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I. Thiaw et al.
a drop between 15% and 34%; and 18% to 36% over the same time horizons under
the RCP8.5 scenario.
On the other hand, these results contradict the work of Azari et al. (2015) in the
Gorganroud watershed of Iran. To simulate the hydrological impact of climate change
on this basin, the authors submitted the outputs of the A1F1, A2 and B1 emission
scenarios to the SWAT model. They found an increase in the mean annual flow of
the Gorganroud of 5.8% (A1F1), 2.8% (A2) and 9.5% (B1). In addition, ArdoinBardin et al. (2009), using a hydrological model at monthly intervals (GR2M), using
GCM outputs (CSIRO-Mk2, ECHAM4, HadCM3 and NCAR-PCM) from the IPCC
third report, underscored the failure of these climate models to reproduce actual
precipitation volumes in the Sahelian zone as well as their failure to simulate the
seasonal dynamics of rainfall in the Guinean zone. For this reason, these studies
used two climate scenarios based on the variations predicted by the HadCM3-A2
model to generate precipitation and ETP data to the end of the twenty-first century.
These data then became inputs to the GR2M model to assess the future impacts of
climate change on the flows of the Senegal, Gambia, Sassandra and Chari rivers.
The results indicate a drop-in flows from the Gambia and Senegal rivers and an
increase in the Sassandra and Chari rivers. Variables such as the differences between
rainfall-flow models, the quality of Global/Regional Climate Models used, and the
geography under study (difference in climate, soil, relief, land use, etc.) can be
decisive factors. Future studies should use rainfall-flow models that integrate, in
addition to the climate, other variables that impact the hydrological dynamics of a
watershed (hydrogeology, topography, pedology, land use, etc.), for example, the
HEC-HMS and SWAT models.
This study demonstrates the negative impact of climate change, especially for
characteristic high flows (DCC), and suggests the importance of integrating analysis
into adaptive management programs. These results will be useful to decision-makers
of the Gambia River Basin Development Organization (OMVG) and the Support
Program for Agricultural Development and Rural Entrepreneurship (PADAER) to
build and improve adaptive water resource management practices in the context of
climate change. However, assumptions based on these results should be cautious due
to weak monitoring networks in the Diarha river basin. Future studies would benefit
from the implementation of a robust monitoring network to provide more reliable
data on water resources in order to improve approaches for long-term exploitation
and sustainable management. Also, this research has not specifically studied the
impact of climate change-related changes in streamflow and characteristics in relation to the water demand-availability balance. Future studies should examine how
climate change will impact different users of Diarha’s water resources and study the
correlation between demand and available water resources in different time horizons
and scenarios. This study will serve as a foundation for this future work.
Author Contributions Ibrahima Thiaw designed the study, developed the methodology and wrote
the manuscript. Ibrahima Thiaw and Bakary Faty collected and processed the data, while Abel
Vincent Manga, Anastasie Mendy, Honoré Dacosta and Amadou Abdoul Sow read and corrected
the manuscript.
I. Thiaw et al.
a drop between 15% and 34%; and 18% to 36% over the same time horizons under
the RCP8.5 scenario.
On the other hand, these results contradict the work of Azari et al. (2015) in the
Gorganroud watershed of Iran. To simulate the hydrological impact of climate change
on this basin, the authors submitted the outputs of the A1F1, A2 and B1 emission
scenarios to the SWAT model. They found an increase in the mean annual flow of
the Gorganroud of 5.8% (A1F1), 2.8% (A2) and 9.5% (B1). In addition, ArdoinBardin et al. (2009), using a hydrological model at monthly intervals (GR2M), using
GCM outputs (CSIRO-Mk2, ECHAM4, HadCM3 and NCAR-PCM) from the IPCC
third report, underscored the failure of these climate models to reproduce actual
precipitation volumes in the Sahelian zone as well as their failure to simulate the
seasonal dynamics of rainfall in the Guinean zone. For this reason, these studies
used two climate scenarios based on the variations predicted by the HadCM3-A2
model to generate precipitation and ETP data to the end of the twenty-first century.
These data then became inputs to the GR2M model to assess the future impacts of
climate change on the flows of the Senegal, Gambia, Sassandra and Chari rivers.
The results indicate a drop-in flows from the Gambia and Senegal rivers and an
increase in the Sassandra and Chari rivers. Variables such as the differences between
rainfall-flow models, the quality of Global/Regional Climate Models used, and the
geography under study (difference in climate, soil, relief, land use, etc.) can be
decisive factors. Future studies should use rainfall-flow models that integrate, in
addition to the climate, other variables that impact the hydrological dynamics of a
watershed (hydrogeology, topography, pedology, land use, etc.), for example, the
HEC-HMS and SWAT models.
This study demonstrates the negative impact of climate change, especially for
characteristic high flows (DCC), and suggests the importance of integrating analysis
into adaptive management programs. These results will be useful to decision-makers
of the Gambia River Basin Development Organization (OMVG) and the Support
Program for Agricultural Development and Rural Entrepreneurship (PADAER) to
build and improve adaptive water resource management practices in the context of
climate change. However, assumptions based on these results should be cautious due
to weak monitoring networks in the Diarha river basin. Future studies would benefit
from the implementation of a robust monitoring network to provide more reliable
data on water resources in order to improve approaches for long-term exploitation
and sustainable management. Also, this research has not specifically studied the
impact of climate change-related changes in streamflow and characteristics in relation to the water demand-availability balance. Future studies should examine how
climate change will impact different users of Diarha’s water resources and study the
correlation between demand and available water resources in different time horizons
and scenarios. This study will serve as a foundation for this future work.
Author Contributions Ibrahima Thiaw designed the study, developed the methodology and wrote
the manuscript. Ibrahima Thiaw and Bakary Faty collected and processed the data, while Abel
Vincent Manga, Anastasie Mendy, Honoré Dacosta and Amadou Abdoul Sow read and corrected
the manuscript.