The river discharge is an important component of the in Earth’s water cycles which couples the continents and oceans in the climate system. These fluxes are difficult to estimate due to un-gauged rivers, submarine groundwater discharges, human activities, and measurement errors. One approach is based on the observed river discharge and a simple annual water balance model for ungauged rivers, but it only provides flux estimates with large uncertainties and low temporal frequency which are unsatisfactory for oceanic modelling needs.