4.2.3 Study limitations
The samples were taken during a drought period (Table 3.3). It
is therefore necessary to be aware that the results might have been different
if the rainy period (November-April) were normal. This is because low rainfall
mobilises less nutrient laden sediments than high intensity (Basnyat et
al., 2000 in Brainwood et al., 2004). It is, however, important
to remember that the studied reservoirs are located in a semi arid region
characterised by low and erratic rainfall as shown by Zirebwa and Twomlow
(1999). Since heavy rains should not be expected in the area, the water
managers can consider that the reservoirs are protected and environmentally
healthier. Water managers should therefore note that water quality
investigations are carried out, as stated by Brainwood et al. (2004),
to provide information on the health of the water bodies and allow them to
develop strategies for better management of catchment and water resources.
4.2.4 Management implications
The results of this study can be used to guide future
management of these and similar man-made reservoirs in rural Zimbabwe.
Reservoirs on communal lands had similar water quality as found in the National
Park, which is attributed to the lack of upstream development surrounding these
particular reservoirs. However, it is believed that if human populations alter
the current use of these water bodies and develop upstream areas, water quality
will suffer. Therefore, it would be stressed that upstream development,
particularly development that would result in an influx of nitrogen and
phosphorus, be limited in these areas. This is particularly important as the
reservoirs contained phytoplankton that would proliferate into toxic algal
blooms with the influx of those particular nutrients. Such blooms would
compromise the quality of water for both human use and the health of the
current aquatic community.
Secondly, this study found that local soil conditions were
very different from water conditions. This result can be attributed to the
presence of a healthy vegetative cover layer surrounding the reservoirs. Such a
vegetative layer acts as a buffer to influxes of elements, and helps to
maintain stable and healthy water conditions. Reservoir managers should
maintain a healthy vegetative buffer around the water body to assist in
mitigating any future changes in local conditions.
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