CIV E 634 - SURFACE WATER HYDROLOGY
SPRING 2011
HOMEWORK 2:   EVAPORATION

  1. Derive the Penman equation (Eq. 2-36, page 46 of text).

  2. Verify Example 2-5 in the text by running PENMAN in onlinehydro.sdsu.edu. Use the month of February.

  3. Use PENMAN-MONTEITH [reference crop] in onlinehydro.sdsu.edu to calculate the evapotranspiration rate of the reference crop (clipped grass 0.12-m high) for the month of February, with the following atmospheric conditions: air temperature Ta = 20 oC; net radiation Qn = 550 cal/cm2/d; wind speed v2 = 200 km/d; relative humidity RH = 70%; and atmospheric pressure = sea level (1013.2 mb).

  4. Use PENMAN-MONTEITH [reference crop] to study the sensitivity of the reference crop evapotranspiration to the relative humidity. Use the same data as in Problem 3. Vary RH between 20% and 100% in increments of 20% and report the results. What can you conclude from the results?

  5. Given the reference crop (clipped grass 0.12-m high), with air temperature Ta = 16 oC; net radiation Qn = 520 cal/cm2/d; and atmospheric pressure = 1005 mb). At what wind speed during January will the reference crop PET at RH = 20% be double that at RH = 100%?

  6. Use THORNTHWAITE in onlinehydro.sdsu.edu to calculate the PET for Ramona (32oN) for the month of June, with the following mean monthly temperatures (January to December): 11, 13, 14, 16, 18, 20, 21, 18, 15, 14, 13, 12.
Submit all onlinehydro.sdsu.edu printed output.