Okavango Delta Management Plan - Ramsar Convention on Wetlands

2.2.6 HYDROLOGY
The flood wave which results from upstream rainfall lasts from January to July, with its
peak in late April or the beginning of May. A five year record from 1997 to 2002 is shown in
. The seasonal flow range is from to 80 to 700m 3/s, and the average annual flow at
Mohembo during this period was 7,500MCM yr -1 while the long term mean annual flow is 9
500MCM yr -1.
2.2.6.1 Panhandle
Popa Falls on the river in Namibia marks the upstream boundary of the Panhandle. The
river is laterally confined by geological faults and sand ridges to a flood plain up to 15km
wide. The river channel meanders across the flood plain, varying in width from around 50
to 100m wide, and 5 to 6m deep. The length of the Panhandle valley is around 100 km,
while the length of the meandering river is around 200km. The gradient of the valley is
from around 1,000m (above mean sea level) to 980m.
At the downstream limit of the Panhandle, which is not clearly defined, between the villages
of Sepopa on the western and Seronga on the eastern margins of the <strong>Delta</strong>, the <strong>Okavango</strong>
River starts to break out into its primary distributaries, marking the start of the <strong>Delta</strong>.
Discharge (m3/s)
Figure 2-6: Inflow at Mohembo (1997–2002)
2.2.6.2 River systems
The <strong>Delta</strong> is conventionally divided into four water and land categories: the Panhandle,
upstream permanent swamps, downstream seasonal flood plains, and large islands and
sandveld tongues. The upstream <strong>Delta</strong> is characterised by the main <strong>Okavango</strong> River
flowing through extensive papyrus swamps, bifurcating into distributary channels which
convey the flow on to extensive perennial flood plains.
The primary distributaries are shown in Figure 2-7. The boundaries between the
distributaries are not well defined, apart from the Chief’s Island clearly separating the
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