The current standards recommend measuring water discharge with vented thin-plate weirs. The ventilation of full-width, thin-plate weirs during discharge hydrograph measurement still poses a problem. An experimental study regarding the design of a new type of ventilating device for hydrograph measurement was performed from 20 October through 5 December 2015 which proved that this device can be used measuring discharge at ventilated nappe according to standard recommendations. During the second part of the experiment, an opportunity was provided for measuring the discharge at non-ventilated nappe as a function of Reynolds and Weber numbers.Keywords: Run-off hydrograph, water discharge, weirs, ventilated nappe.In the present study, water discharge in full-width thinplate weirs, in the case of non-submerged ventilated overflow is calculated using the equationwhere m is the discharge coefficient, B the width of the weir and H is the height of the nappe 1 . Generally, the discharge coefficient is a function of Reynolds number (Re), Weber number (We), H/P and H/B, where P is the height of the weir [1][2][3][4][5][6][7][8] . The following equations are suggested for the calculation of these numbers: Re = [(2gH) 0.5 (BH) 0.5 ]/ and We = (2gHB)/, where the kinematic viscosity coefficient, the density and is the surface tension of water 4,9 . The valid international standards 10,11 and recent studies 2,4,12,13 recommend the equations listed in Table 1 for the discharge coefficient. These equations refer to ventilated nappe. For the height of the nappe H 0.03 m, the influence of Re and We on discharge is negligible 3 . For ventilation of the nappe, the literature recommends making holes beneath it in the channel walls, or using pipes for air supply 1,14 . The problem of ventilation occurs when the nappe separates from the weir due to the position of the holes, while the use of pipes requires blowing air in them. Studies conducted by the present author 1 also confirmed the existence of this problem. The simplest and most efficient ventilation of the nappe has been achieved by running a finger across it.In order to measure discharge using a thin-plate weir, a weir with dimensions B = 0.4 m wide and P = 0.341 m was tested 15 . It has been established that there is a nappe separation limit (H = 0.035 m) when the discharge increases, and a nappe adherence limit (i.e. when the nappe adheres to the thin-plate weir) when the discharge decreases (H = 0.009 m). Air for ventilation has been supplied by pipes and through holes on both sides of the channel. The holes on the channel walls are located at the middle of the weir, on the surface of the non-ventilated nappe. The following equations have been suggested for discharge coefficient calculations at water temperature of 11-14C.