Abstract
In the lower Mekong River Basin, annual flood duration was calculated using flooding and inundation model and the relationship between annual flood duration and NPP, land development was clarified. Also the relationship between scale of the flooding and NPP, was clarified using annual maximum water level of the Mekong River. As a result, it is showed that when annual flood duration is extended for 2 months, the ratio of cropland decreases approximately 10%. NPP showed the peak value at the areas whose flood duration is 7.5 month/year. The landcover of study area could be classified by flood duration. If all natural vegetation area is turned into paddy field and cropland by human, NPP could be decreased by 134gC/m2. Moreover, the seasonal change of NPP is also related to seasonal flood. Furthermore, in floodplain ends, there is positive correlation between annual maximum water level of the Mekong River and NPP. If annual maximum water level changes 1m, NPP value changes approximately 0.28gC/m2/day.
