Climate Change and the Water

Cycle

Richard HardingCentre for Ecology and Hydrology

Drivers of Global Change:

• Increasing population

• Increasing water consumption

• Land cover/use change

• Increasing greenhouse gases

Stern Review (2006)

Water Consumption - after Shiklomanov 2000

0

500

1000

1500

2000

2500

3000

1900 1920 1940 1960 1980 2000 2020 2040

Co

nsu

mp

tio

n,

km3/y

ear

Agriculture

Industry

MunicipalneedsReservoir

Total

Assessment

Forecast

Areas of physical and economic water scarcity (IWMI, 2006)

We represent the earth by a grid of squares, typically of length 150 km or smaller.

The atmosphere and oceans are divided into vertical slices of varying depths.

To predict the future we need the climate models

FIGURE SPM-6. Relative changes in precipitation (in percent) for the period 2090–2099, relative to1980–1999. Values are multi-model averages based on the SRES A1B scenario for December to February (left) and June to August (right). White areas are where less than 66% of the models agree in the sign of the change and stippled areas are where more than 90% of the models agree in the sign of the change.

IPCC 2007

Smoothed annual anomalies for precipitation (%) over land from 1900 to 2005; other regions are dominated by variability.

Land precipitation is changing significantly over broad areas

Increases

Decreases

Climate change scenarios – the changing seasons

• UK winterWetter: Up 10% by 2020s, up to 30% by 2080s

Drier: 20% by 2020s, up to 50% by 2080s

• UK summer

30-yearevent

12-yearevent

4-yearevent

30-yearevent

12-yearevent

4-yearevent

Climate change scenarios – changing extremes

Percentage change in

flows for the 20-year return

period

Climate change scenarios – impact on flows

10km

Glacier melt in the Himalayas

1989

2000

1978

1996

SAGARMATHA: Snow and Glacier Aspects of Water Resources Management in the Himalaya

-80

-60

-40

-20

0

20

40

60

0 1 2 3 4 5 6 7

Decade

% c

han

ge Uttarkashi

Haridwar

Kanpur

Allahbad

%change in decadal mean flow for Ganges from

regional climate model output (RCM2)

http://www.nwl.ac.uk/ih/www/research/SAGARMATHA/

WATCH

WB7

Assessing the vulnerability of water resources

WB6

Past, present and future population, LUCC and

water demand

WB2

Extremes and scales of

hydrological events

WB4

Feedbacks in the climate hydrological

system

WB5

21st Century Global water cycle

20th Century Global water cycle

WB3

WB1

Management, training anddissemination

WATCH

WB7

Assessing the vulnerability of water resources

WB6

Past, present and future population, LUCC and

water demand

WB2

Extremes and scales of

hydrological events

WB4

Feedbacks in the climate hydrological

system

WB5

21st Century Global water cycle

20th Century Global water cycle

WB3

WB1

Management, training anddissemination

WB7WB7

Assessing the vulnerability of water resources

WB6

Assessing the vulnerability of water resources

WB6

Past, present and future population, LUCC and

water demand

WB2

Past, present and future population, LUCC and

water demand

WB2

Extremes and scales of

hydrological events

WB4

Extremes and scales of

hydrological events

WB4

Feedbacks in the climate hydrological

system

WB5

Feedbacks in the climate hydrological

system

WB5

21st Century Global water cycle

20th Century Global water cycle

WB3

WB1

21st Century Global water cycle21st Century Global water cycle

20th Century Global water cycle20th Century Global water cycle

WB3

WB1

Management, training anddissemination

The WATCH Integrated Project:

25 European partners: hydrology, climate and resource scientists

13m euros of effort

International programme

research, workshops, training, dissemination

Thank You