Congo Basin Hydrology, Climate, and Biogeochemistry. Группа авторов

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Congo Basin Hydrology, Climate, and Biogeochemistry - Группа авторов


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6.6 Comparative interannual evolution of the runoff (LE) of the Ubangi basin at Mobaye and Bangui (from 1938 to 2015). The periods 1950, 1958–1969, 1971, and 1975–2014 have been reconstructed from the Ubangi discharges at Bangui.

      6.5.2. Diversity of Major Climatic Ruptures in the Ubangi Basin at Mobaye

      Over the period studied 1951–1995, only the two basins of the Kotto (at Bria and Kembe) show a downward trend in their flows despite the resumption of rainfall in the early 1990s (Figs. 6.4 and 6.5). On the other hand, in the 1990s flows in the two Mbomu basins are increasing and seem to explain the increase observed on the Ubangi at Mobaye. This is explained by the impact of forest cover on the hydrological regime of the Mbomu, compared to the savannah environment drained by the Kotto. Furthermore, the results show much more marked hydrological deficits on the Kotto than on the Mbomu.

Schematic illustration of interannual evolution of river depletion coefficient from the Ubangi at Mobaye and water volume of the aquifer (1938–1976).

      6.5.3. Opposing Roles of Savannah and Forest on the Hydropluviometric Dynamics of the Sub‐Basins of the Ubangi River at Mobaye

      A concerted examination of the statistical breaks in the rainfall and hydrological time series of the sub‐basins making up the Ubangi basin at Mobaye reveals a difference in hydropluviometric behavior between the Kotto basin, north–south oriented, with a large savannah domain, and the Mbomu, NE–SW oriented with 10% of equatorial forest and 30% of wooded savannah: i) on the Kotto, the hydropluviometric deficit has only increased since 1970 with a marked increase in the hydrological deficit from 1985 onwards (Table 6.3) and with no sign of resumption of flows despite a resumption of rainfall around 1992 (Figure 6.4); and ii) on the Mbomu, a semblance of resumption of flows in the early 1990s.

Schematic illustration of relationship of water runoff as a function of the precipitated water level (in mm) on the Ubangi basin at Mobaye and its sub-basins. Schematic illustration of decennial evolution of runoff coefficients (CE) from the Ubangi at Mobaye and from its tributaries. Schematic illustration of relationship between the runoff coefficient (CE) and the rate of no-wooded savannah surface in the sub-basins of the Ubangi at Mobaye.
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