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Ayman98

Evaporation/Evapotranspiration in GSSHA

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Hello,

I am trying to include the evaporation/evapotranspiration in GSSHA, the modeled area only includes about 10% vegetation and the rest of the landuse is dry areas (roads, gravel, open spaces, commercial, urban). My question is what about the paramere values in case of no vegetation, can I put zero (0) or I have to use certain values for vegitation radiation coefficient, canopy stomatal resistance. Is there a standard values/tables for these parameters to have an idea and obtain approximates appropriate for my stuy area (Sinai, Egypt). Also, if I used the evapotranspiration table as shown above, does th model will calculate the evaporation from the soil/land uses during the rain storms?

Best regards

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The best I can do is to point you in the right direction.  The Deardorff method is a bare-earth method and does not consider the resistance of the plant canopy to evaporation.  This can result in higher evaporation and lower soil moisture than the Penman method, which considers the vegetation canopy but requires more information.  You might try the Deardorff method and compare the results with the Penman method.  I'm not sure what would happen if you enter values of zero for a parameter like the vegetation height...you could try it and if GSSHA crashes, try a small value like 0.01.  You would not want to enter values of 0.0 for all the inputs in the Penman method for bare earth.  Some values would be 1.0 (like the vegetation radiation coefficient) and other values would be 0.0 or close to 0.0 (like the canopy resistance and the vegetation height).  You can find more information along with sample values on the following web pages:

http://gsshawiki.com/Mapping_Table:Mapping_Tables#12.3.8_Evapo-transpiration

http://gsshawiki.com/Continuous:Computation_of_Evaporation_and_Evapo-transpiration (the really useful information starts toward the middle of the page)

http://gsshawiki.com/Long-term_Simulations:Evapotranspiration_model

Regards,

Chris

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