Angkor, the ancient city in Cambodia that was the seat of the Khmer empire, flourished from the 9th to the 15th century. Today, tourists still appreciate the remnants of its architecture and sophisticated hydro-engineering systems, composed of canals, moats and large reservoirs known as barays.

Researchers now studying sediments from one of the reservoirs report that prolonged droughts and overuse of the soil may have interfered with Angkor’s water management system and led to the empire’s decline.

“When Angkor collapsed, there was a drop in water levels,” said Mary Beth Day, an earth scientist at the University of Cambridge in England. “And much less sediment was delivered to the baray at the time.”