrological system, that was first developed by the Wari and the Chavin people who built a flourishing culture in the Andes, some 1400 years ago. They ‘dug systems of stone-lined and earthen canals to channel excess rainwater from streams to areas where the ground could soak up more of the water’ reports Ars Tecnica. It is a remarkably efficient way of retrieving and storing water from streams and rivers. The water is stored in the earth and it slowly flows through the soil until it emerges in springs downslope, where it was used in the dry season. It was found that water from the canals was still flowing several weeks into the dry season.
Conceptual representation of how the pre-Inca infiltration system works. Water is diverted during the wet season using canals that transport surplus water during the wet season to high permeability zones. Water penetrates the soil and emerges in downstream springs after weeks or even months, which provides water during the dry season. Image: Ochoa Tocachi et al., Nature Sustain., 2019.
Indigenous communities knowledge of water supply
This technology is similar to hydrological systems developed in Muslim Spain and still used in parts of North Africa and India. According to Ars Tecnica most of these canals “called’ amunas’ in the Quechua language—lie abandoned or clogged.” Indigenous communities in Huamantanga continue to use some of the ancient canals, for both their drinking water and to irrigate their crops. In recent years they have upgraded some of them with the help of a non-governmental organization and they have proven to be remarkably effective.
A team from Imperial College and their colleagues decided to gauge if the ancient system could help to provide water to Lima and other urban centers during the dry season. This was the first attempt to use ancient engineering to solve the modern supply problems. According to the Imperial College of Science website, “they used dye tracers and hydrological monitoring to study the system.” They found that it took the water over 40 days to emerge from the soil. They then created a model based on the ancient system to try and determine if it could be scaled to help to provide water security for Lima and its surrounding areas.
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Panoramic view of a diversion canal as part of the pre-Inca infiltration system during the wet season. Canals like this divert water during the wet season to zones oh high permeability. Water is stored in the soils and becomes available during the dry season. The city of Lima would be located downstream in the horizon background. Image: Sam Grainger, Imperial College London, 2015.
They were astonished by what they found. According to the Imperial College of Science, the system increased the “water available in the dry season by up to 33 percent in the early months, and an average of 7.5 percent for the remaining months.” In effect, if the ancient water system was scaled it could greatly help the water situation in the dry season and could effectively extend the wet season. It appears that the ancient hydrological technology developed by the Wari and the Chavi could help to solve a modern problem.
A possible solution?
The researchers believe that this system by itself would not solve the problem of water security and they believe that a variety of solutions must be adopted. They argue that other systems from the past should also be studied. Phys.Org reports that using ‘pre-Inca systems with classic structures, such as smaller dams’ could really improve coastal Peru’s water supply. This is a natural and environmentally friendly way of managing this most precious resource. The study shows how ancient problem-solving skills could compliment modern technology to solve some of our greatest challenges.
Researchers are continuing to study the system and social scientists are collaborating with local people so that they can learn more about the ingenious engineering skills of historic Andean cultures. It is hoped that the findings will encourage the Peruvian government to fund hydrological projects based on Pre-Incan engineering. The findings of the research are published in the journal Nature Sustainability.
Top image: This diversion canal is part of the pre-Inca infiltration system during the dry season. Canals like this divert water during the wet season and could help stabilize the Peru water supply. Source: Musuq Briceño, CONDESAN, 2012.
By Ed Whelan