The drawback of traditional free flow spillways is their low specific discharge. The paper below shows how C.I.S. (Combining Innovative Spillways) may increase fivefold the discharge at low cost. Two spillways may be associated: PK- Weirs and Concrete Fuse Plugs.
Africa has specific conditions, as well physical as economical. Criteria for dams designs used in other continents may need an in depth review for adapting them to these conditions and to the association of hydropower with other renewable energy sources.
The design of medium or low irrigation reservoirs and relevant criteria or regulations may be very specific to Africa.
Since 1950, the annual worldwide investments in dams have been in the range of 30 to 40 billion USD (2008 value) and presently total about 2 000 billion USD.
According to the ICOLD analysis of the Role of Dams in the 21st Century and also present trends, it is likely that this annual rate of investment will continue into the next decades and possibly even increase. Much of this will be in developing countries, possibly reaching over 500 billion USD within the next twenty years.
While 75 per cent of dams more than 60 m high are in the industrialised countries, 75 per cent of those below 30 m have been built in the developing countries with little money or machinery (labour-intensive embankments and masonry) whose dispositions vary in different regions.
When one talks of “safety” in large engineering construction and particularly in dams, experienced engineers as well as laymen think first of the intrinsic safety of the structure, that is, all those provisions in the design and performance of the work devised to prevent the total or partial collapse of the structures, and thus to prevent damage to future users and residents in the area adjacent to the work being constructed.
At the time the International Commission on Large Dams was formed in 1930, the world dam inventory numbered 2500 between 15m and 30m high, of which 80% were embankment dams, and 500 more than 30m high, of which 70% were masonry or concrete structures, a few being more than 100m high. Ninety per cent of these dams were found in Japan, Europe and the USA. There were about one hundred reported failures.