A recent study published in the Proceedings of the National Academy of Sciences shed light on environmental factors that contributed to the collapse of Angkor in the 14th century. Periods of drought were inferred from a palaeoenvironmental study of the West Baray spanning 1,000 years, revealing a large amount of sedimentation (and thus water input) to the man-made lake prior to the 14th century, and much less sedimentation in the 14th and 15th century.
Paleoenvironmental history of the West Baray, Angkor (Cambodia)
Mary Beth Daya, David A. Hodell, Mark Brenner, Hazel J. Chapman, Jason H. Curtis, William F. Kenney, Alan L. Kolata and Larry C. Peterson
Proceedings of the National Academy of Sciences
Published online 03 January 2012
Drought Led to Demise of Ancient City of Angkor
LiveScience, 02 January 2012
Ancient Capital Wilted When Water Ran Low
New York Times, 02 January 2012
Abstract from the paper:
Angkor (Cambodia) was the seat of the Khmer Empire from the 9th to 15th century AD. The site is noted for its monumental architecture and complex hydro-engineering systems, comprised of canals, moats, embankments, and large reservoirs, known as barays. We infer a 1,000-y, 14C-dated paleoenvironmental record from study of an approximately 2-m sediment core taken in the largest Khmer reservoir, the West Baray. The baray was utilized and managed from the time of construction in the early 11th century, through the 13th century. During that time, the West Baray received relatively high rates of detrital input. In the 14th century, linear sedimentation rates diminished by an order of magnitude, yielding a condensed section that correlates temporally with episodes of regional monsoon failure during the late 14th and early 15th century, recorded in tree ring records from Vietnam. Our results demonstrate that changes in the water management system were associated with the decline of the Angkorian kingdom during that period. By the 17th century, the West Baray again functioned as a limnetic system. Ecologic and sedimentologic changes over the last millennium, detected in the baray deposits, are attributed to shifts in regional-scale Khmer water management, evolving land use practices in the catchment, and regional climate change.