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.

Ancient pre-Columbian Peru, Bolivia and Mesoamerica

Irrigation agriculture is a transformational technology used to secure high food yields from undeveloped lands. Specific to ancient South America, the Chimú Empire occupied the north coast of Peru from the Chillon to the Lambeyeque Valleys (Figure 1.1.1) from800 to 1450 CE (Late Intermediate Period (LIP)) and carried canal reclamation far beyond modern limits by applying hydraulics concepts unknown to Western science until the beginning of the 20th century. The narrative that follows examines hydraulic engineering and water management developments and strategies during the many centuries of agricultural development in the Chimú heartland of the Moche River Basin. The story examines how Chimú engineers and planners managed to greatly expand the agricultural output of valleys under their control by employing advanced canal irrigation technologies and the economic and political circumstances under which large-scale reclamation projects took place. The following time period conventions are used in the discussion that follow: Preceramic and Formative Period (3000–1800 BCE) Initial Period (IP) 1800–900 BCE Early Horizon (EH) 900–200 BCE Early Intermediate Period (EIP) 200 BCE–600 CE Middle Horizon (MH) 600–1000 CE Late Intermediate Period (LIP) 1000–1476 CE Late Horizon (LH) 1476–1534 CE. Chimú political power and state development was concentrated in Peruvian north coast valleys. Each valley contained an intermittent river supplied by seasonal rainfall runoff/glacial melt water from the adjacent eastern highlands. Over millennia, silts carried by the rivers from highland sources formed gently sloping alluvial valleys with fertile desert soils suitable for agriculture. An arid environment tied the Chimú economy to intravalley irrigation networks supplied from these rivers; these systems were supplemented by massive intervalley canals of great length that transported water between river valleys, thus opening vast stretches of intervalley lands to farming. The Chimú accomplishments and achievements in desert environment agricultural technologies brought canal-based water management and irrigation technology to its zenith among ancient South American civilizations, with practically all coastal cultivatable intervalley and intravalley lands reachable by canals brought under cultivation.

Hydraulic Engineering and Water Management Strategies ofAncient Societies

Societies of widely different social, economic, political, religious, and technical innovation characteristics in opposing world hemispheres developed urban and rural population centres with water and agricultural systems to maintain stable economies and expanding populations. Despite vast historical, cultural, and world view differences between these societies, one common thread united them: the necessity for mastery of engineering skills to provide water for cities and agricultural systems. Although it may be thought that the technical basis to support water engineering practice is accompanied with pre-scientific concepts, many recent discoveries reveal the contrary: sophistication in the concept, design, and execution of water supply and distribution systems indicating knowledge of hydraulic principles beyond the scant hydraulics literature that survived the centuries. In the absence of ancient treatises on hydraulics practices, archaeological analysis of hydraulics works coupled with modern analysis methods provides a way to understand their technological accomplishments through ‘reverse engineering’ methodologies involving computer modelling techniques. Thus computer methodologies play a role to uncover the design intent, functionality, and operation of ancient water systems to provide insight into ancient engineering practices and their theoretical/empirical basis. In South American archaeology, the large variation in ecological conditions and landscape barriers provided the stage for the rise of civilizations and largely determined their agricultural practices. As an example, the Chimú civilization (800–1480 CE) occupied Peruvian coastal regions extending 500 km from the southern Chillon Valley to the northern Lambeyeque Valley. The desert coastal zone extends only a few kilometres inland from the Pacific Ocean before being bounded by the Cordillera Negra mountain chain. Agriculture was possible in coastal alluvial valleys through networks of canal systems originating from intermittent seasonal rivers. The temperature near the equator is near constant throughout the year while coastal rainfall averages about 2mm/year; occasional massive El Niño events which can deposit up to 150cm of rainfall in a few days occasionally break this pattern and cause extensive flooding and Weld erosion. Clearly, hydraulic practices related to the control of limited (and sometime excessive) water resources were vital for survival. Defensive measures to protect fill aqueduct structures against excessive El Niño rainfall and flooding events are expected to appear in the technology base as flood control was vital to sustainability.

The Ancient Middle East

The origins of Nabataean Petra began c. 300 BCE from nomadic settlement origins and extended to later Roman administration of the city at 106 CE with final Byzantine occupation (Basile 2000) to the 7th century CE. Trade networks that extended throughout much of the ancient orient and Mediterranean world intersected at Petra and brought not only strategic and economic prominence but also the impetus to develop water resources to sustain increasing population and city elaboration demands. City development was influenced by architectural, cultural, and technological borrowings from Seleucid, Syro-Phoenician, Greek, Roman, and Far Eastern civilizations. The city water distribution system utilized many hydraulic technologies derived from these contacts that together with original technical innovations helped to maintain a high living standard throughout the centuries. Analysis of Nabataean piping networks indicates that design criteria were employed that promoted stable flows within piping, employed sequential particle settling basins to purify potable water supplies, promoted open-channel flow within piping at critical (maximum) flow rates that avoided leakage associated with pressurized systems, and matched spring supply rates to the maximum carrying capacity of pipelines. This demonstration of engineering capability indicated a high degree of skill in solving complex hydraulics problems to ensure a stable water supply and is a key reason behind the many centuries of flourishing city life. Because of Petra’s location between Egyptian, Babylonian, and Assyrian territories, many exterior influences dominated the Nabataean cultural landscape over time. The sacred spring created by Moses, as described in Exodus accounts, has been equated with the Ain Mousa spring outside of Petra although controversy exists as to its location (and historical accuracy) with contending Sinai sites. Biblical and Koranic references to areas around Petra relate to the use of water channels and springs by the inhabitants to maintain agriculture and settlements; Assyrian texts ascribed to the Sargonic era (715 BCE) mention tent cities in this area. The earliest proto-Nabataean period (6th century BCE) is derived from Edomite agriculturalists assimilating with nomadic tribal groups familiar with caravan-based trade activities. Although the origins of the Nabataeans remain controversial (Gleuck 1959, 1965; Taylor 2001; Guzzo and Schneider 2002), their final consolidation in areas around Petra in the early 3rd century BCE is evident from the archaeological record.

Ancient South-East Asia

Cambodia is situated in southeast Asia on the coast of the Gulf of Thailand and shares borders with Vietnam to the east, Thailand to the west, and Laos to the north. Lake Tonle Sap occupies ~2.5% of Cambodia’s land area and plays a vital role in the rice agriculture of the country. The total cultivatable area is about 2.1 million hectares, of which 1.8 million is devoted to rice agriculture. The growing season is largely coupled to the monsoon cycles: the bimodal wet season starts in May and ends in October with peaks in June and September/ October resulting from diVerent rainfall origins. Rainfall levels vary around the country: although average levels are about 1.5 m, amounts vary from about 1.0m at Svay Check in the western province of Banteay Meanchey to nearly 4.7m in the southern province of Kampot. The Tonle Sap River reverses flow twice each year: from July to October, water flows into Tonle Sap Lake from branches of the Mekong River, swelling its area from 2,600 to 10,500 km²; in November when the flow rate of the Mekong River decreases, the Tonle Sap River reverses flow and water flows into the Mekong once again. Since 85% of Cambodia’s land area is included in the Mekong River basin, river water levels coupled to groundwater levels play a role in agricultural systems. The dry season from November to April requires irrigation to support rice agriculture making water storage and high groundwater levels important. Based on recent research (FAO 2005), the net renewable water balance (volume in flows minus volume) is equal to about 120km³ with about 18 km³ stored in groundwater reduced by 13 km³ per year by river drainage. Of the total amount of water withdrawal per year (520_10⁶m³), about 94% is devoted to agriculture; given the dependence on rice farming through the ages, it is likely that a similar percentage was used for agriculture in ancient times as now to support like-sized agrarian populations. In the 10th to 14th centuries ce, Angkor’s water supply system was based on four (baray) reservoirs (not all functioning simultaneously) with a total capacity of 100–150_10⁶m³.

Introduction

The purpose of this book is six-fold: . to introduce the technical advances and historical development of selected irrigation-based, hydraulic societies of the pre-Columbian New World (Peru, Bolivia, and Guatemala) and describe their contributions to the history of the hydraulic sciences; to record the final testament from sites now destroyed by modern development or natural erosion processes that contain information on technology achievements . to address open questions in the archaeological literature regarding hydraulic and hydrological issues for Old World, New World, and South- East Asian societies with new information and research results from computational Xuid dynamics (CFD) computer modelling studies; to present Wndings relevant to hydraulic sciences from sites not previously reported in the literature . to introduce new findings from analysis of selected water systems of the ancient Old World and South-East Asia (specifically Petra, Ephesos, Priene, Aspendos, Caesarea, Angkor Wat, and Bali) related to innovations in hydraulics technology . to present mathematical models and examples of the working dynamics of New World hydraulic societies that show that their underlying actions are based on logical economic and engineering principles that maximize food resources commensurate with population growth and climatic challenges . to show that ancient NewWorld societies installed and managed urban and agricultural water systems based on sound engineering principles that took into account climate variations (floods and droughts) and developed defensive hydraulic strategies to combat their negative effects . to provide insight into the thought processes of the technocrats of ancient societies responsible for agricultural development and use of land and water resources through application of engineering principles (as they understood them); to discuss facets of their administrative structure and political economy, and show that technical innovation altered the historical development of societies through increased economic advantages. One path in the development of history of technology originates from discovery processes that utilize archival historical and archaeological resources. From these sources, early scientific and engineering principles that form the technology foundation of modern societies are uncovered, analysed, and categorized and then shown to be early steps to later useful, modern inventions. An alternative, but less deterministic, path originates from the viewpoint that while some engineering developments may serve a society dealing with survival and economic development issues, they represent an empirical trial-and-error process with no real understanding of underlying scientific principles and thus hold only academic interest with minor relevance to the history of science.