Jayavarman II settles north of the Tonle Sap, possibly to put distance between himself and the seaborne Javanese.

He builds several capitals before establishing one, Hariharalaya, near the site where the Angkorian complexes are built.

Indravarman I (877-89) extends Khmer control as far west as the Korat Plateau in Thailand, and he orders the construction of a huge reservoir north of the capital to provide irrigation for wet rice cultivation.

His son, Yasovarman I (889-900), builds the Eastern Baray (reservoir or tank), evidence of which remains to the present time.

Its dikes, which may be seen today, are more than six kilometers long and one point six kilometers wide.

The elaborate system of canals and reservoirs built under Indravarman I and his successors are the key to Kambuja' s prosperity for half a millennium.

By freeing cultivators from dependence on unreliable seasonal monsoons, they make possible an early "green revolution" that provides the country with large surpluses of rice.

Kambuja's decline during the thirteenth and fourteenth centuries probably is hastened by the deterioration of the irrigation system.

Attacks by Thai and other foreign peoples and the internal discord caused by dynastic rivalries divertshuman resources from the system's upkeep, and it gradually falls into disrepair.