Water of sufficient quantity and quality is indispensable for multiple purposes like domestic use, irrigated agriculture, hydropower generation and ecosystem functioning. However, in many regions of the world water availability is limited and even declining. Moreover, water availability is variable in space and time so that it does not match with the spatio-temporal use pattern of the water consumers. To overcome the temporal discrepancy between availability and consumption, reservoirs are constructed. Monitoring and predicting the water available in the reservoirs, the needs of the consumers and the losses throughout the water distribution system are necessary requirements to fairly allocate the available water for the different consumers. In this article, the water allocation problem is considered as a Network Flow Optimization Problem (NFOP) to be solved by a spatio-temporal optimization approach using Mixed Integer Linear Programming (MILP) techniques.