Infoscience

Student project

Variability of Rainfall in a Semi-Arid Catchment in Burkina Faso

The climate in the Sahel is marked by the spatial and temporal variability of rainfall. As the agriculture is mainly rainfed in Burkina Faso, the information about rainfall is crucial to help the farmers in their decisions. A network of wireless sensorscope stations is installed in the catchment of the Singou River (in the Gourma region of Burkina Faso) and monitor at a time step of 5 minutes meteorological parameters such as rain.The raindata of 2010 was evaluated and unreliable stations were excluded from the dataset. The rain events for the period of May to August were identified. More rain is measured in the month of August, which is rather due to thr higher frequency of rain events than to the intensity of the events. The accuracy of the Davis and précis rain gauges was evaluated through outdoor and laboratory experiments. At low intensities, the proposed error range for the Davis raingauges is +-15% and for the précis rain gauge data a correction factor of 2 (multiplication) should be applied. Indigenous knowledge was integrated in the thesis through a survey on the perception of rain in Tambarga. The most important aspects of rain are the quantity, the regularity of rain events and wind (which may destroy houses). The conditions that favour the development of a storm are analyzed through principle components analysis (PCA). The analysis showed that only few events are clearly influenced by one single parameter (soil moisture, latent heat flux, sensible heat flux, antecedent rain). The persistence of rainfall patterns was also subjected to analysis. A certain persistence of the rainfall patterns was detected for the month of August during which the rain events succeed closely each other. Finally, the validity of the formula of time of ponding based on Richard’s equation was evaluated (using the data from the infiltration experiments). The formula is valid for the catchment only in the case when continous flow in the river is observed without the contribution of rain. The results of the different analyses presented in the thesis give different insights on the characteristics of the rain events. Some information can already be used, but in order to obtain more meaningful results the analyses can be repeated with data that covers several years.

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