coaltech upper olifants river catchment wetland inventory ...

3.5.1.2 Groundwater recharge
Various wetland types, including floodplain and riparian wetlands may contribute to
groundwater recharge. Pans may also contribute to groundwater recharge. This outward
seepage from the pans may help to regulate the build-up of dissolved solids in the system.
Seeps are responsible for groundwater discharge and almost never contribute to
groundwater recharge (Palmer et al 2002, Allan et al 1995, Kotze 2000, Kotze et al 2000).
3.5.2 Water purification
3.5.2.1 Nitrogen removal
It is difficult to determine the amount of nitrogen removal by a wetland without measuring the
input and output nitrogen. The transformation processes, such as denitrification, requires
specific conditions in order to proceed. The reaction rate of this process is a function of the
reactant concentration and the applicable bacteria. These processes are therefore more
likely to take place in wetlands and wetland areas with more organic material (Palmer et al
2002, Kotze 2000, Kotze et al 2000).
The three transformation processes of nitrogen are plant uptake, nitrification and
denitrification (Palmer et al 2002). The specific processes and rate of the process depends
on the specific characteristics of the wetland. It should be taken into account that all three of
the processes may take place in the same wetland (Palmer et al 2002, Kotze 2000, Kotze et
al 2000, Brady & Weil 1999).
3.5.2.2 Phosphate removal
Phosphates enter a wetland from various sources, both natural and anthropogenic.
Phosphate removal is not a microbial process, but a physiochemical process. As with
nitrogen removal the amount of phosphate removed cannot be determined without
measuring the input and output phosphate. Unlike nitrogen removal, however, the removal of
phosphates is not dependant on the presence of bacteria. The removal of phosphates takes
place via precipitation, absorption onto clay particles or uptake by plants. These phosphates
can therefore be released into the environment by a change in the micro-environment or by
the natural die-back of plants (Palmer et al 2002, Kotze 2000, Kotze et al 2000).
Wetland Database for UORC - 35 -