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6.3 Indirect use values in the Okavango Delta Ramsar site
6.3.1 Introduction
A review of the different indirect use values led to the conclusion that five indirect uses are most
important. These are groundwater recharge, wildlife refuge, carbon sequestration, water purification
and scientific and educational value. The value of flood attenuation is minimal, as the delta has the
capacity to absorb high water levels internally without significant outflows. Even if outflows would
occur, it is expected that very little damage will occur downstream as there are hardly any vulnerable
settlements and pieces of infrastructure (e.g. bridges, roads, power lines). Most of the outflow would
be channelled into the Boteti River and lake Ngami, both of which have been dry mostly since the
1990s. They would be able to absorb most outflows that might emerge from the delta. Similarly, the
value of sedimentation retention is minimal as the outflow is minimal, and virtually all sedimentation is
retained inside the delta, mostly in the channels (Jacobson et al. 2005). Sedimentation is estimated
to be 209 000 t/ annum of clastic 3 sedimentation (170 000 t/annum of bed load) on the upper fan and
381 000 t/annum of dissolved load on the lower fan (Jacobsen et al. 2005, p. 2 app.3). Bed load is
only transported in the primary channels and other loads through channels and overland flows. All
sedimentation stays in the swamps.
Below, the estimates of the five remaining indirect uses are discussed prior to the integral discussion
of the indirect use value of the delta.
6.3.2 Groundwater recharge
The Okavango Delta provides a conduit for the recharge of groundwater aquifers which are utilised
around the perimeter of the wetland. Since most of the population of the Ramsar site is concentrated
close to the perimeter of the wetland it is reasonable to assume that the groundwater used by these
communities has been replenished from the delta. The value of groundwater abstraction in the study
area is thus attributed to the delta.
The recharge value is estimated as follows. Firstly, the actual amount of groundwater abstraction has
been estimated. Next, the unit value of groundwater has been estimated. Multiplication of both
figures gives the indirect use value of groundwater recharge. Groundwater is abstracted in
settlements for domestic use, businesses and government. It is also used for livestock. Other uses
are minimal and have not been included. The estimate of groundwater abstraction for settlements
has been derived from the Ramsar site land use plan (Plantec et al. 2006). Groundwater abstraction
for livestock has been estimated using the livestock figures for Ngamiland and standard daily water
consumption per type of livestock 4 . The groundwater abstraction is estimated to be 5.8 Mm 3 for the
entire Ramsar site (Table 6-3). This amounts to around five percent of the estimated annual
recharge. The remaining 95% of recharge evaporates, serves the ecosystem, or is available for
future use (option value).
Table 6-3. Estimated annual groundwater abstraction
Category of use Details Annual GW consumption (in Mm 3 ) Ramsar site
Domestic use and businesses Maun 2.3
other settlements 1.3
Livestock Cattle 1.5
Goats 0.1
Sheep 0.0
Donkeys 0.6
Total groundwater consumption per year 5.8
3 clastic sediment—rock and soil eroded from the land
4
It has been assumed that livestock relies on groundwater for ten months per year.
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