changement global du système terre global change context within earth system

LES FLUX PARTICULAIRES ET LES FLUX PARTICULAIRES ET DISSOUS DISSOUS

DES CONTINENTS AUX OCEANS, DES CONTINENTS AUX OCEANS, EVOLUTION RECENTE DUES AUX EVOLUTION RECENTE DUES AUX

EFFETS ANTHROPIQUES EFFETS ANTHROPIQUES

• 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

M. MEYBECKUMR Sisyphe, CNRS / Univ. Paris VI

ALASKA PRISTINE RIVER BASINALASKA PRISTINE RIVER BASIN

• 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...

BE1

PRISTINE RIVER CHEMISTRYPRISTINE RIVER CHEMISTRY

VARIABILITY OF NATURAL RIVER VARIABILITY OF NATURAL RIVER CHEMISTRY AND LITHOLOGYCHEMISTRY AND LITHOLOGY

Sum of cations (µeq/L) Dominant ions Example

50 Ca2+, Cl- Rio Negro * (Amazonia) quartz sands

70 Na+, HCO3- Rio Tefe * (Amazonia) quartz sands

500 Mg2+, Ca2+, HCO3- Basaltic basins

600 Mg2+, HCO3- Peridotite basins

4 000 Ca2+, HCO3- Carbonated basins

5 000 Mg2+, SO42- Coal schists

9 000 Na+, SO42- Semliki R. Rift Valley

20 000 Na+, SO42- Bituminous Shale (Montana)

50 000 Na+, Cl- Urubamba tributary (Amazonia)

* Rain and vegetation control

There is no mean river water that can be used as a global or even regional reference


GLOBAL OCCURENCE (% of area) OF WATER TYPES GLOBAL OCCURENCE (% of area) OF WATER TYPES AND THEIR ORIGINS (Pristine rivers model)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

Origin Rock dominatedType

% Total Raindominated Silicate Carbonate Pyrite Evaporites

Evaporated

Na2SO4 3,2

NaCl 6,8

Na2CO3 3,6

MgCO3 2,4

MgSO4 2,0

MgCl2 0,1

CaSO4 5,2

CaCO3 76,9

Total 100 2,6 35,4 45,1 5,2 3,6 8,2


PRISRI : GLOBAL DISTRIBUTION OF DIC PRISRI : GLOBAL DISTRIBUTION OF DIC MEDIUM-SIZED BASINSMEDIUM-SIZED BASINS

3 500 - 200 000 km3 500 - 200 000 km22, rheic basins (n = 480) , rheic basins (n = 480)

% HCO3- / - DIC CONCENTRATION DIC EXPORT

99,599

90

75

50

25

10

10,5

RARE

UNCOMMON

COMMON

VERY COMMON

COMMON

UNCOMMON

RARE

10 50 1000,5 1 10 100

DIC mg/L

0,1 1 10 50

g C.m-2.y-1

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

%


WHAT IS GLOBAL CHANGE?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:

U.S. B

ureau of the Census

NOAA Vitousek (1994)

Mackenzie et al (2002)

Richards (1991), W

RI

(1990)Reid &

Miller (1989)

GLOBAL CHANGEGLOBAL CHANGE

GLOBAL SYNDROMES OF RIVERINE GLOBAL SYNDROMES OF RIVERINE CHANGESCHANGES

(examples)(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)

TROPICAL FOREST CLEARINGTROPICAL FOREST CLEARING

• 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

PD9

PRESSURES ON HYDROSYSTEMSPRESSURES ON HYDROSYSTEMS

IMPERIAL ROME APPARTMENT BUILDING IN OSTIA IMPERIAL ROME APPARTMENT BUILDING IN OSTIA (200 AD)(200 AD)

• 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

FB2

MAN AND WATER INTERACTIONS : NOTHING NEWMAN AND WATER INTERACTIONS : NOTHING NEW

BLAST FURNACE AT COPCA MICAS BLAST FURNACE AT COPCA MICAS (RUMANIA, 1970 ’s)(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 1976PF1


AGROCHEMICALS, FERTILIZERS AND OLIGO-AGROCHEMICALS, FERTILIZERS AND OLIGO-ELEMENTS (Zn, Cu, Mo, B, …)ELEMENTS (Zn, Cu, Mo, B, …)

Agrochemicals may increase soil metal contentsFertilizers leaks provide nitrate and total phosphorous

PF34

EMC


Global impacts of reservoirs on land to Global impacts of reservoirs on land to oceans fluxesoceans 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

COLORADO HOOVER DAM (1935)COLORADO HOOVER DAM (1935)

• The first giant dam ever built• South California and Arizona economies have greatly

depended on Hoover dam

FA50

US Geol. Survey (Nat. Water Summary, 1984)


A VANISHED RIVER : THE COLORADO RIVER A VANISHED RIVER : THE COLORADO RIVER MOUTHMOUTH

• 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

NEOARHEISMNEOARHEISM

RIVER FLUXES TRENDS AFTER DAMMING RIVER FLUXES TRENDS AFTER DAMMING THE COLORADO EXAMPLE (1910-1960)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

NEOARHEISMNEOARHEISM

HIGHLY TURBID RIVER IN HIGHLY TURBID RIVER IN HIMALAYAHIMALAYA

• 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

PD34

SEDIMENT TRANSFERSEDIMENT TRANSFER

YELLOW RIVER COURSE CHANGES OVER YELLOW RIVER COURSE CHANGES OVER THE LAST 2000 YTHE LAST 2000 Y

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 plainThe last dike outbreak in the 1930’s, due to war action, has

caused one million casualties, mostly due to famine

AE33

RIVER BED SILTINGRIVER BED SILTING

Yang Tse Kiang

Yellow Sea

Pohai Sea

SOURCES, SINKS AND TRANSFERS OR RIVER SOURCES, SINKS AND TRANSFERS OR RIVER PARTICULATESPARTICULATES

NATURAL VS ANTHROPOCENE CONDITIONSNATURAL VS ANTHROPOCENE CONDITIONS

• 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)

OceanHead waters

SEDIMENT TRANSFERSEDIMENT TRANSFER

Sediment transfer : solving contradictionsSediment 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

SEDIMENT TRANSFER AND RIVER BED SILTINGSEDIMENT TRANSFER AND RIVER BED SILTING

GLOBAL SALINITY HAZARDGLOBAL SALINITY HAZARD

PC26

• 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

WD Williams (Ambio)

SALINIZATIONSALINIZATION

CHLORIDE POLLUTION OF THE RHINE RIVER CHLORIDE POLLUTION OF THE RHINE RIVER BY POTASH MINES (1945-2000)BY POTASH MINES (1945-2000)

During this period the daily release of NaCl has been regulated so that Cl- did not exceed 200 mg/L

UG53

GLOBAL SYNDROMES OF RIVERINE GLOBAL SYNDROMES OF RIVERINE CHANGESCHANGES

Dum

ping

into

the

Rhi

ne (k

g/se

c)

IMPERIAL ROMA BIGGEST SEWAGE IMPERIAL ROMA BIGGEST SEWAGE COLLECTOR : THE CLOAQUA MAXIMACOLLECTOR : 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

GG9 XIXth cent. drawing

ASPHIXIATION AND FAECAL CONTAMINATIONASPHIXIATION AND FAECAL CONTAMINATION

RHINE RIVER ASPHIXIATION (1960-1995)RHINE RIVER ASPHIXIATION (1960-1995)

The O2 minimum period lasted 15 years until sewage collection and Oxygen Demand treatment

was implemented (1960-1975)

OG17

R. Breukel

ASPHIXIATIONASPHIXIATION

River Rhine near Lobith, oxygen saturationpe

rcen

tage

1950 70 9560 80 90

average

minimum

SCHEMATIC TRENDS OF SEDIMENT SCHEMATIC TRENDS OF SEDIMENT CONTAMINATION IN ESTUARINE CORESCONTAMINATION IN ESTUARINE CORES

• 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

TE3

CONTAMINATIONCONTAMINATION

ATRAZINE HERBICIDE USE MAP IN THE USAATRAZINE HERBICIDE USE MAP IN THE USA

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

SC22

XENOBIOTICS OCCURENCEXENOBIOTICS OCCURENCE

RIVER EUTROPHICATION : DAILY pH CYCLES RIVER EUTROPHICATION : DAILY pH CYCLES IN THE LOIRE RIVER(AT DAMPIERRE)IN THE LOIRE RIVER(AT DAMPIERRE)

• 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

PA68

F. Moatar (1999, Univ. Tours)

EUTROPHICATIONEUTROPHICATION

∆pH

Dis

char

ge

A SUCCESS STORY : NUTRIENTS CONTROL IN THE A SUCCESS STORY : NUTRIENTS CONTROL IN THE RHINE R.RHINE R.

• The major effort of sewage collection was between 1960 and 1975 : it resulted in particulate P abatment and NH4

+ decrease• P-PO4

3- control then decrease was only achieved after the 1985 ban of P detergents and the dephosphatation in most treatment plants

Van Dijk & Marteijn, 1993


mg P /L

mg P /L

NITRATE TRENDS IN WORLD RIVERSNITRATE TRENDS IN WORLD RIVERS

From 1960 to 1990 nitrate has increased in most

large riversMaximum rates are observed in smaller

catchments exposed to intensive fertilizer use

SD11

Seine

Rhine

Danube

Mississippi

Thames


IRRIGATION, RESERVOIRS & IRRIGATION, RESERVOIRS & EUTROPHICATION : EUTROPHICATION :

THE SILICA RETENTIONTHE 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


1900 200048 0,9

TOWARDS GLOBAL PICTURES OF TOWARDS GLOBAL PICTURES OF RIVERINE CHANGESRIVERINE 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

COASTAL ZONE SEGMENTATIONCOASTAL ZONE SEGMENTATIONTHE NATURAL CONNEXION BETWEEN CONTINENTS AND THE NATURAL CONNEXION BETWEEN CONTINENTS AND

OCEANS THROUGH RIVERS IS COMPLEXOCEANS 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)

• 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

COASTAL ZONE SEGMENTATION : AVERAGE RUNOFF PER COASTAL ZONE SEGMENTATION : AVERAGE RUNOFF PER SEGMENT (mm/y)SEGMENT (mm/y)

GLOBAL MAPPINGGLOBAL MAPPING

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

COASTAL ZONE SEGMENTATION:COASTAL ZONE SEGMENTATION: AVERAGE POPULATION DENSITY PER SEGMENT (p/km AVERAGE POPULATION DENSITY PER SEGMENT (p/km22))

GLOBAL MAPPINGGLOBAL MAPPING

Global nitrogen fluxes through rivers : preindustrial vs contemporary

UNHGreen et al. 2003

• 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

POSSIBLE FUTURE OF RIVER POSSIBLE FUTURE OF RIVER SYSTEMSSYSTEMS

• 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)

WORKING HYPOTHESES ON THE EVOLUTION WORKING HYPOTHESES ON THE EVOLUTION OF WATER QUALITY ISSUES IN WESTERN OF WATER QUALITY ISSUES IN WESTERN

EUROPEEUROPE(accelerated scale)(accelerated scale)

• 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)

WESTERN EUROPE

CL

CR

CN

PRISTINE

SEVERE IMPACT

MODERATE IMPACT

NEGLIGIBLE IMPACT

- 2000 0 1000 1492 1900 1950 1970 2000

MetalsFaecal

Nitrate

Xenobiotics

Radionucl.

LOCAL IMPACTS REGIONAL GLOBAL ANTHROPOCENE

MAN AND RIVER RELATIONSMAN AND RIVER RELATIONS

Meybeck, 2003, Philosophical transaction

Anthropogenic climate variability

ENVIR. REGUL.ATM. POLL. CONTROLRENATUR. / RESTOR.SEWAGE COLL. /TREAT.

REGULATION/RESTORATIONRESPONSES

HUMAN PRESSURES AGROCHEMICALSATM. POLLUTIONMINING IMPACTSURBAN POP. IMPACTS

LAND USERIVER ENGINEERING

TIME0 18001000 1900 1950 2000

ART. GW RECHARGEECOL. FARMING

< 0,1% global area affected 0,1 to 1% Natural climate variability

1 to 10 %10 to 50 %

> 50 %

Figure M6 : Working hypotheses on the occurrence of some major pressures on terrestrialaquatic systems at the global scale and related environmental remediation responses (notethe time acceleration)(adapted from Meybeck, 2001)

CLIMATE VARIABILITY






TIME0 18001000 1900 1950 2000



1 to 10 %10 to 50 %

> 50 %


CLIMATE VARIABILITY






TIME0 18001000 1900 1950 2000



1 to 10 %10 to 50 %

> 50 %


CLIMATE VARIABILITY



AGROCHEMICALS

MINING IMPACTSURBAN POP. IMPACTS

LAND USE


Figure M6 : Working hypotheses on the occurrence of some major pressures on terrestrial aquatic systems at the globalscale and related environmental remediation responses (note the time acceleration)(adapted from Meybeck, 2001)

0,1 to 1%

10 to 50 % ANTHROPOGENICCLIMATE VARIABILITY

< 0,1% GLOBAL AREA AFFECTED

NATURAL CLIMATE VARIABILITY1 to 10 %

> 50 %

HUMAN PRESSURESATM. POLLUTION

RIVER ENGINEERING

TIME0 18001000 1900 1950 2000

CLIMATE VARIABILITY

Human responses to environmental impacts are usually delayed

Anthropocene evolutionAnthropocene evolution

PRESSURES ON AQUATIC SYSTEMS AND PRESSURES ON AQUATIC SYSTEMS AND ENVIRONMENTAL RESPONSESENVIRONMENTAL RESPONSES

Meybeck, 2001

SCHEMATIC POSITIONS OF CONTINENTAL AQUATIC SYSTEMS SCHEMATIC POSITIONS OF CONTINENTAL AQUATIC SYSTEMS SHARED BY SOCIO-SYSTEMS AND EARTH SYSTEMSHARED BY SOCIO-SYSTEMS AND EARTH SYSTEM

• 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

EARTH SYSTEM

COMPONENTS

GLOBAL CHANGE DRIVERS

HUMAN DRIVERS

RESOURCESERVICES

RIVERINE SYNDROMES

EARTH SYSTEM

RESPONSE

EARTH SYSTEMS CHANGES

SOCIO-SYSTEMS EARTH SYSTEM

SHORT TERM REACTION

LONG TERM REACTION

SOCIETAL RESPONSES

SOCIAL AND ECONOMIC

IMPACTS

CONTINENTAL AQUATIC SYSTEMS

CONTROL

FUNCTIONS

PRESSURE

USE


EVOLUTION OF CONTINENTAL AQUATIC EVOLUTION OF CONTINENTAL AQUATIC SYSTEMS FROM HOLOCENE TO SYSTEMS FROM HOLOCENE TO

ANTHROPOCENEANTHROPOCENEPossible 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

A

BCP

100Ź000 10Ź000 1Ź000 1Ź800 1Ź950 2Ź000 2Ź050 TIME

100Ź000 10Ź000 1Ź000 1Ź800 1Ź950 2Ź000 2Ź050 TIME

STATE INDICATOR

STATE INDICATOR

MODELS SCENARIOSŹ/ŹPROJECTIONS

DIRECT SURVEYS

ARCHEOLOGICALŹ/ŹHISTORICALŹDATA

ENVIRONMENTAL ARCHIVES

RESPONSES OF CONTINENTAL AQUATIC SYSTEMS TO CLIMATEVARIABILITY, LAND COVER CHANGE & DIRECT HUMAN PRESSURES

RESPONSES OF C.A.S. TO WATER USES & LAND USE

QMHM

HmQm

BP BP AD

ANTHROPOCENE

HOLOCENE


CONCLUSIONSCONCLUSIONS

• 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)

changement global du système terre global change context within earth system

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