The region was naturally irrigated to some extent by the great lake near the city. In June when the rainy season was at its height, water flowed down the Mekong River to its tributaries in the south. Because of the excess water in the silted up tributaries, it flowed back up to fill a large depression in the land formed when the area lay below sea level millions of years ago.
This lake conserved water which irrigated the land during the dry season. However, to support the vast number of courtiers, councilors, slaves, concubines, administrators and nobility who made up the royal court, a more extensive irrigation system had to be developed.
Indravarman I, who ruled Cambodia from around AD877 to around AD889, was the first to set up this irrigation system. It enabled the Khmers to have a densely populated capital in a small area from which they ruled their empire. He built reservoirs, called [G 04 / barays], and from these a system of canals was developed which ran through the city to the farms in the surrounding areas. Through this irrigation system, up to three rice crops could be grown each year to feed the population of Angkor.
