Imminent and ongoing changes in the Mekong River such as climate change, hydropower and irrigation schemes will impact the natural hydrological characteristics of the river. Typically, a monsoon dominated climate drives the hydrological cycle in the basin, resulting in a predictable annual flood pulse peaking between July and September. Due to modifications in the natural flow regime, impacts on key functions of the river such as the role in agriculture, aquatic ecosystem functionality and sediment transport will be significant. It is therefore important to comprehend possible future situations, the impacts on the basin, and the magnitude of change and the uncertainty. MMA uses models and analytical techniques of varying complexity to investigate different future scenarios using the latest climate predictions to simulate the complete hydrological cycle of the Mekong and the delta to ascertain the impacts that may result. Underlying the prediction of change in river fluxes (not only flow but sediment, nutrients and water quality) it is essential to have proven hydrological models.