Adding extra spillway discharge capacity, a few dam refurbishment examples in Sweden

As required by the revised dam-safety guidelines, the spillway discharge capacity of a large number of the existing dams must be increased so as to release the higher design floods without jeopardizing the structural safety. The extra capacity required falls usually within the scope of 2030%, but in some cases it can as high as 50%. To modify an existing spillway is often the most inexpensive alternative to increase its capacity. When this is difficult due to practical restraints, a new spillway, placed either separately or adjacent to the existing one, needs to be constructed. This paper illustrates several practical examples of dam rebuilding in Sweden that involve either a new spillway or modifications of an existing one.