Different solutions for establishing the power plant may be considered and their efficiency
can be measured in terms of the expected income relative to the costs of establishing the
power plant. However, a number of factors are important for the evaluation of the income and
the costs of establishing the power plant. These are e.g. the period of time where the plant will
be operating and produce electricity and the capacity of the power plant in terms of kWh.
Moreover, the future income from selling electricity will depend on the availability of water,
which depends on the future snow and rainfall. But also the market situation may change and
competing energy recourses such as thermal and solar power may cause a reduction of the
market price on electricity in general.
In addition the different possible solutions for establishing the power plant will have different
costs and different implications on the safety to personnel. Obviously, the more capacity of
the power plant, i.e. the higher the dam the larger the construction costs will be, but also the
potential flooding (consequence of dam failure) will be larger in case of dam failure and more
people would be injured or die, see Figure 1.3.
Water reservoir Dam
TownFigure 1.3: Water reservoir/dam for exploitation of hydraulic power.
The safety of the people in a town downstream of the reservoir will also be influenced by the
load carrying capacity of the dam structure relative to the pressure loading due to the water
level in the reservoir. The strength of the dam structure depends in turn on the material
characteristics of the dam structure and the properties of the soil and rock on which it is
founded. As these properties are subject to uncertainty of various sources as shall be seen, the
load carrying capacity relative to the loading may be expressed in terms of the probability that
the loading will exceed the load carrying capacity or equivalently the probability of dam
failure.
Finally, the environmental impact of the power plant will depend on the water level in the
reservoir, the higher the water level the more land will be flooded upstream of the dam
structure and various habitats for animals and birds will be destroyed. On the other hand the
water reservoir itself will provide a living basis for new species of fish and birds and may
provide a range of recreational possibilities for people such as sailing and fishing which
would not be possible without the reservoir.
In order to evaluate whether or not the power plant is feasible it is useful to make a list of the
various factors influencing the benefit and their effects. As the problem may be recognized to
be rather complex, consideration will be made only of the interrelation of the water level in
the reservoir, the load carrying capacity of the dam structure, the costs of constructing the