4 Climate Change and Water Resources in West Africa …
65
reveals 47 years of excess, including 33 in the first period and 14 in the second, and
49 years of deficit, including 16 in the first period and 33 in the second. More recent
years remain affected by drought.
In Burkina Faso, from the years 1921 to 2016, there was a rainfall break in
1969, confirmed by the Standardized Precipitation Index, the tests of Pettitt and
Lee and Heghinian, and by the segmentation of Hubert (Figs. 8, 9, and 10). Thus,
we found that the period from 1921 to 1969 was on the whole wet, with an average
rainfall of 927.4 mm, marked by a dry period between 1970 and 2016, despite a
significant increase from 2008 to 2016, with an average of 805.3 mm. The difference
in rainfall between the two periods mentionned above is 122.1 mm and corresponds to
a decrease in rainfall of 13.2%. The wettest years are scattered within the first period,
with 1033.6 mm in 1922, 1064.6 mm in 1933, 1044.9 mm in 1951, 1048.7 mm in
-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
1921
1924
1927
1930
1933
1936
1939
1942
1945
1948
1951
1954
1957
1960
1963
1966
1969
1972
1975
1978
1981
1984
1987
1990
1993
1996
1999
2002
2005
2008
2011
2014
SPI 1969
Fig. 8 Evolution of the Standardized Precipitation Index in Burkina Faso from 1921 to 2016
Fig. 9 Evolution of Pettitt’s
test results in Burkina Faso
from 1921 to 2016