CALIBRATION OF THREE COMMON FLOW MEASUREMENT DEVICES FOR OPEN CHANNELS

The aim of this research was to test and calibrate some water flow measurement devices, which were appropriate for on-farm management in Egypt. To fulfill this purpose, three of the common water- flow measurement devices (v-notch, rectangular weir and cutthroat flume) were calibrated in the Laboratory of Hydraulics Research Institute in Qanater City (Egypt, القناطر). The calibration was carried out using an ultrasonic flow- meter. Results of this study showed that under low discharges, i.e. 5 and 10 Ls-1, the most accurate device was the v-notch, under high discharges 15, 20, 25, 30 and 35 L s-1, the most accurate one was the rectangular weir. Increasing discharge rate from 5 to 35 L s-1 resulted in increases in error percentage in the readings of the v-notch. On the other hand, the corresponding error percentages in readings of both the rectangular weir and the cutthroat flume were obviously decreased. The decreases seemed inversely related to the increase in rate of discharge. Effect of time interval on error percentage seemed to be irregular. From the aforementioned results, it could be deduced that the v-notch weir is preferable for measuring the discharge at a rate ranging from 5 to 10 L s-1, beyond which the rectangular weir, as well as the cutthroat flume, would be preferable.