Ancient Water Management

Why Peru is reviving a pre-Incan technology for water

Why it is important to travel and learn from other cultures. Mankind has been for millennia on this planet and our current climate problems are not the first and will not be the last either. Although we often consider our current civilization superior to those in the past, if we drop some of that arrogance we might learn many things from the past. The ancient water channels in Peru are a good example.

The past 5000 years several civilizations flourished in the Peruvian desert and rough highlands with extreme temperatures and limited rain. To survive, people cultivated deep knowledge of water and the underground, deploying strategies that still astonish. By respecting nature and constructing ingenious hydraulic systems they prepared themselves for droughts and floods. Freelance journalist Erica Gies went to visit some of these channels in the highlands around the village of Huamantanga. She travelled with scientists who were studying local farmers’ use of a 1,400-year-old technique to extend water availability into the long dry season.

Peru is among the world’s most water-insecure countries. The capital Lima, home to a third of the country’s population, sprawls across a flat desert plain and receives just 13mm (0.5 inches) of annual rainfall. To support that human abundance, it relies on three rivers born in the Andes that rise behind the city, soaring to 5,000m (16,400ft) in just 150 kilometres. Lima residents are not alone in this reliance on mountain water. An estimated 1.5 billion people worldwide could depend on water flowing from mountains by 2050, up from 200 million in the 1960s.

Water scarcity in Peru is getting worse as a result of climate change. Within living memory, mountain glaciers have melted and the rainy season has shrunk to just a couple of months. Already Lima’s water utility Sedapal can only supply customers 21 hours a day, a rate that Ivan Lucich, executive director of the national water regulator Sunass, says he expects to further decline in the coming years. As climate change brings water change worldwide, conventional water control structures are increasingly failing. A 2019 World Bank report evaluating drought risk in Peru concluded that the capital’s current strategies to manage drought – dams, reservoirs, storage under the city – will be inadequate by as early as 2030.

Several years ago, desperate for water security, the country’s leaders did something radical: they passed a series of national laws requiring water utilities to invest a percentage of their customers’ bills in “natural infrastructure”. These funds – called Mechanismos de Retribucion por Servicios Ecosistemicos (Mechanisms of Reward for Ecosystem Services) or MRSE – go to nature-based water interventions, such as restoring ancient human systems that work with nature, protecting high-altitude wetlands and forests, or introducing rotational grazing to protect grasslands. Before, it was considered a misuse of public funds if utilities invested in the watershed. Now it’s required.

Today, modern Peruvians are redeploying ancient knowledge and protecting natural ecosystems such as high-altitude wetlands to help the country adapt to climate change. It’s one of the world’s first efforts to integrate nature into water management on a national scale. Human interventions tend to confine water and speed it away, erasing natural phases when water stalls on land. Nature-based solutions, on the other hand, make space and time for these slow phases. They work with local landscapes, climates and cultures rather than try to control or change them. They provide multiple other benefits too, including carbon storage and homes for threatened plants and animals.

For these reasons, conserving wetlands, river floodplains and mountain forests for water management is a growing movement worldwide, including among institutions such as the United Nations and the World Bank. But most projects to date are small and disconnected, so people tend to think of them as attractive side features, rather than a key tool. It’s akin to the long-held attitude toward solar and wind power that is swiftly becoming outdated: they’re nice but were thought not to be capable of playing a major role in meeting our energy needs. Peru’s national program, however, has the potential to demonstrate how effective slow water solutions can be when implemented on the scale of watersheds.

Yet despite Peru’s forward-thinking policies, putting it into practice has been slow going, due in part to high turnover in government – including five presidents in five years. Another big hurdle, and one that most countries face: overcoming ingrained practices in the water sector to try something new.

In 2018, Global Affairs Canada and the United States Agency for International Development pledged to invest $27.5m over five years to help Peru get its innovative program off the ground. The money went to Forest Trends, an NGO that has been working on nature-based solutions for water in Peru since 2012. The executive director of its Lima office, Fernando Moimy, has long championed the idea, first in government as the former chief of Sunass, then via Forest Trends. The NGO’s initiative, called Natural Infrastructure for Water Security, aims to provide technical know-how, says Gena Gammie, deputy director of the project.

Now the effort is gaining momentum. Forty of the country’s 50 water utilities are collecting MRSE funds and have raised more than $30m. Sunass expects them to raise at least $43m by 2024. That money is being invested in more than 60 projects across the country. Among those being supported by Lima’s water utility Sedapal are projects shoring up an ancient water storage technique and protecting rare, high-altitude cushion bogs.

Planting the water
The people who live in Huamantanga are comuneros: members of an agricultural collective. They use water canals called amunas – a Quechua word meaning “to retain” – to divert wet-season flows from mountain streams and route them to natural infiltration basins. The strategy, invented by an ancient people called the Huari (WAR-i), is still practiced here and in a few other Andean villages. Because the water moves more slowly underground as it travels through gravel and soil, it emerges downslope from springs months later, when the comuneros collect it to water their crops. Because much of their irrigation soaks into the ground and eventually makes its way back to the rivers that supply Lima, repairing abandoned amunas scattered throughout the highlands could extend water into the dry season for city dwellers too. Hence Sedapal’s interest.

Built by carefully placing rocks together, the amunas are about two feet wide and a couple of feet deep. They wind like sinuous snakes along the contour of the hills. It’s July, mid-dry season, and the amuna Erica visits is nearly empty of water, having delivered its liquid riches to a rocky, bowl-shaped depression where it infiltrated into the ground. One comunera, Lucila Castillo Flores, a grandmother in a skirt and white-brimmed hat, likens what happens here to sowing water, using the verb sembrar: to plant. “If we plant the water, we can harvest the water,” Flores says. “But if we don’t plant the water, then we will have problems.”

Just before the diversion into the amuna, researchers installed a small weir, a metal plate set vertically across the stream with a V-shaped notch. A classic tool to monitor stream flow, the weir creates a small pond, raising the water level so it flows through the V even when low, explained one of the scientist companions, hydrological engineer Boris Ochoa-Tocachi, chief executive of the Ecuador-based environmental consultancy firm ATUK and an advisor to Forest Trends. Water height is measured with a pressure transducer, an instrument submerged in the weir’s pond. Greater weight on the sensor means higher water. Data collected here informed a study of the amunas that was part of Ochoa-Tocachi’s thesis at Imperial College in London and published in Nature Sustainability in 2019.

One of the most remarkable things about the amunas is that the comuneros know which canal feeds which spring, meaning they understand the path water takes underground. Co-author Perez’s interviews with local people documented this knowledge, which had been passed down through the generations.

Urbanites tend to discount the expertise of rural and Indigenous people, says Ochoa-Tocachi, but the researchers were able to verify their information as “very accurate” by adding tracers to amunas’ flows and then using sensitive detectors to track those molecules’ emergence in the spring-fed ponds. This finding “surprised us”, says Ochoa-Tocachi. “It shows that we can use indigenous knowledge to complement modern science to provide solutions to current problems.” He and his coauthors then modeled how restoring the many abandoned amunas scattered throughout the Andean highlands could increase water supply for Lima, which already comes up about 5% short – a deficit of about 43 million cubic metres.

Focusing just on the largest watershed of the three that supply Lima, they calculated a diversion of about 35% of the wet-season stream flows into the amunas, leaving the rest in the river to support aquatic life. They assumed that half of the diverted water would also go to the environment, deep underground or released into the atmosphere via plants. Nevertheless, what remained was 99 million cubic metres – more than double what Lima needs. They also showed that the diverted water spends between two weeks to eight months underground, with an average delay of 45 days. Slowing this water would increase river flows at the start of the dry season by 33%, postponing Lima’s need to dip into its reservoirs.

Because engineers who make decisions about water projects require hard data like this to deploy projects, such research is critical to changing how we manage water. It translates slow water projects’ efficacy into the language engineers use. Encouraged by the findings, Sedapal plans to invest $3m in shoring up 12 amunas above Huamantanga, building two more, and restoring the neighboring grassland, according to Oscar Angulo, water and sanitation coordinator for natural infrastructure investment with Forest Trends.

Locations that are easier to visit as a tourist and where you can admire ancient old hydraulic technics include: Nasca, Cumbe Mayo and Chavin de Huantar in Peru and Tiahuanaco in Bolivia.
More about the use of ancient technics and natural landscapes to reduce problems with/ from water and climate change you can find in the following interesting articles by Erica Gies:
Slow Water;
The radical groundwater storage test in California; 
Sponge Cities.