Investigation of Rainfall – Runoff of a short duration rain

OBJECTIVE:

To investigate the rainfall-runoff relation of a short duration rain storm on dry catchment.

APPARATUS:

  1. Basic Hydrology Apparatus
  2. Stopwatch

CONSTANTS:

  1. Rainfall intensity=20L/min.
  2. Time interval=30sec.

GRAPH:

Plot a hydrograph between time (x-axis) and discharge (y-axis).

 

PROCEDURE:

  1. Set the slope of hydrology apparatus as zero.
  2. Make sure that the catchment is dry.
  3. Turn off all the outlet valves (all four) except the one at the point of concentration (outlet valve).
  4. Now set the flow at 20L/m.
  5. Turn on the rain valve and allow the rain over the catchment area for as long as the discharge at the outlet (in L/s) gets constant.
  6. Note the discharge in L/s for every 30s intervals.

OBSERVATIONS:

 

S/No.

Time T

(sec)

Discharge Qt

(l/sec)

 

S/No.

Time T

(sec)

Discharge Qt

(l/sec)

1          
2          

PRECAUTIONS:

  1. There should be no losses at the outlet; to ensure that keep all the four discharge valves closed.
  2. Set the discharge at the assigned value not considering the back-pressure phenomena
  3. Note some additional readings too, so that falling limb can be plotted easily

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