The minimum pressure head along the upper flat pipe section is recognized as a critical control parameter for ensuring hydraulic safety and operational stability in pumped-storage power stations. A mathematical model for transient flow analysis in the water conveyance system is developed

and a Sobol-based global sensitivity analysis method is incorporated. The influences of upstream surge chamber installation

along with three key design parameters—the inflow-outflow coefficient

throttled orifice diameter

and surge chamber diameter—on the minimum pressure at two selected control cross sections are systematically investigated. The minimum internal pressure at these sections is found to be effectively improved by the provision of an upstream surge chamber

by the optimization of the inflow-outflow coefficient

and by the increase of both the throttled orifice diameter and the surge chamber diameter. Among all influencing factors

the flow variation rate is identified as the dominant variable affecting the minimum pressure at the two sections. By means of the Sobol method

not only the individual effects of each parameter but also their pairwise interaction effects on the minimum pressure are quantitatively evaluated. The sensitivity indices are calculated

and the throttled orifice diameter is shown to exert the most significant influence

followed by the surge chamber diameter and the inflow-outflow coefficient

in descending order. Technical support for the evaluation and optimization of pipeline layout parameters in similar hydraulic systems is provided by the obtained results.