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Delft University of Technology (2006)

Impact of land-use intensity on evaporation and surface runoff : processes and parameters for Eastern Burkina Faso, West Africa

Bagayoko, Fafré

Titre : Impact of land-use intensity on evaporation and surface runoff : processes and parameters for Eastern Burkina Faso, West Africa

Auteur : Bagayoko, Fafré

Université de soutenance : Delft University of Technology

Grade : Doctor 2006

Description
Land-use is one of the main factors affecting the hydrological cycle. In the Volta river basin, two major projects (VinVal and GLOWA Volta) are dealing with the development of a land-use planning and a decision support system for sustainable agricultural production and water resources management. Both projects, especially GLOWA Volta, need information about the surface runoff and the seasonal dynamics of the actual evaporation.
Actual evaporation was measured during the first long-term eddy covariance measurement campaign over savanna vegetation in West Africa. The investigation took place in the Eastern Burkina Faso (11°07’ N ; 0°33’ E), and the analysis covers almost two years, including one relatively wet (2003) and one relatively dry (2004) year. Following the pattern of coupling and decoupling of actual evaporation, a new formulation was proposed. Lands Surface Models were also found to be insensitive to these inter-annual and seasonal dynamics. Recommendations were given to enhance the overall performance of the models in the savanna environment.
Surface runoff and its scale effects were investigated in three adjacent watersheds with different land-use intensities during the 2004 rainy season. The study shows a clear inter-annual and seasonal dynamics of surfaces fluxes. A clear reduction of the surface runoff with increasing slope length and with decreasing land-use intensity was observed. A difference in the interception and the frictional resistance of the vegetation was found to account for these observations.
The results will be relevant inputs of the eco-hydrological models in the semi-arid region of West Africa.

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