This paper provides algorithms for water resources distribution among riparian countries in international river basins. The algorithms are based on selected keys and arguments for sharing. water, which are supported by different interpretations of the relevant international law principles. The main objective of the paper is to derive and test algorithms for water resources distribution based on selected criteria such that water is not double counted and water is distributed as fairly as possible, taking into account the availability of both blue and green water. The algorithms are applied to the Zambezi case, in which the internal water resources are simulated using a river basin simulation model (STREAM). A comparison of the results shows that different algorithms appear to perform better in different river basins, depending on where the availability of resources is concentrated. Furthermore it appears that in river basins where most of the water is generated in upstream countries, green water can have a significant effect on the distribution of blue water.