Hydrological change in the Mekong - Entering the Anthropocene?

The Mekong's hydrological future is uncertain. The basin is undergoing changes in its hydrology due to changing climate and extensive development in water resources exploitation. The hydrology of the Mekong is known to have varied between wetter an drier periods of decadal lengths over several centuries. However, during past few decades the climate variability has increased significantly in the basin. The inter-annual variability between very dry and very wet years has increased resulting in more severe droughts and floods. The palaeoclimatological proxies suggest that recent levels of inter-annual variability have not been experienced for at least for last 700 years. The increased variability has been linked partly to El Niño-Southern Oscillation (ENSO), which has become more variable during the recent decades. El Niño (La Niña) phases of ENSO events are associated in the Mekong with drier (wetter) years with a lower (higher) annual flood pulse. Future climate projections based on climate models suggest that temperatures and rainfall are likely to increase in the Mekong. The extent of that change is, however, uncertain as the magnitude varies between the model estimates. The future changes in river flows due to climate change are highly uncertain, as the models disagree on the direction and magnitude of the changes. It is further estimated that hydropower development in the basin would have a large impact on river flows, cutting the flood peak and increasing dry season flow. Increased climate variability and uncertainties in future climate and water resources development may result in unexpected cumulative hydrological impacts. The productivity of ecosystems, local livelihoods, economy and food security are highly dependent on hydrological conditions in various parts of the basin. Therefore, more research is needed to understand these cumulative hydrological changes as well as uncertainties related to them.