Accurate water delivery ensures equity in water distribution and enhances the optimum usage of water resources. Nowadays, modern water measurement equipment could increase the accuracy of water delivery; however, the cost of investment and operation as well as the needs of the skillful operator restrict the widespread use of these equipment. Therefore, the traditional water measurement structures are widely used in irrigation networks. In this research, a new form of the flow measurement flume with a trapezoidal cross-section and an invert elevation coincide with the main conduit bottom was experimentally investigated. The design criteria for such flumes were presented hereafter. The proposed structure, which is classified as a long throated flume, is easily applicable in existing networks. The main advantages of the proposed structure are prevention of sediment accumulation and rather low backwater effects, and with such low backwater effects the critical depth could be established in flume section. Based on the compiled data, a method for calculating the required energy grade line in the approach channel and the structure head loss were presented.