De mondiale watercyclus

Arjen Hoekstra - IHE Delft

Gastcollege in de collegeserie

‘Duurzaamheid van Energievoorzieningssystemen’

Utrecht, 17 september 2001

Overzicht

• Overzicht van waterbeschikbaarheid op aarde• Overzicht van typen watergebruik

• Wat is waterschaarste?• Wat gebeurt er bij intensief watergebruik?• Dynamiek van watersystemen.• Wat betekent klimaatsverandering voor de

watervoorziening?• Wat weten we eigenlijk over zeespiegelstijging?• Zijn oorlogen over water waarschijnlijk?• Water in de context van wereldhandel en

globalisering

Water on earth

Position of planets in the phase diagram of water

Global annual hydrological cycle

Terrestrial water balance

Available water stocks

Available water flows

Water use by man

Global water demand

0

200

0

400

0

600

0

800

0

100

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120

00

140

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160

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180

00

190

019

20

194

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60

198

020

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202

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40

206

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80

210

0

e12

kg

/yr

Fa

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L'v

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ite (

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Wa

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nd

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s

Volume of large reservoirs (in km3)

Global hydropower generation capacity

Adequate water supply and sanitation in developing countries

Why do poor people have no access to public water supply?

Poorcannot pay

No costrecovery

Nomaintenance

Systembreak-down

Noservice

Investmentsneeded

The viciouscircle of the

poor

Why do rich people use so much water?

The richbecomericher

Increasingwater demand

Increasinginvestments

Expansionof supplycapacity

Increasedwater use

Increasedbenefits

The self-enforcing

circle of therich

The rainbow of water

• Blue water

runoff (surface water, groundwater)

• Green water

transpiration by plants

• White water

evaporation through interception or directly from the soil

• Black water

fossil groundwater

• Brown waterwastewater

• Grey watertreated wastewater, for reuse

• Virtual water

water ‘hidden’ in an agricultural or industrial product

(the quantity of water used in the production process)

Water scarcity

Causes of ‘water scarcity’

Aridity

Permanent water shortage due to a dry climate.

Drought

An irregular phenomenon occurring in dry years.

Dessication

Drying up of the landscape, particularly the soil, due to activities such as deforestation, overgrazing, lowering groundwater tables.

Water stress

Scarcity due to increasing number of people relying on limited resources.

Arid and semi-arid areas

Aridity

P = precipitation

Ea = actual evapotranspiration

Ep = potential evapotranspiration

S = moisture surplus (in the wet season)

D = moisture deficit (in the dry season)

pE

DS

6.0Index Aridity ste'Thornthwai

P

EaIndex Aridity Simple

The importance of ‘evaporative demand’

Growth factors(relative increase since 1900)

0

2

4

6

8

10

12

14

16

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

Gross worldproduct

Industrialproduction

Water demand

Irrigated cropland

Population

Indicators of water scarcity

Utilisation level (use-availability ratio) =

Water demand / total runoff

Alternatives:– stable runoff instead of total runoff– consumptive instead of total demand

Water competition level =

Population / total runoff

Water availability per capita =

Total runoff / population

Marginal cost of water supply

Use of water compared with internal water availability

Utilisation of total (internal+external) water resources

Conflicts over water

Water conflicts in international rivers

National water availability

Rivers in the Middle East

Southeast Anatolia Project

Euphrates and Tigris:

• Turkey, Syria, Saudi Arabia, Iraq, Iran.• 1992: Atatürk Dam in Turkey.

Turkey: “Allah gave oil to them, but water to us.”

The Atatürk Dam

River Euphrates:Change of water distribution

Criteria for a fair water distribution

Effects ofintensive water use

Human pressures on the hydrological cycle

Direct diversion of water flows

Water withdrawals.

Transformation of the stream network

Dams and reservoirs, river canalisation.

Changing drainage basin characteristics

De-/reforestation, urbanisation, drainage of wetlands, agricultural practices.

Activities altering regional or global climate

Burning fossil fuels, consumptive water use, land cover changes.

Historical change of the Ganges river runoff

Historical change of the Colorado river runoff

Shrinkingof the

AralSea

Shrinking of the Aral Sea

Effect of groundwater abstraction on groundwater table

Time

Gro

un

dw

ate

r le

ve

l

1

2

3

4

Water pollution

P.m.

Effects of land use changes

P.m.

Effects of climate change

Global annual hydrological cycle

‘Predicted’ change of the annual hydrological cycle

River runoff calculation by a GCM

Predicted change of Rhine river runoff (near Lobith)

Impacts of climate change on terrestrial hydrology

Distribution of the world’s major biomes

Impact of global warming on water supply

Global freshwater vulnerability

Sea level rise

Mechanisms of anthropogenic sea-level change

Water storage in glaciers

Globalmeantemp.

Land cover changes

(e.g. deforest.)

Water consump-

tion

Building reservoirs

Soil erosion

Water storage in ice sheets

Thermal expansion

of oceans

Sea level

Net precipitation

on land

+ +/-

Groundw. use

Soil moisture storage

Fresh groundw. storage

Fresh surface water

storage

---

-

+/-

- + + + +

-

----

+

Greenh.gas

emissions

++/-

Sea level rise (mm)IPCC assessment 1995

1890-1990 1990-2100

Low Middle High Low Middle High

Estimated

Thermal expansion 20 40 70 - 280 -Glaciers 20 35 50 - 160 -Greenland ice sheet -40 0 40 - 60 -Antarctica ice sheet -140 0 140 - -10 -Fresh surface and ground water -50 5 70 - 0 -

Total -190 80 370 130 490 940

Observed

Total 100 180 250 - - -

Contribution of groundwater losses to sea level rise

Korzun et al. (1978):

Period 1900-1964: 52 mm

Gornitz et al. (1982):

Period 1880-1980: ‘a few centimetres

Sahagian et al. (1994):

Period 1900-1990: at least 9 mm

Hoekstra (1998):

Period 1900-2000: 35-95 mm

Period 2000-2100: 240-390 mm

Sea level rise (mm)

Sea-level rise

in mm

Past (1900-2000) Future (2000-2100)

Hierar. Egal. Indiv. Hier. Egal.n Indiv.

Thermal expansion 40 40 40 280 340 220

Glaciers 35 45 25 200 270 128

Greenland ice sheet 6 29 4 44 92 26

Antarctica ice sheet 6 41 3 -19 48 -35

Groundwater loss 68 95 35 393 243 290

Deforestation 1 1 1 2 0 5

Drainage of wetlands 13 13 13 3 1 5

Artificial surface

reservoirs

-21 -21 -21 -7 -4 -12

Total sea-level rise 148 243 100 896 990 627

Cost of protection against 1 m sea level rise