Dam design and operation to optimize fish production in impounded river basins. CIFA TECHNICAL PAPER No. 11.
A series of guidelines is presented which is intended to aid dam design and operating engineers to manipulate the artificial aquatic environments upstream and downstream so as to optimize fish production. The guidelines are based on reviews and in some cases new analyses of the known effects of dam design and operation on African reservoirs, downstream river channels and coastal marine habitats. The study indicates that the following dam design or operational features are desirable: maximum possible crest elevation; discharge structure intakes positioned at highest possible elevation; artificial reoxygenation of tailrace discharge water; annual water level fluctuation of the reservoir to be within the range of 2.5–4.0 m and drawdown rate not to exceed 0.6 m/month; and downstream discharge to include an annual artificial flood event. Installation of fish ladders is generally not recommended. An incomplete register of 320 large dams/reservoirs in Africa was assembled, but the actual number is thought to be between 600 and 800. The combined surface area is about 41 000 km2 at full capacity. The historical trend of dam construction in Africa was examined.
Key words: large dams, reservoirs, dam engineering, drawdown, environmental impact, impounded rivers, lagoons, estuaries, coastal erosion, aquatic macrophytes, bivalves, fish biology, fisheries, Africa.