he five components of the Mediterranean Sea water budget, together with the net inflow of Atlantic water through the Strait of Gibraltar that from the Black Sea at the Dardanelles Strait, evaporation, and precipitation. In terms of absolute values, river discharge (R) represents the smallest contributionto this budget. In fact, climatological annual mean discharge is less than 20% of the atmospheric water budget evaporation minus precipitation (E - P), and the amplitude of its seasonal cycle is almost negligible with respect to the seasonal cycle of E-P. Nevertheless, discharge together with precipitation is the only freshwater input into the basin, and during spring the two basin-integrated components E -P and R are fairly comparable.
We collected historical river discharge monthly series from different hydrological database in order to assess the river discharge contribution to the Mediterranean fresh water input. We identified 68 rivers discharging into the Mediterranean and we estimated the climatological annual mean Mediterranean discharge with an accuracy of about 78%, see Fig.1
Fig. 1 Climatological seasonal cycle of total discharge into the Mediterranean Sea and its decomposition by continent of origin. Represented here is at least 78% of the actual Mediterranean totals (solid line), 76% of discharge from Europe (short dashed), 40% of that from the Middle East (dotted), and 86% of discharge from North Africa (long dashed). (Values are in m3/s.) From "River Discharge into the Mediterranean Sea: Climatology and Aspects of the Observed Variability" , M.V. Struglia, A. Mariotti, A. Filograsso, Journ. Clim. Vol.17 (2004), No. 24 pp. 4740-4751.
Regional projections of river discharge in the Mediterranean catchment
Among all the possible physical impacts of climate change in the Mediterranean area, the one related to the availability of water resources is crucial both for natural equilibrium of biological ecosystems and for social and economic activities of the inhabitants of the Mediterranean countries. Project