CIV E 634 - SURFACE WATER HYDROLOGY
SPRING 2011
HOMEWORK 6:   RUNOFF MODELING

  1. The watershed of the La Leche river has the following time-area histogram:

    Time (hr)             0          1          2          3          4

    Area (km2)              148      252      318       189

    Use onlinerouting06 (the time-area method) to calculate the flood hydrograph for the following effective storm pattern:

    Time (hr)                                 0         1         2         3         4         5         6

    Effective rainfall (cm/hr)               1          3         4         3          2         1

  2. Use onlinerouting07 (the Clark UH) to calculate a 2-hr unit hydrograph for the La Leche basin, with the following time-area histogram:

    Time (hr)             0          1          2          3          4

    Area (km2)              148      252      318       189

    • Assume Δt = 1 hr, and K = 3 hr.

    • Assume Δt = 1 hr, and K = 4 hr.

    • Assume Δt = 1 hr, and K = 5 hr.

    What happens to the peak flow as K increases?

  3. Use onlinerouting08 (cascade of linear reservoirs basin routing) to calculate a flood hydrograph for the La Leche basin, with the following data:

    basin area A = 907 km2;

    storage constant K = 2 hr;

    number of reservoirs N = 2;

    time interval, 1 hr;

    number of increments of effective rainfall, 6;

    increments of effective rainfall intensity (cm/hr): 1,3,4,3,2,1.

  4. Using ONLINE DIMENSIONLESS UH CASCADE calculate the cascade-of-linear-reservoirs unit hydrograph (CLR UH) for the data of Prob. 3. Then use ONLINE CONVOLUTION with the the CLR UH and the data of Prob. 3 to confirm that the cascade of linear reservoirs and the unit hydrograph convolution give the same answer when the cascade parameters are used to calculate the unit hydrograph used in the convolution.