Browsing by Author "Charles, Onyutha"

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Abating eutrophication on urban lakes: a case study of Kabaka's Lake, Uganda
(IWA Publishing Water Practice & Technology, 2023-07) Anne, Nakagiri; Abel, Mutyaba; Charles, Onyutha; Kenan, Okurut
Eutrophication of water bodies is a challenge in many urban areas. This study measured and modelled quantitatively the pollutant nutrient load of an urban lake (80,596 m2), and assessed both external (constructed wetland) and internal (dredging) eutrophication extenuation measures. For the past 25 years, there has been redistribution (p < 0.005) of the lake's catchment land use, with built-up area increasing by 78.5%, and a reduction in vegetated (37.2%) and water surface (1.8%) areas. A 92.2% reduction in the lakes receiving wetland footprint (p = 0.000003) was noted, with increased nutrient load. The lake's light attenuation was found to be dominated by algae, limited by nitrogen and classified under the oligotrophic class (Trophic State Index < 40), with a threat of eutrophication in an estimated 25 years. Scenario analyses show that the construction of a wetland in the remaining 0.54 hectares of natural wetland will reduce total phosphorus by 35% and total nitrate by 45% (p = 0.05), whereas dredging the lake could reduce them by 80% each (p = 0.0005). Watershed management is the only sustainable solution to control nutrient flow into the lake and enable self-cleansing, factoring in the design of the receiving wetland and groundwater sources.
Changes in extreme precipitation over Mpologoma catchment in Uganda, East Africa
(Heliyon, 2023-02-17) Ambrose, Mubialiwo; Adane, Abebe; Charles, Onyutha
Changes of five Extreme Precipitation Indices (EPIs) over Mpologoma catchment were examined. The EPIs were obtained from the long-term (1948–2016) gridded (0.25◦ × 0.25◦ ) Princeton Global Forcing (PGF) daily precipitation dataset. The number of days with precipitation intensity greater than 5 mm/day (NWD5) and 10 mm/day (NWD10) were part of the five EPIs. Trend and variability analyses were by the nonparametric technique based on the cumulative sum of the difference between exceedance and non-exceedance counts of data. The simple multiplicative bias correction method was employed to bias correct the PGF dataset using observed rainfall from nine weather stations. The number of wet days were decreasing although insignificant (p > 0.05). On the other hand, the annual total precipitation considering days with rainfall intensities greater than 5 mm/day (SPre5) exhibited a significant (p < 0.05) decrease. However, annual maxima rainfall (ANMS) increased even though insignificant. This indicates that less frequent rains are received over the study area but some events having high intensity. The insights from the findings of this study constitute a good baseline for predictive planning of water resources management applications across Mpologoma catchment.
Contributions of human activities and climatic variability to changes in river Rwizi flows in Uganda, East Africa
(MDPI, 2021-09) Charles, Onyutha; Resty, Nyesigire; Anne, Nakagiri
This study employed Soil and Water Assessment Tool (SWAT) to analyze the impacts of climate variability and human activities on River Rwizi flows. Changes in land use and land cover (LULC) types from 1997 to 2019 were characterized using remotely sensed images retrieved from Landsat ETM/TM satellites. SWAT was calibrated and validated over the periods 2002–2008 and 2009–2013, respectively. Correlation between rainfall and river flow was analyzed. By keeping the optimal values of model parameters fixed while varying the LULC maps, differences in the modeled flows were taken to reflect the impacts of LULC changes on rainfall–runoff generation. Impacts due to human activities included contributions from changes in LULC types and the rates of water abstracted from the river as a percentage of the observed flow. Climate variability was considered in terms of changes in climatic variables such as rainfall and evapotranspiration, among others. Variability of rainfall was analyzed with respect to changes in large-scale ocean-atmosphere conditions. From 2000 to 2014, the portion of River Rwizi catchment area covered by cropland increased from 23.0% to 51.6%, grassland reduced from 63.3% to 37.8%, and wetland decreased from 8.1% to 4.7%. Nash–Sutcliffe Efficiency values for calibration and validation were 0.60 and 0.71, respectively. Contributions of human activities to monthly river flow changes varied from 2.3% to 23.5%. Impacts of human activities on the river flow were on average found to be larger during the dry (14.7%) than wet (5.8%) season. Using rainfall, 20.9% of the total river flow variance was explained. However, climate variability contributed 73% of the river flow changes. Rainfall was positively and negatively correlated with Indian Ocean Dipole (IOD) and Niño 3, respectively. The largest percentages of the total rainfall variance explained by IOD and Niño 3 were 12.7% and 9.8%, respectively. The magnitude of the correlation between rainfall and IOD decreased with increasing lag in time. These findings are relevant for developing River Rwizi catchment management plans.
“Here, your only relative is money…” why slum social networks do not facilitate neighborhood community development: insights through a sanitation lens
(BMC Public Health, 2023-11) Japheth, Nkiriyehe Kwiringira; Joseph, Rujumba; Paulino, Ariho; James, Mugisha; Henry, Zakumumpa; Liz, Perry Mohlin; Mathias, Akugizibwe; Innocent, Kamara Tumwebaze; Charles, Onyutha
Introduction Though social networks which are deemed vehicles of community development exist in slum areas, underdevelopment still persists in these areas. We explored the nature and role of social networks in facilitating community development in the slums of Kampala through a sanitation lens. Methods Qualitative Social Network Analysis (SNA) was done to understand the nature of slum social networks primarily through the analysis of sanitation behavior. Data were collected through six Focus Group Discussions (FGD), six In-depth Interviews (IDIs), and 18 Key Informant Interviews (KII) with Government, civil society and private stakeholders. We used both inductive and deductive thematic analysis. Results Four themes emerged in our analysis; i); Unsupportive environments, uncooperative neighbours and uncertainty of tenure: participants reported slums as unsupportive of community development due to a shortage of space, poverty and unplanned services. Tenants perceived landlords as exploitative and predatory and wished the tables are turned. This notion of cyclic exploitation did not encourage collective action for community good. Short-term economic survival trumped long-term community interests ii) Patronage and poor service delivery: varying degrees of patronage led to multiple forms of illegalities and violations such as tax evasion. Due to vested interests and corruption among public officials, the slum population was lethargic. iii) Intersecting realities of poverty and unemployment: slum dwellers lived on the margins daily. Hence, poor living conditions were a secondary concern. iv) Social relations for personal development: Slum social networks were driven by individual interests rather than community good. Slum dwellers prioritized connections with people of common socio-economic interests. As such social networks were instrumental only if they ‘added value’. Conclusion Social networks in slums are only concerned about survival needs. Slums require responses that address the complexity of slum formation and broader livelihood challenges, as well as re-assessing the meaning of community. We posit that more needs to be done in understanding the meaning and workings of a sociology beyond physical societies. Poverty is a modifier of social systems and processes and should be a concern for all stakeholders involved in slum development.
Improving household water treatment: using zeolite to remove lead, fluoride and arsenic following optimized turbidity reduction in slow sand filtration
(Sustainable Environment Research, 2024-03) Charles, Onyutha; Emmanuel, Okello; Rebecca, Atukwase; Pamella, Nduhukiire; Michael, Ecodu; Japheth, Nkiriyehe Kwiringira
Despite the United Nations 2030 agenda, large number of both urban and rural dwellers in low-income countries continue to lack access to improved water. Thus, increased effort is required towards enhancing low-cost drinking water treatment technologies especially for developing countries. Slow sand filter (SSF) is one of the most commonly used low-cost and efficient technologies for treating household drinking water. However, effectiveness of SSF is sub- stantially affected by very high turbidity and relatively large amounts of dissolved heavy metals. To enhance removal of both turbidity and heavy metals, this study optimized sand bed depth (SBD) of SSF and investigated the potential of natural zeolite from Uganda for removal of lead, arsenite (As(III)) and fluoride ions from water. To remove lead ions, the zeolite was used in its natural form. However, to remove As(III) and fluoride, the natural zeolite was modified using hexadecyltrimethylammonium bromide solution. Removal of high turbidity was found to require a large optimal SBD. Furthermore, efficiency of treating synthetic turbid water increased with increasing initial turbidity. Variation of final turbidity with SBD was found to be best described by an exponential function. Optimal SBDs on top of an underdrain gravel layer of 0.2 m were 453, 522, 561, and 580 mm for turbidity of 60, 80, 100, and 120 NTU, respectively. Opti- mized SBD used achieve at least 95% efficiency in removing suspended particles from water with turbidity 120 NTU was found to save up to 35% of the total cost for acquiring sand volume required by a conventional SSF. For a par- ticular zeolite mass, removal efficiencies of lead, As(III) and fluoride generally increased with increasing contact time. Removal efficiencies of lead, As(III), and fluorides were also shown to increase with increasing zeolite mass. Lead removal efficiencies using natural zeolite were 75 and 98% under 20 and 40 min, respectively. Removal of As(III) using modified zeolite mass was 91% within contact time of 10 min. Adsorption of fluoride on modified zeolite was 80% within 5 min. Adsorption of lead, As(III), and fluorides indicated promising potential of natural zeolites from Uganda for treating polluted water.
Influence of physical and water quality parameters on residual chlorine decay in water distribution network
(Heliyon, 2024-05-07) Julius, Caesar Kwio-Tamale; Charles, Onyutha
Chlorine is the most common disinfectant in drinking water distribution practice. World Health Organization recommends 0.2–5.0 mg/l of residual chlorine in drinking water. This paper analyzed influence of physical and water quality parameters on chlorine decay in drinking water distribution. Principal component analysis, directed tree and regression were used to investigate influence of these parameters on chlorine from water treatment plant to water consumption points. Results show that initial chlorine, electrical conductivity and distance explain 62 % of chlorine decay with estimated error of 0.045 mg/l. The decision-tree feature importance scores of initial chlorine and electrical conductivity were 0.47 and 0.23 respectively. The combined feature importance scores of physical parameters of distance (0.09), pipe diameter (0.06), flow velocity (0.03), pressure (0.02) and travel time (0.046) were less than that for initial chlorine concen- tration (0.47) alone. These results show that conventional chlorination at water treatment plants removes largely fast inorganic reactants leaving traces of slow organic reactants as the dominant secondary contaminants in water distribution system. The key policy recommendation is to use water quality parameters more than physical parameters in order to enable water utility man- agers maintain residual chlorine within safe public health standards.