Hydrology miscellaneous

Hydrology miscellaneous

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Hydrology

Hydrology miscellaneous
  1. Isopleths are lines on a map through points having equal depth of








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    Isopleths are line joining points of equal evapotranspiration (PET)

    Correct Option: C

    Isopleths are line joining points of equal evapotranspiration (PET)

Direction: Ordinates of a 1-hour unit hydrograph at 1 hour intervals, starting from time t = 0, are 0, 2, 6, 4, 2, 1 and 0 m³/s.

  1. Catchment area represented by this unit hydrograph is








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    Total volume of water = area under unit hydrograph
    = 60 × 60 × 1 × (0 + 2 + 6 + 4 + 2 + 1 + 0) = 54000 m³
    ∵ Unit hydrograph, rainfall excess is 1 cm, i.e. 10–2 m.
    A × 106 × (1 × 10-2) = 54000 (106 to make it km²)

    ∴ A =
    54000
    		 = 5.4 km²
    104

    Correct Option: D

    Total volume of water = area under unit hydrograph
    = 60 × 60 × 1 × (0 + 2 + 6 + 4 + 2 + 1 + 0) = 54000 m³
    ∵ Unit hydrograph, rainfall excess is 1 cm, i.e. 10–2 m.
    A × 106 × (1 × 10-2) = 54000 (106 to make it km²)

    ∴ A =
    54000
    		 = 5.4 km²
    104

Direction: At a station, Storm I of 5 hour duration with intensity 2 cm/h resulted in a runoff of 4 cm and Storm II of 8 hour duration resulted in a runoff of 8.4 cm. Assume that the φ-index is the same for both the storms.

  1. The intensity of storm II (in cm/h) is








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    Let intensity of storm-II be P cm/hr

    ∴ 1.2 =
    P × 8 - 8.4
    8

    ⇒ 1.2 × 8 + 8.4 = P × 8
    P = 2.25 cm/hr

    Correct Option: D

    Let intensity of storm-II be P cm/hr

    ∴ 1.2 =
    P × 8 - 8.4
    8

    ⇒ 1.2 × 8 + 8.4 = P × 8
    P = 2.25 cm/hr

  1. The φ-index (in cm/h) is








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    φ-index =
    2 × 5 - 4
    5

    =
    10 - 4
    		 =
    6
    		 = 1.2 cm/hr
    55

    Correct Option: A

    φ-index =
    2 × 5 - 4
    5

    =
    10 - 4
    		 =
    6
    		 = 1.2 cm/hr
    55

Direction: The drainage area of a watershed is 50 km². The φ index is 0.5 cm/hour and the base flow at the outlet is 10 m³/s. One hour unit hydrograph (unit depth = 1 cm) of the watershed is triangular in shape with a time base of 15 hours. The peak ordinate occurs at 5 hours.

  1. For a storm of depth of 5.5 cm and duration of 1 hour, the peak ordinate (in m³/s) of the hydrograph is








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    For 1 cm depth, peak ordinate, Q0 = 18.52 m³/s
    ∴ For sum, Q = 18.52 × 5 = 92.6 m³/s.

    Correct Option: C

    For 1 cm depth, peak ordinate, Q0 = 18.52 m³/s
    ∴ For sum, Q = 18.52 × 5 = 92.6 m³/s.