The basic components of the power plant output are the product of the head (concentrated gradientof the watercourse) and the water flow rate. In mountainous catchments, watercourse gradientsdecrease as one moves away from the sources, but in turn water resources increase. Consequently,the viable options for the construction of run-of-river hydropower plants are limited. To thisend, existing hydrotechnical structures used to correct the longitudinal gradient of the streamare often utilized. The analysis was conducted using the example of the Brennica River catchment(89.74 km2), identifying potential locations based on existing weirs. In the study, in addition todetermining the gross power of the power plant in the proposed sections, the study showed thepotential for using selected types of turbines and calculated the useful power and annual energyproduction.