The circular-crested weir is used for flow measurement and has wide applications in hydraulic engineering, where it serves as an overflow structure. It can be used to control the water level in farm ponds and reservoirs. The discharge coefficient of such a weir is obtained experimentally as a function of the dimensionless total head of the approaching flow. It is shown that changing the upstream slope does not alter the weir-discharge coefficient. However, increasing the downstream weir slope appears to increase the discharge coefficient. The weir crest pressure is determined as a function of the dimensionless head and its variation is related to the weir-discharge coefficient. The experimental data indicate that the circular-crested weir behaves like a sharp-crested weir, when the dimensionless total head is extremely large.
