The Rhine is 1300km long – 800km of which are navigable – and spreads over an area of 185,000km2. The Rhine basin is shared by nine countries. Germany (55 per cent of basin area), Switzerland (18 per cent), France (13 per cent) and the Netherlands (6 per cent) share most of the basin (Wolf et al, 1999). The parts of the basin in Austria, Belgium, Italy, Liechtenstein and Luxembourg are very small. About 60 million people live in the basin. The average discharge at the mouth is 2200m3 s–1. The hydrology and flow distribution throughout the year are favourable for navigation, which explains why it represents one of the most important transport routes in Europe (Huisman et al, 2000). Apart from navigation the river is used as a water supply for domestic, agricultural and industrial purposes (including cooling water), for waste water disposal, hydropower generation, fisheries, and recreation.