This study investigates the spatio-temporal variability of soil moisture in relation to drought estimation over the period 1981-2022 in the District des Savanes of C？te d’Ivoire. Hydro-climatic data were used to compute the Standardised Soil Water Index (SSWI) at a six-month cumulative time scale (SSWI-6). Stationarity and trend tests were applied to identify breakpoints (Pettitt test), monotonic trends (Mann-Kendall test), and the magnitude of these trends (Sen’s Slope) in the SSWI-6 series. In addition, the Inverse Distance Weighting (IDW) interpolation method was employed to assess the spatial variability of drought. Overall, the results reveal predominantly negative trends, indicating an intensification of agricultural drought since 1991. The period from 1995 to 2001 was characterized by particularly high rainfall across much of the district. However, a significant drought episode emerged in 1994 and became widespread across the district by 2010, except in the Korhogo region. The duration of the most frequent agricultural droughts exceeded five months, with prolonged episodes particularly affecting Boundiali, Ferkessédougou, and Kong. The findings highlight that the district has been highly exposed to recurrent droughts, although a slight recovery in soil moisture was observed between 1995 and 2001. Interannual variations of the index further revealed alternating dry and wet periods across the District des Savanes.
References
[1]
World Meteorological Organization (WMO) (2021) Atlas of Mortality and eco-Nomic Losses from Weather, Climate and Water Extremes (1970-2019). WMO.
[2]
Huang, J., Yu, H., Guan, X., Wang, G. and Guo, R. (2015) Accelerated Dryland Expansion under Climate Change. NatureClimateChange, 6, 166-171. https://doi.org/10.1038/nclimate2837
[3]
Intergovernmental Panel on Climate Change (IPCC) (2023) Climate Change 2023: Synthesis Report. Contribution of Working Groups I, II and III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. IPCC.
[4]
Kouakou, K.E., Kouassi, K.B., Kouassi, W. and Koffi, Y.B. (2017) Rainfall Variability and Trends in West Africa: Case of Côte d’Ivoire. Atmospheric and Climate Sciences, 7, 256-274.
[5]
Descroix, L., Mahé, G., Lebel, T., Favreau, G., Galle, S., Gautier, E. and Mamadou, I. (2015) Evolution of Surface Hydrology in the Sahelo-Sudanian Strip: A Spatio-Temporal Approach. Journal of Hydrology, 375, 90-102.
[6]
Bodian, A. (2014) Analyse de la variabilité hydroclimatique et de ses impacts sur les ressources en eau du bassin du Sénégal. Master’s Thesis, Université Cheikh Anta Diop de Dakar.
[7]
Karimou, Y., Lawin, A.E. and Boko, M. (2015) Impacts des sécheresses sur l’agriculture et l’élevage en Afrique de l’Ouest: Analyse et perspectives. Revue de Géographie du Laboratoire Leïdi, 13, 29-44.
[8]
Goula, B.T.A., Brou, Y.T. and Savané, I. (2006) Impacts de la variabilité climatique sur les ressources hydriques en zones tropicales: Cas du bassin du N’zo-Sassandra (Côte d’Ivoire). Sécheresse, 17, 187-194.
[9]
Savanes, D., N’Guessan, K. and Kouadio, A. (2001) Analyse de la variabilité pluviométrique et allongement de la saison sèche en Côte d’Ivoire. Cahiers Agricultures, 10, 305-311.
[10]
Ministère de l’Agriculture et du Développement Rural (MINADER) (2017) Rapport annuel 2017. MINADER.
[11]
Kouao, J., Kouakou, K.E. and Kouassi, K.B. (2020) Assessment of Drought in Côte d’Ivoire Using Standardized Precipitation and Evapotranspiration Index (SPEI). International Journal of Climatology, 40, 175-188.
[12]
Consultative Group on International Agricultural Research (CGIAR) (2025) Soil Moisture and Climate-Smart Agriculture. CGIAR Research Program on Climate Change, Agriculture and Food Security (CCAFS).
[13]
Andriano, A., Smith, J. and Lopez, R. (2024) Soil Moisture Monitoring as a Tool for Drought Assessment: A Global Perspective. Environmental Research Letters, 19, Article ID: 045012.
[14]
Ministère de l’Agriculture (MINAGRI) (2014) Rapport sur l’état de l’agriculture en Côte d’Ivoire. MINAGRI.
[15]
Institut National de la Statistique (INS) (2021) Recensement Général de la Population et de l’Habitat, Résultats globaux du RGPH 2021. Institut National de la Statistique.
[16]
McKee, T.B., Doesken, N.J. and Kleist, J. (1993) The Relationship of Drought Frequency and Duration to Time Scales. Proceedings of the 8th Conference on Applied Climatology, Anaheim, 17-22 January 1993, 179-184.
[17]
Naumann, G., Barbosa, P., Carrao, H., Singleton, A. and Vogt, J. (2012) Monitoring Drought Conditions and Their Uncertainties in Africa Using TRMM Data. JournalofAppliedMeteorologyandClimatology, 51, 1867-1874. https://doi.org/10.1175/jamc-d-12-0113.1
[18]
Beguería, S., Vicente-Serrano, S.M., Reig, F. and Latorre, B. (2013) Standardized Precipitation Evapotranspiration Index (SPEI) Revisited: Parameter Fitting, Evapotranspiration Models, Tools, Datasets and Drought Monitoring. InternationalJournalofClimatology, 34, 3001-3023. https://doi.org/10.1002/joc.3887
[19]
Hosking, J.R.M. (1984) Testing for the Presence of a Trend in Hydrological Data. Journal of Hydrology, 73, 107-120.
Kendall, M.G. (1975) Rank Correlation Methods. 4th Editions, Charles Griffin.
[22]
Sen, P.K. (1968) Estimates of the Regression Coefficient Based on Kendall’s Tau. JournaloftheAmericanStatisticalAssociation, 63, 1379-1389. https://doi.org/10.1080/01621459.1968.10480934
[23]
Nascimento, D.T.F., Santos, C.A.G. and Galvão, C.O. (2015) Detection of Trends and Break Points in Streamflow Time Series of Northeastern Brazil. Water Resources Management, 29, 1237-1250.
[24]
Lloyd, C.D. and Atkinson, P.M. (2002) Non‐stationary Approaches for Mapping Terrain and Assessing Prediction Uncertainty. TransactionsinGIS, 6, 17-30. https://doi.org/10.1111/1467-9671.00092
[25]
DIRSK (Direction de la Recherche Scientifique) (1998) Étude des précipitations annuelles et méthodes d’interpolation spatiale.
[26]
Vera, C., Higgins, W., Amador, J. and Alves, L. (2003) Climate Variability in South America Associated with El Niño and La Niña Events. Journal of Climate, 19, 5989-6007.
[27]
Hagos, S.M., Cook, K.H. and Neupane, N. (2008) Influence of Sea Surface Temperature Anomalies on Atmospheric Circulation and Rainfall Variability over Africa. Journal of Climate, 21, 4518-4539.
[28]
Kouassi, F.K., Kouadio, K.H. and Yao, A. (2022) Rainfall and Temperature Variability across Côte d’Ivoire: Trends and Breakpoints. Theoretical and Applied Climatology, 147, 573-590.
[29]
Faye, C. (2017) Variabilité climatique et dynamiques des ressources hydriques en Afrique de l’Ouest. Master’s Thesis, Université Cheikh Anta Diop.
[30]
Ouattara, S. (2018) Changements climatiques et ruptures pluviométriques en Af-rique subsaharienne. Revue de GéographieTropicale et d’Environnement, 2, 55-71.
[31]
Yao, A.B., Kouadio, K.H. and N’Guessan, E.A. (2013) Analyse des tendances pluviométriques en Côte d’Ivoire de 1940 à 2010. International Journal of Climatology, 33, 1391-1405.
[32]
Soro, T.D., Kouadio, K.H. and Yao, A. (2017). Variabilité de la migration de l’ITCZ et son impact sur les précipitations en Côte d’Ivoire. Revue Ivoirienne de Géographie, 1, 77-92.
[33]
Kouabré, T., Ouedraogo, M. and Paturel, J.E. (2017) Analyse de la variabilité plu-viométrique en Afrique de l’Ouest et perspectives pour la gestion des ressources hy-driques. Climatologie, 14, 37-52.
[34]
World Meteorological Organization (WMO) (2012) Standardized Precipitation Index: User Guide (WMO-No. 1090). WMO.
[35]
Soro, T.D., Kouassi, F.K., Kouamé, K.F. and Yao, A.B. (2014) Caractérisation des sé-cheresses pluviométriques en Côte d’Ivoire à partir d’indices standardisés. Climatologie, 11, 57-71.
[36]
Makougoum, P. (2020) Analyse des tendances pluviométriques et impacts sur l’agriculture dans la région sahélienne. African Journal of Environmental Science and Technology, 14, 256-266.
[37]
Brou, T., Servat, E. and Paturel, J.E. (2005) Évolution des régimes pluviométriques de l’Afrique de l’Ouest soudano-sahélienne au cours des dernières décennies. Hydrological Sciences Journal, 50, 223-238.
[38]
Goula, B.T.A., Brou, T., Savane, I. and Fadika, V. (2007) Impacts de la variabilité climatique sur les ressources en eau des régions de la Côte d’Ivoire. Sécheresse, 18, 65-73.
