To investigate the rainfall-runoff relation of a long duration rain storm on dry catchment.
- Basic Hydrology Apparatus
- Rainfall intensity=20L/min.
- Time interval=30sec.
Plot a hydrograph between time (x-axis) and discharge (y-axis).
- Set the slope of hydrology apparatus as zero.
- Make sure that the catchment is dry.
- Turn off all the outlet valves (all four) except the one at the point of concentration (outlet valve).
- Now set the flow at 20L/m.
- 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.
- Note the discharge in L/s for every 30s intervals.
- Note the time for max discharge that shall be the time of concentration Tc.
- There should be no losses at the outlet; to ensure that keep all the four discharge valves closed.
- Set the discharge at the assigned value not considering the back-pressure
- Note some additional readings too, so that falling limb can be plotted