[Figure 11]
The inter-annual variations and cumulative departures of rainfall and
discharge were also explored to understand their interactions in the
Congo basin (Fig. 9). The inter-annual variations during the
1901- 2010 period was consistent and captures the wettest period
(1960- 1970) in the basin (Fig. 9a). Their cumulative departures
are somewhat similar but show an apparent inconsistent trend during the
1930-1950 and post 1999- 2010 periods (Figs. 9b-c). Generally,
there seems to be a change in the hydrological regimes of the Congo
river, (especially after 1994) owing to the rather pervasive influence
of extreme droughts. This again could be the aftermath of extreme
droughts, which fluctuated between 50% (i.e., affected areas) in the
early years of the century and 40% during the 1994-2014 period
(Ndehedehe et al., 2019). This change is reflected in the observed
temporal relationship between maximum rainfall and discharge (Figs.
10a-d). For example, the rainfall-discharge relationship was stronger in
1961-1990 (r = 0. 77) and 1991-2010 (r =
0. 69) compared with other climatological periods when
correlations were weak (Figs. 10c and d). Moreover, the temporal series
associated with the ICA-localised spatial rainfall patterns over the
Congo basin are correlated with discharge (Fig. 11). As shown in the
leading independent modes (Fig. 11), the discharge-rainfall relationship
is strongest at the extreme south (r = 0. 65) and north
(r = 0. 64) of the basin. These sections of the basin are
characterised by considerable amplitudes in annual and seasonal rainfall
(EOF-1, Figs. 5a-b, 6a-b and cf. 3). The relationship (rainfall and
discharge) is also significant in other catchments where correlations of
0.56, 0.59 and 0.51 have been observed although temporal relationships
of localised rainfall at the equator with discharge are poor and
insignificant (α = 0. 05). Given the trajectory of water
inflow in the Congo basin, the considerable association of rainfall with
discharge implies that the wetland hydrology of the Cuvette central is
nourished mostly by rainfall, in addition to exchanges of fluxes in the
floodplain wetlands.