CIV E 445 - APPLIED HYDROLOGY
SPRING 2014
HOMEWORK No. 10

  1. Route the following triangular inflow hydrograph through a linear reservoir: peak inflow = 240 m3/s, baseflow = 0 m3/s, time-to-peak = 6 h, time base = 16 h, storage constant K = 2 h, and time interval Δt =1 h. Use a spreadsheet. Verify using ONLINE ROUTING 01.

  2. Solve Problem 1 by the storage indication method. Use a spreadsheet. Verify using ONLINE ROUTING 02.

  3. Determine the actual freeboard for the following dam, reservoir, and flood conditions: dam crest elevation = 125 m; emergency spillway crest elevation = 120 m; coefficient of spillway rating = 1.7; exponent of rating = 1.5; width of emergency spillway (rectangular cross section) = 20 m.

    Elevation-storage relation:

    Elevation (m) 120 121 122 123 124 125
    Storage (hm3) 3.00 3.15 3.35 3.70 4.35 4.95

    Inflow hydrograph to reservoir:

    Time (h) 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
    Inflow (m3/s) 0 15 30 45 70 100 125 150 185 175 150 125 100 80 60 50 33 25 14 9 7 5 1 0

    Assume the initial reservoir pool level at spillway crest. Use ONLINE ROUTING 03.

  4. Design the emergency spillway width (rectangular cross section) for the following dam, reservoir, and flood conditions: dam crest elevation = 483 m; emergency spillway crest elevation = 475 m; coefficient of spillway rating = 1.7; exponent of spillway rating = 1.5. Elevation-storage relation:

    Elevation (m) 475 477 479 481 483
    Storage (hm3) 5.0 5.3 6.0 7.0 8.5

    Inflow hydrograph to reservoir:

    Time (h) 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
    Inflow (m3/s) 0 10 30 50 90 150 250 350 280 210 190 170 130 100 90 75 50 40 30 15 10 5 2 1 0

    Assume design freeboard = 2 m (to within 0.01 m accuracy: 1.99-2.01 m) and initial reservoir pool level at spillway crest. Use ONLINE ROUTING 03. [Hint: Try several values of spillway length L (width). Determine width to an accuracy of 0.1 m].