This paper presents a simple, generic groundwater-balance-based methodology that uses a set of type-curves to assist with decision-making on the scope for developing sustainable groundwater irrigation supplies, and to help understand how cropping choices influence the potential areal extent of irrigation. Guidance to avoid over-exploitation of the resource is also provided. The methodology is applied to two sites in West Africa with contrasting climatic and subsurface conditions. At both sites, the analysis reveals that there is significant potential for further groundwater development for irrigation while allowing provisions for other sectoral uses, including basic human needs and the environment.