The above figure were derived from the maximum available historical data (usually the period 1960 to 2004) at each mainstream hydrological station.

All curves have been smoothed to produce more useful reference values. For example, due to the rapid variation of flow caused by single rainstorms the maximum ever observed value for a particular day may lie much higher than the curves presented, but may lie significantly lower for the next. The data “smoothing” averages out these fluctuations and provide more useful values indicative of the trends in the various thresholds through the dry months.

The flow at Prek Kdam is based on a relationship between observed water levels at Kompong Luong, Phnom Penh port and Prek Kdam.