Journal Articles

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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.
An advanced continuum damage mechanics model for predicting the crack progress process based on the consideration of the influence of crack direction under quasi-static load
(Elsevier: International Journal of Mechanical Sciences., 2017-09) Yun, Kumchol; Wang, Zhenqing; Ronald, Sakaya; Pak, Yongchol
In reality the wrong crack path can be generally obtained in the case of arbitrary crack propagation by traditional continuum damage mechanics (CDM). In this paper a novel advanced continuum damage mechanics (ACDM) method is proposed, which can predict the crack propagation and fracture behavior correctly for the structures. The material property degradation method, which is usually used when simulating the structures within the framework of CDM, is advanced based on considering the influence of crack direction. The maximum tensile stress criterion is used to predict the damage initiation and crack propagation direction and the advanced CDM used to predict the damage evolution process in meso-level under the quasi-static load. It can directly evaluate the propagation process of the discrete crack and the fracture strength for structures using the continuum model as well as not using discontinuum model. The algorithm for the application of our advanced CDM theory in the numerical simulation based on finite element method (FEM) is presented. ACDM model is not only a simple and useful model which can easily be used in FEM framework but also a phenomenological model based on the concept of crack propagation. The simulation results by our ACDM are compared with the experiment results and the ones and from cohesive zone method and extended finite element method for good agreements to be achieved.
African food insecurity in a changing climate: the roles of science and policy
(Wiley Online Library: Food and Energy Security, 2018-12-12) Onyutha, Charles
African population is projected to double to 2.48 billion people by 2050. The population increase poses a serious challenge of increasing food supply to meet the future demand. This challenge is compounded by climate change impacts on agriculture. In this paper, how poverty contributes to household food insecurity is explored and measures suggested to help address this challenge. To plan adaptation measures, linkages among food insecurity, poverty, and illiteracy should be considered. For the sub-Saharan Africa (SSA), adaptation (focused on poverty alleviation) should be prioritized and preferred to mitigation. Enhancement of adaptive capacity should not only be tailored toward empowerment of women but also made highly localized to household levels. Generally, efforts could be geared toward yield gap closure, addressing challenges regarding food distribution, promoting non-farm income-generating activities, and unification of government priorities in agriculture and food security. Government in each country of the SSA should ensure that governance strongly embraces transparency, accountability, and integrity otherwise as it is said a fish rots from the head down. Estimates of uncertainty in predicting future climate and their implications on expenditure related to adaptation should to always be made in an integrated way and reported to support actionable policies. To increase credibility in climate prediction especially at local scales, advances toward improving climate models (for instance by refining spatiotemporal scales, enhancing models’ capacity to reproduce observed natural variability in key climatological variables like rainfall) should be made, and this requires support from the investment in climate science. Science–policy interfacing is required in planning and implementation of measures for adapting to climate change impacts. In summary, food insecurity and persistent poverty especially in the SSA should be of direct relevance and concern at a global scale. Thus, global collaboration in science is key to achieve food security in the SSA.
Amplification of compound hot-dry extremes and associated population exposure over East Africa
(Climatic Change, 2024-09-09) Ayugi, Brian Odhiambo; Onyutha, Charles; Zhu, Huanhuan; Babousmail, Hassen; Chung, Eun-Sung; Sian, Kenny Thiam Choy Lim Kam
Quantifying the vulnerability of population to multi-faceted climate change impacts on human well-being remains an urgent task. Recently, weather and climate extremes have evolved into bivariate events that heighten climate risks in unexpected ways. To investigate the potential impacts of climate extremes, this study analyzes the frequency, magnitude, and severity of observed and future compound hot-dry extremes (CHDEs) over East Africa. The CHDE events were computed from the observed precipitation and maximum temperature data of the Climatic Research Unit gridded Timeseries version five (CRU TS4.05) and outputs of climate models of Coupled Model Intercomparison Project Phase 6 (CMIP6). In addition, this study quantifies the population exposure to CHDE events based on future population density datasets under two Shared Socioeconomic Pathways (SSPs). Using the 75th/90th and 25th/10th percentile of precipitation and temperature as threshold to define severe and moderate events, the results show that the East African region experienced multiple moderate and severe CHDE events during the last twenty years. Based on a weighted multi-model ensemble, projections indicate that under the SSP5-8.5 scenario, the frequency of moderate CHDE will double, and severe CHDE will be 1.6 times that of baseline (i.e., an increase of 60%). Strong evidence of an upward trajectory is noted after 2080 for both moderate and severe CHDE. Southern parts of Tanzania and northeastern Kenya are likely to be the most affected, with all models agreeing (signal-to-noise ratio, SNR > 1), indicating a likely higher magnitude of change during the mid- and far-future. Consequentially, population exposure to these impacts is projected to increase by up to 60% for moderate and severe CHDEs in parts of southern Tanzania. Attribution analysis highlights that climate change is the primary driver of CHDE exposure under the two emission pathways. The current study underscores the urgent need to reduce CO2 emissions to prevent exceeding global warming thresholds and to develop regional adaptation measures.
Analyses of precipitation and evapotranspiration changes across the lake Kyoga basin in East Africa
(MDPI: Water, 2020-04-16) Onyutha, Charles; Acayo, Grace; Nyende, Jacob
This study analyzed changes in CenTrends gridded precipitation (1961–2015) and Potential Evapotranspiration (PET; 1961–2008) across the Lake Kyoga Basin (LKB). PET was computed from gridded temperature of the Princeton Global Forcings. Correlation between precipitation or PET and climate indices was analyzed. PET in the Eastern LKB exhibited an increase (p > 0.05). March–April–May precipitation decreased (p > 0.05) in most parts of the LKB. However, September–October–November (SON) precipitation generally exhibited a positive trend. Rates of increase in the SON precipitation were higher in the Eastern part where Mt. Elgon is located than at other locations. Record shows that Bududa district at the foot of Mt. Elgon experienced a total of 8, 5, and 6 landslides over the periods 1818–1959, 1960–2009, and 2010–2019, respectively. It is highly probable that these landslides have recently become more frequent than in the past due to the increasing precipitation. The largest amounts of variance in annual precipitation (38.9%) and PET (41.2%) were found to be explained by the Indian Ocean Dipole. These were followed by precipitation (17.9%) and PET (21.9%) variance explained by the Atlantic multidecadal oscillation, and North Atlantic oscillation, respectively. These findings are vital for predictive adaptation to the impacts of climate variability on water resources.
Application of black soldier fly larvae in decentralized treatment of faecal sludge from pit latrines in informal settlements in Kampala city
(Frontiers in Environmental Science, 2023-02) Richard, Tokwaro; Swaib, Semiyaga; Charles, B. Niwagaba; Anne, Nakagiri; Jotham, Ivan Sempewo; Chimdi, Muoghalu; Musa, Manga
Introduction: Faecal sludge management (FSM) in urban areas of low-and middle-income countries (LMICs) is not properly implemented due to inaccessibility of sanitation facilities and high faecal sludge (FS) emptying costs, amongst others. Unlike in solid waste and fresh human excreta, use of black soldier fly larvae (BSFL) in treatment of FS from pit latrines - which are the most common sanitation facilities in urban areas of LMICs - has not yet been explored. Moreover, the optimal conditions for efficient FS degradation, such as moisture content, feeding rate and larval density are not yet well known. Against this backdrop, the overarching aim of this study was to determine the effectiveness of BSFL in treating FS under different conditions of moisture content, feeding rate and larval density. Also, the quality of residue left after treatment was assessed. Methods: FS samples were collected from lined and unlined pit latrines in Bwaise I parish in Kampala, Uganda and experiments were set up to feed 10-day old larvae. Results and Discussion: The optimum feeding rate, larval density and moisture content were found to be 50 mg/larvae/day, 1.33 larvae/cm2 and 60%, respectively. The reduction efficiency at optimum conditions were 72% and 66% for FS from lined and unlined pit latrines, respectively. It was further noted that BSFL can feed on FS from pit latrines without dewatering it, hence there is no need for a dewatering unit. The properties of the residue left after treatment were within the allowable limit for use as compost except for helminth egg concentration. Thus, in informal urban settlements, BSFL can be applied for effective treatment of FS from pit latrines while generating good quality residue thereby providing an additional value chain in FSM.
An assessment of the impact of construction activities on the environment in Uganda: a case Study of Iganga Municipality
(Journal of Construction Engineering and Project Management., 2012-11-15) Muhwezi, Lawrence; Kiberu, Faisal; Kyakula, Michael; Batambuze, Alex O.
Construction while being an economic activity that provides facilities and infrastructure, it is beneficial to man in some aspects and detrimental in others. There have been environmental concerns related to construction activities globally which mainly focus on atmospheric emissions, depletion of natural resources and energy issues. This study was carried out to assess the impacts of construction activities on the environment in Iganga Municipality and to propose measures for their mitigation. The methodology included: review of relevant literature, observations of the general environmental effects of construction activities, focus groups and a survey conducted among construction industry role players to determine their perceptions and opinions regarding environmental impact of construction activities. The collected data was presented in tabular form and analysed by description of responses to questions. The study revealed that forests were the most greatly degraded due to high demand of timber for construction followed by wetlands degradation. The findings of this study will be useful to architects, designers and builders in order to carefully design buildings and other infrastructure that are environmentally friendly and sustainable. Construction materials and their mode of acquisition are harmful threats to the environment. There is need to reduce the consumption of these materials through recycling and reusing wastes to reduce on waste generation, use of virgin materials and the subsequent waste of energy used in new material production.
Biochar as a novel technology for treatment of onsite domestic wastewater : A critical review
(Frontiers in Environmental Science, 2023-02) Chimdi, Muoghalu; Prosper, Achaw Owusu; Sarah, Lebu; Anne, Nakagiri; Swaib, Semiyaga; Oliver, Terna Iorhemen; Musa, Manga
Globally, about 2.7 billion people depend on onsite sanitation systems (OSS) (e.g., septic tanks) for their sanitation needs. Although onsite sanitation systems help in providing primary treatment for domestic wastewater, they don’t effectively remove nutrients, pathogens, and other inorganic contaminants. Previous studies have posited that the use of post treatment systems which incorporate biochar leads to improved contaminant removal efficiency. However, the mechanism through which contaminants are removed and factors potentially affecting the removal are still understudied. To fill this knowledge gaps, this review discusses factors which affect efficiency of biochar in removing contaminants found in onsite domestic wastewater, modifications applied to improve the efficiency of biochar in removing contaminants, mechanisms through which different contaminants are removed and constraints in the use of biochar for onsite wastewater treatment. It was noted that the removal of contaminants involves a combination of mechanisms which include adsorption, filtration, biodegradation, ion exchange, pore entrapment. The combination of these mechanisms is brought about by the synergy between the properties of biochar and microbes trapped in the biofilm on the surface of the biochar. Future areas of research such as the modification of biochar, use of biochar in the removal of antibiotic resistant genes (ARGs), application of wet carbonization methods and resistance of biochar to physical disintegration are also discussed. This study provides useful information that can be applied in the use of biochar for the treatment of wastewater and guide future design of treatment systems for optimized treatment performance.
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.
Changes in precipitation and evapotranspiration over Lokok and Lokere catchments in Uganda
(Bulletin of Atmospheric Science and Technology volume : Springer Link, 2021-03-24) Mubialiwo, Ambrose; Chelangat, Cyrus; Onyutha, Charles
This study analysed long-term (1948–2016) changes in gridded (0.25° × 0.25°) Princeton Global Forcing (PGF) precipitation and potential evapotranspiration (PET) data over Lokok and Lokere catchments. PGF-based and station datasets were compared. Trend and variability were analysed using a nonparametric technique based on the cumulative sum of the difference between exceedance and non-exceedance counts of data. Seasonal (March-April-May (MAM), June-July-August (JJA), September-October-November (SON), December-January-February (DJF)) and annual precipitation exhibited negative trends (p < 0.05). Positive anomalies in precipitation occurred in the 1950s as well as in the early 2000s till 2016. Negative anomalies existed between 1960 and 2000. Both seasonal and annual PET mainly exhibited increasing trend with alternating positive and negative anomalies for the entire period, except in the southern region. The H0 was rejected (p < 0.05) for SON PET in the North and South of the study area. The H0 was rejected (p < 0.05) for DJF PET in the North. However, H0 was not rejected (p > 0.05) for MAM, JJA and annual PET. Positive and negative correlations were observed between PGF and station precipitation varying from one location to another. The PGF-based PET were lower than the observed PET at Kotido by about 40%. Besides, a close agreement was noticeable between PGF-based and MODIS PET from May to November. This showed the need to improve on the quality of PGF data in reproducing the observed climatic data in areas with low meteorological stations density. Nevertheless, the findings from this study are relevant for planning of predictive adaptation to the effects of climate variability on the water resources management applications. Impacts of human factors and climate change on the hydrology of the study area should be quantified in future research studies.
Combined use of graphical and statistical approaches for analyzing historical precipitation changes in the black sea region of Turkey
(MDPI: Water, 2020-03-05) Cengiz, Taner Mustafa; Tabari, Hossein; Onyutha, Charles; Kisi, Ozgur
Many statistical methods have been developed and used over time to analyze historical changes in hydrological time series, given the socioeconomic consequences of the changes in the water cycle components. The classical statistical methods, however, rely on many assumptions on the time series to be examined such as the normality, temporal and spatial independency and the constancy of the data distribution over time. When the assumptions are not fulfilled by the data, test results are not reliable. One way to relax these cumbersome assumptions and credibilize the results of statistical approaches is to make a combined use of graphical and statistical methods. To this end, two graphical methods of the refined cumulative sum of the difference between exceedance and non-exceedance counts of data points (CSD) and innovative trend analyses (ITA)-change boxes alongside the classical statistical Mann–Kendall (MK) method are used to analyze historical precipitation changes at 16 stations during 1960–2015 in the Black Sea region of Turkey. The results show a good match between the results of the graphical and statistical methods. The graphical CSD and ITA methods, however, are able to identify the hidden trends in the precipitation time series that cannot be detected using the statistical MK method.
A comparative analysis of existing models and a new pushover analysis model of reinforced concrete sections
(Engineering Structures, 2023-01) Kimeze, Henry; Kyakula, Michael
Pushover analysis is mainly carried out using the concentrated plasticity model whereby when a point reaches yield, a hinge is placed at that point. The other is the yielded block spread plasticity model, whereby when a point reaches yield, an elastic sub-element of the beam is replaced by a yielded sub-element having a reduced cross-section and second moment of area. Both of these models ignore cracking. This study aims at giving an insight into the effects of considering cracking during modelling on the accuracy of estimating deformations in reinforced concrete (RC) structures during pushover analysis by proposing a spread cracking and yielding block model. The proposed model introduces a cracked sub-element to account for the gradual spread of cracking in the beam. A single-storey RC frame is used because it doesn’t pose the challenge of lateral load distribution. A comparison between the proposed model and the existing models shows an increment in the accuracy of the rotational, displacement, moment and lateral load capacities of 63.64%, 56.86%, 64.33% and 55.56% respectively. Experimental results show that all theoretical models underestimate the ultimate floor displacements and lateral load capacities. The proposed model, however, has better accuracy on both fronts than both existing theoretical models.
A computational methodology for simulating quasi-brittle fracture problems
(Elsevier: Computers & Structures, 2019-04-15) Yun, Kumchol; Wang, Zhenqing; Chang, Mengzhou; Liu, Jingbiao; Kim, Tae-Jong; Son, Namjin; Ji, Kyongsu; Ronald, Sakaya
The paper focuses on an efficient and simple methodologies for simulating the three dimensional (3D) quasi-brittle fracture problems. Strain-softening is performed on the elements by a developed anisotropic continuum damage model that has more effective capability in crack path prediction and is easily available in standard finite elements. In the present damage model, the damaged stiffness tensor is constructed to form a crack surface, and the energy dissipation in the damaged element is only allowed in the direction perpendicular to the crack plane. Crack surface is divided into crack lines and crack triangles based on the first introduced crack surface discretization, and the application scope of local tracking algorithm is extended from two dimension to 3D. The present tracking algorithm not only guarantees the continuity and stability of the predicted crack path by solving the topological problems but also has low computational cost, keeping the advantages of local tracking. The method does not identify the crack plane within each element, but it couples well with smeared crack method by identifying all the elements through which the crack surface passes. The high efficiency and stability of the present approach are verified by resolving several 3D benchmark problems in failure analysis.
Contribution of climatic variability and human activities to stream flow changes in the Haraz River basin, Northern Iran
(Journal of Hydro-environment Research, 2019-06) Pirnia, Abdollah; Darabi, Hamid; Choubin, Bahram; Omidvar, Ebrahim; Onyutha, Charles; Haghighi, Ali Torabi
In northern Iran’s Haraz River basin between 1975 and 2010, hydrological sensitivity, double mass curve, and Soil and Water Assessment Tool (SWAT) methods were applied to monitoring and analysing changes in stream flow brought on by climatic variability and human activities. Applied to analyse trends in annual and seasonal runoff over this period, the sequential MK test showed a sudden change point in stream flow in 1994. The study period was, therefore, divided into two sub-periods: 1975–1994 and 1995–2010. The SWAT model showed obvious changes in water resource components between the two periods: in comparison to the period of 1975–1994, sub-watershed-scale stream flow and soil moisture decreased during 1995–2010. Changes in evapotranspiration were negligible compared to those in stream flow and soil moisture. The hydrological sensitivity method indicated that climatic variability and human activities contributed to 29.86% and 70.14%, respectively, of changes in annual stream flow, while the SWAT model placed these contributions at 34.78% and 65.21%, respectively. The double mass curve method indicated the contribution of climatic variability to stream flow changes to be 57.5% for the wet season and 22.87% for the dry season, while human activities contributed 42.5% and 77.13%, respectively. Accordingly, in the face of climatic variability, measures should be developed and implemented to mitigate its impacts and maintain eco-environmental integrity and water supplies.
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.
COVIDiStress diverse dataset on psychological and behavioural outcomes one year into the COVID-19 pandemic
(Scientific data, 2022) angélique, M. Blackburn; Sara, Vestergren; The COVIDiStRESS II Consortium
During the onset of the COVID-19 pandemic, the COVIDiSTRESS Consortium launched an open-access global survey to understand and improve individuals’ experiences related to the crisis. a year later, we extended this line of research by launching a new survey to address the dynamic landscape of the pandemic. this survey was released with the goal of addressing diversity, equity, and inclusion by working with over 150 researchers across the globe who collected data in 48 languages and dialects across 137 countries. The resulting cleaned dataset described here includes 15,740 of over 20,000 responses. the dataset allows cross-cultural study of psychological wellbeing and behaviours a year into the pandemic. It includes measures of stress, resilience, vaccine attitudes, trust in government and scientists, compliance, and information acquisition and misperceptions regarding COVID-19. Open- access raw and cleaned datasets with computed scores are available. Just as our initial COVIDiStRESS dataset has facilitated government policy decisions regarding health crises, this dataset can be used by researchers and policy makers to inform research, decisions, and policy.
Dam breach analysis of Kibimba Dam in Uganda using HEC-RAS and HEC-GeoRAS
(Springer, 2023-10) Kiwanuka, Moses; Chelangat, Cyrus; Mubialiwo, Ambrose; Lay, Francis Joel; Mugisha, Ayubu; Mbujje, Webster Joel; Mutanda, Hosea Eridadi
Dam failures have severe consequences on human life and property. In the case of an earth filled Kibimba Dam located in Eastern Uganda, the occurrence of a food equal to or larger than the probable maximum food (PMF) could result in catastrophic economic losses including loss of human life. This study utilized the USACE Hydrologic Engineering Center’s River Analysis System (HEC-RAS) and Hydrologic Engineering Center’s Geographic River Analysis System (HEC-GeoRAS) to analyze the potential dam break of Kibimba Dam, considering overtopping and piping failure scenarios. The results of the analysis revealed that the spillway of Kibimba Dam possesses sufficient capacity to safely discharge a food resulting from a probable maximum food peak of 400 m3/s. Therefore, the dam is not susceptible to breach under the overtopping failure mode. However, the dam failed under the piping failure mode. To assess the downstream impact of the dam break, the breach hydrographs resulting from piping failure were examined. Consequently, the study investigated the effects of food propagation downstream of the dam. This resulted in varying inundation depths of up to 6 m and velocities ranging from 1.2 to 10 m/s. These findings highlight the devastating consequences of Kibimba Dam’s failure, particularly affecting rice field plantations, infrastructure, and other economic activities in the downstream area. Therefore, the outcomes of this study are crucial for the development of Emergency Action Plans that incorporate dam breach and food routing analyses specific to the affected downstream regions. Keywords Dam breach, HEC-RAS, HEC-GeoRAS, Kibimba
Does training improve sanitary inspection answer agreement between inspectors? Quantitative evidence from the Mukono district, Uganda
(MDPI, 2020-10-10) King, Richard; Okurut, Kenan; Herschan, Jo; Lapworth, Dan J.; Malcolm, Rosalind; McKeown, Rory Moses; Moses, Rory
Sanitary inspections (SIs) are checklists of questions used for achieving/maintaining the safety of drinking-water supplies by identifying observable actual and potential sources and pathways of contamination. Despite the widespread use of SIs, the effects of training on SI response are understudied. Thirty-six spring supplies were inspected on two occasions, pre- and post-training, by an instructor from the research team and four local inspectors in the Mukono District of Uganda. SI score agreement between the instructor and each inspector was calculated using Lin’s concordance correlation coefficient. Average SI score agreement between the instructor and all inspectors increased post-training for the Yes/No answer type (0.262 to 0.490). For the risk level answer type (e.g., No, Low, Medium, High), average SI score agreement between the instructor and all inspectors increased post-training (0.301 to 0.380). Variability of SI scores between the four inspectors was calculated using coefficient of variation analysis. Average SI score variability between inspectors reduced post-training for both answer types, Yes/No (21.25 to 16.16) and risk level (24.12 to 19.62). Consistency of answer agreement between the four inspectors for each individual SI question was calculated using index of dispersion analysis. Average answer dispersion between inspectors reduced post-training for both answer types, Yes/No (0.41 to 0.27) and risk level (0.55 to 0.41). The findings indicate that training has a positive effect on improving answer agreement between inspectors. However, advanced training or tailoring of SI questions to the local context may be required where inconsistency of responses between inspectors persists, especially for the risk level answer type that requires increased use of inspector risk perception. Organisations should be aware of the potential inconsistency of results between inspectors so that this may be rectified with appropriate training and, where necessary, better SI design and customisation.
Drought severity across Africa: a comparative analysis of multi-source precipitation datasets
(Springer, 2024-04) Lim Kam Sian, Kenny Thiam Choy; Onyutha, Charles; Ayugi, Brian Odhiambo; Njouenwet, Ibrahim; Ongoma, Victor
An accurate analysis of climate extremes is essential for impact assessment and devising appropriate adaptation measures. There is an urgent need to assess precipitation products in capturing the increasing occurrence of climate extremes. This study evaluates the ability of 20 observational datasets, including gauge-based, satellite-based and reanalyses, in representing different drought severity (moderate, severe and extreme drought) over Africa and its nine sub-regions at varying time scales (3-, 6- and 12-months) during 1983–2014. Drought is represented using the Standardized Precipitation Index (SPI). The results demonstrate that while most datasets are suitable for drought studies over the continent, the African Rainfall Climatology version 2 (ARC2) and Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks Climate Data Records (PERSIANN_CDR_v1r1) are less fitted for such investigations. Moreover, regions such as the Sahara (SAH), Central Africa (CAF) and North Eastern Africa (NEAF) show a larger disparity among the datasets, requiring more caution when selecting a dataset for use in such areas. Generally, the datasets present low agreement toward the lower end of the range (5–30%) because the individual datasets estimate varying drought severities at different grids and months. This is observed in the coefficient of variation of 20–25% of the datasets falling outside the ± 1 standard deviation range. Therefore, using an ensemble to represent the datasets remains an indispensable tool. The datasets present better agreement in the timing of drought events than the spatial distribution. The findings provide valuable insights into the complexity of drought assessment using diverse precipitation datasets. Furthermore, the results highlight the significance of considering spatial and temporal dimensions, as datasets may capture drought events at varying locations and times, revealing subtle variations in drought impact.
Dynamically dimensioned search embedded with piecewise opposition-based learning for global optimization
(2019-05-26) Xu, Jianzhong; Yan, Fu; Yun, Kumchol; Ronald, Sakaya; Li, Fengshu; Guan, Jun
Dynamically dimensioned search (DDS) is a well-known optimization algorithm in the field of single solution-based heuristic global search algorithms. Its successful application in the calibration of watershed environmental parameters has attracted researcher’s extensive attention. The dynamically dimensioned search algorithm is a kind of algorithm that converges to the global optimum under the best condition or the good local optimum in the worst case. In other words, the performance of DDS is easily affected by the optimization conditions. Therefore, this algorithm has also suffered from low robustness and limited scalability. In this work, an improved version of DDS called DDS-POBL is proposed. In the DDS-POBL, two effective methods are applied to improve the performance of the DDS algorithm. Piecewise opposition-based learning is introduced to guide DDS search in the right direction, and the golden section method is used to search for more promising areas. Numerical experiments are performed on a set of 23 classic test functions, and the results represent significant improvements in the optimization performance of DDS-POBL compared to DDS. Several experimental results using different parameter values demonstrate the high solution quality, strong robustness, and scalability of the proposed DDS-POBL algorithm. A comparative performance analysis between the DDS-POBL and other powerful algorithms has been carried out by statistical methods by using the significance of the results. The results show that DDS-POBL works better than PSO, CoDA, MHDA, NaFA, and CMA-ES and gives very competitive results when compared to INMDA and EEGWO. Moreover, the parameter calibration application of the Xinanjiang model shows the effectiveness of the DDS-POBL in the real optimization problem.

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