Model and prototype studies for the Chucás hydro scheme, Costa Rica

The 50 MW Chucás hydroelectric project was developed by Enel to sell electricity to the national utility. Up to 8100 m3/s of flood discharge is handled through a ski-jump spillway chute discharging in the rock bed downstream of the dam. A critical consideration in this kind of spillway is the plunge pool, which will form because of rock scour under the free falling jet. The plunge pool formation and risk of erosion at Chucás were very difficult to assess theoretically or by numerical means, and therefore, a physical model study was carried out. The powerplant was commissioned in November 2016, and in October 2017 was subjected to a very large flood, of about 100 year return period. The results of the studies and the behaviour of the spillway are reported in this paper.