316
B. Lèye et al.
IPCC baseline. However, this increase is subject to seasonal variation: the months of
December, January, August and September will become significantly warmer than
usual, while the months of November and March will experience smaller increases
in heat.
The annual volume of water flow by 2025 and 2050 for each of the country’s four
watersheds were forecast based on these projections using MAGICC/SCENGEN
climate model data (MECV/BF 2007). Projections indicate that by 2025, the volume
of water flowing annually will decrease by 45.6% on the Comoe and 54.7% on the
Mouhoun watersheds compared to the mean annual of the 1961–1990 period. On
the other hand, the annual volumes of water flowing from the Nakanbe and Niger
basins are projected to increase by 35.9% and 47%, respectively, over the same
period. Known as the “Sahelian paradox,” this contradiction is attributable to land
degradation in the Said basins, resulting in greater runoff despite a reduction in
rainfall (Albergel 1987; Gal et al. 2017; Descroix et al. 2018). In 2050, as compared
to the 1961–1990 period, there will be a decrease of 68.9% for the Comoe, 73% for
the Mouhoun, 29.9% for the Nakanbe and 41.4% for the Niger.
2.3 Groundwater
Two main types of aquifer formation are found within the crystalline basement, which
constitutes 82% of the territory, and the sedimentary zones. Groundwater is related
to cracking, fracking or alteration of rocks. Sedimentary zones range from southwest
to north and south-east. Flow rates in the crystalline basement are generally between
0.5 and 20 m
3 /h, whereas sedimentary flows can reach 100 m
3 /h or more. A map
illustrating aquifer types and productivity is in Fig. 7.
The volume of groundwater is estimated at 32.43 billion m
3 . Groundwater
is replenished annually by rainwater, especially through runoff. Therefore, when
rainfall decreases, groundwater recharge is highly reduced.
Groundwater fluctuation data show that after a steady decline around the 1980s,
there was an increase in the 1990s, followed by another decline and then some
stabilization. The various sedimentary aquifers discharge their renewable waters
into the Mouhoun (127 million m
3 ), the Comoe (123 million m
3 ) and finally into
the Bafing (0.438 million m
3 ), with a total discharge of 250,438 million m
3 /year
(MEE/DGH 2001). Because of the incidence of waterborne disease caused by the
consumption of raw water from reservoir dams, it is generally recommended to use
water from drillings and boreholes, which have become the main sources of water
supply for the rural population.
B. Lèye et al.
IPCC baseline. However, this increase is subject to seasonal variation: the months of
December, January, August and September will become significantly warmer than
usual, while the months of November and March will experience smaller increases
in heat.
The annual volume of water flow by 2025 and 2050 for each of the country’s four
watersheds were forecast based on these projections using MAGICC/SCENGEN
climate model data (MECV/BF 2007). Projections indicate that by 2025, the volume
of water flowing annually will decrease by 45.6% on the Comoe and 54.7% on the
Mouhoun watersheds compared to the mean annual of the 1961–1990 period. On
the other hand, the annual volumes of water flowing from the Nakanbe and Niger
basins are projected to increase by 35.9% and 47%, respectively, over the same
period. Known as the “Sahelian paradox,” this contradiction is attributable to land
degradation in the Said basins, resulting in greater runoff despite a reduction in
rainfall (Albergel 1987; Gal et al. 2017; Descroix et al. 2018). In 2050, as compared
to the 1961–1990 period, there will be a decrease of 68.9% for the Comoe, 73% for
the Mouhoun, 29.9% for the Nakanbe and 41.4% for the Niger.
2.3 Groundwater
Two main types of aquifer formation are found within the crystalline basement, which
constitutes 82% of the territory, and the sedimentary zones. Groundwater is related
to cracking, fracking or alteration of rocks. Sedimentary zones range from southwest
to north and south-east. Flow rates in the crystalline basement are generally between
0.5 and 20 m
3 /h, whereas sedimentary flows can reach 100 m
3 /h or more. A map
illustrating aquifer types and productivity is in Fig. 7.
The volume of groundwater is estimated at 32.43 billion m
3 . Groundwater
is replenished annually by rainwater, especially through runoff. Therefore, when
rainfall decreases, groundwater recharge is highly reduced.
Groundwater fluctuation data show that after a steady decline around the 1980s,
there was an increase in the 1990s, followed by another decline and then some
stabilization. The various sedimentary aquifers discharge their renewable waters
into the Mouhoun (127 million m
3 ), the Comoe (123 million m
3 ) and finally into
the Bafing (0.438 million m
3 ), with a total discharge of 250,438 million m
3 /year
(MEE/DGH 2001). Because of the incidence of waterborne disease caused by the
consumption of raw water from reservoir dams, it is generally recommended to use
water from drillings and boreholes, which have become the main sources of water
supply for the rural population.