Field investigations have been carried out, in two six-month periods, on an arch dam reservoir located in southwest Iran. The main goal of these field measurements was to study the characteristics of turbid flow, which transports the main suspended load of sediment into the dam reservoir. The main specifications of turbid flow, such as thickness, current direction and velocity, sediment concentration, and transport rate, were measured at several cross-sections of the reservoir. Based on the field measurements and mining of recorded data, a govern regime for sedimentation in dam reservoir is recognized which can be used to optimize the flushing of the reservoir through the bottom outlet.