Comment on 'Changes of inundation area and water turbidity of Tonle Sap Lake : responses to climate changes or upstream dam construction?'

Abstract

Recent hydropower development in the Mekong River has triggered a lot of discussion about its impact on flood dynamics along the river, as well as in one of the world's most productive lake-floodplain systems-the Tonle Sap Lake. A recent article by Wang et al (2020 Environ. Res. Lett. 15 0940a1) in this journal conclude that changes in precipitation have played a much larger role than the operation of hydropower dams, contradicting existing research. However, we argue that by using an annual mean discharge and inundation area Wang et al (2020 Environ. Res. Lett. 15 0940a1) ignore the fundamentals of the system: the difference between dry season water level and peak water level, and thus the extent of the flooded area, which is the key function of the flood pulse. Further, by using annual mean discharge authors are not able to capture the actual operation of hydropower dams, and thus their impacts. Hydropower dams consume very little water through evaporation, but shift the flow regime from wet to dry season. We show here that when taking into account the characteristics of the system, and analysing changes from anthropogenic impacts on low and high flows separately, dams play a central role in recent changes in the flood characteristics of the Mekong.