Global analysis of river systems: from Earth system controls to Anthropocene syndromes

Abstract

Continental aquatic systems from rivers to the coastal zone are considered within two perspectives: (i) as a major link between the atmosphere, pedosphere, biosphere and oceans within the Earth system with its Holocene dynamics, and (ii) as water and aquatic biota resources progressively used and transformed by humans. Human pressures have now reached a state where the continental aquatic systems can no longer be considered as being controlled by only Earth system processes, thus defining a new era, the Anthropocene. Riverine changes, now observed at the global scale, are described through a first set of syndromes (flood regulation, fragmentation, sediment imbalance, neo-arheism, salinization, chemical contamination, acidification, eutrophication and microbial contamination) with their related causes and symptoms. These syndromes have direct influences on water uses, either positive or negative. They also modify some Earth system key functions such as sediment, water, nutrient and carbon balances, greenhouse gas emissions and aquatic biodiversity. Evolution of river syndromes over the past 2000 years is complex: it depends upon the stages of regional human development and on natural conditions, as illustrated here for the chemical contamination syndrome. River damming, eutrophication and generalized decrease of river flow due to irrigation are some of the other global features of river changes. Future management of river systems should also consider these long-term impacts on the Earth system.

A safe operating space for humanity

“…The global freshwater cycle has entered the Anthropocene (Meybeck 2003), because humans are now the dominant driving force altering global-scale river flow (Shiklomanov and Rodda 2003) and the spatial patterns and seasonal timing of vapour flows (Gordon et al 2005). An estimated 25% of the world's river basins run dry before reaching the oceans, due to use of freshwater resources in the basins (Molden et al 2007).…”

Relating seasonal dynamics of enhanced vegetation index to the recycling of water in two endorheic river basins in north-west China

“…These rivers commonly terminate in deserts as a result of strong evaporation (X. . Endorheic basins are extremely sensitive to land cover and climate variability (Meybeck, 2003). Therefore, understanding the water cycle in these areas is extremely important for the long-term sustainability (Pilgrim et al, 1988) of desert oases in north-west China.…”

“…River basins not connected to oceans (endorheic basins; Meybeck, 2003) occupy about 13 % of the total land surface of the earth (Meybeck et al, 2001) and generate about 2.3 % of global runoff (Shiklomanov, 1998). Most of these basins are located in water-limited regions of the world, generally in the middle of continents remote from oceanic sources of atmospheric moisture or blocked by mountain ranges (Meybeck et al, 2001;Warner, 2004).…”

“…Most of these basins are located in water-limited regions of the world, generally in the middle of continents remote from oceanic sources of atmospheric moisture or blocked by mountain ranges (Meybeck et al, 2001;Warner, 2004). Rivers associated with endorheic basins in north-west China are typically sourced by precipitation forming in mountains.…”

Catastrophic flood effects in alpine/foothill fluvial system (a case study from the Sudetes Mts, SW Poland)

“…Soils may be eroded, land surfaces polluted and the ecology modified when water and sediment invade the floodplain. It is well known that forest growth induces lowered discharge due to higher evapotranspiration, and lower soil erosion due to increased soil infiltration capacity (e.g., Brown and Quine, 1999;Macklin and Lewin, 1989;Meybeck, 2003). In addition, pasture land provides a good protection against soil erosion.…”