Ing. W.P. Spaan : Water conservation at the central plateau in Burkina Faso

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25 Jun 2003 16:00
Unit: Wageningen University
Location: Aula (gebouw 362), Gen. Foulkesweg 1, Wageningen
Promotor: prof.dr.ir. L. Stroosnijder (Erosion and Soil & Water Conservation)

 Regeneration of degraded soils requires interventions for effective water conservation and improvement of water holding capacity. At the Central Plateau in Burkina Faso there is a preference of semi-permeable line measures that slow down runoff but prevent water logging. To evaluate the effectiveness of contour vegetation barriers under semi-arid in conditions, an on station field experiment was executed. Seven local plant species (grasses, woody species and a succulent) were planted in 21 plots of 20 x 20 m as contour vegetation barriers. Stone rows and barriers of natural vegetation replaced some of the less successful species. Runoff plots with different slope lengths were laid out to determine the efficiency of the barriers and the influence of slope length and alley treatment. Grass barriers and stone rows proved to be very effective in reducing runoff, woody species and the succulent less effective. Runoff could be well predicted by total rainfall. The influence of rain intensity on runoff was marginal. For longer slopes all factors that determine runoff became less important, runoff volumes exceeded quantities that can be dammed by the barrier. Barriers of grass and natural vegetation proved to be very effective in diminishing sediment transport. Less effective barriers only slightly reduced sediment transport. Sediment yield could be best predicted by rain intensity and runoff volume. Despite the differences in effectiveness of the barriers and soil water dynamics, there were no striking differences in crop yields. Effective barriers conserved during dry years enough water to compensate own consumption and increased crop yields over a distance of 6 m. In dry years less effective barriers competed for water with crops. In wet years effective barriers caused water logging and less effective barriers improved yields a few meters upstream. The contour vegetation barrier constitutes a cheap option in terms of labour and material requirements, and do not explain the low adoption and poor maintenance of vegetation barriers. The labour requirement in the beginning of the growing season is not a real constraint. At The Central Plateau well-managed contour vegetation barriers can play a vital role in conserving soil and water and can contribute to the regreening of the area.
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