Nowaday, dams and hydraulic structures are constructed in immense size for keeping back and controlling large volume of water under high pressure. The discharge to the riverbed can damage related hydraulic structures, especially water energy when flow over the spillway with high velocity. This results the maintenance cost to prevent erosion in the base of the structures higher. Thus, it is necessary to reduce some excessive energy by means of the bucket type energy dissipator, one of the ways in dissipating energy before it reaches the channel bottom. The study ratio of energy loss for a better shape of energy dissipator by the above mentioned way in a hydraulic model of spillway uses the scale 1:25 in accordance with the law of similitude. The value of parameter [equation], is equal or less than 26. Furthermore, the similar outcome experimentation of McPherson-Karr and WES is studied and taken as standardize comparison between roller bucket, elliptical bucket and parabolical bucket. The discharge flow over the model spillway to each dissipator is valued y1 and y2 by point gage and transparent plastic well respectively before the surge will form a free-jet by lift gage control. The gatered values with be calculated to find out ratio of energy loss per energy before the jump on the various Froude number without considering effects of boundary friction, erosion and surface tension. The effect of this experimentation shows that parabolical energy dissipator has more efficiency in dissipating energy than roller bucket and elliptical bucket on condition that hydraulic jump is strong jump. However, the roller bucket will be better than the others if the hydraulic jump is steady jump.
