Method

Step 1

Find a suitable, safe section of a river taking care to look for risks along banks. At this point measure a stretch of river from 1-3 m in length from upstream to downstream placing markers at either end of the measured distance along the river bank

Step 2

Place the buoyant object eg. dog treat in the middle of the river upstream from the initial measured point

Step 3

Start the stopwatch when the Treat passes the first marker then measure how long it takes to travel the measured distance 

Step 4

In order to calculate the surface velocity you divide the measured length by the recorded time, this will provide the surface velocity in m/s

Step 5

In order to calculate the discharge of the Discharge you need the velocity and the area of the channel. To calculate the cross section first measure the width of the channel and then at regular intervals using a meter stick take depth measurements

Step 6

To calculate the cross sectional area multiply each depth measurement by the regular interval that was used for taking measurements. Then add all the values together, this will give the area of the channel at a given point. This can be done at multiple points along the river, within the measured lengths, with these areas being averaged to provide a more reliable result.

Step 7

Calculating the Discharge

To calculate the discharge multiply the surface velocity by the cross section area this will provide the Discarge in M^3/S (cumecs)