Precipitation trends in the Gambia River basin (Senegal) for the period 1971-2010

Cheikh Faye

Abstract


Since the 1970s, West African streams experienced profound modifications connected to pluviometric deficit, which have influenced on a strong decrease of water resources. The objective of this study is to analyze trends of precipitation at the six selected stations in the Senegalese part of Gambia River basin, using graphical and statistical approach. Methodology is consisted of an analysis of monthly, seasonal and annual variability of precipitation for the 1971-2010 period, through Non-parametric tests. Study revealed a strong variability and often a contrasting evolution between various stations (Kédougou, Simenti, Tambacounda, Kounghel, Nioro and Goudiry). Between the periods 1971-1990 and 1991-2010, the value U of Mann-Whitney, had changed from 60 to 40 at Tambacounda, 64 to 59 at Kédougou and 63 to 51 at Simenti station, which showed non-significant trends in annual total precipitation for the studied period. Sen’s estimator revealed significant descending trends on Kédougou station (9.812 mm/year for the period 1971-1990 and 0.309 mm/year for the period 1991-2010), and Simenti station too. On the other hand (in the whole article), on the stations of Tambacounda, Goudiry and Koungheul, the reduction is noticed for the period 1971-1990 (3.658 mm/year on Tambacounda), and an increase is noticed in the period 1991-2010 (13.21 mm/year on Tambacounda). For the station Nioro, on other hand, increase is noted in both periods (3.801 mm/year and 8.841 mm/year). The assumption is that these significant trends of precipitation during the last four decades could be attributed to the climate changes.

Key words: rainfall, trend, non-parametric tests, Gambia River, Senegal

© 2018 Serbian Geographical Society, Belgrade, Serbia.
This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Serbia


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References


Ali, A. & Lebel, T. (2009). The Sahelian standardized rainfall index revisited. International Journal of Climatology, 29(12), 1705-1714.

Ali, A., Lebel, T. & Amami, A. (2008). Signification et usage de l'indice pluviométrique au Sahel. Sécheresse, 19(4), 227-235.

Burn, D.H. & Elnur, M. (2002). Detection of Hydrological Trends and Variability. Journal of Hydrology, 255, 107-122.

Dione, O. (1996). Evolution climatique récente et dynamique fluviale dans les hauts bassins des fleuves Sénégal et Gambie. Thèse de doctorat, Université Lyon 3 Jean Moulin.

Faye, C. (2013). Evaluation et gestion intégrée des ressources en eau dans un contexte de variabilité hydroclimatique : cas du bassin versant de la Falémé. Thèse (PhD). Université Cheikh Anta Diop de Dakar.

Faye, C., Sow, A. A. & Ndong, J.B. (2015). Étude des sècheresses pluviométriques et hydrologiques en Afrique tropicale: caractérisation et cartographie de la sècheresse par indices dans le haut bassin du fleuve Sénégal. Physio-Géo - Géographie Physique et Environnement, 9, 17-35.

Goula, B. T. A., Savane, I., Konan, B., Fadika, V. & Kouadio, G.B. (2005). Comparative study of climatic variability impact on water resources of N’zo and N’zi watersheds in Côte d’Ivoire – Sciences & Nature, 2(1), 10-19.

Ifeka, A. & Akinbobola, A. (2015). Trend Analysis of Precipitation in Some Selected Stations in Anambra State. Atmospheric and Climate Sciences, 5, 1-12.

Iskander, S.M., Rajib, M.A. & Rahman, M.M. (2014). Trending Regional Precipitation Distribution and Intensity: Use of Climatic Indices. Atmospheric and Climate Sciences, 4, 385-393.

Kahya, E. & Kalayci, S. (2004). Trend Analysis of Stream Flow in Turkey. Journal of Hydrology, 289, 128-144.

Kendall, M. (1975). Multivariate Analysis. London: Charles Griffin & Company.

Lamagat, J.P. (1989). Monographie hydrologique du fleuve Gambie Collection M&m. ORSTOM-OMVG.

Mann, H.B. (1945). Nonparametric Tests against Trend, Econometrica. 13(3): 245-259.

Murugan,V., Mukund, R., Ramesh, M.B., Hiremath, A., Joseph, R.K. & Shetty, P.K. (2008). Centennial Rainfall Variation in Semi-Arid and Tropical Humid Environments in the Cardamom Hill Slopes, Southern Western Ghats, India. Caspian Journal of Environmental Sciences, 6, 31-39.

Niang, A.J. (2008). Les processus morphodynamiques, indicateurs de l'état de la désertification dans le Sud-Ouest de la Mauritanie. Approche par analyse multisource. Thèse de Doctorat, Université de Liège (Belgique).

Oliver, J.E. (1980). Monthly Precipitation Distribution: A Comparative Index. Professional Geographer, 32, 300-309.

Ouoba, A.P. (2013). Changements climatiques, dynamique de la végétation et perception paysanne dans le Sahel burkinabè. Thèse de Doctorat Unique, Université de Ouagadougou (Burkina Faso).

Ozer, P., Hountondji, Y.C. & Laminou Manzo, O. (2009). Évolution des caractéristiques pluviométriques dans l'Est du Niger de 1940 à 2007. Geo-Eco-Trop, Revue de Géographie et d'Écologie Tropicale, 33, 11 - 30.

Panthou, G., Vischel, T., Lebel, T. (2014). Recent trends in the regime of extreme rainfall in the Central Sahel. International Journal of Climatology, 34, 3998-4006.

Sen, P.K. (1968). Estimates of the Regression Coefficient Based on Kendall’s Tau. Journal of the American Statistical Association, 63, 1379-1389.

Sighomnou, D. (2004). Analyse et redéfinition des régimes climatiques et Hydrologiques du Cameroun : perspectives d’évolution des ressources en eau. Thèse Doctorat d’Etat, Université de Yaoundé 1, Département des Sciences de la Terre.

Sow, A. A. (2007). L’hydrologie du Sud-est du Sénégal et de ses Confins guinéo-maliens : les bassins de la Gambie et de la Falémé. Thèse (PhD). Université Cheikh Anta Diop de Dakar.

Yue, S. & Wang, C.Y. (2004). The Mann-Kendall test modified by effective sample size to detect trend in serially correlated hydrological series, Water Resources Management Journal, 18, 201-218.


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