Experimental instrumentation
Runoff from each of the 12 experimental plots passed into a gravel
filled trench located at the bottom edge of each plot. An impermeable
membrane was installed at a depth of approximately 0.5 m below the
ground on the bottom and opposite side of the trench to the plot to
capture both surface and sub-surface lateral flowing water exiting the
experimental plots. A V-shape base of the trench ensured that all water
exited the trench at the same point, where it was channelled into a
V-notch weir fitted with a baffle plate to smooth out changes in the
height of the water. The height of the water within the weir was
monitored via an ADCON LEV1 level sensor (0 – 1 m range) positioned
within a stilling well. Data were recorded every minute via a Delta T
GP1 data logger as millivolt values and converted to discharge using a
regression equation established under laboratory calibration conditions.
To allow for the areal difference between the control plots (340
m2) and the buffer treatment plots (340
m2 + 120m2 = 460
m2), the runoff volumes were adjusted by multiplying
them by a correction factor calculated using the formula: