Irrigation and Persistence in the Dry Zone of Sri Lanka: A Geoarchaeological Study

Abstract

This thesis presents an independent, sediment-based record of landscape change within an agricultural hinterland. Established historical and archaeological sequences document the primary occupation of Anuradhapura, Sri Lanka’s ancient capital, beginning ca. 400 BC and lasting until it was largely abandoned in AD 1017. Anuradhapura is located in the island’s dry zone, which depends almost completely on the unpredictable Northeastern Monsoon for water. Oral history and historical narratives have long held that large-scale irrigated rice cultivation took place in the hinterland to produce an agricultural surplus that sustained the urban and monastic populations. However, until the onset of the Anuradhapura Hinterland Project in 2005, the archaeological record of the hinterland was undocumented, leaving existing narratives untested. The geoarchaeological research presented here was undertaken as part of the Hinterland Project, in order to document the chronology and cultural and environmental processes that contributed to the formation of this irrigated landscape. Optical dating of sediments demonstrates that the onset of large-scale irrigation began ca. 400 BC, and the construction of new works continued until Anuradhapura’s late occupation period. Sampled reservoirs and channels began to infill, indicating widespread disuse, within ca. 100 years of Anuradhapura’s abandonment. Soil micromorphology and bulk sediment characterisation document hinterland habitation, water management, and cultivation activities prior to the establishment of large-scale irrigation. This work illustrates the coping strategies that people employed to deal with the vagaries of the dry zone environment and demonstrates that hinterland land use changed throughout the primary occupation period. Although largescale irrigation works infilled relatively rapidly, cultural activity and land use re-emerged following this period of disuse.