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studies not only in Dar es Salaam, Tanga and Zanzibar, where only a very limited area has been covered, but also in other parts of Tanzania where virtually no information on this subject exists.
2.6.2 Subject coverage
Most of the studies reported in the various papers and reports covered the area of pollution, mainly that emanating from sewage. Fewer studies have looked at other sources of water quality degradation and their impacts on the
natural environment and on human health. Consequently, there are reports on nutrient loads and distribution, BOD levels and coliforms. Studies on heavy metal pollution and that emanating from organic compounds and
agrochemicals are few and far between. These include a study by Mmochi and Mberek 1998 on pesticide pollution and those by Machiwa 1992a,b which assessed pollutionby heavy metals and toxic material.
Moreover, there are only few studies that have looked at the effects of pollutants, on the water quality in Tanzania. A good example is a report by Munisi 1998 who discussed the results of a determination on the effects of
discharges from a fertiliser factory on intertidal floral communities in Tanga. Both Tanga and Dar es Salaam have relatively high concentrations of manufacturing concerns. Since few industries in Tanzania treat their wastes
before they are discharged into the environment, it is obvious that they are principal sources of industrial pollution in the country. Given the current pace of industrial development in the country and the fact that only few studies
on industrial pollution have been done, it is important that more studies should be carried out to generate both baseline information as well as to follow trends on the impact of these wastes on the water quality.
2.6.3 Duration of studies longshort
A great majority of the studies are of short duration. Given that most of the studies reported in this review were carried out by students either on short weeks study programs or on field attachments, invariably the studies
tended to be very short. Where researchers did the studies, the duration of the studies was determined by the amount and source of funding. For obvious reasons, studies for Masters and PhD theses tended to be
comparatively longer than, for example, undergraduate reports and degrees. Similarly, studies that aimed to monitor long- term effects of a contaminant on the environment were longer than the average consultancy report.
On the whole though, long term studies were very rare.
From the above discussion it is obvious that specific efforts need to be taken to address the issue of time frame for sampling. It is important to identify which aspects or parameters that deserve to be addressed through long term
and which through short-term studies. The question of seasonality is also important. In Tanzania, seasonality is intrinsically linked to study duration. The annual weather cycle in the east African coastal areas is generally made
upof two periods of rainfall alternating with periods of dry weather. This cycle is essentially driven by the monsoon winds. Conceivably, this weather pattern has a large influence not only on waste discharges including
that from upland agricultural areas but also on dispersal patterns along the coast. Few studies that looked at temporal patterns are available. Consequently, temporal variationseasonality studies should be carried out when
addressing both agricultural as well as municipal waste discharges. Such studies are also important when assessing waste dispersal patterns and their effect on the biota.
Point source discharges are inherently long-term events. They are therefore ideally examined through long-term studies. Long-term studies over one or two years are also essential when one requires basic data to help prepare
a model of waste discharge and dispersion patterns. Long-term data therefore affords predictive capability.
2.6.4 Age of studies
As mentioned earlier, most of the available information in the literature is quite new as the bulk of the studies were carried out relatively recently. Of notable absence is historical information on the amounts and effects of
different contaminants on the natural environment.
2.6.5 Information accessibility
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Information on water quality and pollution is generally buried in private files and records and hence inaccessible to the general public. Poor organisation of reports in many departmental libraries makes the situation worse.
University theses are only available at the university and have proved less readily available to people outside the university community.
2. 7 Recommendations for future work
2.7.1 Methods quality, comparability
As mentioned earlier, the methods used in the different studies are generally accepted as of good quality. However, it is important to ensure comparability of results from different researcherslaboratories. This can only
be achieved by standardising analytical techniques. In this regard, the following are recommended.
• All laboratories use internationally accepted standard analytical techniques.
• To eliminate systematic errors, regular inter-calibration exercises should be conducted in the
country. Such exercises can be internal between a number of scientists in a laboratory or can be between laboratories.
• The use of internationally recognised reference standards where available. This will eliminate errors
that can arise from use of locally prepared standards.
2.7.2 Geographical Subject coverage and duration of studies
Geographical coverage has been discussed in detail above. Obviously however, some guidance is needed to direct research in areas where gaps in knowledge exit. TCMP is obviously better placed to lead such efforts.
With regard to subject coverage, there is a need for studies on other water contaminants such as pesticides, fertilisers, toxic chemicals and sediments. These have so far received only minimal attention. Agricultural
chemicals in particular, could be important contributor to water pollution in coastal waters that are recipient of input from farm lands, through rain and river run-offs.
To start with, priority should be given to filling gaps in areas where there little or no data available before embarking on long term studies. Consequently short-term, studies should take priority over monitoring programs.
However, this should be decided on a case by case basis, as there are areas that urgently require monitoring of both pollution inputs and its effects on natural environment. Because of the severity of the situation in such areas
as Tanga and Dar es Salaam, these areas qualify for long term monitoring of water quality.
With regard to instrumentation and techniques of sampling, priority should be given to the later as poor sampling techniques and sampling regimes can lead to unnecessary errors as well as render results very difficult to interpret
and hard to relate to management decisions.
2.7.3 Sampling frequency and duration and data analysis
