Temperature - European Investment Bank

WEST AFRICAN POWER POOL (WAPP) PÖYRY ENERGY LTD.
Mount Coffee HPP ESIA and RAP 2012-09-18
ESIA Report Page 224
28.5 Conclusions and Preliminary Identification of Mitigation Measures
The advantage of the cascade from an energy generation point of view is quite obvious.
Given the very marked seasonal variation in river discharge, and especially the very low
dry season flows, it is quite obvious that with ROR power schemes it will not be
possible to produce a sufficient amount of electricity in the dry season. Therefore, Via
reservoir is the cornerstone for the development of the entire cascade, because only with
this in place will there be enough storage capacity. There is no doubt that the country
needs a sufficient, reliable and affordable supply of energy, and hydropower is certainly
a good solution. The positive environmental (by substituting fossil fuel) and socioeconomic
(by considerably improving the living conditions of the entire population)
effects are obvious.
On the other hand, as has been shown above, Via reservoir is also the component with
the most important, and most marked, negative environmental and social impact
(change in river dynamics, submerging of forests, risk of GHG emissions, resettlement).
From this, it is clear that adequate mitigation measures will have to be taken with the
aim of reducing negative impacts to an acceptable level.
First of all, each component of the cascade will have to undergo an ESIA process, and a
RAP will have to be prepared for each of them. This is a legal requirement, and a
prerequisite of all financing institutions. But, more importantly, it is a very real
necessity for properly identifying impacts and for being able to mitigate them.
A few possible (or probable) mitigation measures are mentioned here briefly (whereby
the order in which they are presented in no way implies an order of importance):
� Fish passes: in case of important fish migrations, fish passes (or fish ladders) can
be a way to maintain them. It is not possible, at this point in time, to decide
whether such structures would be required in the case of the St. Paul River
cascade. Obviously, these structures have two main negative effects, namely the
costs involved and the loss of water. Therefore, the situation has to be analysed
carefully before a decision is being taken. Furthermore, there are certain
conditions which must be given for allowing the installation of a fish pass. It
would seem that in the case of MC HPP, this would be possible. The other dams,
however, are considerably higher, more than 40 m, and there the effectiveness of
a fish pass is difficult to achieve. In general it can be stated that there are no
effective fish passes for dams with a height of more than 30 m. The available
studies made so far do not mention the possibility of fish passes.
� Fish and fisheries management in the reservoirs: reservoirs can be suitable
fishing grounds. However, in many cases fish populations soared shortly after
impoundment, due to the high availability of nutrients in the water, but then
decreased again considerably after a few years. The introduction of exotic fish
species into reservoirs has often created problems, especially considerably
reducing the diversity of the local fish fauna. For these reasons, a comprehensive
fish and fisheries management program should be developed for larger
reservoirs, drawing on experience from other reservoirs.
� Pre-impoundment clearing: the risk of GHG development was mentioned. The
only way to prevent this, in the case of large reservoirs, is an adequate preimpoundment
clearing, which mainly serves the purpose of reducing the amount
of biomass that will be submerged. Studies made so far apparently proposed