Rectangular weirs are used to extract water laterally in order to emulate the effect of offtake discharges in real irrigation canals. These weirs have a width of 39 cm and were constructed starting from a 35 cm canal height, except for the end weir (W4) that starts from the canal invert (Sepúlveda 2007). From this minimum height of 35 cm, it is possible to increase the height of the weir by placing PVC pieces in metal rails, one on top of the other. These pieces are 5 cm, 10 cm, 20 cm and 35 cm. With different combinations, it is possible to cover a broad range of weir heights, and thereby to achieve a broad range of output flow through the weir. This structure allows easy measurement of the extracting flow rate measuring the water level upstream of the weir. The features of the sharp-crested weir are shown in Table 11.