Hydroelectric Power Generation - Renewable Energy: Technology, Economics and Environment - page 378

tial for accidental damage during the production process is generally - with some
specific exceptions (e.g. steel smelting) - relatively low.
Additionally, there are environmental effects linked to the construction of hy-
droelectric power stations - and hydroelectric power stations with reservoirs in
particular - at the plant location. To give some examples, the following possible
environmental effects in the context of the new construction, reactivation or mod-
ernisation of hydroelectric power stations during the building phase, are to be
mentioned here /8-13/.
• Water pollution caused by construction material or fine soils getting into the
stream, release of fine particles caused by excavation, improper cleaning of
building machinery, etc.
• Oil losses due to improper handling during construction and maintenance
works.
• Oil seepage, commonly from hydraulic systems, e.g. during demolition works.
These environmental pollutants can be avoided, or at least minimised by introduc-
ing the appropriate operational procedures and observing the existing safety and
environmental regulations. Additionally, there is a corresponding accident poten-
tial - also with supra-regional environmental effects - especially when building
hydroelectric power stations with large dams and reservoirs or larger run-of-river
power stations (e.g. in the case of flooding). However, if the appropriate regula-
tions are observed, no significant environmental effects have to be expected.
Normal operation. During the operation of hydroelectric power stations, no toxic
substances are released directly, with the exception of potential lubricant losses.
The resulting environmental effects can be kept low or ruled out by using biode-
gradable lubricants, or, in the case of small hydroelectric power stations, by using
lubricant-free machines.
In addition, hydropower plants often serve multiple purposes (especially in the
case of power stations with reservoirs) such as water sports, fishing, irrigation,
flood protection, storage of drinking water. This may in some cases also lead to
ecological advantages, for example a positive influence on the groundwater table,
the creation of aquatic biotopes, the enrichment of water with oxygen through tur-
bine operation.
However, the use of hydroelectric power can influence the environment in
other ways. The main three problem areas are described below (see also /8-13/, /8-
14/, /8-15/, /8-16/, /8-17/).
Impoundments. River and diversion type power stations generate backwater ef-
fects or reservoirs which influence the ecological conditions in the affected river
sections and the adjacent riverline habitats. In the impoundments, the flow veloci-
ties are significantly reduced and thus the shear stress at the river bottom de-
creases. This leads to an increase in sedimentation of small-grained bedload mate-
rial which is usually in suspension (e.g. fine sand, silt and clay). Coarse structures
of the riverbed that had existed so far (such as riffles, runs or pools) and hence the