Volumetric Streamflow Method
Volumetric analysis or the ‘bucket and stopwatch method’ involves the measurement of the time taken for a container of known capacity to be filled. This is a simple method for measuring small streams where all of the flow can be concentrated (such as naturally within a rock cascade, or by constructing a temporary dam with a pipe). The method can also be used in larger streams which have flow concentrated or partitioned by culverts, pipes or weirs. A short, wide container is more suitable to fit under the falling water, than a tall, narrow one. The container volume should be such that it takes at least 3 seconds to fill. It is important that the bucket is held upright and that multiple (>3) readings are taken to reduce measurement error. An alternative approach is to hold down and open a heavy-gauge plastic garbage bag on the stream bed, time its filling and empty the bag contents into a measuring container (Hauer & Lamberti, 1996). The bag can also be weighed and the volume calculated if the density of the water is known.
Stream discharge (Q) in L/s is calculated as
(Equation 1)
Q = V/t
where V is the contained volume (L) during time t (s).
References
- Hauer FR, Lamberti GA, 1996. Methods in stream ecology. Academic Press.