Temperature - European Investment Bank

WEST AFRICAN POWER POOL (WAPP) PÖYRY ENERGY LTD.
Mount Coffee HPP ESIA and RAP Date 2012-09-18
ESIA Report Page 137
19.2 Main Impacts
The impacts identified and listed in the matrix are described and characterised shortly
here. It should be noted that in every group of environmental parameters the first
column is a kind of "summary": it is considered as affected when one or several of its
components are affected.
When talking about effects, a distinction needs to be made between structures and
activities: it is possible that a structure has little or no impact on the environment, while
its construction does have an impact.
Below, the entries in the matrix are discussed briefly. This should also contribute to
clarifying the definitions provided above.
19.2.1 Assessment of the Impacts Caused by Structures
The main structure in terms of environmental impacts is the reservoir, the main impact
is on land use, fauna and flora and settlements; the impact is considered as relatively
small for fauna and flora and medium for the human population, since the size of the
reservoir is rather small and since the entire area to be affected already was a reservoir
20 years ago. It causes the following impacts:
� Climate: reduction of temperature amplitude, increase in humidity; negligible
due to the small area which will be additionally submerged.
� Water: small influence on hydrology since Mount Coffee HPP will be operated
as run-of-river scheme with a very limited regulation capacity; the main negative
impact will be on the 4 km of river between spillway and confluence with the
tailrace channel. Negligible influence on hydrogeology. It could have a small
impact on water quality, which could be partly reduced by reservoir clearing.
The water quality depends also on the contamination of the water due to
activities upstream of the HPP like mining activities, agriculture, etc. The water
quality data show currently a generally good quality in most parameters reaching
drinking water standards.
� Vegetation and terrestrial fauna: plants and animals are affected negatively
through loss of habitat. Small impact, since the reservoir was already existent
and no exceptionally valuable habitats have developed in the short time,
especially given the fact that the wider area is strongly influenced by human
activities (charcoal production and crop plantations).
� Aquatic fauna: medium impact since the migration pattern of some fish species
could be interrupted due to the dam, the part of the river between spillway and
tailrace channel confluence will be affected, and a change in species composition
will occur.
� Landscape: ambiguous effect: the reservoir will be clearly visible and change the
aspect of the landscape. This can be considered as positive (lake) or negative
(change of natural aspect, drawdown). No protected areas affected.
� Human population: medium negative impact through the submersion of six
settlements and of 219 ha of agricultural fields. This can and has to be mitigated.