Cu07821 3 precipitation and evapotranspiration
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Transcript of Cu07821 3 precipitation and evapotranspiration
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Precipitation and evapotranspiration
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Example Hydrological cycleevapotranspiration
Transpiration275 mm
Evaporation75 mm
350 mm
Atmosphere
Precipitation800 mm
Ground level
Surfacerunoff25 mm 250 mm
425 mm
Sea
700 mm
275 mm
Open surface water system
Soil Moisture orUnsaturated zone
crops
Capillary rise50 mm
Absorption by roots
Water table orGroundwater level
Percolation orrecharge475 mm
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Distribution Precipitation1961 - 1990
mm per year
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Shortage precipitation in summer
-Average numbers
- Depends on use of land
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Effective precipitation (EP)(effectieve neerslag)
Volume of water available for recharge of groundwater.
Effective P = Precipitation - Evapotranspiration EP = P - EA (mm)
EA = Actual Evapotranspiration (depends on crops)
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EP grassland and agriculture
EP grassland(mm per year)
EP agriculture(mm per year)1
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Extreme Precipitation (neerslag)
1998: The “Westlandbui” (100 mm in 24 hour) caused 0,5 billion euro damage.
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Policy on preventing flooding
• Nationaal Bestuursakkoord Water (2003)
Use of land Flooding Rainfall[1/year]
Grass 5 percent 1/10
Agriculture 1 percent 1/25
Horticulture 1 percent 1/50
Cultivation under glass 1 percent 1/50
Urban Area 0 percent 1/1002
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STOWA rapport
• Conversion form standards (for example 1/10) to data for calculation / modelling
• Based on rainfall in the period 1906-2003 De Bilt.
• Use of statistics calculations
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Rainfall (mm), the stormsyear
hours days
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Rainfall distribution scheme
• Distribution scheme during rainfall• Standard schemes independent of rain
volume• There are 7 schemes which have the
same change • See excel-file
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Climate scenario’s
http://www.climatescenarios.nl/scenarios_summary/index.html
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Evapotranspiration
• PE potential evapotranspiration: Crops have optimal supply of water. Evaporation and transpirationDepends on type of crops
• AE Actual evapotranspiration; Is always less than the PE. In reality crops sometimes a shortage of water.
• mm/day
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Example Hydrological cycleevapotranspiration
Transpiration275 mm
Evaporation75 mm
350 mm
Atmosphere
Precipitation800 mm
Ground level
Surfacerunoff25 mm 250 mm
425 mm
Sea
700 mm
275 mm
Open surface water system
Soil Moisture orUnsaturated zone
crops
Capillary rise50 mm
Absorption by roots
Water table orGroundwater level
Percolation orrecharge475 mm
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PE potential evapotranspirationNetherlands:Makkink-reference Evapotranspiration (Em)(mm/day)Potential Evapotranspiration of grass
International:Penman, is based on evaporation of surface water (Eo
MOW) (mm/day)
EoMOW = 1,25 x Em
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Crops factors (gewasfactoren)
cropsUncovered soilGrass
GrainMaize / corn
LilyNarcissusTulipBulbous plantLeekCeleriacChicorySowing OnionOnion plantsLegumeSugar BeetsPotato's
Large Fruit
Tree cultivation
Nature plantsPoor grasslandHeather
Moorland