Okavango Delta Management Plan - Ramsar Convention on Wetlands

Of the three main distributaries, the Thaoge River in the west terminates in a series of
lagoons and permanently inundated plains near its upstream end, choked by
sedimentation and vegetation. The Jao/Boro comprises pemanent swamp in its upstream
end. The middle part (essentially the Boro and Kunyere/Xudum/Matsibe) is a system of
seasonally inundated floodplains. In the downstream end it is flowing in confined channels,
discharging to the Thamalakane and to Lake Ngami. The Maunachira and Khwai, as well as
the Santantadibe in the east, have permanently inundated plains along the entire length,
with only narrow bands of seasonal floodplains. The Gomoti floods only in higher rainfall
years. The Khwai, Santantadibe and Gomoti end in single channels. The two latter ones
used to connect to the Thamalakane, which, however, has not been observed since 1989.
The Khwai usually dries out within its channel, but in the past it was probably a major
provider of water to the Mababe depression; travellers around 1850 described the
depression as a lake.
2.2.6.3 Outflow
The course of the Thamalakane River follows the Thamalakane Fault line which runs
perpendicular to the main axis of the <strong>Delta</strong> and demarcates its downstream limit. The river
flows south west, and functions as a collection drain for the distributaries from upstream.
In low flood years, however, flow in the distributaries succumbs to evaporation and
infiltration before reaching the Thamalakane River.
In high flood years, flow in the lower Boro discharges to the Thamalakane, and upstream
bifurcates into the Kunyere/Xudum/Matsibe to discharge into Lake Ngami, from which
there is no outflow. Flow in the eastern Maunachira bifurcates into the Mboroga River and
may also reach the Thamalakane River. In contrast to the inflow to the <strong>Delta</strong> of
7,500Mm 3/annum, the average outflow in recent years has been 20Mm 3/annum (Figure
2-8Figure 2-8: Outflow at Boro Junction (1997–2002)). About 98% of the entire inflow is
lost to evapotranspiration and infiltration to ground water.
Discharge (m3/s)
Figure 2-8: Outflow at Boro Junction (1997–2002)
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