the role of tourism in natural resource management in the okavango ...

A further significant impact of soils in the region is on the quality of the water.
Compared to most other rivers, the waters of the Okavango contain exceptionally
small amounts of mud and dissolved chemicals or minerals. The main reason for this
clarity and purity is that most of the water in the system filters out of sandy soils
consisting largely of quartz grains. These do not easily dissolve or break-up to
release soluble chemicals or tiny particles that would otherwise be washed in the
river as minerals and mud. The sands also serve to control the flow of water since
most rainwater sinks into the ground rather than running off the surface and into the
tributaries of the major rivers. Flows are therefore much more even than those along
rivers that drain rocky areas. Within the catchment, the effects of sand in producing
clean and steady flows are more pronounced in the sandiest areas, especially in the
Cuito sub-Basin. Flows off basement rocks in the hillier Cubango sub-Basin are
more variable and most of the nutrients and sediments that find their way into the
Okavango Delta tend to come from this western area (Mendelsohn and el Obeid,
2004).
The map of soils (Figure 5.6) provides a basic perspective on how soils vary across
the Okavango River Basin. The fine to medium grained sands that are present in so
much of the Basin are more generally known as Kalahari sands. These sands
generally extend to a depth of at least one metre, but may be up to 300 metres deep
in some areas overlying older consolidated sedimentary rocks of the Karoo Age
(Mbaiwa, 2002). Sand grains generally make up more than 70 percent of the body of
the soil, with less than 10 percent consisting of clay and silt. There are few nutrients
(especially nitrogen, potassium and phosphorous) in the sand and the porous
structure results in little runoff or water erosion. As such, water drains rapidly
through the body of soil leaving little moisture at depths to which most plant roots
can reach (Mendelsohn and el Obeid, 2004).
5.3.3.3 Vegetation Resources
The character of the Okavango Delta probably owes more to its flora than to any
other single element as without the influence of its vegetation the region would
probably amount to little more than a vast salt lake (Bailey, 1998). The vegetation of
the Okavango is not simply a passive spectator to the passing of the seasons. On
the contrary, it is an active player in shaping the Delta. The plants, or more correctly,
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