Streamflow measurement
Stream flow or discharge is the rate at which a volume of water passes through the cross section of the stream per unit time, and as such has SI units of cubic metres per second (m3/s) or cumecs. Other common units used in Australia include megalitres per day (ML/d) or litres per second (L/s).
The common methods for measuring stream flow (Brassington, 1988; Hauer and Lamberti, 1996) are:
Volumetric Analysis
Velocity-Area Method
Slope-Area Method
Dilution Gauging
Thin Plate Weirs
Stream water levels are commonly taken at stream gauging stations. This involves recording the stage or the height of the water surface from a benchmark. By also measuring stream discharge (Q), particularly at various flow regimes, a relationship between stream stage and flow can be developed for the site. This relationship is called the flow rating curve and typically takes the form:
(Equation 1)
Q=a(h-z)b
where h is the measured gauge height, Z is the gauge height at zero-flow conditions, and a and b are best-fit coefficients using non-linear regression. In this way, a time-series of stream flow called a hydrograph can be generated from any continuous monitoring of stream level at the site. Streamflow measurement
Further Information
Water level measurement
Hydrographic analysis
References
Brassington R, 1988. Field Hydrogeology. Geological Society of London Handbook Series. Open University Press. Hauer FR and Lamberti GA, 1996. Methods in stream ecology. Academic Press.