Environmental and Climate Perspectives on New World, Old World, and South-East Asian Societies’ Achievements in the Hydraulic Sciences

The foregoing chapters detail the many technical innovations in water supply, distribution, and management for several Old World, New World, and South- East Asian societies. For most of the New World’s societies, basic water resource problems evolved around securing their agricultural base given the unique environmental and water resource conditions prevalent in their locations. Diverse New World societies occupying different environment niches from dry coastal margins to wet highlands, often subject to vastly different average temperatures, crop types, and water variation cycles, were shown to devise different approaches to the development of their agricultural bases. While rainfall runoff from mountain watersheds sourced the many rivers of coastal Peruvian valleys and provided the basis for canal irrigation, excessive rainfall and cold in Andean highland locations allowed groundwater-based farming using raised Welds that had thermodynamic advantages based on conservation of the sun’s heat to prevent root crop destruction during freezing nights. The presence of varying climate cycles (excessive rainfall and drought) was seen to influence modifications in coastal canal systems. Alterations in canal size and placement to accommodate reduced-water supplies were evident in intravalley coastal systems where modifications were relatively straightforward in sandy environments. Intervalley water transfers through massive canal systems were a further characteristic of a flexible response to maintain the water resource base and this often involved the transfer of river water from one valley to another depending on agricultural, economic, and political priorities. With increased need for more agricultural lands to meet population demands, increasingly lower slope canals were surveyed to include further downslope lands. Here technical innovation was a key factor in providing surveying expertise to maintain low-slope contour canals. While such canals are found at very early Formative and Preceramic sites, surveying techniques became more refined in time to permit greater use of land areas reachable by low-slope canals. Here both Old and New World societies share their dependence on surveying technology to meet water transfer demands. While Roman surveying favoured the most direct aqueduct routing necessitating long, linear aqueduct structures interspersed with siphons and multitier aqueducts structures where appropriate, New World surveying was different in that canal designs following landscape contours were prevalent and, in some cases, optimized to produce specific and/or maximum flow rate designs. Specific measures to create hydraulic control structures to defend against El Niño destruction are evident in the New World archaeological record indicating an active, innovative engineering response to climate and weather-induced disasters, probably based on the memory of prior destructive events.