Calibration of a Compound Weir for Discharge Measurement in Small Headwater Streams Subjected to Climate Change

The paper presents a procedure to calibrate a triangular-rectangular compound weir for measuring discharges in small unmonitered streams subjected to climate change conditions. The main purposes are to obtain the discharge coefficients and the rating curve for a compound weir model in the laboratory with the purpose to use them for the real-scale, prototype weir in the nature. The experiments and measurements for the compound sharp-crested weir were carried out on a glass-walled, recirculating, rectangular flume within the Hydraulics laboratory in the University Politehnica of Bucharest. Global discharge coefficient values were fitted with two different functions for the two stages of the weir. The head-discharge relationship was fitted with a 3^rd degree polynomial function which gave the best mean square error. Computed sensitivity analysis proves the V-notch is more suited to measure low discharges, whereas the rectangular, upper stage is better for higher discharge values during intense rainfall events.