Interconections between a delta and its drainage basin – state-of-the-art (the case of Danube Delta). Deltas represent similar centres of “gravity” of drainage basins in what regards the concentration of water volumes, sediments, transported pollutants, etc. The majority of the deltas experience a mixture of drainage basin fresh waters and of the riparian marine/oceanic basin salty waters, fact that produces different mineralisation gradients which play a major role in the existence of a variety of ecosystems and obviously of a huge biodiversity. In view of it, deltas are points of attraction for numerous economic activities that make use of their natural resources – agricultural (and mainly fish-rearing), industrial (oil and natural gas deposits), transport, tourism, etc. These activities are associated with large concentrations of populations which put pressure on the ecological conditions of the environment, already in a fragile state of equilibrium. Hence increased vulnerability through pollution, loss of biodiversity, that is of natural capital. Although the Danube Delta is not particularly overpopulated, yet human intervetion did affect this area, as did its drainage basin of 817,000 km² afferent to 16 states, mostly industrialised ones, with a population of 80 million people. In order to single out the relationships between drainage basin and the delta, and the consequences involved, and based on the models devised at the Workshop on “Improving the Planning and Management of Modified Mega-Deltas”, The Hague, The Netherlands, September 24-26, 2001, the state of the Danube Delta was circumscribed to the following aspects: hydrological modification, sediment loss, eutrophication, and toxic substances.