The proposed technique allows estimating the efficiency of individual elements of hydraulic structures that perform similar functions and work together, and determining the impact of their current state on the entire structure performance. The technique was elaborated for a separate evaluation of drainage and impervious elements of bases of concrete dams on bedrock when they work together. To implement this task, the authors used the method of numerical simulation (modeling) and comparisons with field observations data, which allowed calibrating the ground model. The technique was tested on one of the gates at Bureyskaya HPP, and the influence of drainage and impervious elements effectiveness upon the backpressure on the base of the concrete dam was estimated. The result of these studies allows the authors to suggest appropriate safety criteria K1 and K2. It should be noted that the developed technique allows giving priorities in determining the composition and volume of the repair and / or reconstruction of hydraulic structures elements.