Abstract. The Romans were perhaps the most impressive exponents of water resource management in preindustrial times with irrigation and virtual water trade facilitating unprecedented urbanization and socioeconomic stability for hundreds of years in a region of highly variable climate. To understand Roman water resource management in response to urbanization and climate variability, a Virtual Water Network of the Roman World was developed. Using this network we find that irrigation and virtual water trade increased Roman resilience to interannual climate variability. However, urbanization arising from virtual water trade likely pushed the Empire closer to the boundary of its water resources, led to an increase in import costs, and eroded its resilience to climate variability in the long term. In addition to improving our understanding of Roman water resource management, our cost-distance-based analysis illuminates how increases in import costs arising from climatic and population pressures are likely to be distributed in the future global virtual water network.

Abstract. The Romans were perhaps the most impressive exponents of water resource management in preindustrial times with irrigation and virtual water trade facilitating unprecedented urbanisation and socioeconomic stability for hundreds of years in a region of highly variable climate. To understand Roman water resource management in response to urbanisation and climate variability, a Virtual Water Network of the Roman World was developed. Using this network we find that irrigation and virtual water trade increased Roman resilience to climate variability in the short term. However, urbanisation arising from virtual water trade likely pushed the Empire closer to the boundary of its water resources, led to an increase in import costs, and reduced its resilience to climate variability in the long-term. In addition to improving our understanding of Roman water resource management, our cost-distance based analysis illuminates how increases in import costs arising from climatic and population pressures are likely to be distributed in the future global virtual water network.

ORBIS is a geospatial transportation network model of the Roman world, simulating historical travel patterns by modeling the major roads, rivers, and sea routes active during the Roman Empire. With such a model, historians can more accurately examine not only individual route patterns, but also emergent structures of the network as a whole. By defining traditional world systems networks as a particular movement profile for application on a geospatial transportation network, we can begin to see regions of the network using community analysis and analyze those regions for historical patterns.World Systems [1] has represented networks of exchange-whether of goods, people, or information-in various ways, most of them not resembling traditional network graphs and following ChaseDunn and Hall's theoretically and visually uncomplicated format that emphasizes the nested nature of bulk goods, political-military, prestige goods, and information networks. While this format is useful to demonstrate a global connectedness that allows for the exchange of goods, people, and ideas, it is less useful for understanding the regional disconnectedness implied by the very same movement. With the development of sophisticated historical geo-spatial transportation network models, such as ORBIS [2], the variation in regional expression of network communities based on the different priorities implied by the movement of goods, people, and ideas can be more formally analyzed and represented.ORBIS was built by combining existing accounts of sites and routes of the Roman period as represented in Pleiades [3] and the Barrington Atlas [4], combined with modern river tracks and sea routes derived using a computational model calibrated with historical accounts [5]. The result is a simplified model of the Roman transportation network that is subject to seasonal modification based on route cost change and availability due to changing winds, currents, heavy seas, or winter inaccessibility of certain mountain roads.

Elijah Meeks is the lead developer at the Center for Interdisciplinary Digital Research in the Stanford University Library and can be reached at emeeksstanford.edu.C reating a network model of the Roman world presented an exciting opportunity to implement techniques for the study of the past that had only previously been seen in computational geography departments and as interactive toy demos. Such a visualization would allow scholars the capacity to explore how the Roman world may appear differently from different perspectives within the system, highlighting a sense of distance and space that was inherently topological and perspectival.The role of neogeography in disseminating radical cartography and GIS methods outside of academic geography departments cannot be overstated. Radical cartography refers to challenging the implied neutrality of geographic systems and functions, such as map projection. Neogeography, in contrast, refers to the use of geographic information systems (GIS) and map-making by journalists, artists and designers outside of the professional community of cartographers and the academic community of geographers. Both of these developments factored into the creation of ORBIS, a network model that represents the movement of goods and people in the Roman world.In 2011, Walter Scheidel, classics professor at Stanford University, was exposed to the concept of a distance cartogram via the work of designer Tom Carden [1]. Carden, well-entrenched in the field of information visualization and web mapping, had produced a geospatial information visualization of the London subway system that showed the routes using a traditional geographic projection but then distorted the geographic location of each subway stop and line to reflect the time taken from one stop to another. Cartograms are not new in academic geography circles, but the accessibility of this relatively simple information visualization was what allowed someone in Scheidel's position to understand and use such a representation, which was more in line with the manner in which Romans would have historically viewed space. C O N T E N T S N E X T P A G E > N E X T A R T I C L E > < P R E V I O U S P A G E EDITOR'S SUMMARYORBIS is a geospatial model of the Roman world representing the network of cities and travel routes that enabled movement across the Roman Empire. It is an example of neogeography, use of geographic information systems and mapmaking techniques by nonexperts. ORBIS was created using data from both primary sources and computational geography simulations about travel, wind and sea patterns, seasonal access, costs and other considerations to plot realistic transport networks. Through the development process, server infrastructure and user interface upgrades supported the volume of data, user needs and extended functionalities, such as revealing the most efficient routes between points. The result provides scholarly information on life and travel in the Roman era. ORBIS illustrates how network and hierarchical data can be used to vis...