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Trends and Shifts in Time Series of Rainfall and Runoff in the Gambia River Watershed

Received: 7 August 2014     Accepted: 20 August 2014     Published: 30 August 2014
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Abstract

For several decades, climate change and climate variability issues and their impacts on the hydrological regime of rivers have constituted a major topic for hydroclimatological sciences research and water resources planning policies. Understanding of these issues needs enough long time series of rainfall and runoff data covering a large period, and a comprehensive diagnosis of the existing trends and shifts in these time series of data. This can be done by applying robust statistical tests to relevant rainfall and runoff time annual series. The aim of this paper is to highlight the effect of climate change in the Gambia River Basin and its impacts on the availability of the water resources of this basin. To reach this objective, we have selected runoff time series of the Gambia River Basin at Mako, Kedougou Diaguéri streamgauges and rainfall time series at Koulountou’s rain gauge. Statistical tests for shift detection presented in the Khronostat software, such as Pettit, Hubert and Buishand ellipse tests are first used, Mann Kendall test for annual trend are then applied to check whether trends exist or not in these times series. When the null hypothesis of no trend is rejected, the non parametric Sen’s test is then applied to validate the Mann Kendall trend test and to estimate the magnitude of the trend and its direction. Tests for homogeneity show an increasing shift for rainfall time series of Koulountou raingauge and for runoff time series of Mako and Diaguéri and a decreasing shift for Kedougou streamgauge. According to the Mann Kendall trend test, there is an upward trend for Koulountou rainfall time series, and Mako and Diaguéri runoff time series, and a downward trend for Kedougou annual runoff time series. The Buishand ellipse and the Hubert test indicate generally the same year of the beginning of the shift. Interesting perspectives for decision makers in evaluation and precise management of water resources and water projects in the Gambia River basin are offered as well.

Published in International Journal of Environmental Protection and Policy (Volume 2, Issue 4)
DOI 10.11648/j.ijepp.20140204.13
Page(s) 138-146
Creative Commons

This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.

Copyright

Copyright © The Author(s), 2014. Published by Science Publishing Group

Keywords

Climate Variability, Hydrometeorological Data, Statistical Hydrology, Water Resources, Watershed, Gambia River, Management, Decision Making, Country Planning

References
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Cite This Article
  • APA Style

    Vieux Boukhaly Traore, Soussou Sambou, Mohamed Talla Cisse, Séni Tamba, Sidy Fall, et al. (2014). Trends and Shifts in Time Series of Rainfall and Runoff in the Gambia River Watershed. International Journal of Environmental Protection and Policy, 2(4), 138-146. https://doi.org/10.11648/j.ijepp.20140204.13

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    ACS Style

    Vieux Boukhaly Traore; Soussou Sambou; Mohamed Talla Cisse; Séni Tamba; Sidy Fall, et al. Trends and Shifts in Time Series of Rainfall and Runoff in the Gambia River Watershed. Int. J. Environ. Prot. Policy 2014, 2(4), 138-146. doi: 10.11648/j.ijepp.20140204.13

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    AMA Style

    Vieux Boukhaly Traore, Soussou Sambou, Mohamed Talla Cisse, Séni Tamba, Sidy Fall, et al. Trends and Shifts in Time Series of Rainfall and Runoff in the Gambia River Watershed. Int J Environ Prot Policy. 2014;2(4):138-146. doi: 10.11648/j.ijepp.20140204.13

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  • @article{10.11648/j.ijepp.20140204.13,
      author = {Vieux Boukhaly Traore and Soussou Sambou and Mohamed Talla Cisse and Séni Tamba and Sidy Fall and Amadou Tahirou Diaw and Hyacinthe Sambou and Malanda Edmond Nimy},
      title = {Trends and Shifts in Time Series of Rainfall and Runoff in the Gambia River Watershed},
      journal = {International Journal of Environmental Protection and Policy},
      volume = {2},
      number = {4},
      pages = {138-146},
      doi = {10.11648/j.ijepp.20140204.13},
      url = {https://doi.org/10.11648/j.ijepp.20140204.13},
      eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.ijepp.20140204.13},
      abstract = {For several decades, climate change and climate variability issues and their impacts on the hydrological regime of rivers have constituted a major topic for hydroclimatological sciences research and water resources planning policies. Understanding of these issues needs enough long time series of rainfall and runoff data covering a large period, and a comprehensive diagnosis of the existing trends and shifts in these time series of data. This can be done by applying robust statistical tests to relevant rainfall and runoff time annual series. The aim of this paper is to highlight the effect of climate change in the Gambia River Basin and its impacts on the availability of the water resources of this basin. To reach this objective, we have selected runoff time series of the Gambia River Basin at Mako, Kedougou Diaguéri streamgauges and rainfall time series at Koulountou’s rain gauge. Statistical tests for shift detection presented in the Khronostat software, such as Pettit, Hubert and Buishand ellipse tests are first used, Mann Kendall test for annual trend are then applied to check whether trends exist or not in these times series. When the null hypothesis of no trend is rejected, the non parametric Sen’s test is then applied to validate the Mann Kendall trend test and to estimate the magnitude of the trend and its direction. Tests for homogeneity show an increasing shift for rainfall time series of Koulountou raingauge and for runoff time series of Mako and Diaguéri and a decreasing shift for Kedougou streamgauge. According to the Mann Kendall trend test, there is an upward trend for Koulountou rainfall time series, and Mako and Diaguéri runoff time series, and a downward trend for Kedougou annual runoff time series. The Buishand ellipse and the Hubert test indicate generally the same year of the beginning of the shift. Interesting perspectives for decision makers in evaluation and precise management of water resources and water projects in the Gambia River basin are offered as well.},
     year = {2014}
    }
    

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  • TY  - JOUR
    T1  - Trends and Shifts in Time Series of Rainfall and Runoff in the Gambia River Watershed
    AU  - Vieux Boukhaly Traore
    AU  - Soussou Sambou
    AU  - Mohamed Talla Cisse
    AU  - Séni Tamba
    AU  - Sidy Fall
    AU  - Amadou Tahirou Diaw
    AU  - Hyacinthe Sambou
    AU  - Malanda Edmond Nimy
    Y1  - 2014/08/30
    PY  - 2014
    N1  - https://doi.org/10.11648/j.ijepp.20140204.13
    DO  - 10.11648/j.ijepp.20140204.13
    T2  - International Journal of Environmental Protection and Policy
    JF  - International Journal of Environmental Protection and Policy
    JO  - International Journal of Environmental Protection and Policy
    SP  - 138
    EP  - 146
    PB  - Science Publishing Group
    SN  - 2330-7536
    UR  - https://doi.org/10.11648/j.ijepp.20140204.13
    AB  - For several decades, climate change and climate variability issues and their impacts on the hydrological regime of rivers have constituted a major topic for hydroclimatological sciences research and water resources planning policies. Understanding of these issues needs enough long time series of rainfall and runoff data covering a large period, and a comprehensive diagnosis of the existing trends and shifts in these time series of data. This can be done by applying robust statistical tests to relevant rainfall and runoff time annual series. The aim of this paper is to highlight the effect of climate change in the Gambia River Basin and its impacts on the availability of the water resources of this basin. To reach this objective, we have selected runoff time series of the Gambia River Basin at Mako, Kedougou Diaguéri streamgauges and rainfall time series at Koulountou’s rain gauge. Statistical tests for shift detection presented in the Khronostat software, such as Pettit, Hubert and Buishand ellipse tests are first used, Mann Kendall test for annual trend are then applied to check whether trends exist or not in these times series. When the null hypothesis of no trend is rejected, the non parametric Sen’s test is then applied to validate the Mann Kendall trend test and to estimate the magnitude of the trend and its direction. Tests for homogeneity show an increasing shift for rainfall time series of Koulountou raingauge and for runoff time series of Mako and Diaguéri and a decreasing shift for Kedougou streamgauge. According to the Mann Kendall trend test, there is an upward trend for Koulountou rainfall time series, and Mako and Diaguéri runoff time series, and a downward trend for Kedougou annual runoff time series. The Buishand ellipse and the Hubert test indicate generally the same year of the beginning of the shift. Interesting perspectives for decision makers in evaluation and precise management of water resources and water projects in the Gambia River basin are offered as well.
    VL  - 2
    IS  - 4
    ER  - 

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Author Information
  • Hydraulics Laboratory and Fluid Mechanics (LHMF), Faculty of Science and Technology, Department of Physics, University Cheikh Anta Diop (UCAD) BP 5005, Dakar-Fann, Senegal

  • Hydraulics Laboratory and Fluid Mechanics (LHMF), Faculty of Science and Technology, Department of Physics, University Cheikh Anta Diop (UCAD) BP 5005, Dakar-Fann, Senegal

  • University of Thies, Facultty of Technological Sciences, Department of Experimental Sciences, Thies, Senegal

  • Thies Polytechnic School, Department of Civil Engineering, PB 10, Thies, Senegal

  • Office Lake Guiers Company for the Development and Operation of Lands Senegal River Delta and the Valleys of the Senegal River and Falémé (SAED), Saint Louis, Senegal

  • Teaching Laboratory and Research in Geomatics (LERG), Faculty of letters and Social Sciences, Department of Geography, University Campus of Polytechnic High School of Dakar BP 5005 Dakar-Fann, Senegal

  • Teaching Laboratory and Research in Geomatics (LERG), Faculty of letters and Social Sciences, Department of Geography, University Campus of Polytechnic High School of Dakar BP 5005 Dakar-Fann, Senegal

  • Hydraulics Laboratory and Fluid Mechanics (LHMF), Faculty of Science and Technology, Department of Physics, University Cheikh Anta Diop (UCAD) BP 5005, Dakar-Fann, Senegal

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