Abstarct: Side weir is a hydraulic control structure that is designed and installed to divert water from the main channel into lateral channels, when water level exceeds a specified level. In many hydraulic channels, due to the severe changes in runoff in different seasons of the year, many fluctuations occur in water level. These fluctuations could play an important role in the amount of both water intake and accuracy in calculation of diverted discharge. Considering the special geometrical shape of compound weirs, they have the capability to divert a certain amount of discharge to the lateral channel when water surface in the main channel is in its lowest level. In addition, these types of weirs provide the possibility of accurate calculation of diverted discharge values and prevent any damages to the channels and adjacent structures by the flow when the flood occurs. Having widespread application and simple structure, in this study the sharp-crested compound rectangular-rectangular and triangular-rectangular side weirs were investigated experimentally. To investigate the efficiency of relations suggested by authors for simple triangular and rectangular side weirs in determining the amount of diverted discharge from the compound weirs, some of the most common relations were selected. Comparing estimated total discharge from compound weirs which obtained from simple section with experimental data showed that this method is not appropriate for side weirs and it is of limited accuracy. Therefore, in the next step, discharge coefficient was calculated using three methods including direct, De Marchi and elementary methods and parameters affecting them were determined using dimensional analysis method. Then, for each one of these methods, relations were proposed for discharge coefficients. Due to non-linearity of proposed equation in elementary method, Genetic Algorithm (GA) was employed in calculations. Afterwards, extracted relations of discharge coefficient were verified using experimental data and error statistics and investigation of statistical indicators confirmed the capability of proposed relations. In addition, water surface profile in the centerline of channel and close to the weir was calculated using elementary method and was compared with experimental results. From this comparison is concluded that in general, De Marchi and elementary methods are efficient and of good accuracy for calculation of discharge from compound weirs as well as simple weirs. However, regardless of the complexity of the calculations, elementary method is of higher accuracy in determining discharge from weirs and calculating water surface profile in channels.