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A coupled model system, consisting of a distributed hydrological model and an economic optimisation model, communicating via model interfaces, is developed and applied to investigate regional interdependencies between irrigated agriculture and regional water balance and to identify optimised cultivation strategies. The coupled model is employed in the context of a case study in the Atankwidi catchment in the northern Guinea Sudan zone of West Africa. The physically based hydrologic model WaSiM [Schulla, J., Jasper, K., 2001] is used to simulate the water balance of this catchment including a small reservoir-irrigation system complex. The economics of irrigated crop cultivation are optimized under hydrological constraints using the non-linear optimisation model GAMS-ECIM, encoded in GAMS (General Algebraic Modelling System). The coupled model system is utilized for empirical model testing under fictitious scenarios involving variable water availability for irrigation. Interdependencies between irrigation water application quantities and the water balance were identified and maximum agricultural profit was calculated using the coupled model system. The coupled model system is designed as decision-support tool for local authorities and agricultural stakeholders in the Ghanaian Upper East Region (UER). (C) 2007 Elsevier Ltd. All rights reserved.