| Issue
Siting and design must be appropriate to the energy system and where appropriate multiple purpose needs of a hydropower development. However, if siting and design considerations are limited to or dominated by engineering and economic considerations, the impacts on environmental and social values can have significant repercussions.
Siting and design influence the geometry of a reservoir, and hence the surface area of land flooded, the degree of loss of significant natural habitat and wildlife, and in cases the populations of people affected and risks to heritage values. Siting and design, along with operating patterns, determine the degree of impact to a hydrological system, including diversion out of or augmentation into a river system, reservoir residence time, and patterns of downstream flow delivery.
Particular assessment needs to be undertaken where considering a hydropower option sited on the mainstem of large river systems and in the lowland regions. Reservoirs sited in tropical lowlands must consider relative risks of disease and aquatic weed problems with different siting options. Siting on mainstem rivers versus tributary streams can influence a number of other environmental impacts, including the number of fish and other aquatic species affected.
Design is closely interrelated with siting, but has its own issues. In the absence of adequate environmental assessments on a range of siting and design options, potential problems such as reservoir stratification and passage of aquatic species may not be identified. It is far more costly to try to mitigate such issues post-development than to design measures into the scheme itself (e.g. multi-level offtakes or fish passage facilities). |
