Changement global du système terre Global change context within Earth System

1. LES FLUX PARTICULAIRES ET DISSOUS DES CONTINENTS AUX OCEANS, EVOLUTION RECENTE DUES AUX EFFETS ANTHROPIQUES M. MEYBECK UMR Sisyphe, CNRS / Univ. Paris VI • Changement global du système terre • Global change context within Earth System • Pressions sur les systèmes fluviaux • Man and rivers: growing pressures • Distribution globale des changements fluviaux • Mapping global river changes • Interactions homme - fleuve, passées, présentes, futures • Man / river interactions: past, present, future Académie des Sciences, Septembre 2003

2. PRISTINE RIVER CHEMISTRY ALASKA PRISTINE RIVER BASIN BE1 • True pristine basins, with very limited land use and minimum contaminated atmospheric fallout, are now uncommon in the temperate zone • Such Alaska and Southern Chile sites are selected by scientists to study the natural N and P cycles, sediment transfers, natural river chemistry, etc...

3. PRISTINE RIVER CHEMISTRY VARIABILITY OF NATURAL RIVER CHEMISTRY AND LITHOLOGY * Rain and vegetation control There is no mean river water that can be used as a global or even regional reference

4. PRISTINE RIVER CHEMISTRY GLOBAL OCCURENCE (% of area) OF WATER TYPES AND THEIR ORIGINS (Pristine rivers model) • Ionic types in pristine rivers are more diverse than originally thought by Gibbs (1972) • CaCo3 is dominating in 77% of rivers (area weighted) • Rain and vegetation recycling is dominating over 2.6% of the continents area and the evaporation over 8.2% (rheic realm only, runoff > 3 mm) • Rock weathering control extends over 89% of the continents area • Evaporated waters may result in many chemical types

5. 99,5 99 90 75 50 25 10 1 0,5 10 100 0,5 1 10 50 100 PRISTINE RIVER CHEMISTRY PRISRI : GLOBAL DISTRIBUTION OF DIC MEDIUM-SIZED BASINS3 500 - 200 000 km2, rheic basins (n = 480) • DIC CONCENTRATION % • DIC EXPORT % HCO3- / - RARE UNCOMMON COMMON VERY COMMON COMMON UNCOMMON 50 1 10 0,1 RARE g C.m-2.y-1 DIC mg/L In 50% of basins HCO3- exceed 80% of anions DIC concentration ranges over 2 orders of magnitude DIC export ranges over 3 orders of magnitude

6. GLOBAL CHANGE U.S. Bureau of the Census Mackenzie et al (2002) Richards (1991), WRI (1990) Reid & Miller (1989) NOAA Vitousek (1994) WHAT IS GLOBAL CHANGE? • Global Change is more than Global Climate Change • It has natural PLUS human/social dimensions • A constellation of changes, many global in domain For example, we see large changes in:

7. GLOBAL SYNDROMES OF RIVERINE CHANGES(examples) • Flow regulation (Nile) • River course fragmentation (Volga, Colorado) • Neoarheism (Colorado, Amu Darya, Nile) • Salinization (Rhine, Don, Murray, Colorado, Amu Darya) • River bed silting (Huang He) • Chemical contamination asphixiation (Thames, Seine, Rhine) inorganic contamination (Tinto, Seine, St Lawrence) xenobiotics occurence • Acidification (Scandinavia, SE Canada) • Eutrophication (Loire) • (Microbial contamination) (Ganges) • (Aquatic species introduction & invasion)

8. PRESSURES ON HYDROSYSTEMS TROPICAL FOREST CLEARING PD9 • Forest clearing is one of the major land use change of the last 50 years • Short term impacts on river fluxes include high supply of eroded material and loss of nutrients (although very limited compared to other human impacts) • Long term impacts are likely to occur for aquatic biota diversity and for the water balance

9. MAN AND WATER INTERACTIONS : NOTHING NEW IMPERIAL ROME APPARTMENT BUILDING IN OSTIA (200 AD) FB2 • Such building had drinking water supply up to the first floor, common flush toilets, and collected sewage • Roof runoff and street runoff were also collected in drains

10. PRESSURES ON HYDROSYSTEMS BLAST FURNACE AT COPCA MICAS (RUMANIA, 1970 ’s) Environmental regulations and surveys were abundant in Former socialists countries although barely enforced, thus resulting in pollution hotspots Nat. Geogr. Mag., June 1976 PF1

11. PRESSURES ON HYDROSYSTEMS AGROCHEMICALS, FERTILIZERS AND OLIGO-ELEMENTS (Zn, Cu, Mo, B, …) PF34 EMC Agrochemicals may increase soil metal contents Fertilizers leaks provide nitrate and total phosphorous

12. Global impacts of reservoirs on land to oceans fluxes • Most major rivers are impounded (neocastorization, Vörösmarty et al., 1997) - North Am : Columbia, Churchill, Colorado, Rio Grande, Missouri, James Bay - South Am : Caroni, Parana, Tocantis - Africa : Volta, Nile, Zambezi, Orange, Niger - Europe : Volga, Danube, Don, Dniept, Dniestr, Spain - Asia : Yang Tse, Yellow, Indus, Tigris, Euphrate - Australia : Murray • Global reservoirs area : 500 000 km2 • Global impacts - biodiveristy : loss of connectivity, regulated rive regimes - biogeochemistry : retention of DOC, POC, N, P and silica - hydrology : river aging (up to 2 y), hydrograph distortion - geomorphology : river bed changes downstream dam, sediment starving in coastal zone and related erosion

13. PRESSURES ON HYDROSYSTEMS COLORADO HOOVER DAM (1935) FA50 US Geol. Survey (Nat. Water Summary, 1984) • The first giant dam ever built • South California and Arizona economies have greatly depended on Hoover dam

14. NEOARHEISM A VANISHED RIVER : THE COLORADO RIVER MOUTH • All river water is used in the basin including the water left at the US/Mexico border and desalinized at Yuma according to the bilateral treaty • Local indian culture in the Colorado delta does not longer exist QB2 Nat. Geogr. Mag., 1979

15. NEOARHEISM RIVER FLUXES TRENDS AFTER DAMMING THE COLORADO EXAMPLE (1910-1960) A : annual water flow B : annual sediment flux • Colorado changes are some of the most dramatic change documented in a river system • This evolution was triggered by the construction of the Hoover Dam in 1936 TE17

16. SEDIMENT TRANSFER HIGHLY TURBID RIVER IN HIMALAYA PD34 • Due to very active tectonic uplift and glacial abrasion Himalayan rivers are naturally very turbid (1 < TSS < 10 g/L) • Such rivers would be qualified as unsuitable for most water uses in most water quality scales

17. Pohai Sea Yellow Sea Yang Tse Kiang RIVER BED SILTING YELLOW RIVER COURSE CHANGES OVER THE LAST 2000 Y AE33 Due to the high sediment load (natural, then enhanced) the Huang He has changed its river mouth location over 975 km, thus flooding several times its enormous flood plain The last dike outbreak in the 1930’s, due to war action, has caused one million casualties, mostly due to famine

18. SEDIMENT TRANSFER SOURCES, SINKS AND TRANSFERS OR RIVER PARTICULATESNATURAL VS ANTHROPOCENE CONDITIONS Head waters Ocean • Sediment transfer in fluvial systems is a complex set of erosion/sedimentation/remobilization processes • Human activities may completely modify and control sediment transfer quantity and quality (e.g. reservoirs, pollution)

19. SEDIMENT TRANSFER AND RIVER BED SILTING Sediment transfer : solving contradictions • There is world wide evidence of increased erosion and transport in headwaters as a result of land use change - forest clearing - agriculture - urbanisation • The Huang He sediment flux has increased 10 times between 1000 AD and 1950 • Yet most long term records of suspended sediment fluxes in large river do not present significant increase (Walling et al., 2002) • Most of the generated sediment is stored within basins from slopes to floodplains and in lakes. This retention is also accelerated by reservoir construction • The natural retention is minimal in small and steep basins as those encountered in SE Asia. The world sediment budget to oceans is now taking it into account (Milliman & Syvitski, 1992) • Sediment sources and pathways and their associated carbon, nutrients and pollutants loads are now more and more generated and controlled by human activitites

20. SALINIZATION GLOBAL SALINITY HAZARD PC26 WD Williams (Ambio) • Salinity hazard, linked to the water balance, is wide spread on all continents • Unadequate irrigation may result in salt-build up in soils, long-term salinization of ground waters, and of rivers, thus limiting downstream water uses • Endorheic regions (e.g. Central Asia) are particularly concerned • Climate change may augment this risk

21. GLOBAL SYNDROMES OF RIVERINE CHANGES CHLORIDE POLLUTION OF THE RHINE RIVER BY POTASH MINES (1945-2000) Dumping into the Rhine (kg/sec) UG53 During this period the daily release of NaCl has been regulated so that Cl- did not exceed 200 mg/L

22. ASPHIXIATION AND FAECAL CONTAMINATION IMPERIAL ROMA BIGGEST SEWAGE COLLECTOR : THE CLOAQUA MAXIMA • Urban water supply and sanitation was at its best in Imperial Roma • It has been probably unequalled until modern sanitation (e.g. London) in the late 1800 ’s XIXth cent. drawing GG9

23. average percentage minimum 1950 60 70 80 90 95 ASPHIXIATION RHINE RIVER ASPHIXIATION (1960-1995) River Rhine near Lobith, oxygen saturation OG17 R. Breukel The O2 minimum period lasted 15 years until sewage collection and Oxygen Demand treatment was implemented (1960-1975)

24. CONTAMINATION SCHEMATIC TRENDS OF SEDIMENT CONTAMINATION IN ESTUARINE CORES TE3 • Heavy metals (A) have peaked in the 1960 ’s (USA) to the 1980 ’s (some W. Europe rivers), their trends are barely documented on other continents • Carcinogenic polyaromatic carbons may still increase in some regions • Polychlorinated biphenyls do not exist in nature (xenobiotics) : they trace the modern human pressure • Both PAHs and PCBs are inadequately surveyed in rivers

25. XENOBIOTICS OCCURENCE ATRAZINE HERBICIDE USE MAP IN THE USA SC22 The Corn Belt is the essential user of herbicides which are carried some 2000 km downstream to the Gulf of Mexico through the Mississippi system

26. EUTROPHICATION RIVER EUTROPHICATION : DAILY pH CYCLES IN THE LOIRE RIVER(AT DAMPIERRE) ∆pH Discharge PA68 F. Moatar (1999, Univ. Tours) • During spring and summer algal blooms (chloro A > 100 µg/L) the daily pH cycles may reach 1.2 pH units • Such events can only be noted during stable low flows : they are destroyed by floods

27. EUTROPHICATION A SUCCESS STORY : NUTRIENTS CONTROL IN THE RHINE R. mg P /L Van Dijk & Marteijn, 1993 • The major effort of sewage collection was between 1960 and 1975 : it resulted in particulate P abatment and NH4+ decrease • P-PO43- control then decrease was only achieved after the 1985 ban of P detergents and the dephosphatation in most treatment plants

28. EUTROPHICATION NITRATE TRENDS IN WORLD RIVERS Thames From 1960 to 1990 nitrate has increased in most large rivers Maximum rates are observed in smaller catchments exposed to intensive fertilizer use Seine Rhine Danube Mississippi SD11

29. EUTROPHICATION IRRIGATION, RESERVOIRS & EUTROPHICATION : THE SILICA RETENTION • Already 4 000 km3/y (= 5% world runoff) loss through irrigation (Shiklomanov, 1998) • The retention of nutrients by reservoir eutrophication, as for silica, combined with increased N and P loads in the last 50 y has generated major changes of N:P:Si ratio in some riverine fluxes to coastal zone, hence causing dystrophy as for the Danube and Mississippi coastal zone Si:N (g/g) trend in Mississippi

30. TOWARDS GLOBAL PICTURES OF RIVERINE CHANGES • Geographic Information systems provide a new tool permitting the combination of multiple informations layers • Information layers are now available at fine resolutions (1 to 50 km) for most Earth system components (runoff, river network, relief, lithology...) to map past natural river state • Socio-economic layers (water uses, environmental pressures, water needs) are still being developed or available at coarser resolutions • First global maps of present river state are coming out

31. COASTAL ZONE SEGMENTATIONTHE NATURAL CONNEXION BETWEEN CONTINENTS AND OCEANS THROUGH RIVERS IS COMPLEX • Some river basins are presently not active as in Sahara (arheism) • Some rivers are flowing to internal water bodies as Caspian Sea, Aral Sea, Chad Lake (endorheism) • Some rivers can still be somewhat connected to oceans (Okawango-Zambezi, Kerulem-Amur) • Some endorheic basins are mostly dry (Tarim, Lake Eyre)

32. GLOBAL MAPPING COASTAL ZONE SEGMENTATION : AVERAGE RUNOFF PER SEGMENT (mm/y) • Coastal basins morphology is highly variable from narrow strips (Peru-Chile) to very deep basins (Mississippi-Amazon) • Mean runoff in coastal basins range over 3 orders of magnitude as for other river fluxes (sediments, carbon, nutrients) • Mediterranean seas as Hudson/Foxe/Ungawa and Golf of Mexico/Caribean may intercept a major portion of riverine fluxes to oceans

33. GLOBAL MAPPING COASTAL ZONE SEGMENTATION: AVERAGE POPULATION DENSITY PER SEGMENT (p/km2) Population pressure within coastal basins varies over more than 2 orders of magnitude from 0.3 inhab/km2 for the Laptev Sea or the Gulf of Carpentaria to more than 300 inhab/km2 in South and East Asia

34. Global nitrogen fluxes through rivers : preindustrial vs contemporary • The global N fluxes (tot N) have increased more than 3 times • Regionally the fluxes have increased more than 10 times • Agriculture and urbanization are the two major N sources Green et al. 2003 UNH

35. POSSIBLE FUTURE OF RIVER SYSTEMS • Understanding the Past Man and River interactions is a clue to future scenarios • Interactions are complex depending on local natural condition, water needs, water literacy, heritages (pressures, mental,...), econmic factors • Interactions should consider far-reaching impacts (teleconnections) and long-term impacts, particularly on Earth system (climate, biogeochemical cycles, coastal zone, aquatic biodiversity)

36. MAN AND RIVER RELATIONS WORKING HYPOTHESES ON THE EVOLUTION OF WATER QUALITY ISSUES IN WESTERN EUROPE(accelerated scale) Meybeck, 2003, Philosophical transaction • There is no simultaneity of water quality issues • New issues have occured in the last 50 years • Some issues have no been handled (e.g. faecal and organic pollutions)

37. Anthropocene evolution PRESSURES ON AQUATIC SYSTEMS AND ENVIRONMENTAL RESPONSES Meybeck, 2001 Human responses to environmental impacts are usually delayed

38. MAN AND RIVER RELATIONS USE FUNCTIONS PRESSURE CONTROL SOCIETAL RESPONSES EARTH SYSTEM RESPONSE SOCIAL AND ECONOMIC IMPACTS EARTH SYSTEMS CHANGES SCHEMATIC POSITIONS OF CONTINENTAL AQUATIC SYSTEMS SHARED BY SOCIO-SYSTEMS AND EARTH SYSTEM HUMAN DRIVERS RESOURCE SERVICES CONTINENTAL AQUATIC SYSTEMS EARTH SYSTEM COMPONENTS GLOBAL CHANGE DRIVERS SHORT TERM REACTION LONG TERM REACTION RIVERINE SYNDROMES EARTH SYSTEM SOCIO-SYSTEMS • The Driver-Pressure-State-Impact-Response cycle in socio-systems is generally observed at short to medium periods (10-50 y) • The parallel Environmental impacts-Earth System response- Regional to Global Change is a long term reaction (100-1000 y) still poorly known

39. MAN AND RIVER RELATIONS EVOLUTION OF CONTINENTAL AQUATIC SYSTEMS FROM HOLOCENE TO ANTHROPOCENE Possible scenarios A : stabilized level, major Earth System change, unmanageable for Human development (laissez-faire) B : stabilized level with maximal acceptable risk for Human development and marked Earth System change (suppression of most polluted sites) C : stabilized level : acceptable risk for Human development with minimal Earth System change (precaution principle) P : return to pre-anthropocene level

40. CONCLUSIONS • Only 30% of continents is actively exposed to river transfer (92% of fluxes) • Regional and local references must be looked for • Present-day natural chemistry and fluxes are variing over 2 to 3 orders of magnitude • Locally Humans may have modified some ionic and nutrient fluxes by one order of magnitude • Half of the world rivers are not any more in pristine state • Such global scale evolution confirms the occurrence of a new era where Human controls on Earth System match the natural ones : the Anthropocene (Vernadski, Crutzen)