Temperature - European Investment Bank

WEST AFRICAN POWER POOL (WAPP) PÖYRY ENERGY LTD.
Mount Coffee HPP ESIA and RAP 2012-09-18
ESIA Report Page 114
m³/s
120
100
80
60
40
20
0
80.00 85.00 90.00 95.00 100.00
Figure 16-3: River flow and plant operation during low flow conditions
As stated above (Section 8.2.3), a residual flow will have to be released from the
spillway in order to maintain river conditions (and mainly fish and other aquatic
organisms) in the section of the river between spillway and confluence with tailrace
channel), This amount, proposed as 8 m³/s, is not available for energy production
(difference between total and available flow in the Figure). As long as there is a
minimum total flow of 42 m³/s, one unit can be operated at 40% capacity, releasing 34
m³/s. This situation is exceeded during 92% of the time, which means that on average
during 29 days per year there is less water. During such a condition, water could be
turbined for a limited time, and in order to fill the reservoir again, the power plant
would have to be shut down for about 4 h for each hour of operation.
On days with a flow corresponding to the residual flow, no power production would be
possible, since all the water flowing into the reservoir would have to be released as
residual flow. This situation will occur on about 1% of the time, i.e. on average on 4
days of the year.
16.2.3.1 Additional Risk Due to Climate Change
St Paul River low flow situation
% exceedance
total flow
available flow
residual flow
1 unit 100%
1 unit 40%
Long term measurements of sea level reveal an increase of about 20 cm during the 20 th
century; this is shown in the following Figure.