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In a context of water scarcity, managers are dealing with quantitative and qualitative management of surface and groundwater resources. For a long time, scientists and water managers have looked at groundwater and surface water as two separate entities. Through the Charente basin example, we explain how a coupled surface-groundwater modelling can improve water management for low flows. The papers is structured into three parts: (1) a global presentation of water resources and water management situation of the Charente basin; (2) the place of modelling techniques and tools in quantitative water management; and (3) according to the Charente basin's water management situation and goals, discussion around the choice of an adapted model for low flow water management, comparison with the decision support system model use currently in Charente (TBR) and first conclusions concerning coupled model usefulness in water management

In France, the development of irrigation since the 1970s is an important cause of imbalance between available water resources and demands. In the Charente river basin, dry climatic conditions during summer and intensive water uses create severe low flow period, which could be prolonged very late in the season (until December). In this context of water scarcity, managers need to deal with both surface and groundwater resources and not as there are two separate entities. Through the Charente basin example, we try to explain how a coupled surface-groundwater modelling can improve water management for low flows. Moreover, management tools, as decision support system (DSS), could provide essential information to managers for their decisions on allocation of water resources. Indeed, managers are faced with the task to identify optimal or near-optimal water management solutions in highly complex hydrosystems. The model TBR used in Charente, a water resources dashboard (Tableau de Bord de la Ressource en eau), is a DSS model with hydrologic and irrigation water demand modules. However, the TBR model need to be improved for low flow forecasting while considering the interrelationships between surface and groundwater component. In the Charente basin, the exchange between the aquifer and the river and the influence of irrigation withdrawals on the rivers flows are dominating and need to be included in the TBR management tools.