Senior author Dr Wouter Buytaert, of Imperial's Department of Civil and Environmental Engineering, said: "The people of Lima live with one of the world's most unstable water situations. There's too much water in the wet seasons, and too little in the dry ones.
"The indigenous peoples of Peru knew how to get around this, so we're looking to them for answers."
Ancient Peruvian civilisations in 600 AD created systems within mountains to divert excess rainwater from source streams onto mountain slopes and through rocks.
The water would take some months to trickle through the system and resurface downstream -- just in time for the dry season.
To study this, the researchers looked at one such system in Huamantanga. They used dye tracers and hydrological monitoring to study the system from the wet to dry seasons of 2014-2015 and 2015-2016. Social scientists involved also worked with Huamantanga's local people to understand the practice and help map the landscape.
They found the water took between two weeks and eight months to re-emerge, with an average time of 45 days. From these time scales, they calculated that, if governments upscale the systems to cater to today's population size, they could reroute and delay 35 per cent of wet season water, equivalent to 99 million cubic metres per year of water through Lima's natural terrain.
This could increase the water available in the dry season by up to 33 per cent in the early months, and an average of 7.5 per cent for the remaining months. The method could essentially extend the wet season, providing more drinking water and longer crop-growing periods for local farmers.
Boris F. Ochoa-Tocachi, Juan D. Bardales, Javier Antiporta, Katya Pérez, Luis Acosta, Feng Mao, Zed Zulkafli, Junior Gil-Ríos, Oscar Angulo, Sam Grainger, Gena Gammie, Bert De Bièvre, Wouter Buytaert. Potential contributions of pre-Inca infiltration infrastructure to Andean water security. Nature Sustainability, 2019; DOI: 10.1038/s41893-019-0307-1 [doi.org]