The World Heritage site of Angkor, in Cambodia, is famous for its monumental religious constructions, which have been studied in great detail over the last century. Recent research has uncovered an equally
impressive feature of this medieval capital: an extensive hydrological network stretching across a thousand square kilometers. Although Angkor's hydrology is not nearly as well understood as its religious architecture, it seems as though this system may have played a key role in the city operation and may also have played a role in the demise of this urban complex in the middle of the second millennium CE.

The Greater Angkor area can be divided to three hydrological zones: upper, middle and lower. In the upper zone the water was taken from the natural rivers running from the Kulen Mountains and spread to the North-South aligned channels. In the middle zone the water was collected in big barays, water reservoirs, and temple moats for multifunctional purposes. The lower zone operated like a drainage system for the temple area and dispread water down in the Tonle Sap Lake.

Airborne synthetic aperture radar (AIRSAR-TOPSAR) data have been used to create a GIS database of the network of canals, reservoirs and embankments used to manage water in Angkorean times. Using the GIS database, TOPSAR elevation model and powerful hydraulics and hydrological models it is possible to investigate how the hydrological network was developed, how it worked and why and when it collapsed. Understanding the water management of the Angkor area will help us to better understand how the urban complex operated and may offer new information about the decline of Angkor.