Problems that have surfaced in the operation of domestic hydroprojects, for which a mating scheme is adopted for the pools by discharging the flow from the dam, are indicated. Cases when use of a discharge is justified, and the conditions for which the energy of the discharged flow is dissipated on stabilization directly beyond the dam is preferable, are indicated. One of the most critical problems in high-dam design is selection of the type of mating between the pools beyond these dams: discharge of the flow into an unstabilized or sta- bilized channel, or with provision for dissipation of a large part of the energy of the flow in a submerged hydraulic jump on stabilization directly beyond the structure. Regulatory literature contains recommendations for hy- draulic analysis of a number of designs, with the use of which mating of the pools is provided. Despite the high qual- ity of theses in-service entities, there has been essentially no codification of experience gained with their operation, and comparison with analytical hypotheses. The type of mating for each hydroproject is selected on the basis of requirements set forth in the Construction Rules and Regulations, and from personnel experience acquired by specialists taking part in the design, and only for unique entities, for example, for the Sayano-Shushenskaya HPP — on the basis of laboratory in- vestigations. For the Zeya and Bureya HPP with dams 110 and 130 m high, respectively, discharge of a jet into the lower pool was adopted prior to laboratory verification. It should be noted that even with consideration of such substantiation in no way can everything be foreseen. Subse- quent operating experience with the hydroproject indicates that many difficulties and additional expenditures could be avoided had a more well-founded solution been adopted in the design and construction. In connection with a prolonged low-water period when spillway structures are not in service, or the flow rates over them are small, there is no negative operating experience, and the solutions adopted relative to the problem under consideration are rather unreliable. On the other hand, failures (for example, the damage sustained by bottom stabilization of the toe basin at the Sayano-Shushen- skaya HPP in 1981, and the failure in 1985 (1) may occur due to unsatisfactory fabrication of the components of the structures during construction, and mistakes committed dur- ing temporary service. Surficial analysis of these events may lead to rejection of use of energy extinguishment in a hydrau- lic jump directly beyond the dam on future hydroprojects. Practice has demonstrated that selection of the type of mating between pools is a complex problem, and publica- tions permitting adoption of a more proven solution are re- quired. In our opinion, this paper may be useful for solution of this problem. Normally, it is the discharge of the flow from the struc- ture that is first considered. If negative consequences prevail with the discharge of a jet, stabilization is adopted on the ba- sis of feasibility analysis with consideration of expected reli- ability of the structure, operating conveniences, and condi- tions for the passage of flows in the construction and service periods, ensuring extinguishment of energy in a hydraulic jump beyond the dam, satisfactory service from the stabiliza- tion over the course of prolonged operation, and appreciably lower flow velocities, wave formation, and localized channel deformation in the tail race. It is obvious that use of a jet discharge is expedient when: — expected scouring of the channel will not threaten the stability of the dam and structures of the tailrace;