Abstract: A set of theoretic hydraulic calculation method for X-shape flaring gate is presented for the first time to provide theoretical support for engineering design and scientific research. The water of X-shape flaring gate is divided into two parts: the water in the notch and the water above the notch. Through momentum equation, the hydraulic jump equation is derived and is converted mathematically in equivalence and simplified to get the conjugate depth ratio η, and then the depth after the jump is obtained. As an illustration, the measured data of Suofengying project and Shatuo project are taken to calculate corresponding parameters, which are subsequently put into the simplified water jump equation to calculate the conjugate depth ratio η. Finally, the maximum relative error between the calculated water depth after the jump and the test value is only -5.11%, indicating that the equation is convenient and is derived correctly and reliably.

Key words: X-shape flaring gate pier, hydraulic jump equation, hydraulic calculation, conjugate water depth ratio, Suofengying hydropower station