The document summarizes a study on hydraulic modeling of a side-channel spillway at Iven Dam in Mongolia. The goals were to determine flow regimes using physical and numerical modeling, study hydraulic modeling methodology, and identify ways to improve standard design methods. Hydraulic modeling methods used included analytical fluid dynamics, experimental fluid dynamics with a physical model, and computational fluid dynamics. Results from physical and CFD models showed significant differences from the standard design method, indicating the need to update standard methods. The study concluded the spillway capacity should be increased and validated all hydraulic structures with physical and numerical models before construction.