HUMAN IMPACT ON WATER CYCLE NGO People and Water, SK ENKI, CZ Třeboň , 16th June 200 9

HUMAN IMPACT ON WATER CYCLE

NGO People and Water, SK

ENKI, CZ

Třeboň, 16th June 2009

FRESHWATER STOCKS ON EARTH

NEOLITIC REVOLUTION

Ca 10.000 years agoPictures: M. Gojda, Krajinná archeologie,

Západočeská univerzita

The Slavonic countries stretch from the Mediterranean Sea through to the Northern Seas... The Slavs build most of their own castles...on meadows rich in water and bushes... They till the soil very intensively... Famines caused by long-term drought don't exist in [their] lands... If it rains only a little, they do not have poor results, because these lands are damp...

/Ibrahim Ibn Jacqub at-Turtushi, About the

Western Slavs, middle of the 10th century/

Deforestation

J. A. Foley et al. - Green surprise? How terrestrial ecosystems could affect earth’s climate, Front Ecol Environ 2003;

BIOTIC PUMP

CURRENT RATE OF DEFORESTATION

• 120 000 km2/year

• i.e. 1.3 % annual decrease of remaining 30% wood on Earth

/According to FAO/

DEFORESTATION & AGRICULTURE

Deforestation / some forms of farming cause:

• increase of runoff (and erosion)

• lower infiltration (groundwater recharge)

• lower evaporation (change of regional climate)

• decrease of organic matter content in soil (decrease of ability to hold water)

Whoever

improves the soil,

cultivates land

lying waste and

drains swamps,

is making conquest

from barbarism.

/Frederick II, King of

Prussia in 1740-86/

DRAINING SWAMPS

In civilised countries, the rule should be that rivers and streams are canals ...

[The river should be] directed into single bed with gentle curves... where it is practicable, a straight line...

/Johann Gottfried Tulla, ThePrinciples of Future Work on theRhine, 1809/

ALTERATION OF RIVERS

• natural meanders removed

• adjacent swamps drained • shortening length

increases slope• acceleration of runoff • deepening of the riverbed • lowering/draining

groundwater table• lowering land's ability to

retain water

ALTERATION OF RIVERS

URBAN REVOLUTION – SEWERS, CANALIZATION

PAVEMENT IMPACT

• infiltration decreases (groundwater recharge decreases)

• evaporation decreases (air humidity decreases)

• runoff increases (through sewage to rivers and sea)

Free surface

Paved surface

IMPERVIOUS SURFACES AND RUNOFF

RUNOFF FROM URBAN

AND FOREST ENVIRONMENTS

RUNOFF FROM URBANAND FOREST ENVIRONMENTS

Decrease of runoff is overlooked flood prevention measure

SOIL SEALING IN CITIES

• impervious surfaces cover 5% of the EU

• about 20 billion m3 of rainwater sluiced from municipalities of Europe annually

Precipitation

(mm/ year)

Volume of water circulating

Runoff (indicator of soil sealing)

Europe 750 7 790 km3 36 %

Slovakia 762 37 km3 34 %

Prešov, SK (City center)

628 12 mil. m3 72 %

Plot of land 630 0,5 mil. m3 37 %

Residential house

630 766 m3 76 %

WATER BALANCE OF THE INVESTIGATED TERRITORY

LAND USE TRANSITION

J.A. Foley et al. - Global Consequences of Land Use, Science, 2005

EXTENT OF HUMAN LAND USE

J. A. Foley et al. - Green surprise? How terrestrial ecosystems could affect earth’s climate, Front Ecol Environ 2003;

SOIL SEALING DESTROYSSMALL WATER CYCLE(S) ON LAND

EARTH – WATER BUDGET

Oceans

Atmosphere

Land Evaporation361 000 km³/year

Precipitation324 000

km³/year

Runoff37 000

km³/year

Precipitation99 000

km³/yearEvaporation

62 000

km³/year

There is more water in „small“ water cycles than in „large“ water cycle!!!

(PARTIAL) CONCLUSION

• Human activities have a significant impact on the water cycle

THANK YOU FOR YOUR ATTENTION!