Past Water Futures: A Digital Survey of Purvey Dams in the Central Andes

Abstract

Water is essential for life on earth. This is true in the present as it was in the past. Water scarcity and concomitant climate change are increasingly seen as the main threat to human economies across large areas of the world. The Peruvian Andes faced a similar threat during the Medieval Climate Anomaly (c. ad 750–1250). In response, past indigenous communities invested in hydraulicengineering to offset water scarcity due to retreating tropical glaciers. Then as now, the main solution was to build microdams along the headwaters of the Cordilleras. Ancient microdams existed alongside watershed management strategies that incorporated wetland and aquifer protection, terracing and canals. All these constructions, including the dams, were the product ofmillennia-long engineering projects that integrated these technologies with their immediate environs. European colonisation in the sixteenth century and concomitant population decline led to their abandonment. Modern microdam construction is now destroying the remaining vestiges of these past hydraulic technologies. In documenting and studying these features, the Past Water Futures project led by Kevin Lane has compiled a geographic database of ancient dams in the Cordillera Negra region, Department of Ancash, Peru. We began by systematising all existing data, documenting both recent and ancient dams and compiling information from previous surveys undertaken by both the Peruvian government agencies and varied research projects. Thereafter, we conducted a survey employing digital imagery (recent and historical), testing out a series of locational parameters including elevation, geology and other aspects. Finally, we selected several hotspots to undertake ground survey of the dams, including a photographic and photogrammetric record of the structures.