Browsing by Author "Ogendi, George"

Now showing 1 - 5 of 5
  • Publication
    Publication
    Can Sanitary Surveys Replace Water Quality Testing? Evidence from Kisii, Kenya
    (MDPI, 2017-02-07) Misati, Aaron Gichaba; Ogendi, George; Peletz, Rachel; Khush, Ranjiv; Kumpel, Emily
    Information about the quality of rural drinking water sources can be used to manage their safety and mitigate risks to health. Sanitary surveys, which are observational checklists to assess hazards present at water sources, are simpler to conduct than microbial tests. We assessed whether sanitary survey results were associated with measured indicator bacteria levels in rural drinking water sources in Kisii Central, Kenya. Overall, thermotolerant coliform (TTC) levels were high: all of the samples from the 20 tested dug wells, almost all (95%) of the samples from the 25 tested springs, and 61% of the samples from the 16 tested rainwater harvesting systems were contaminated with TTC. There were no significant associations between TTC levels and overall sanitary survey scores or their individual components. Contamination by TTC was associated with source type (dug wells and springs were more contaminated than rainwater systems). While sanitary surveys cannot be substituted for microbial water quality results in this context, they could be used to identify potential hazards and contribute to a comprehensive risk management approach.
  • Publication
    Publication
    Characteristic Relationships between Phosphorous Accrual, Ecosystem Aspects and Water Level Fluctuations in Tropical Lakes: Naivasha Ramsar Site, Kenya
    (Scientific Research, 2021-01) Obegi, Beatrice; Ogendi, George; Omondi, Reuben; Jomo, Boston; Morara, George; Rindoria, Nehemiah; Orina, Sagwe
    Hydrological dynamics affect water levels and thus affecting ecosystem structure and functions. Lake levels in tropical ecosystems affect phosphorous input through runoff from adjacent watersheds. The resultant biological community, water and sediment quality of the lakes due to water level changes is a reflection of the geology of the area and the anthropogenic activities in the watershed. The study conducted between January 2018 and December 2019 was to explore relationships between the phosphorous input and Water Level Fluctuations (WLF) recorded by Water Resource Authority (WRA). Lake water samples were analyzed in the laboratory for phosphorous using molybdenum blue-ascorbic method and recorded using spectrophotometer. Chlorophyll-a was determined by extracting a filtered sample with 15 ml acetone and incubating overnight and thereafter read using a double beam spectrophotometer. Total Suspended Solids (TSS) was determined by filtering 200 ml of a water sample and dried overnight at 105°C. The lowest and highest phosphorous concentrations recorded were 0.2 mg/l and 0.42 mg/l at NST7 and NST2, respectively. Measurements of Chlorophyll-a were 0.32 mg/l and 0.42 mg/l at NST9 and NST2, respectively. Secchi transparency measurements were 32.9 cm at NST3 and 84 cm at NST1. The highest and lowest TSS concentrations were 0.14 mg/l and 0.13 mg/l at NTS1 and NST8, respectively. The hydrodynamic regime in most tropical lakes plays a significant role in the re-reaction of phosphorous that consequently influences productivity. Tropical lakes have extreme lake level fluctuations which accelerate the production process. The influence of water level changes on aquatic productivity is crucial in most tropical lakes and should be taken into consideration when assessing the environmental impacts.
  • Publication
    Publication
    Groundwater Resource Mapping through the Integration of Geology, Remote Sensing, Geographical Information Systems and Borehole Data in Arid-Subarid Lands at Turkana South Sub-County, Kenya
    (2019) Nyaberi, Daniel; Barongo, Justus; Kariuki, Patrick; Ogendi, George; Basweti, Evans
    The integrated approach of various techniques which historically have been used independently is key to successful exploration, development, exploitation and management of the groundwater resources. The integration of Remote Sensing (RS), Geographical Information Systems (GIS) and Borehole data has been used in the study area to assess their applicability in groundwater investigation. The area of study lies in the arid and semi-arid lands (ASALs) where principally remote sensing data has been used in extraction of various thematic maps (lithology, lineament, drainage density, and Digital Elevation Model Maps) for groundwater assessment. The GIS platform was used in integrating the RS data and data of productive boreholes. The lineaments generated through remote sensing agree well with structural geology of the area, where high density lineament points overlays the points of intense faulting. Lineaments found in the area correlate well with fault zones, fractures, and lithological contrasts as supported by geological map and structural map. Weathering, faulting and fracturing of the rocks mean a possible increase or a reduction in specific capacities as observed in productive boreholes in sedimentary rocks or igneous/basaltic rocks of the area. Similarly, it is noted that the degree of faulting affects the degree of radius of influence of a borehole in a particular area. These analyses show that groundwater potential within the Sub-County varies spatially with high dependency on geological structures in the basement region and more on geology within the volcanic and younger sediments.
  • Publication
    Publication
    Groundwater Resource Mapping through the Integration of Geology, Remote Sensing, Geographical Information Systems and Borehole Data in Arid-Subarid Lands at Turkana South Sub-County, Kenya
    (Scienctific Reseach, 2019-12-16) Nyaberi, Daniel; Barongo, Justus; Kariuki, Patrick; Ogendi, George; Basweti, Evans
    The integrated approach of various techniques which historically have been used independently is key to successful exploration, development, exploitation and management of the groundwater resources. The integration of Remote Sensing (RS), Geographical Information Systems (GIS) and Borehole data has been used in the study area to assess their applicability in groundwater investigation. The area of study lies in the arid and semi-arid lands (ASALs) where principally remote sensing data has been used in extraction of various thematic maps (lithology, lineament, drainage density, and Digital Elevation Model Maps) for groundwater assessment. The GIS platform was used in integrating the RS data and data of productive boreholes. The lineaments generated through remote sensing agree well with structural geology of the area, where high density lineament points overlays the points of intense faulting. Lineaments found in the area correlate well with fault zones, fractures, and lithological contrasts as supported by geological map and structural map. Weathering, faulting and fracturing of the rocks mean a possible increase or a reduction in specific capacities as observed in productive boreholes in sedimentary rocks or igneous/basaltic rocks of the area. Similarly, it is noted that the degree of faulting affects the degree of radius of influence of a borehole in a particular area. These analyses show that groundwater potential within the Sub-County varies spatially with high dependency on geological structures in the basement region and more on geology within the volcanic and younger sediments.
  • Publication
    Publication
    Organochlorine Contaminants in Nile Tilapia, Oreochromis niloticus (Linnaeus 1758) in Densely Populated Areas of South-Western Kenya
    (2020) Nyaundi, Joseph; Getabu, Albert; Mwamburi, Job; Onchieku, James; Kinaro, Zachary; Ogendi, George; Babu, Miruka; Gichuru, Nicholas
    Concentrations of OCP (Organochlorine Pesticide) residues were determined in cultured Nile tilapia (Oreochromis niloticus) fish in target stations within 1st order wetland of River Kuja, Kenya, between February-November, 2017. The aim was to assess the residue levels in wild and pond cultured fish within a heavily populated agricultural area of South Western Kenya. Biota samples were analysed for selected HCHs (Hexachlorocyclohexane) isomers, DDT (Dichlorodiphenyltrichloroethane) and metabolites and cyclodienes pesticide residues using GC-ECD (Gas Chromatography Equipped with Electron Capture Detector). Most of OCPs observed were BDL (Below Detection Limit) to detectable levels. Larger percentages (> 50%) of DDTs and HCHs were BDL and exhibited consistency, with significant (p < 0.05) differences in mean contamination levels in fish within the wetland, with average muscle tissue pesticides concentrate ranging between 0.229-2.541 g/kg for Nile tilapia. Most dominant isomer in target species was Lindane (-HCH) (3.417 ± 0.983 g/kg) and Endosulfans. Mean Endosulfan sulfate was 2.499 ± 0.071 g/kg d.w. and most frequently detected, and Methoxychlor (2.235 ± 1.459 g/kg), respectively. Mean Aldrin and Dieldrin was 2.028 and 0.574 g/kg d.w. Concentration for DDT and its metabolites was 0.27-3.71 g/kg for p, p’-DDE (DichlorodiphenylDichloroEthene), BDL-1.098 for p, p’-DDD (DichloroDiphenylDichloroEthane), and 0.105-3.518 g/kg for p, p’-DDT with significant differences in mean values and ranges whose levels were below the WHO (World Health Organization) maximum acceptable thresholds of 0.2, 2, 20 and 5.0 g/kg in fish and sea food.