Dam development in the upper reaches of the Mekong has led to changes in seasonal flows, with increased dry season flows and decreased wet season flows. Both phenomena are observed in the LMB, with the impact on the flow regime becoming progressively less noticeable further downstream. 

The findings of the Eyes on Earth study have not yet well taken into account the complexities of rainfall and runoff, thus not reflecting the actual hydrological conditions in the Basin. The conclusions drawn are based on calculated flows and not an analysis of the actual flows at Chaing Saen set against the long term trends. 

As the methods presented by the authors are highly empirical and calibrated on the period 1997-2001, various complex hydrological and physical processes that determine the runoff from the catchments and the river are not captured in the regression functions. 

Our preliminary analysis of hydrological and rainfall data showed that the 2019 drought in the basin was due largely to insufficient rainfall during the wet season with a delayed arrival and earlier departure of monsoon rains and an El Nino event that created an abnormally higher temperature and higher evapotranspiration. 

Inadequate information on water infrastructures in the Mekong River Basin and the way these infrastructures are operated have made it challenging to forecast short-term impacts. 

If the Member Countries and China are to share more information with the MRC, especially data and information on water use and infrastructure operation, the Commission will be in a better position to support seasonal water resource planning and management, and can correct misperceptions by the public and in the media.