Browsing by Funder "African Development Bank (AfDB)"

Now showing 1 - 4 of 4
  • Publication
    Publication
    A Test of the Applicability of the Lake Habitat Survey for Hydromorphological Monitoring of a Tropical Alkaline Lake (Simbi) with a Fisheries Potential
    (International Journal of Fisheries and Aquatic Studies, 2019-09) Opiyo, Stephen; Getabu, Albert Mochache; Sitoki, Lewis Morara; Shitandi, Anakalo
    The Lake Habitat Survey (LHS) is an ecological integrity monitoring tool developed for temperate lakes by an independent team of researchers to support the implementation of the EU Water Framework Directive (WFD). It has been widely applied but more testing is needed in different settings, therefore this study investigated the applicability of the LHS protocol in assessing the habitat quality of a tropical alkaline lake in the face of increasing impacts of anthropogenic pressure and climate change. The LHS metrics of Lake Habitat Quality Assessment (LHQA) and Lake Habitat Modification Score (LHMS) estimated for Lake Simbi collectively suggested that the physical habitat quality of the lake is moderate since its hydromorphology is moderately modified. In conclusion, LHS is effective for monitoring ecological condition of water bodies to inform decision making for conservation and management hence it is suitable for adoption in Kenya and the tropics as one of the standard tools for lake environmental assessments.
  • Publication
    Publication
    Analysis of spatial and temporal drought variability in a tropical river basin using Palmer Drought Severity Index (PDSI)
    (Acadamic Journals, 2017-08-31) Wambua, Raphael; Mutua, Benedict; Raude, James
    Analysis of spatial and temporal drought variability in the upper Tana River basin using Palmer Drought Severity Index (PDSI) was conducted. The drought is critical for formulation of mitigation measures in the river basin. A monthly temporal and 90-m spatial resolution was applied. This was achieved within ArcGIS environment. Climatic data for 1970 to 2010 was used for computation of the PDSI while the missing data sets were filled using Artificial Neural Networks (ANNs). The results of PDSI for dry and wet seasons at meteorological stations indicate that the time series plots for the PDSI values for dry season are generally lower than those for the wet seasons. The PDSI values for meteorological stations located at the lower elevation of the basin are lower than those located at higher elevation. On the other hand, spatially distributed drought severity based on PDSI show that the ranges of maximum and minimum drought severity values in 1970 are -0.868 to -0.804 and -0.675 to -0.610 respectively. These values of drought severity occur respectively in the north-western and south-eastern areas of the basin. PDSI values increased from the range -0.675 to -0.610 in 1970 and from -1.087 to 0.957 in 2010 for the north-eastern areas of the upper basin. The south eastern areas of the basin are more prone to drought risks than north-western parts. Use of the PDSI reflects the spatial heterogeneity and temporal variability of drought across the basin. The drought assessment offer technical approach for comprehensive understanding of drought for effective drought-induced disaster mitigation and its management, with a view to reducing adverse effects on livelihoods.
  • Publication
    Publication
    Application of the Carlson’s Trophic State Index for the Assessment of Trophic Status of Lake Simbi Ecosystem, a Deep Alkaline-Saline Lake in Kenya
    (International Journal of Fisheries and Aquatic Studies, 2019-08) Opiyo, Stephen; Getabu, Albert Mochache; Sitoki, Lewis Morara; Shitandi, Anakalo; Ogendi, George Mokua
    Eutrophication is increasingly becoming the greatest threat to the ecological health of global water resources hence constant screening of the trophic state of these ecosystems is important. This study was aimed at defining the trophic status of Lake Simbi through the Carlson’s Trophic State Index (CTSI) which is based on the interactions of three water quality variables viz., Secchi depth (SD), total phosphorus (TP) and the chlorophyll-a (Chl-a). The classification scale for Trophic State Index (TSI) runs from 0 to 100, and the results of this study showed that the mean TSI for SD was 67.60, for TP was 118.56, for Chl-a was 74.86 and finally the overall CTSI was 87.01. These show that Lake Simbi is hypereutrophic which reflects the high concentration of nutrients in the lake. The lake suffers from cultural eutrophication which symptomatically manifests in the prevalent proliferation of algal bloom in the lake. The study therefore recommends adoption of an efficient multi-sectoral plan for monitoring and controlling nutrients loading and other pollutants input into the lake.
  • Publication
    Publication
    Assessment of the Temporal and Spatial Variability in the Phytoplankton Dynamics of a Tropical Alkaline-saline Lake Simbi, Kenya
    (International Research Journal of Environmental Sciences, 2020-10-22) Opiyo, Stephen
    This study evaluated the phytoplankton dynamics of abundance, species composition and diversity across spatial and temporal scales in Lake Simbi for the period between December 2018 and May 2019. This was necessary, considering the significance of phytoplankton communities in this lake for conservation and ecological role. Sampling was done on a monthly basis for 6 months at six fixed stations systematically selected. A total of 84 phytoplankton species were identified comprising of Cyanophyceae (36 species), Chlorophyceae (25 species), Bacillariophyceae (11 species), Zygnematophyceae (4 species), Dinophyceae (3 species) and Euglenophyceae (3 species). Although, the Cyanophyceae family still dominated in Lake Simbi, a shift in the species composition was realized and this can be probably attributed to the changes in the water quality regime of the lake. The results showed a high phytoplankton density in the lake due to its eutrophic nature. However, reduced abundance of the cyanobacterial species, especially Spirulinaspecies on which flamingos feed and the subsequent dominance of the toxin producing Microcystis species might have contributed to the decline of the flamingo population. All the phytoplankton characteristics of density and diversity indices evaluated in Lake Simbi exhibited no significant spatial and temporal variations. Generally, activities that help to improve and maintain ecosystem integrity need to beadopted by all stakeholders to promote sustainability of all aquatic resources in Lake Simbi.