Modelling of water resources: water balance, water use and water security

This paper presents three interacting models that facilitate the establishment of water management policies targeting sustainable and equitable use of water. For a given sub-basin, the water balance model attempts to establish the balance of water flows across the system boundary. Considering the whole system, the inflows have to balance the outflows. However, the water use model, set inside the system, allows for water within the system to be used many times over, thus increasing water availability. The water security model defines a multi-dimensional metric for water security depending on the water use model. The model structure allows for compatibility across boundaries, enabling construction of a composite mode for a basin, and hence a model for the country considering trans-basin exchanges.