The Mekong river plays an important role in socio-economics for the Cut! Long River Delta in particular and Vietnam in general. In recent years, the flow regime in the Mekong river has changed significantly due to climate change and water consumption activities along the river. Die lower riparian countries have been facing drought and salt intrusion issues. To manage and mitigate the negative impacts o f a decreased flow, a distributed rainfall-runoff model should be established. Due to lack o f information and poor-quality hydro-meteorological data, reanalysis datasets can be potential sources to represent the climate conditions for the whole basin. In this study, a 2-parameters water balance model coupled with a routing procedure was used to simulate monthly flow along the Mekong river using the Aphrodite dataset. The model was calibrated and validated at several hydrological stations along the river and the Nash-Sutcliffe model efficiency coefficient (NSE) was used to evaluate the model performance. The calibration and valuation results showed a good performance o f the model in reproducing monthly flow. The NSE results at the hydrological stations vary from 0,82 to 0,92. As a result, the findings o f this study offer a great promise in applying this model and the Aphrodite dataset for use in climate change impact studies on water resources systems and drought warnings in the Mekong river basin.