Tidal Current Energy

Hydroelectric Power
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the one hand, too little or no minimum ecological flow (often still guaranteed
in current hydro concessions) make existence impossible for fish, while on the
other hand hydro-peaking creates habitat characteristics too rough for most of
the riverine fauna.
The construction of a dam and the filling of the reservoir always cause land
losses through inundation, which, in the case of mega-dams, can be huge. The
loss of land is one of the main impacts on the local population, especially when
housing or agricultural land is affected. Resettlement is one of the major problems
in the context of hydropower and the compensation schemes reveal unsolved
difficulties in practice. The alteration of water bodies, habitats and landscape,
as well as the loss of land that occurs from electricity generation in hydropower
schemes, also affects other businesses or branches of industries. These effects can
be positive or negative, but the latter are at the heart of many conflicts of use.
While energy-intensive industries in the proximity of hydropower plants benefit
from cheap and reliable electricity supply, the cost–benefit analysis for other sectors
may not be as advantageous. In the case of tourism, the provision of a new
technical attraction possibly conflicts with the alteration of landscape, the loss of
natural river course and sometimes even the loss of unique historical sites. On
the other hand, reservoirs serve as recreational areas providing opportunities for
boating and all kinds of water sports. Effects on agriculture vary from the provision
of irrigation to the loss of land through inundation. The problem here is that
the local population usually bears the negative impacts through land losses, while
more distant agricultural businesses benefit from irrigation. Salination and negative
changes of aquifers are further aspects of dam construction that may occur.
Also, local fisheries can suffer from the alteration of watercourses.
Health impacts are not to be underestimated, especially in the case of large
hydropower schemes in tropical regions. Studies from Africa, South America
and the Caribbean report on bilharzias (schistosomiasis), malaria and other mosquito-borne
infections being triggered through the existence of reservoirs [15] .
Involuntary resettlement and loss of habitat and livelihood can lead to mental
health problems among oustees (resettled people), having consequences from
individual depressions to violence and social breakdown. Industrial pollutants
or other waste from upstream civilization, accumulating in reservoirs, can enter
the food chain of the local population. Further problems can arise from biological
toxins like algae or from methyl-mercury found in many large reservoirs [5] .
Figure 11.4 summarizes the impact of hydropower schemes.
Sedimentation can be a major problem for reservoirs. It is mostly determined
by the vegetation, geological composition and land use of the catchment area,
and has been underestimated for many decades. It can be avoided by the offstream
placement of the main reservoir [6] . The consequences of strong sedimentation
are the loss of reservoir capacity over time and increased erosion of
the turbines. Depending on the latitude, altitude and area of the reservoir, emissions
of greenhouse gases can be a substantial problem. This is less of a problem
in boreal regions but can be a serious problem in the tropics, where the inundation
of rainforests without prior cutting of the forests can emit large amounts