CIV E 445 - APPLIED HYDROLOGY
SPRING 2014
LAB No. 12

  1. A 45-km2 catchment has a 6-h time of concentration, with isochrones at 2-hr intervals resulting in the following time-area histogram:

    Time (hr) 0-2 2-4 4-6
    Area (km2) 9 21 15

    Use the time-area method to calculate the outflow hydrograph from the following effective storm pattern:

    Time (hr) 0-2 2-4 4-6 6-8 8-10 10-12
    Total rainfall (cm/h) 0.5 1 2 3 1 0.5

    Verify with ONLINE ROUTING 06.

  2. Use the method of cascade of linear reservoirs to route the following effective storm hyetograph for a 1000-km2 basin. Use N= 2, Δt = 1 hr; and K = 2 hr. Verify with ONLINE ROUTING 08.

    Time (hr) 0-1 1-2 2-3 3-4 4-5 5-6
    Total rainfall (cm/h) 1 2 5 4 3 0.5

  3. Using Example 10-2 of the text and ONLINEROUTINGCLARK, find the ratio between peak outflows calculated between the Clark unit hydrograph and Ponce's modified version of the Clark unit hydrograph. Use the unit hydrograph duration of 2 hr. Use K = 2, Δt = 1 hr, and the following time-area histogram:

    Given the watershed area A = 100 km2, and the time of concentration tc = 4 hr: What basin shape combination (Try, for example: 40, 30, 10, 20) would produce the largest difference between peak outflows by the two methods?