Abstract
The aim of this paper was to analyze theoretical aspects of calculating steady water flow through unsubmerged circular orifices. Theoretical analysis shows that the values of discharge obtained by using formulas intended for small orifices are greater than those calculated using formulas for large orifices. These differences attain a maximum value when the water level reaches the upper edge of the orifice, and decrease when water head increases. It has been proven that the volumetric flow rate for circular unsubmerged orifices can be calculated by formulas for small orifices when the water level above the center of gravity is at least four times as high as the diameter of the orifice.