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!