15 Impacts of Climate Change on Water Resources …
339
a 3.7% increment. For maximum temperatures, rates of change of 6.1% and 2.7%
were observed for Sudan and Guinea Savannah, respectively (UNFCCC 2015b).
3.2 Changes in Historical Rainfall Amounts
Rainfall has been variable across the basin and over time (Oguntunde et al. 2006).
From 1901 to 2002, the 1970s and 1980s was the driest period, while the 1930s and
1950s were the wettest (Oguntunde et al. 2006). Inter-annual variability was more
pronounced in the northern part than the southern part of the basin (Kasei 2009, van
de Giesen et al. 2010). The northern part has only one rainfall season from about
May/June to September/October, and rainfall totals are lower in the north than in the
south, with about 500 mm or less in the Sahelian zone in the far north and about
1100 mm or more in the Guinean zone in the south (Lemoalle and de Condappa
2009). Hence, rainfall variability produces stress on human lives and socioeconomic
activities, especially in the upper reaches of the basin. Droughts there have become
very frequent since the 1970s (van de Giesen et al. 2010). Mean annual rainfall for
1901–1969 was 1100 mm; for 1970–2002 the mean was 987 mm. Furthermore, if the
year 1970 alone is eliminated from rainfall trend analysis, no rainfall trend is evident,
meaning that rainfall amounts varied from 1970 to 2002 without any particular trend.
Analysis of historical data from Burkina Faso’s National Communication
(UNFCCC 2015a) showed a movement of isohyets for the periods 1931–1960, 1961–
1990 and 1971–2000 as shown in Fig. 2. The wettest 30-year period was 1931–1960,
followed by 1961–1990. 1971–2000 was the driest thirty-year period. From 1931 to
1960, a 1200 mm isohyet was discernible in the southwestern corner of the country.
whereas in the latter periods it was completely absent. This observation is consistent with findings that the isohyets in the Sahel and Sudano-Sahelian zone in the
Volta basin moved about 150 km south during the climate transition period of the
early 1970s (L’Hote and Mahe 1996). Furthermore, even though 1971–2000 was the
driest period, there was no significant change in the number of rainy days compared
to 1961–1990. Because the two 30-year periods 1961–90 and 1971–2000 overlap,
further research is required to validate the migration of isohyets southwards in the
basin. In the southern part of the basin, the Sudan and Guinean agro-climatic zones
in Ghana also show variable rates of change in rainfall without any clear trend
(UNFCCC 2015b).
4 Climate Scenarios and Projection of Climate Change
in the Basin
Methods for assessing climate change in the basin have been varied, and range
from simple to robust. Some national climate change reports used old emission
339
a 3.7% increment. For maximum temperatures, rates of change of 6.1% and 2.7%
were observed for Sudan and Guinea Savannah, respectively (UNFCCC 2015b).
3.2 Changes in Historical Rainfall Amounts
Rainfall has been variable across the basin and over time (Oguntunde et al. 2006).
From 1901 to 2002, the 1970s and 1980s was the driest period, while the 1930s and
1950s were the wettest (Oguntunde et al. 2006). Inter-annual variability was more
pronounced in the northern part than the southern part of the basin (Kasei 2009, van
de Giesen et al. 2010). The northern part has only one rainfall season from about
May/June to September/October, and rainfall totals are lower in the north than in the
south, with about 500 mm or less in the Sahelian zone in the far north and about
1100 mm or more in the Guinean zone in the south (Lemoalle and de Condappa
2009). Hence, rainfall variability produces stress on human lives and socioeconomic
activities, especially in the upper reaches of the basin. Droughts there have become
very frequent since the 1970s (van de Giesen et al. 2010). Mean annual rainfall for
1901–1969 was 1100 mm; for 1970–2002 the mean was 987 mm. Furthermore, if the
year 1970 alone is eliminated from rainfall trend analysis, no rainfall trend is evident,
meaning that rainfall amounts varied from 1970 to 2002 without any particular trend.
Analysis of historical data from Burkina Faso’s National Communication
(UNFCCC 2015a) showed a movement of isohyets for the periods 1931–1960, 1961–
1990 and 1971–2000 as shown in Fig. 2. The wettest 30-year period was 1931–1960,
followed by 1961–1990. 1971–2000 was the driest thirty-year period. From 1931 to
1960, a 1200 mm isohyet was discernible in the southwestern corner of the country.
whereas in the latter periods it was completely absent. This observation is consistent with findings that the isohyets in the Sahel and Sudano-Sahelian zone in the
Volta basin moved about 150 km south during the climate transition period of the
early 1970s (L’Hote and Mahe 1996). Furthermore, even though 1971–2000 was the
driest period, there was no significant change in the number of rainy days compared
to 1961–1990. Because the two 30-year periods 1961–90 and 1971–2000 overlap,
further research is required to validate the migration of isohyets southwards in the
basin. In the southern part of the basin, the Sudan and Guinean agro-climatic zones
in Ghana also show variable rates of change in rainfall without any clear trend
(UNFCCC 2015b).
4 Climate Scenarios and Projection of Climate Change
in the Basin
Methods for assessing climate change in the basin have been varied, and range
from simple to robust. Some national climate change reports used old emission