The difference between the types of flow is explained in the beginnig . Then the methods by which we arrive at the flow in open troughs are explained. For the needs of energy, agriculture, water management, ecology and flood protection, we measure some basic parameters of watercourses, such as flow and water level, and their mutual relationship which we can see in consumption curve.Water level is measured continuously at water stations and the flow area and flow depend on it. Measurement of watercourse flow is based on determining the reference velocity of liquid flow through the riverbed and determining the flow surface of watercourses, because their product gives us the flow in 𝑚3𝑠. This method is called the reference speed method and is the basis for all types of measurements we perform. The flow cross-section of watercourses is obtained by means of geodetic recorded terrains and ADCP devices that measure bottom elevations at the speed of flow using acoustic signals. Reference velocities can be obtained using various methods such as ADCP, hydrometer wing, tracer, and various types of overflows (Bazinov, Venturi, and Thompson).