CIV E 445 - APPLIED HYDROLOGY
SPRING 2014
LAB No. 4 SOLUTION

  1. The water discharge is calculated with ONLINECHANNEL15. The sediment discharge is obtained from the Colby rating curve shown below.

    Stage y
    (m)    		 Bottom width b
    (m)    		 Size slope z Manning's n Bed slope S Water discharge Q
    (m3/s)    		 Sediment discharge Qs
    (M. Tons/day)
    0.5 155 2 0.030 0.00013 18.57 900
    1.0 155 2 0.030 0.00013 59.05 6,500
    1.5 155 2 0.030 0.00013 116.2 15,000
    2.0 155 2 0.030 0.00013 187.9 22,000
    2.5 155 2 0.030 0.00013 273.0 37,000
    3.0 155 2 0.030 0.00013 370.5 53,000


  2. The answers to the questions are the following:

    • Yes, evapotranspiration measures transpiration from leaves of plants, and it also measures direct evaporation from open water and soil.

    • The ETgage measures reference potential evapotranspiration ETo. It uses a ceramic evaporating cup to simulate crop color (albedo) and leaf properties (vapor diffusion resistance).

    • Preferably at 7 am.

    • One should squeeze the flexible connecting tube at the bottom of the glass tube to make sure the meniscus is not stuck. Once the meniscus settles in equilibrium, one can proceed to read the instrument.

    • The reading on the second day of observation was 0.16 in.

    • A normal ETo measurement is 0.2 in/day.

    • A high ETo measurement is > 0.5 in/day.

  3. Running Online Penman for the given data results in ETo = 1.04 cm/day. In order for ETo to reach 0.5 in/day, i.e., 1.27 cm/day, the relative humidity should reduce to 17%.