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    The School of Agricultural Sciences (SAS)

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    The School of Food Technologies, Nutrition and Bio Engineering (SFTNB)

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    The School of Forestry, Environmental and Geographical Sciences (SFEGS)

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    The Department of Environmental Management (Former MUIENR)

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Will fish pond management principles from the temperate zone work in tropical fingerponds?

Abstract

Fingerponds are small elongate pools excavated by hand in the flood zones of Lake Victoria and the Rufiji River. Within EC Fingerpond project INCO-DEV (ICA4-CT-2001-10037) 24 fingerponds were dug in three participating countries (Kenya, Tanzania, Uganda) during 2002. In each country two village communities each excavated 4 experimental fingerponds of c. 8 x 24 in. individual size and with raised beds between them of c.8 in in width. The project aims to test the possibilities for fish production based on self-stocking and limnological research, and to develop methods for the use of fingerponds on a larger scale. Times of pond digging, flooding, disconnection and isolation for fish production are given for all sites. Methods for field monitoring, measurements and sampling, including primary production, zooplankton and fish censuses, and for the application of organic fertilizers are described. Fish migrants in the Lake Victoria basin which become self-stocked with flood recession are mostly Oreochromis species (tilapias) together with haplochromines, clariids, Protopterus aethiopicus, (lungfish) and one or two smaller species. The roles of fish predators, tadpoles, and adult frogs are considered. Natural primary production (as chlorophyll) and diurnal shifts in oxygen concentrations were indicative of relatively low nutrient availability for long term fish production. Water conductivities ranged from 100 mu S/cm to > 10 000 mu S/cm and chlorophyll concentrations were maximally 40 mu g/L and generally about 10 mu g/L. Quantities and sizes of zooplankton were relatively small. Management measures to increase fish production and natural fish food supply, notably zooplankton, are discussed.. Additions of organic fertilizers resulted in raised primary and fish production without substantial falls in oxygen concentrations, but in dry periods fertilizers should be applied carefully to avoid oxygen deficiency in shallow water. Other measures such as fish harvesting, stock equalisations, single sex selections, water level variations (uncontrolled) and fish predator stocking, are discussed in terms of their potential effects on fish yields. Principles of food chain functioning in tropical fingerponds are compared with temperate aquaculture where three basic situations may be distinguished relating water quality and biological status to fish stock levels namely: low fish density with large sized zooplankton; medium fish density with high biodiversity and turnover of zooplankton; and high fish stock density with low biomas and tiny zooplankton. The roles of zooplankton and phytoplankton in tilapia production are discussed and indicators for fish pond management in the tropical zone suggested.

 
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A preliminary assessment of the aquaculture potential of two wetlands located in the northern shores of Lake Victoria, Uganda.

Abstract

Wetlands are important for the livelihoods of millions of people. They provide food and income, support biodiversity and form a hydrological and ecological buffer between upland areas and water bodies. Population growth and the associated environmental degradation exert increasing pressure on wetlands. An example is the Lake Victoria region in East Africa, where human population growth, introduction of exotic fish species, overfishing and eutrophication have led to a deterioration of the wetland resources. For the riparian communities, this means a threat to their livelihoods as they depend on the wetland for food and income from fishing, seasonal agriculture and harvesting of wetland products. There is a need for integrated food production and waste processing technologies that enable communities to secure their livelihood without endangering the integrity of the natural resources. One such technology is integrated wetland pond aquaculture, or “fingerponds”. Ponds are dug from the landward edge of wetlands and extend like fingers into the swamp (hence the term “fingerponds”). Soil from the ponds is heaped between the ponds to form raised beds for crop cultivation. The ponds are stocked with fish through natural flooding in the rainy season. As the waters recede, the trapped fish are cultured using manure, crop and household wastes to fertilize the ponds and feed the fish. UNESCO-IHE and partners in Tanzania, Uganda, Kenya, Czech Republic and UK are currently involved in an EU-funded project to investigate the feasibility of this technology. Research focuses on the technical aspects, and on the socio-economic and environmental impacts of this technology. Also, options for integrating fingerponds with other wetland technology, such as the use of natural or constructed wetlands for wastewater treatment, need to be evaluated. Initial results of the research from Kenya and Uganda show that flooding can yield enough fish for stocking the ponds and that manuring of the ponds can increase their productivity.


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Kinawataka wetland: a functional ecosystem that can be used as a reference to conserve other wetlands in Uganda.

Abstract

Kinawataka, like other urban wetlands in Uganda has been diminished by industrial and agricultural activities over the last decade. However, the importance of this wetland has been recognised in the recent past and efforts are underway to conserve and manage it wisely. The wetland receives wastewater and storm water that flows through it from Nakawa-Ntinda industrial area before reaching Lake Victoria. The forces behind the encroachment of Kinawataka wetland, as well as its functions for wastewater purification and floodwater retention as well as for other socio-economic functions are reported in this paper and management options are suggested. A one year water quality study indicated that the wetland retained 96% of total suspended solids, 69.7% orthophosphate-P, 87.8% ammonium-N and 99.9% of faecal coliforms. The wetland also acts as habitat for fauna and flora, as shown by a survey. The local communities harvest papyrus reeds for making mats, thatching houses, making fences and for use as a fuel. Of the seventeen families of the plants identified in the wetland, nine have a medicinal value and are being used by the local communities. The various institutions that enforce environmental management, industrial development and general investment laws in Uganda seem to be functioning perfectly well on individual basis but lack a cohesive general coordination to work as a system that legally facilitates industrial and investment development and environmental conservation. Conflicting interests still exist where policy and legislation affecting wetlands are concerned and implementation of any plan requires agreement and coordination among the authorities.

 
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Discrimination efficacy of fecal pollution detection in different aquatic habitats of a high-altitude tropical country, using presumptive coliforms, Escherichia coli, and Clostridium perfringens spores

Abstract

The performance of rapid and practicable techniques that presumptively identify total coliforms (TC), fecal coliforms (FC), Escherichia coli, and Clostridium perfringens spores (CP) by testing them on a pollution gradient in differing aquatic habitats in a high-altitude tropical country was evaluated during a 12-month period. Site selection was based on high and low anthropogenic influence criteria of paired sites including six spring, six stream, and four lakeshore sites spread over central and eastern parts of Uganda. Unlike the chemophysical water quality, which was water source type dependent (i.e., spring, lake, or stream), fecal indicators were associated with the anthropogenic influence status of the respective sites. A total of 79% of the total variability, including all the determined four bacteriological and five chemophysical parameters, could be assigned to either a pollution, a habitat, or a metabolic activity component by principal-component analysis. Bacteriological indicators revealed significant correlations to the pollution component, reflecting that anthropogenic contamination gradients were followed. Discrimination sensitivity analysis revealed high ability of E. coli to differentiate between high and low levels of anthropogenic influence. CP also showed a reasonable level of discrimination, although FC and TC were found to have worse discrimination efficacy. Nonpoint influence by soil erosion could not be detected during the study period by correlation analysis, although a theoretical contamination potential existed, as investigated soils in the immediate surroundings often contained relevant concentrations of fecal indicators. The outcome of this study indicates that rapid techniques for presumptive E. coli and CP determination may be reliable for fecal pollution monitoring in high-altitude tropical developing countries such as those of Eastern Africa.

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Nitrogen and phosphorus removal in subsurface-free pilot constructed wetlands with horizontal surface flow in Uganda.

Abstract

In constructed wetlands (CWs) with horizontal sub-surface flow, nutrient removal, especially phosphorus, is limited because the root biomass fills the pore spaces of the substrate (usually gravel), directing wastewater flow to deeper wetland media; plants are not regularly harvested; the litter formed by decomposing vegetation remains on the surface of the substrate and thus does not interact with the wastewater; and the substrate media often used provide only limited adsorption. Effective nutrient removal including rootzone oxidation, adsorption and plant uptake therefore requires sufficient interaction of wastewater with the treatment media. We assessed the feasibility of biological nutrient removal from wastewater using substrate-free CWs with horizontal flow, planted with two tropical macrophytes namely, Cyperus papyrus and Miscanthidium violaceum. The objectives were to evaluate the system treatment efficiency under semi-natural conditions, and to assess microbial and plant biomass contributions to nutrient removal in the CWs. Results showed high removal efficiencies for biochemical oxygen demand, ammonium-nitrogen (NH4-N) and phosphorus (P) fractions in papyrus-based CWs (68.6-86.5%) compared to Miscanthidium (46.7-61.1%) and unplanted controls (31.6-54.3%). Ammonium oxidizing bacteria in CW root-mats (10(8)-10(9) cells/gram dry weight) and residual nitrite and nitrate concentrations in the water phase indicated active system nitrification. Papyrus showed higher biomass production and nutrient uptake, contributing 28.5% and 11.2%, respectively, of the total N and P removed by the system compared to 15% N and 9.3% P removed by Miscanthidium plants. Compared to literature values, nitrification, plant uptake and the overall system treatment efficiency were high, indicating a high potential of this system for biological nutrient removal from wastewaters in the tropics.

Comparative assessment of the value of papyrus and cocoyams for the restoration of the Nakivubo wetland in Kampala, Uganda

Abstract

Nakivubo wetland, located on the northern shores of Lake Victoria, separates the city of Kampala from the Inner Murchison Bay of Lake Victoria (the sole raw water supply for Kampala). It provides tertiary treatment for the secondary effluent from the Bugolobi sewage treatment works, and heavily polluted wastewater (run-off, domestic and industrial effluents) from the Nakivubo channel. However, more than half of the wetland has been drained for agriculture and the natural papyrus vegetation (Cyperus papyrus) has been progressively replaced by cocoyams (Colocasia esculenta). In order to provide information that could be used in the restoration of Nakivubo wetland, a pilot study was carried out to assess the ecological characteristics (nutrient retention and growth characteristics) of the two plants. The plants were grown in wastewater effluent from the Bugolobi sewage treatment works, in experimental buckets under floating and rooted conditions. The wastewater was replaced every seven days. Papyrus plants were more efficient at removing NH4-N while growing floating in wastewater or rooted in gravel (maximum values being 89.4% and 79%, respectively) than were cocoyams (67.7% and 68.3%) or the controls without plants (11% and 9%, respectively). The removal of orthophosphate by papyrus was also greater under the two growing conditions (values being 80% and 73%) than by cocoyams (66% and 63%) or the controls (11% and 14%). Biomass densities of papyrus were also higher (16.9 kg Dw/m(2) for the floating plants and 18.7 kg Dw/m(2) for the rooted ones) than of yams (5.9 kg DW/m(2) and 6.8 kg DW/m(2), respectively). It was also observed that the rhizomes of yams did not develop well under the floating conditions and were often rotten. It is concluded that, since papyrus has better wastewater treatment efficiency and superior growth characteristics, it should be encouraged to grow again in the wetland. It was also noted that if encroachment of the wetland by agricultural activities is halted, papyrus would eventually out-compete the yams. Keeping Nakivubo wetland inundated would offer papyrus a competitive advantage, since yams grow poorly when floating in water. (c) 2005 Elsevier Ltd. All rights reserved.

The impact of Mpererwe landfill in Kampala – Uganda, on the surrounding environment.

Abstract

Mpererwe landfill site receives solid wastes from the city of Kampala, Uganda. This study was carried out to assess and evaluate the appropriateness of the location and operation of this landfill, to determine the composition of the solid waste dumped at the landfill and the extent of contamination of landfill leachate to the neighbouring environment (water, soil and plants). Field observations and laboratory measurements were carried out to determine the concentration of nutrients, metals and numbers of bacteriological indicators in the landfill leachate. The landfill is not well located as it is close to a residential area (<200 m) and cattle farms. It is also located upstream of a wetland. The landfill generates nuisances like bad odour; there is scattering of waste by scavenger birds, flies and vermin. Industrial and hospital wastes are disposed of at the landfill without pre-treatment. The concentration of variables (nutrients, bacteriological indicators, BOD and heavy metals) in the leachate were higher than those recommended in the National Environment Standards for Discharge of Effluent into Water and on Land. A composite sample that was taken 1500 m down stream indicated that the wetland considerably reduced the concentration of the parameters that were measured except for sulfides. Despite the fact that there was accumulation of metals in the sediments, the concentration has not reached toxic levels to humans. Soil and plant analyses indicated deficiencies of zinc and copper. The concentration of these elements was lowest in the leachate canal.

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Contrasting occurrence of Chromobacterium violaceum in tropical drinking water springs of Uganda.

Abstract

Occurrence of Chromobacterium violaceum in six protected drinking water springs in Uganda was investigated. C. violaceum showed a contrasting occurrence, which was independent of human impact as assessed by faecal pollution indicators. It was isolated from two springs (S1 and S2) that were located close to each other (3 km) but not in the rest. In S1 C. violaceum was continuously detected, in concentrations ranging from 6 to 270 cfu 100 ml21, while in S2 it was detected on only one sampling occasion. C. violaceum was never detected in the investigated upper soil layers (down to 15 cm) in the immediate surroundings (50m radius) of the springs, despite continued isolation of faecal indicators. The results of the study indicate that C. violaceum may not be ubiquitous in spring water, but could occur in significant numbers in particular potable groundwaters as an autochthonous member.

Key words | Chromobacterium violaceum, faecal indicators, protected springs, tropical waters, water quality


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More Articles ...

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  2. Managing Uganda’s forests in the face of uncertainty and competing demands: what is the precautionary approach?
  3. Patterns of crop raiding by primates around the Budongo Forest Uganda
  4. Proceedings of the symposium on alternative approaches to urban market crop wastes management held on July 14, 2005, Hotel Equatoria, Kampala, Uganda.
  5. Differences in basic density and strength properties of Milicia excelsa, Maesopsis eminii, Cynometra alexandri and Celtis gomphophylla from Budongo forest, Uganda.
  6. Relative efficiency of sawmill types operating in softwood plantations in Uganda.
  7. Morphometric and genetic differentiation of two Labeo victorianus populations in Lake Victoria.
  8. Genetic consequences of war and social strife in sub-saharan Africa: the case of Uganda’s large mammals.
  9. Six new polymorphic microsatellite loci Isolated and characterised from the African savannah elephant genome.
  10. Transaction costs analysis of input demand by smallholder cotton producers in Eastern Uganda.
  11. Determinants of demand for purchased fertilisers in Mbale district in Uganda.
  12. Tuber utilisation options among sweet potato producers in eastern Uganda.
  13. Unravelling the genetic diversity of the three main viruses involved in Sweet Potato Virus Disease (SPVD), and its practical implications.
  14. Paterns of Crop Raiding by Primates around the Budongo Forest Reserve Uganda
  15. Patterns of frugivory of the Budongo Forest chimpanzees, Uganda

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