FRIEND 2002—Regional Hydrology: Bridging lite Gap between Researcli and Practice (Proceedings ofthe Fourth International FRIIIND Conference held at Cape Town. South Africa. March 2002). IAI IS Publ. no. 274. 2002. 329 Water sharing in the Volta basin MARC ANDREINI Center for Development Research, GLOW A Volta Project, PO Box 645, Tamale, Ghana PAUL VLEK & NICK VAN DE GIESEN Center for Development Research, Bonn University, Waller-Flex-Slrasse 3, D-53113 Bonn, Germany e-mail: nick@iini-bonn.de Abstract The geography of the Volta basin is briefly described. This is followed by an overview of water use developments in the two main riparian countries, Ghana and Burkina Faso. Ghana's water use consists mainly of hydropower generation for the urbanized south whereas in upstream Burkina Faso agricultural water use dominates. Analysis of the water balance shows a large sensitivity of surface water resources with respect to changes in precipitation and thereby to global and regional climate change. Finally, the GLOWA Volta project is introduced which addresses the issue of optimal water use under changing water demand and supply. Key words international basins; West Africa; integrated basin management; GLOWA INTRODUCTION No alternative resource can stand in for the critical role that water plays in development. Especially in sub-humid and semiarid regions, water is becoming a critical constraint and is clearly a resource no country can do without. Yet the economic impact of water resources has not enjoyed the painstaking analysis devoted to resources for which alternate options do exist, such as oil. Since the early seventies, there has been an awareness of the economic importance of oil and the relationships among producing and consuming countries have been examined in detail. Now, as the scarcity of water increases, tensions among riparian states sharing international river basins are emerging with increasing frequency, full attention must be focused on the impact of water resources. The countries sharing the Volta River basin are no exception. In this paper, we will show the different expectations with respect to the use of water resources that exist in the main riparian countries, Ghana and Burkina Faso. We then sketch the availability and sensitivity of water supply at the (sub)continental level and the extent to which the riparians depend on water flowing into the country. We finish with a brief overview of a new research project that seeks to model present trends in water supply and demand in an integrated fashion. The Volta River basin drains approximately 400 000 km" (Fig. 1). There are six riparian countries sharing the basin: Ghana, Burkina Faso, Togo, Côte d'Ivoire, Benin and Mali. In this paper we will concentrate on Ghana and Burkina Faso. These two countries comprise the bulk of the basin; approximately three quarters of Ghana (42% of the basin) and two thirds of Burkina Faso (43% of the basin) are drained by the Volta River system. The Black Volta flows from Burkina Faso along the border of