June 2011

Conversations With Irrigation Systems: An Analysis of the Archaeological Potential of Irrigation Systems

Mon, May 09, 2011

By Julie Mushynsky

A particular site’s archaeological potential is difficult to determine without some knowledge of what archaeology is.  One of the most all encompassing definitions of archaeology comes from maritime archaeologist Johan Rönnby who explains that “[a]rchaeological writing differs from fiction because it is a dialogue between an author and real physical material remains” (1995:128 cited in Flatman 2003:144).  This dialogue can be considered as a question and answer process similar to Bowen’s (2008) detective analogy.  Bowen explains that at the scene of a crime, detectives ask questions of physical evidence and draw conclusions based on the merits of the evidence (2008:4).  In archaeology, questions are also asked of physical evidence until it becomes a question and answer dialogue between the author and object(s).  A good example of this is the study of shipwrecks.  Shipwrecks can be considered a great contributor to archaeological dialogue.  Firstly, researchers can glean a vast amount of information from the wreck itself.  A wreck can be classified cross-culturally almost always exhibiting a type of cultural signature from its morphology and its construction, often answering questions of origin and construction style.  The conversation can be extended by relating the wreck to other objects found on or around it, such as coins and ceramics (Ericson and Stickel 1973:357-358).  One can also gain information such as deposition dates, cultural contact and even answer questions regarding the cultural and psychological circumstances surrounding deposition (cf. Gibbs 2006:7-17).  Some physical remains can be better conversation partners than others and often physical evidence can be contradictory (Bowen 2008:4).  However, new questions can still be developed by relating objects to different perspectives or theories to further the dialogue.  For example, approaching objects from a maritime cultural landscape perspective can add dimension to an object often only viewed from land.  Ultimately, the more questions that can be asked and answered, the more the dialogue develops and the richer the archaeological research project can be.

Perhaps an often underused archaeological conversation partner is the irrigation system.  Irrigation systems may not normally be considered archaeologically fruitful and more a topic for agriculturalists.  However, there is some evidence that irrigation systems are worth studying and worthy of the term “heritage”.  One way, but certainly not the only way, to determine if a site has archaeological value is to have it on the UNESCO World Heritage List.  UNESCO operational guidelines indicate that sites given the title of “world heritage” have universal value in terms of history, art and science (UNESCO 2008:13).  Irrigation systems make their way on the list with the Oman aflaj irrigation systems, which date as far back as A.D. 500, and, in a somewhat indirect way, the rice terraces of the Philippine Cordilleras (UNESCO 2010).  Irrigation systems can have similar archaeological impacts when considered as part of the maritime cultural landscape of an area.  This essay examines the archaeological potential of irrigation systems as a site for contributing to the archaeological dialogue of maritime cultural landscapes and seascapes.  To do this, the essay examines a number of case studies including sites and techniques from South America, the Middle East and Asia.  This essay explains how irrigation systems are the physical remains that can provide scope and an understanding of human settlement patterns, cultural movement, social organization, religion and human technology.  This essay argues that irrigation systems are not only inland objects for farming areas, but also coastal systems and viable objects of research for maritime archaeology.  To conclude, the elements of this essay are brought together in a concluding discussion along with a brief comment on further potential for irrigation systems in maritime archaeology.    

Settlement Patterns and Cultural Movement

Irrigation systems have a number of human-made and visible landscape features for potential analysis including canals, quarries, wells, ancient routes, and cultivation sites, to name a few (Wilkinson 1998:64).  A number of studies indicate that these features of irrigation systems can have distinct cultural signatures.  J.C. Wilkinson’s (1998) book on the irrigation systems of Oman describes the features and techniques in this region.  In Oman, there exist two different types of systems referred to as aflaj for exploiting water resources; the ghayl aflaj, and qanat aflaj.  Although much more complex than what is described here, essentially a ghayl aflaj is a channel or canal that takes water from the surface layers of valleys and mountain wadis to gardens.  These canals are the primary means of distributing water to small interior villages.  The qanat aflaj taps into underground water supplies, such as wells sunk into aquifers, and then run underground stretching kilometres in length.  By analysing and tracing the qanat, archaeologists are able to develop a dialogue concerning cultural movement and influence.  The origins of the qanat technique is dated to be in the first or second millennium B.C. from northern Elburz and Armenia and first adopted by Tehran and Qazwin (Wilkinson 1977:73-76).  The first major spread of the qanats was associated with the Achaemanids, who used them extensively to colonize new land throughout their empire (Goblot 1963 cited in Wilkinson 1977:76).  Qanats then made their way into Arabia and Oman between the sixth century B.C. and the seventh century A.D. (Lightfoot 2000:224).  There are even slight structural differences that appear in the same technique.  For example, baked clay hoops were used to reinforce Persia’s qanat structure, but were not found as part of the construction in Oman (Wilkinson 1977:80). 

Butzer et al’s (1985) study is an elaborate one developed to measure how irrigation systems can be used to examine cultural change and adaptation.  Butzer et al identify a number of techniques used for irrigation in Eastern Spain and examine whether they are from Roman or Islamic origins.  Some of these techniques include the Archimedean screw primarily used in Egypt, the shaduf from Mesopotamia, the Persian waterwheel, the current-wheel, and Persian qanats.  By analysing irrigation features and historical accounts, the authors were able to determine the diffusion of Islamic irrigation techniques into Spain.  The authors describe the change in Spanish irrigation from Roman to Islamic methods as evolutionary, not revolutionary, as Spain first used Roman techniques for agriculture and then adapted these with Islamic methods to increase efficiency.  Interestingly, after incorporating Islamic irrigation techniques, there was a subsequent revival of Roman modes of irrigation (Butzer et al 1985:481-501, 503-504).  The analysis was able to shed light on contact periods in Europe as well as forms of cultural adaptation.     

Similarly, Lansing’s (1991) extensive study of Balinese irrigation systems identifies differences between the Balinese and the Javanese systems.  Expansion of irrigation in Bali according to archaeologists began in the first millennium A.D. and went from manipulating coastal swamps for local crops of taro, bananas and rice to kilometre-long systems of irrigation tunnels managed for rice crops.  The irrigation system used for rice crops in Bali is known as the subak system of local level irrigation control.  The system begins by capturing the flow from high level, rapid flowing rivers and streams.  Weirs, shunts and dams are strategically constructed along the water source to divert water into canals and down the steep landscape, eventually submerging large blocks of rice terraces.  The whole water system physically connects crops and the farmers who own land watered by a common source.  These groups of connected farmers are known as subaks.  The main identifier of the Balinese system in Lansing’s study is the interconnectedness of canals and the existence of water temples.  Subak water temples are erected to commemorate where water originates, either at the spring, river, lake or weir and to assist in the control of water.  The subak system never developed in neighbouring Java, where irrigation systems are built on gently sloping land.  In the first millennium A.D., approximately 80 percent of the Javanese settlements were in close proximity to rivers.  Thus, the Javanese systems were managed by and constructed for smaller autonomous villages and communities who did not rely on a large interconnected system of irrigation like Bali (Lansing 1991:37, 48; Lansing 2006:24-25, 32-34, 42-47, 52).

In terms of settlement patterns, Wilkinson argues that access to fresh water resources has above all determined settlement patterns in Oman.  Fresh water in Oman was synonymous with life.  The bedu of Oman refer to rain as haya, which means life, and personal greetings often included asking “have you life in your area?” (Wilkinson 1977:38).  It may be somewhat obvious that most inland agriculturalists would choose to settle near irrigation systems or some type of water source.  However, the open irrigation systems and drainage basins determine the settlement patterns on Oman’s Batina coast as well.  At the northern and southern tips of the Oman mountain range, the mountains drop straight into the ocean.  However, settlement patterns at either end are very different.  In the north there is only one settlement of significance due to the small wadi and fresh water storage: a less exploitable water source.  In the south, the exploitable drainage basins are much larger and thus, there are a number of settlements surrounding the wadi mouth, some which have become sizable ports.  The ideal place for crops on the southern tip is where the wind blows marine salt particles which meet with the fresh water irrigation systems (Wilkinson 1977:32-36, 47-49).  Not only are settlement patterns surrounding exploitable water sources for irrigation valuable for archaeological dialogue, but these coastal settlement areas also may be potential sites for maritime archaeologists to consider.

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The ancient city of Angkor sat at the center of the once powerful Khmer Empire of Southeast Asia. Located north of Tonle Sap Lake in Cambodia, the capital city flourished between the 9th and 15th centuries. The royal family abandoned the city in the 15th century, and the city was swallowed by the surrounding jungle, though never entirely abandoned. Now a World Heritage Site, the ruins of the ancient city cover some 400 square kilometers. Angkor has been called one of the most important archeological sites in Southeast Asia by the United Nations Educational, Scientific and Cultural Organization (UNESCO), and the vestige of its prosperity can be found in the Angkor ruins.

Perhaps the most famous site in Angkor is Angkor Wat, a vast temple complex built by Suryayarman II in the early 12th century to honor the Hindu god Vishnu. The temple complex is clearly visible in the above image as the small black frame just below the image center. The frame is created by a 190-meter wide causeway (of water), which encircles three galleries and five central shrines that tower up to 65 meters. The entire complex occupies an area of 1.5 x 1.3 kilometers.

To the north of Angkor Wat is the larger square of Angkor Thom, the inner royal city built in the 12th century. The now dry moat around Angkor Thom is still visible as a pale pink square cut through the surrounding green vegetation. Within the square is a palace, homes for priests and government officials, and government administration buildings.

West of Angkor Thom is the vast Western Baray, a reservoir built in the 11th century. The earthen walls constructed to hold water form a perfect rectangle, oriented exactly east-west. It is thought that the Western Baray and its predecessor, the Eastern Baray, were built to provide water to the city, control water levels on the Siem Reap River, and provide irrigation water to the surrounding plain. Though filled with silt today, the smaller Eastern Baray is also visible in this image. Its earthen walls form a 1.8 by 7.5 kilometer rectangle east of Angkor Thom. Constructed in the 9th Century, the Eastern Baray was probably about 3 meters deep and held an estimated 37.2 million cubic meters of water.

The simulated natural color image was acquired on February 17, 2004, by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA’s Terra satellite. It is centered near 13.4 degrees North latitude, 103.9 degrees East longitude, and covers an area of 22.4 x 29.9 km. In this image, water is black and blue, vegetation is bright green, and bare earth is pink.

NASA image created by Jesse Allen, Earth Observatory, using data provided courstesy of NASA/GSFC/METI/ERSDAC/JAROS, and the U.S./Japan ASTER Science Team.

Source: Photo NASA; Caption Text: Wikimedia Commons

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Social Organization and Religion

In describing archaeology, Mortimer Wheeler explains that, “archaeology is digging up, not things, but people” (Wheeler 1954 cited in Flatman 2003:147).  The presentation of data is just not enough.  Archaeology must address the way “social interactions involving people and objects create meaning” (Gosden and Marshall 1999:169; Kopytoff 1986; Ingold1990:6-7; Pfaffenberger 1992; Conneller 1999 cited in Flatman 2003:147).  Lansing’s research explains how the components of irrigation systems create meaning for the Balinese by serving as a basis for Balinese social organization and religion.  The subak system, briefly explained above is not about the canals that distribute the water, but about the social organization of the system that relies on the hierarchy of subak temples and on what Lansing calls “hydrological interdependency” (1991:38, 48).  Lansing explains that the social organization of Balinese rice farmers is dictated by water temples and is completely separate from the state.  The organization of both temples and subaks is hierarchical, both physically and socially.  Master water temples, located at the highest elevation, are sites for organizing irrigation calendars and the creation of new subaks.  New subak members with new crops must make the pilgrimage up to the master temple to receive blessings from the gods.  High priests, also found at the master water temple, are considered irrigation experts and monitor and control all canal and tunnel building.  As the water flows down, smaller subak temples are erected where groups of farmers are connected by a common water source.  Periodically, representatives from each subak meet at the commemorative water temple to set cropping patterns and irrigation schedules and discuss rules of the planting season.  At a more local level, the Balinese system is an interconnected, interdependent system where each group of farmers relies on those living at higher elevations to shunt water properly allowing it to flow down to lower lying, more coastal crops.  It is this reliance that characterizes subaks as cooperative social institutions bound and organized by the components of their irrigation systems.  The water temples become physical and symbolic sites for determining economic roles for production and determining social roles in an interconnected system (Lansing 1987:330, 335-338; Lansing 1991: 44-45, 38-48, 128; Lansing 2006:47- 48). 

Lansing’s study also examines water temples as places for ritual.  Each water temple is home to a number of shrines: one for the temple’s principle deity as well as others for related gods.  Offerings are made to these shrines to ensure that each irrigation component and the flow of water are controlled by the temple’s god.  Controlling water is extremely important, as only controlled water can promote growth or bear away impurities.  Each subak temple “creates” its own holy water, known as tirtha, from upstream sources through the rituals performed at the temples.  Tirtha is considered sacred and serves to culminate the relations between the ancestral and natural worlds.  It is evoked from the ancestors and serves as nutrients for crops and is often used for a number of rites of passage, ceremonies, blessings and personal offerings to ancestors.  Tirtha is so important to the Balinese farmers that eventually, the religion of Bali became known as the religion of tirtha (Lansing 1991: 52-54, 64, 128; Lansing 2006:51-52).  It is clear that the Balinese irrigation system is much more complex than simply a system of canals.  It is a system of irrigation and society.               

Human Technology and Traditional Knowledge

The way irrigation systems are constructed can say much about human ingenuity and traditional knowledge.  A good example is Farrington’s study of Peruvian irrigation systems.  Farrington’s study analyses the precise engineering of the Peruvian continuous flow system by calculating velocity, discharge and critical flow.  He explains that continuous flow systems, where regulation occurs at intake only, must be built to carry specific amounts of water at certain velocities in order for them to be efficient (Farrington 1980:290).  By excavating sections of supply canals, Farrington states that the prehistoric canal is “an artefact that serves as a testimony to the understanding prehistoric farmers had of open channel hydraulics and the hydrology of their farming system” (1980:302).  When analysing the floors of the Quishuarpata canals in southern Peru, he found that they were fitted, granite slabs, with bevelled edges.  The depths of the bevelled edges fell between one and three centimetres and produce a slightly roughened, irregularly fitted surface.  Farrington explains that the series of bevelled indentations across the canal bottom inevitably causes turbulence within the canal flow and thus serves to reduce velocity.  Farrington also finds evidence that the prehistoric engineer went to great lengths to construct tall aqueducts against hillsides or across valleys in order to maintain a gentle gradient and eliminate heavy erosion and scour.  By mathematically calculating velocity and discharge, and considering the slope of the landscape, Farrington argues that the prehistoric engineer must have recognized sophisticated formulas to determine slope, hydraulic properties and spillage, in order for them to adapt their constructions and accommodate the problems introduced by the Peruvian landscape (Farrington 1980:290, 295-302).     

Human ingenuity is also evident in how the Balinese create artificial ecosystems for their rice crops.  The Balinese irrigation systems rely on the flow of seasonal rivers, lakes and springs, not on stored water from tanks or dams.  During the wet season, river flow can be ten times greater than what flows during the dry season.  No matter the season or the intensity of water flow, the Balinese create and maintain nutrient pulses of wet and dry periods for their crops.  Pulses are created by systematically shunting the flow of water to flood large blocks of rice terraces, while leaving other large areas dry.  During the rainy seasons when water is abundant, the excess water is simply returned to a neighbouring stream.  The purpose of pulsing the flooding of rice paddies is to create a more productive system than what can be created by a steady, unchanged water and nutrient flow.  For example, both potassium and phosphorous are very important for rice growth, but the rate of production of both chemicals occur in different environments; potassium production is ideal during the dry period, while phosphorous production increases when submerged.  Pulsing allows the sufficient production of both by alternating wet and dry periods.  Pulsing also stabilizes soil temperature and promotes the activity of valuable microorganisms.  What is particularly ingenious about pulsing is that it is one of the best ways to control pests.  Pest control is achieved by large groups of farmers coming together to cooperate and coordinate the flooding and burning of fields.  If only one farmer tries to reduce pests and does not coordinate with the surrounding farmers, pests will simply migrate from one field to the next.  Farmers also synchronize their schedules depending on the type of pest they want to get rid of.  Some rice terraces in Bali have been under cultivation for more than a millennium, which suggests that perhaps the successful cycle of wet-dry phases has been practiced for some time.  Surprisingly, rice scientists were unaware of this technique until quite recently (Lansing 1991:38-40).  By studying these methods of water manipulation archaeologists can gain insights not only about human ingenuity, but also farming practices, traditional knowledge, territoriality and technology.   

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The Nile and its irrigated floodplain in the vicinity of Luxor, Egypt. Irrigation, the gift of the Nile, defined in part the very existence of the ancient Egyptian civilization. Wikimedia Commons

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Conclusion

This essay shows that irrigation systems can have great potential for exploring the past and past cultures by contributing to the archaeological dialogue of the maritime cultural landscape and seascape.  Cultural movement, settlement and adaptation can be traced and documented by analysing some of the cultural markers and features systems have, as discussed in the Middle Eastern, Spanish and Indonesian cases.  Settlement patterns can also be determined by access to exploitable water supplies both inland and on the coast, as seen in the example of Oman.  Both the cultural markers and settlement patterns serve as valuable information for the archaeological record.  The Balinese study provides excellent information on how irrigation systems can help explain social organization, ritual and religion.  The Balinese study is a great example of examining archaeology from a more emic, seascape perspective, only in this essay the dialogue on seascapes includes more than cultural perceptions on and relationships with seawater, it includes water from all sources.  Similar to fish traps, irrigation systems and their features can be difficult to identify, especially when systems are unlined, dug out tunnels and canals in the landscape, with no lasting inorganic material.  However, as shown with the Balinese system, irrigations systems can be studied in relation to other items or components, such as water temples and shrines.  This proves to have great potential for understanding human behaviour and beliefs.  Human ingenuity and traditional knowledge can also be ascertained from the structure and strategic planning of systems evident in the technological sophistication needed in Peru and the artificial ecology constructed by the Balinese.  What is of particular importance for maritime archaeology and the maritime cultural landscape is that all the cases explained above can arguably be understood as analysing water-based cultures (Bowen 2008:8; Flatman 2003:146; Westerdahl 1992:5-6).  Like fish traps and many forms of maritime infrastructure, irrigation system constructions are ways of exploiting marine resources and are examples of human utilization of water and maritime space, including lakes and rivers (Westerdahl 1992:5).  For the Balinese, the ability to collectively control water is the basis for social organization and governance.  The Balinese in particular use water to actively shape their identities and sense of place socially, economically and spiritually in a type of hydraulic solidarity (Cooney 2003:323, Lansing 1991:52; McNiven 2003:332-333).              

At a time when the chances of participating in a shipwreck excavation have decreased (Sperry 2009:24), other avenues for exploration are important for maritime archaeologists.  This essay is by no means an exhaustive attempt at analysing the archaeological potential of irrigation systems.  Some further research possibilities could be looking at water intake sites at rivers or lakes and their coastal features as possible structures used for navigation.  Irrigation systems and their relationship to other objects found around them could be further explored.  The presence of Hellenistic potsherds and Late Bronze Age/Iron Age pottery associated with irrigation systems surrounding the Euphrates River (Wilkinson 1998:63, 67, 77) is an example of a site worthy of further analysis.  A more in depth look is needed in connecting irrigation systems and riverscapes especially regarding social practices and interactions between groups settled along lengthy irrigation canals.  Another avenue of exploration could be economic relationships, analysing systems as meeting points of the maritime and agricultural worlds (Esser 1999:19).  By incorporating all potential areas, the archaeological conversation of irrigation systems could turn towards defining a “life-scape” (Flatman 2003:151; Hviding 1996:50, 55-56, 74, 167), where every person identifies as dependent on both land and water for livelihood.

Cover Photo, Top: A Persian Waterwheel. Wikimedia Commons

About the Author

Originally from Canada, Julie Mushynsky is currently a Masters student at Flinders University in South Australia.  Her undergraduate background is in socio-cultural anthropology.  For her masters degree she is conducting research into indigenous seascapes, maritime archaeology and commuity archaeology in Saipan, Commonwealth of the Northern Mariana Islands.  

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