CIV E 634 - SURFACE WATER HYDROLOGY
SPRING 2009
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 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. Using PENMAN-MONTEITH, study the sensitivity of the reference crop evapotranspiration to the relative humidity. Use the same data as in Problem 3. Vary RH between 1% and 100% in increments of 20% (1%, 20%, 40%, 60%, 80%, and 100%) and report 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 will the ratio of reference crop PET at RH = 1% to reference crop PET at RH = 100% equal 2? Assume the month of January.

  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., 21., 22., 20., 18., 16., 12., 12.

Submit all onlinehydro.sdsu.edu printed output.