VOLUNTEERS - FIELD NOTES
Flow Method 1. Bucket & Timer
Flow 1. Technique - Bucket & Timer Measurements for Flow Determination
A bucket is a vessel with a known volume (litres), measuring the time taken (seconds) to fill the vessel provides the most accurate flow (litres/second) measurement to be calculated.
Note - this technique relies on a suitable creek measurement site.
Bucket & Timer Measurement
Bucket and timer flow determination can be the simplest and most accurate of all flow measurements, If flow conditions allow the bucket (and a tin funnel) to capture all of the flow, from a natural weir or a culvert.
To enter the two in one App entry form - I normally calculate each flow, and add these together to make a single entry number set as follows. A single litre/sec flow from the combined (culvert 1 + culvert 2) total flow (eg 0.55 litres/sec + 0.01 litres/sec)= 0.65 litres/sec total flow.
For locations where more than one culvert captures flow
I then assume a single (12 litre) bucket was used and calculate the time to fill this with the total litres/second flow number, so for the bucket 12 litres x 0.65 secs/litre = 7.8 secs (very close to your single culvert 12 litre bucket time average). In the App form I then enter this 7.8 sec time to fill a 12 l bucket - you can either do this three times (to indicate that averaging was done!) or simpler still just add a comment in the “comments” field entry (“summed flow entered from averages from two culverts”)