Lima is facing severe water scarcity exacerbated by climate change and unregulated urban growth. To ensure a sustainable supply of water, the city is now investing in reviving pre-Incan technology to restore ancient channels in nearby mountainous watersheds. In the past, indigenous communities used infiltration techniques that relied on seasonal water flows. During the wet season, water was guided through infiltration ditches, seeping into an underground aquifer. In summer, the water emerged back onto the surface in low-lying parts of the mountain. Communities intimately understood the underground hydrological system – which canal infiltrated to which water spring. This type of water management provided them with a year-round water supply. Through the Natural Infrastructure for Water Security (NIWS) programme, this ancient knowledge is being put into practice once again. The restored water system increases local farmers’ water yield and helps to sustain a reliable supply to Lima downstream.