The macroscopic hydraulic design of stilling basins was the subject of numerous research activities around the world. Fluctuating actions may be responsible for important damages in hydraulic structures caused by the lifting of whole slabs, structural vibrations, fatigue of materials and intermittent cavitation due to instantaneous depressions. The first prototype measurements of pressure fluctuations on baffle blocks were recorded more than 35 years ago at the Salto Grande Dam stilling basin, on Uruguay River, between Argentina and Uruguay. By means of the prototype data acquisition under flood conditions, it was possible to verify the real magnitude of the pressure fluctuations induced by macroturbulent flows in the basin. In particular, cavitation due to instantaneous depressions caused by low frequency pulses with mean pressures even higher to the atmospheric pressure was detected. Based on this research it was possible to demonstrate that in hydraulic jump stilling basins, physical models are excellent tools if their length scale does not exceed 1:50, the minimumdepth is 3 cm and the incident Reynolds number is over 100,000. The model-prototype comparison shows excellent agreement to simulate the fluctuating pressures amplitudes and the dominant frequencies induced by the flow, with a similar shape of the power spectra. This research was the first within the known bibliography, including damage evaluations due to cavitation by pressure pulses in a prototype with respect to instant depression measures in a physical model, demonstrating that these allow evaluating the probability of occurrence. Recently, instantaneous pressures were measured in the model 1:40 of the Gatún Dam (Panamá). For the original design flood, the “cavitation tendency value” p0.1% was over the vapor pressure in the forced dissipation blocks. For the maximum flood registered at the prototype, near 20% over the design discharge, some “cavitation tendency” was detected in very few points of very few blocks in the model. According to the field information, these blocks had "low pitting" in the concrete, due to slight cavitation erosion. These results also demonstrate again the compatibility between data of "tendency to cavitation by pressure pulses" in Froudian models with the real behavior in prototype of a emblematic structure, after more than a century of operation under extreme conditions.
