Delivery and fate of fluvial water and sediment to the sea: a marine geologist's view of European rivers

Despite their relatively small drainage areas, European rivers reflect a wi de variety of hydrologic regimes, although with very few exceptions they ha ve been strongly affected by human activity. Scandinavian rivers (particula rly those draining Iceland and western Norway) can have high runoff, and, e xcept for those draining Iceland, all have very low suspended and dissolved sediment loads. Northern and western European rivers have somewhat lower r unoff, among the lowest suspended sediment yields in the world, and anthrop ogenically enhanced dissolved solid loads. Annual discharge of many of thes e rivers appears to vary inversely with the North Atlantic Oscillation inde x. Rivers discharging from the southern Alps into the Mediterranean Sea hav e relatively high runoff, high suspended sediment yields (reflecting younge r, more easily erodable rocks as well as generally smaller drainage basins) , and high dissolved yields, although presumably with somewhat less human i nfluence. European rivers and their estuaries tend to reflect the terrestri al environments of their drainage basins (i.e. climate, landscape geomorpho logy, geology), but they also display strong anthropogenic signatures. Sedi ment erosion increased dramatically in the last several millenia in respons e to deforestation, farming and mining. In the past 50 years, however, incr eased soil conservation and local reversion of agricultural land to forest, as well as river diversion and dam construction, have decreased the suspen ded sediment loads of many European rivers. Improved mining and manufacturi ng techniques, as well as more effective use of fertilizers and improved wa ste treatment, almost surely will result in lower dissolved solids and nutr ient fluxes to the coastal environments, which presently are the highest in the world. The long-range effects of changed land use on estuarine and coa stal environments remain to be seen, although decreased sediment loads in t he past 20-40 years have already resulted in increased shoreline erosion. D ecreased nutrient fluxes almost certainly will affect water quality in Euro pean coastal waters, and decreased silicate delivery by some dammed rivers may result in proliferation of new (and perhaps harmful) estuarine and coas tal ecosystems. Everything points to further changes as European rivers and their drainage basins continue to change in the coming years.