Sedimentation Status of Lake Victoria: Loading from River Mouth and In-lake Sedimentation

Lake sediments consist of the input of suspended solids by river discharges, the autochthonous produced particulate matter in the water column and the settled material on the lake bottom. The loading, transport, formation and decay of the sediments entering the Lake Victoria from Tanzanian side was monitored for the period 2000 to 2005. The sedimentation study focused on; quantification of settling fluxes of particulate nutrients and organic carbon at the off-shore(Pelagic) and near-shore(Littoral) monitoring stations. Monitored data on sedimentation rate and settling velocities has been sampled and analysed in the period November 2000 to March 2005. The mean sedimentation rate at littoral stations for total particulate phosphorous (TPP) was about twice as compared to pelagic stations. The same situation was observed for total particulate carbon (TPC), however, total particulate silica did not show a clear pattern of variability between littoral and pelagic stations though there was a general tendency of decreasing towards the pelagic stations. Mean value for TPC /TPP sedimentation rate ratio was 117.61 for littoral and 90.74 for pelagic stations respectively compared to TBSi/TPP which was 3.15 for littoral and 2.10 for pelagic stations. The results show that sedimentation rates are highest at the littoral stations compared to pelagic stations. The differences in settling velocities indicate that the settling material consists dead and living material with a contribution of diatoms. The stoichiometriccomposition of the settling material indicates nitrogen limitation and a non-dominance of diatoms

A synthesis of past, current and future research for protection and management of papyrus (Cyperus papyrus L.) wetlands in Africa

Papyrus wetlands (dominated by the giant sedge Cyperus papyrus L.) occur throughout eastern, central and southern Africa and are important for biodiversity, for water quality and quantity regulation and for the livelihoods of millions of people. To draw attention to the importance of papyrus wetlands, a special session entitled ‘‘The ecology of livelihoods in papyrus wetlands’’ was organized at the 9th INTECOL Wetlands Conference in Orlando, Florida in June 2012. Papers from the session, combined with additional contributions, were collected in a special issue of Wetlands Ecology and Management. The current paper reviews ecological and hydrological characteristics of papyrus wetlands, summarizes their ecosystem services and sustainable use, provides an overview of papyrus research to date, and looks at policy development for papyrus wetlands. Based on this review, the paper provides a synthesis of research and policy priorities for papyrus wetlands and introduces the contributions in the special issue. Main conclusions are that (1) there is a need for better estimates of the area covered by papyrus wetlands. Limited evidence suggests that the loss of papyrus wetlands is rapid in some areas; (2) there is a need for a better understanding and modelling of the regulating services of papyrus wetlands to support trade-off analysis and improve economic valuation; (3) research on papyrus wetlands should include assessment of all ecosystem services (provisioning, regulating, habitat, cultural) so that trade-offs can be determined as the basis for sustainable management strategies (‘wise use’); (4) more research on the governance, institutional and socio-economic aspects of papyrus wetlands is needed to assist African governments in dealing with the challenges of conserving wetlands in the face of growing food security needs and climate change. The papers in the special issue address a number of these issues

A Conceptual approach to water resources Management for a catchment in Tanzania

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Integrated hydrological modelling of wetlands for environmental management: the case of the Usangu wetlands in the Great Ruaha catchment

Paper presented at the East Africa Integrated River Basin Management Conference, Sokoine University of Agriculture, Morogoro, Tanzania, 7-9 March 2005. [Vol.1]. Funded by IWMI, and other

Distribution and enrichment of trace metals in benthic, estuarine sediments: Southport Broadwater, Australia

The distribution and enrichment of selected trace metals (Cd, Cr, Cu, Ni, Pb, Sn, Zn) in benthic sediments of the Southport Broadwater, a semi-enclosed coastal body of water adjacent to the Gold Coast city, south-eastern Queensland, Australia, was studied with the objective of assessing the extent and degree of sediment contamination. Sediment samples from the 0–10 cm and 10–20 cm depth intervals of 32 sites within the Southport Broadwater and surrounding residential canals were analysed for particle size distribution, pH, organic C and ‘near-total’ major (Al, Ca, Fe, Mn) and trace (Cd, Cr, Cu, Ni, Pb, Sn, Zn) metal contents. Sediment contamination for each trace metal was assessed by (1) comparison with Australian sediment quality guidelines, (2) calculation of the index of geoaccumulation based on regional background values, and (3) geochemical normalisation against Al (i.e. the abundance of alumino-silicate clay minerals). Based on this approach, the results indicate that submerged sediments in the study area are not presently enriched with Cd, Cr or Ni, with the spatial distribution of these metals being very well explained by the abundance of alumino-silicate clay minerals. However, several sites were strongly enriched with Cu, Pb, Sn and Zn, arising from sources related to either urban runoff or vessel maintenance activities. The study indicates that several varying approaches are needed for a satisfactory assessment of contaminant enrichment in estuarine sediments