Research Articles (Earth Sciences)

Permanent URI for this collectionhttps://hdl.handle.net/10566/273

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Quantifying land use and land cover influences on surface water quality through Sentinel-2 observations in the Letaba catchment, South Africa
(Elsevier B.V., 2026) Dube, Timothy; Mashala, Makgabo Johanna; Ayisi, Kingsley Kwabena
This study evaluates the association between land use and land cover (LULC) and surface water quality in the Letaba Catchment, South Africa, by integrating in-situ physicochemical measurements with Sentinel-2 Multispectral Instrument (MSI) data. Water quality parameters including temperature, pH, dissolved oxygen (DO), electrical conductivity (EC), total dissolved solids (TDS), and salinity (SAL) were measured using a multi-parameter probe. Sentinel-2 spectral bands and derived water indices were analysed using Pearson's and Spearman's correlation coefficients and stepwise multiple linear regression. Statistically significant relationship (p < 0.05) was observed in the visible and red-edge bands with EC and TDS exhibiting strong predictive performance (R2 = 0.84 and 0.87, respectively). Models for DO, SAL, temperature, and pH showed more variable performance, reflecting parameter-specific optical sensitivities. Weak model performance for pH is attributed to its limited spectral expression in the visible-near infrared (VNIR) region. Overall, the results indicate that LULC patterns are significantly associated with spatial variations in water quality, particularly in areas dominated by built up and plantation land uses. The study demonstrates the utility and limitations of Sentinel 2 data for catchment scale water quality monitoring in semi-arid environments.
Urban expansion and ecological implications in Table Bay nature reserve: a multi-temporal remote sensing study
(Multidisciplinary Digital Publishing Institute (MDPI), 2026) Maphanga, Thabang; Koloko, Mosa; Madonsela, Benett Siyabonga
Urban expansion presents significant challenges and opportunities for ecological conservation in developing countries, particularly in regions such as the Table Bay Nature Reserve in Cape Town, South Africa, where urban development interfaces with sensitive ecosystems. This article examines the complex dynamics between urban growth and ecological implications in this unique landscape, employing multi-temporal remote sensing techniques to analyze changes over time. By investigating the historical trajectory of urbanization in Table Bay, alongside its impacts on biodiversity and ecosystem services, we aim to underscore the urgent need for sustainable urban planning and conservation strategies. To analyze land use/land cover (LULC) dynamics over a 24-year period, this study leveraged a time series of satellite imagery processed within the Google Earth Engine (GEE) platform. Data can be accessed using their respective collection IDs within the GEE platform. The use of remote sensing tools aligns with Sustainable Development Goal (SDG) 15, which focuses on the protection, restoration, and sustainable use of terrestrial ecosystems. Urban encroachment analysis indicates that approximately 0.324 km2 of built-up area expanded directly within the reserve boundary, highlighting a measurable degree of infringement into protected zones. The dominance of built-up and bare land classes highlights the early encroachment of urban infrastructure and anthropogenic disturbance, setting the stage for subsequent land cover transformations observed in later years (2012 and 2024). These findings demonstrate a persistent trend of urban encroachment and ecological alteration within the Table Bay Nature Reserve. With the increase in global population levels, urban expansion into protected conservation areas has become a critical environmental concern, threatening biodiversity globally. This challenge is particularly acute in developing countries as seen in regions like the Table Bay Nature Reserve in Cape Town, South Africa, where urban development is interfaced with sensitive ecosystems.
Mapping persistent oil spill risk in the Niger Delta using sentinel-1 SAR and environmental exposure indicators
(Elsevier Ltd, 2026) Oseni, Ridwan; Omosanya, Kamaldeen Olakunle; Mosuro, Ganiyu Omotola; Saka, Hawa Oluwatosin; Oludipe, Victoria; Oshomoji, Adeoye
Oil spills remain a major source of marine and coastal pollution in hydrocarbon-producing regions, where repeated releases can lead to long-term contamination of wetlands, waterways, and adjacent communities. Although satellite remote sensing has improved the detection of oil spills, translating these observations into assessments of cumulative environmental and human exposure is still challenging, particularly in complex deltaic systems. Here, we present a spatially explicit framework for assessing persistent oil spill exposure in the Niger Delta by integrating Sentinel-1 synthetic aperture radar (SAR) observations with ecological, infrastructural, terrain, and demographic data. Rather than focusing on individual spill events, we quantify chronic exposure patterns by finding recurring oil spill signatures and combining them within a multi-criteria risk model. Our results reveal persistent contamination hotspots strongly associated with dense oil infrastructure, low-lying wetlands, flat terrain, and high population density, collectively affecting approximately 9400 km2 over the past decade. Spill exposure extends beyond reported incident locations and includes both protected and upland areas, showing widespread vulnerability across the delta. These findings show that long-term pollution risk in the Niger Delta is governed by cumulative exposure and landscape controls rather than isolated spill events alone. The proposed framework provides a transferable approach for monitoring, assessing, and managing chronic oil pollution in coastal and deltaic environments worldwide.
Biogeochemical controls on soil dispersion and bank stability in the unvegetated, meandering Sulengguole River, Qaidam Basin, China
(SAGE Publications Ltd, 2025) Li, Jiaguang; Grenfell, Michael C; Cheng, Dandan; Alhassan, Jeremiah
Unvegetated meandering rivers play a pivotal role in sediment transport and landscape evolution within dryland environments, yet the interplay between abiotic and biotic factors that govern channel bank stability and migration remains poorly understood. While sedimentological processes have been extensively studied, the combined influence of sediment geochemistry and microbial activity on erosion and bank dynamics remains poorly understood. We investigate a single, nearly unvegetated bend in the Sulengguole River, Qaidam Basin, China, using remote sensing, field observations, and laboratory analyses (grain-size distribution, salinity, ion profiling, and 16S rRNA sequencing) to elucidate how sedimentology, geochemistry, and microbial diversity drive bank erosion and meander migration under uniform seasonal and climatic conditions. Field sampling focused on cavity-rich and compact sediment layers along a representative meander bend. Analyses of grain-size distribution, salinity, ion concentrations, and microbial diversity (via 16S rRNA sequencing) revealed significant spatial and compositional differences in bank stability. Mud-dominated banks, undermined by cavity formation, were found to migrate more than four times faster than interbedded sand-mud banks, as shown by satellite imagery and sedimentological data. High salinity and ion concentrations in finer sediments at elevated bank zones were strongly associated with increased soil dispersion and enhanced erosion. Microbial diversity analysis further indicated that cavity-rich layers were dominated by Brevibacterium and Pseudomonas, taxa known to promote bioerosion, whereas cavity-free layers, enriched with Acinetobacter and Brevundimonas, contributed to sediment cohesion. These findings highlight the critical role of abiotic-biotic interactions in influencing bank stability, sediment transport, and channel migration in unvegetated river systems. By demonstrating how geochemical and biological factors interact to shape riverbank erosion and morphodynamics, this study provides new insights into sediment dynamics in dryland rivers. The results have broader implications for understanding sediment transport in meandering river systems, as well as in interpreting landscape evolution in ancient fluvial records and extraterrestrial environments.
Occupational health and safety hazards associated with informal solid waste scavenging at Richmond sanitary landfill, Bulawayo, Zimbabwe
(Springer International Publishing, 2026) Muringaniza, Kudakwashe C. R.; Simakani, Ashley; Musasa, Tatenda
Solid waste scavenging has historically been a challenge in most developing countries. This study assesses occupational health and safety (OHS) hazards associated with informal solid waste scavenging at Richmond Sanitary Landfill (RSL) in Bulawayo city, Zimbabwe. The case study research design was used combining qualitative and quantitative methods. Data was collected from secondary sources as well as primary sources using questionnaires, interviews, and observations. The participants were sampled using snowball and purposive sampling methods. A total of 90 questionnaires were administered to representatives of selected households involved in scavenging at RSL from which inferences were made. The data was analysed using the Statistical Package for Social Sciences (SPSS). Occupational health and safety hazards at RSL were dominated by ergonomics hazards emanating from manual lifting and awkward postures (86%), dust (79%), leachate ponds (50%), noise (58%), sharp objects (43%), chemical contaminated waste (21%) and pathogen infested waste (17%) all of which have potential to cause injuries and illnesses. OHS hazards were identified as a risk factor and a Chi square test of the association between occupational hazards and injuries encountered (p = 0.00) was done. The Municipality of Bulawayo did not have a documented number of scavengers working at their landfill, or an OSH program. To address OHS issues, there is need for the Municipality to adopt an OSH policy. Training of scavengers and waste pickers is recommended to make them competent in identifying health and safety hazards, effective use of personal protective clothing and enabling them to uphold best safety and health practices.
Putting water resource protection into practice: a decision support system to assess compliance with predefined protection limits for water resources in developing countries
(Elsevier B.V., 2025) Kanyerere, Thokozani; Makanda, Koleka; Nzama, Stanley
A decision support system (DSS) for enhancing policy implementation in water resource management is a tool developed to assist water resource managers to take informed decisions to ensure that policy objectives on water resource protection and sustainable utilization are achieved. Uncertainties associated with not knowing how water resource systems would respond to catchment management actions provide enormous challenges for water resource managers which demands application of adaptive management approach in water resource management practices. This study aimed to develop a conceptual framework for operationalizing adaptive management into a decision support system to promote rationality in water resource management. The feasibility of the framework was assessed with a case study of the Blesbokspruit River Catchment (BRC) in the Republic of South Africa, whereby compliance with legalized protection limits for instream water quality was assessed in a regulated river system. New insight: Adaptability, cost-effectiveness, consistency, transparency, versatility, treatability index and dilution flow adjustments enable application of an adaptive management approach into a DSS to improve decision-making regarding water resource protection. The results indicate that the developed framework serves as a useful tool allowing water resource managers to evaluate different options and select the most suitable solutions. These findings underscore the urgent need for a decision support system to operationalize adaptive management in water resource management to safeguard ecological ecosystem and public health
Risk assessment of hydrological drought in water-donating and water-receiving areas of an inter-basin water diversion project
(Academic Press, 2025) Liu, Dedi; Wang, Junde; Zhou, Wan
Droughts are the most widespread natural disasters in arid/semi-arid regions, causing significant damage to socio-economic and agricultural systems. Inter-basin water diversion projects have been widely adopted to mitigate regional water scarcity. However, the dual impact of drought and water diversion on both water donating and receiving regions remains insufficiently explored. This study investigates the spatiotemporal evolution and risk of hydrological drought (HD) in the context of the Tao River Water Diversion Project (TRWDP) in Gansu province, China. By integrating hydro-meteorological datasets, SWAT-based hydrological modeling, and the Standardized Runoff Index (SRI), HD dynamics were assessed across both water-donating (TRB) and water-receiving regions (ZRB and WRB) from 1970 to 2020. Results indicate that: (1) HD exhibits a worsening trend, with the most pronounced intensification observed in the WRB. (2) Correlation analyses indicate that drought characteristics are driven by diverse climatic and catchment attributes. In the TRB, HD is primarily influenced by seasonal drought index, elevation variability, and proportion of water bodies; in the ZRB, by basin area, river network length, maximum elevation, and forest coverage; and in the WRB, by minimum elevation, river network density, and water area ratio. (3) A risk assessment framework integrating hazard, exposure, and vulnerability highlights critical drought hotspots in the lower TRB and central WRB. Notably, the implementation of the TRWDP has significantly alleviated drought risk in water-receiving regions, particularly in agricultural and densely populated areas. However, the potential redistribution of drought pressure toward water-donating regions underscores the need for balanced inter-basin water governance. These findings bridge the gap in understanding the interplay between water diversion and hydrological drought risk, providing a scientific basis for the adaptive management and sustainable operation of large-scale water transfer projects under climate variability
Regional variability in the acheulian to middle stone age transition in Southern Africa
(Nature Research, 2026) Muir, Robert A.; Blackwood, Alexander F.; Wilkins, Jayne
Homo sapiens emerged in Africa around 300 − 200 thousand years ago (ka). Although the earliest H. sapiens fossils are associated with the Middle Stone Age (MSA), lithic technologies considered diagnostic of the MSA have been found alongside Acheulian technology in eastern Africa and the interior of southern Africa by ~ 500 − 400 ka, suggesting a deep evolutionary history of our species in these regions. The southern coastal plain of South Africa, geographically separated from the interior by the Cape Fold Belt and Great Escarpment, has one of the best documented records of the MSA in Africa; however, only a single site is older than 125 ka and little is known about the origins of the MSA in this region. Here, we report a stratified sequence of Acheulian to MSA lithic assemblages from the open-air site of Amanzi Springs covering the period between ~ 379 to 95 ka. We show that the MSA emerged around 230 ± 18 ka, significantly earlier than previously documented along the southern coast. The pattern of technological change also differs to the interior, with no diagnostic MSA elements found in the late Acheulian, although persistent methods of flake production indicate a gradual transition and continuity into the MSA. The relatively late emergence of the MSA along the southern coast highlights the variable and complex nature of demographic and behavioural change during this period, with regionally distinct technological trajectories extending into the Middle Pleistocene in southern Africa.
3D seismic-based structural and slip tendency analysis of a depleted reservoir offshore South Africa: implications for safe CO2 storage
(Elsevier Ltd, 2026) Mhlambi, Samkelisiwe; Eruteya, O E; Moscariello, A; Samankassou, E; van Bever Donker, Jan M
Carbon capture and storage (CCS) technology is increasingly recognised as a key enabler of a low-carbon energy future, with growing importance for reducing anthropogenic CO2 emissions in resource-rich countries such as South Africa. The long-term success of CCS depends on the availability of secure storage capacity and a robust geomechanical understanding of injection sites, particularly in structurally complex, depleted hydrocarbon reservoirs. This study presents one of the first reservoir-scale integrated deterministic and probabilistic assessments of fault slip potential (FSP) applied to a depleted offshore gas reservoir in the Bredasdorp Basin. A high-resolution 3D seismic dataset was interpreted to characterise the fault network and construct a structural framework comprising fifty (50) selected faults within a syn-rift sandstone reservoir. This framework underpins a combined deterministic geomechanical and probabilistic sensitivity-modelling workflow to evaluate fault reactivation risk during CO₂ injection, using a simplified radial pressure-diffusion formulation. Results show that faults proximal to injection wells exhibit elevated slip potential due to their orientation relative to the regional stress field and their spatial association with pressure build-up. Sensitivity analyses indicate that pore-pressure increase is the dominant control on slip potential, followed by fault friction coefficient (µ), fault strike, and stress-field uncertainty. Variations in permeability primarily affect the magnitude and persistence of pressure build-up, while variations in μ govern slip-onset thresholds. Faults within ∼5 km of injection wells are most susceptible to reactivation. Time-dependent modelling highlights elevated risk during late-stage injection and early post-injection pressure redistribution, underscoring the need for continuous monitoring and adaptive pressure management. Overall, the study provides a rigorous, fault-specific geomechanical framework for CCS operations, and emphasises the importance of explicitly incorporating uncertainty into CCS risk assessments.
Source rock maturity and 1-D basin modelling in blocks 2 and 3 sector, offshore orange basin, South Africa
(Elsevier Ltd, 2025) Opuwari, Mimonitu; Yelwa, Nura Abdulmumini; Mustapha, Khairul Azlan
The passive continental margins of South Africa are virtually unexplored, although some potential is assumed in the Orange Basin and even proven by the Kudu gas field offshore Namibia and the Ibhubesi gas field offshore South Africa. The present research uses source rock samples and basin modelling to evaluate the hydrocarbon potential in the Cretaceous South African exploration license blocks 2 and 3, Sector, Offshore Orange Basin. With an emphasis on the development of source rock maturity, the study seeks to comprehend the geological processes that led to the formation of the Orange Basin. These organic deposits have average TOC values across the several stratigraphic units, with a relatively fair to good TOC composition ranging from 0.53 to 1.89 wt %. Out of the 23 samples that were examined, 17 had TOC concentrations of more than 1 %, and the remaining 6 had contents between 0.53 and 0.98 wt %. The examined organic sediments have a relatively low sulphur (TS, wt.%) content, ranging from 0.21 to 1.18 wt%, with the Turonian–Coniacian sequence having a slightly higher sulphur content of up to 1.18 wt%. These results show that free petroleum exists (S1) and that oil generated by kerogen heat cracking (S2) delivers oil with low petroleum potential. The analysis of the shale deposits shows that their low petroleum potential is supported by the S2 and S3 petroleum yields, which are consistent with TOC content. The average hydrogen index (HI) in the study area indicating low-source rock quality capable of producing type III kerogen. A one-dimensional simulation was constructed for four wells, which reveals subsidence and the influence of multi-tectonism on the burial and thermal history, reaching a maximum burial thickness from Cenomanian to Turonian up to 2110 m. The integrated studies between the analyses of source rocks and petroleum basin modelling from the Orange Basin reveal a certain petroleum potential of the Cretaceous source rocks and three petroleum systems in the lower post-rift pattern and an extrapolated topmost post-rift play
Household water insecurity severity across urban areas with varying aridity levels in Sub-Saharan Africa: examples from Namibia
(Elsevier BV, 2026) Munyayi, Rennie; Swatuk, Larry A; Mazvimavi, Dominic; Chiramba, Thomas; Mapani, Benjamin
Water insecurity is shaped not only by water availability but also by governance and service systems, an issue that is increasingly pressing in cities. In the African policy context, the Africa Water Vision 2063 and Policy, positions water security and safe sanitation as central to achieving Agenda 2063. Framing household water insecurity through reliability and spatial equity, speaks directly to these continental aspirations. This study examines household water insecurity in three Namibian towns, (Ongwediva, Rundu, and Windhoek), which differ in their hydroclimatic conditions and water supply systems. Drawing on the 12-item Household Water Insecurity Experiences (HWISE) scale and supplementary survey data, we examine how the severity of household water insecurity varies across towns and across socio-spatial groups within each town. The findings show significant between- and within-town differences. Windhoek, the capital city and economic hub of the country, faces severe physical water scarcity. Respondents in Windhoek report lower water insecurity scores, which could be explained by the city’s long-standing investment in augmenting the water supply and consistent promotion of water demand management strategies. Rundu, the second-largest town, is located in a water-rich basin (the Okavango Basin) and has the highest household water insecurity scores. These findings could result from inadequate and ageing water infrastructure and institutional constraints that affect the continuity of supply. In Ongwediva, relatively high levels of service coverage do not fully protect households from insecurity, as the system remains vulnerable due to its dependence on a long-distance transboundary transfer corridor that is affected by other factors, such as power cuts. In town comparisons reveal that informal and higher-density suburbs tend to have higher insecurity scores than other residential areas. These findings suggest that household water security is rarely the result of hydrology alone. Infrastructure constraints, institutional capacity, and climate variability often intersect in ways that shape the reliability of water services.
The multiplier effect and systemic patterns of urban reclaimed water utilization
(KeAi Communications Co., 2026) Ma, Nian; Xu, Yongxin
The multiplier effect describes how an initial change in a variable leads to a larger overall impact through interconnected processes. The utilization of reclaimed water offers a promising solution to water scarcity while preserving fresh water for diverse applications. Integrating reclaimed water into urban water systems alters both the balance and composition of water resources and affects system efficiency. However, there is currently no unified method for evaluating the efficiency of reclaimed water utilization (RWU). This paper introduces the concept of the multiplier effect to establish a comprehensive evaluation framework. The mechanism of the multiplier effect is dissected, an accounting methodology for the reclaimed water utilization multiplier (RWUM) developed. We also further identify various RWU patterns and their impacts on the multiplier estimation. By examining case studies in Singapore and Chongqing, the paper explores how to increase the RWUM with the multiplier accounting. We found that the multiplier effect enhances the optimal utilization of available water resources, thereby improving both the effectiveness and efficiency of urban water systems. Improving each component's performance increases RWUM and boosts overall water system efficiency. Selecting an appropriate systemic pattern significantly enhances the efficiency of reclaimed water use. Increasing reclaimed water use rates, refining its application patterns, and improving urban water cycle operations significantly boost RWU efficiency and urban water system performance. The methodology for RWUM evaluation provides a comprehensive and standardized framework for assessing the utilization efficiency of urban reclaimed water, yielding comparable results. This framework can guide the planning and management of urban reclaimed water systems and is applicable to various global water systems for cities alike.
A sediment provenance study of middle Jurassic to cretaceous strata in the eastern Sverdrup basin: implications for the exhumation of the north eastern Canadian Greenlandic shield
(MDPI, 2025) Frei, Dirk; Pointon, Michael A.; Smyth, Helen
The Sverdrup Basin, Arctic Canada, is ideally situated to contain an archive of tectono-magmatic and climatic events that occurred within the wider Arctic region, including the exhumation of the adjacent (northeastern) part of the Canadian-Greenlandic Shield. To test this, a multi-analytical provenance study of Middle Jurassic to Cretaceous sandstones from the eastern Sverdrup Basin was undertaken. Most of the samples analysed were recycled from sedimentary rocks of the Franklinian Basin, with possible additional contributions from the Mesoproterozoic Bylot basins and metasedimentary shield rocks. The amount of high-grade metamorphic detritus in samples from central Ellesmere Island increased from Middle Jurassic times. This is interpreted to reflect exhumation of the area to the southeast/east of the Sverdrup Basin. Exhumation may have its origins in Middle Jurassic extension and uplift along the northwest Sverdrup Basin margin. Rift-flank uplift along the Canadian–West Greenland conjugate margin and lithospheric doming linked with the proximity of the Iceland hotspot and/or the emplacement of the Cretaceous High Arctic Large Igneous Province may have contributed to exhumation subsequently. The southeast-to-northwest thickening of Jurassic to Early Cretaceous strata across the Sverdrup Basin may be a distal effect of exhumation rather than rifting in the Sverdrup or Amerasia basins.
Understanding the spatiotemporal variation of water quality and phytoplankton biomass in subtropical reservoir using the blue–sky multispectral data
(John Wiley and Sons Ltd, 2025) Dube, Timothy; Dalu, Tatenda; Muthivhi, Faith F.
Chlorophyll-a (chl-a) is an optically active compound used as a proxy for phytoplankton biomass to determine the trophic states of aquatic ecosystems. Blue–sky remote sensing technologies present low-cost and effective monitoring techniques for water quality on a large scale. This study was aimed at using readily available Landsat multispectral images to assess the spatial and temporal variation of phytoplankton biomass in Nandoni reservoir, Limpopo Province, and at examining the relationships that exist between the physicochemical variables and chl-a concentration. Landsat 7 ETM+ and Landsat 8 OLI images for June (dry) and December (wet), for the years 2008–2020, were used to derive the distribution of chl-a concentration. Using regression techniques, in situ measured chl-a showed a strong and perfectly linear relationship to the predicted Landsat chl-a in the Nandoni reservoir. There was a negative significant correlation between land use and land cover and water quality variables. Using permutational multivariate analysis of variance (PERMANOVA) analysis, we uncovered significant differences for chl-a concentration in sites, seasons and zones. A significant positive correlation was observed between water temperature and chl-a concentration. In contrast, a strong negative significant correlation was observed for chl-a with salinity and total dissolved solids. chl-a concentration in the Nandoni reservoir was derived using Landsat remote sensing images, suggesting that the Landsat data is suitable for monitoring small reservoirs in a short timescale. The results of this study suggest that remote sensing techniques can be used to control the development of an early warning system for this study and other reservoirs. Furthermore, the results highlight the role of using analysis ready Landsat series data in monitoring phytoplankton biomass and chl-a abundance in freshwater systems.
Climate and groundwater depth relationships in selected Breede Gouritz water management area subregions between 2009 and 2020
(MDPI, 2025) Correia, Monica M.; Kanyerere, Thokozani; Jovanovic, Nebo; Goldin, Jacqueline; John, Moyin
Groundwater resources are changing under the current climate change trajectory. Mitigation and adaptation measures include understanding the inter-working relationships among all climate variables and water resources, specifically groundwater, since it has less direct impacts than surface waters due to its nature. The Breede Gouritz Water Management Area provides an interesting platform to assess these interdependencies, since they have not been assessed before. To assess any underlying dependencies, a multivariate analysis of independent variables including monthly average temperature, summative precipitation, and average evapotranspiration, and a dependent monthly variable, i.e., average groundwater depth, from 14 boreholes was conducted. Moreover, a groundwater depth near-future prediction for each relevant borehole was made. The Multiple Linear Regression model was chosen as the appropriate one since it is cost- and time-effective, entry-level, easy to interpret, and provides a simple and basic understanding of the relationship dependencies. The Kruskal-Wallis test was also performed to elaborate on findings from the Multiple Linear Regression models. Simple linear models incorporating independent and dependent variables can only account for up to 41.7% of the variation in groundwater depth. Groundwater depth is mainly influenced by temperature and evapotranspiration and is expected to be lower for ten dependent variables. The more arid regions in the study area can expect groundwater depth to lower soon and need to use alternative water resources. The temperate west of the study area could expect more favorable outcomes regarding groundwater depth in the near future. Incorporating more variables and using a multi-modal approach to combat non-linear relationships is recommended in future.
Detection of Fall Armyworm infestation in maize fields during vegetative growth stages using temporal Sentinel-2
(Elsevier BV, 2025) Dzurume, Tatenda; Dube, Timothy; Darvishzadeh, Roshanak
Fall Armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), poses a significant risk to global food and income security by attacking various crops, particularly maize. Early detection and management of FAW infestation are crucial for mitigating its impact on crop yields. This study investigated the effect of FAW infestation on the spectral signature of maize fields and classified infestation severity in Bangladesh using Sentinel-2 satellite imagery and Random Forest (RF) classification. Field observations on FAW infestation severity (none, moderate, and severe), collected by the Bangladesh Department of Agricultural Extension during 2019 and 2020, were used to train the RF classifier. Six thousand nine hundred ninety-eight observations were collected from 579 maize fields through weekly scouting. The Kruskal-Wallis test and Dunn's post-hoc test were applied to identify the most significant spectral bands (P < 0.05) for detecting FAW incidence and severity across different maize growth stages. The results demonstrated that the spectral reflectance from Sentinel-2 bands varied significantly among different classes of FAW infestation, with noticeable differences observed during the early developmental stages of maize (vegetative growth stages 3 to 8). RF identified nine spectral bands and two spectral vegetation indices as important for FAW infestation discrimination. The RF classifier was evaluated using five-fold cross-validation, achieving an overall accuracy between 74 % and 84 %. The independent test set's accuracy ranged from 72 % to 82 %. The mean multiclass AUC ranged from 0.83 to 0.95. Moreover, the results demonstrated the feasibility of detecting the severity of FAW infestation using temporal Sentinel-2 data and machine learning techniques. These findings underscore the potential of remote sensing and machine learning techniques for effectively monitoring and managing crop pests.
Depositional environments reflected by benthic foraminifera in the lower cretaceous reservoir section of Southern Pletmos Basin, South Africa
(Elsevier Ltd, 2026) Oghenekome, Monica Enifome; Chatterjee, Tapas Kumar
The Pletmos Basin is one of the several exploratory basins situated along the southern continental margin of South Africa characterized by Lower Cretaceous marine clastic successions influenced by syn-sedimentary tectonic activities. There is still paucity in the understanding of the paleoenvironment of the southern Pletmos Basin off-shore South Africa. Hence this study is the analysis of 38 drill core samples from a high-resolution biostratigraphic study of the reservoir section in an exploratory well within the southern Pletmos Basin. The recovered highly diverse benthic foraminiferal assemblage is dominated by calcareous taxa. The temporal distribution of the foraminiferal assemblages indicates shelf sedimentation with minor shallowing at certain reservoir intervals resulted in the deposition of relatively clean sands. Frequency and diversity of the taxa were found to be moderate throughout the studied interval. Mainly fine sands and siltstones constitute the reservoir in this locality. This study is significant because understanding of benthic foraminiferal assemblages in this interval directly addresses key uncertainties in the reservoir's distribution, paleodepth of deposition, stratigraphic architecture, and basin evolution, thereby enhancing the petroleum-system evaluation and reducing exploration risk in this underexplored offshore basin.
Understanding the equivalent relationship of the flood control storage between Cascade Reservoirs
(John Wiley and Sons Inc, 2026) Liu, Dedi; Wang, Zhenyu; Mu, Zhenyu
Joint flood control operations in cascade reservoirs are critical for mitigating flood disasters. To explore the full potential of flood control in cascade reservoirs, it is necessary to find the equivalent relationship among the cascade reservoirs. After defining the concepts of equivalent flood control storage and the equivalent ratio, its general equivalent relationship has been derived for the downmost reservoir regardless of its flood regional composition and upstream reservoirs operation rules. The cascade reservoirs in the upstream of the Changjiang River and the Three Gorges Reservoir are taken as our case study. Driven by the six design floods, the impacts of flood magnitude, hydrograph, and the amount of the occupied upstream flood storage on the equivalent ratio of the Three Gorges Reservoir have been figured out. The results show that the equivalent ratio increases with flood magnitude. If the main part of the peak of the flow at the downmost reservoir is from the regional flow, and the flood peak at the interval region is part of the first half of the downstream flood peak, the equivalent ratio is approaching 0. The impact of the amount of occupied upstream flood storage on the equivalent ratio is found to be dependent on the magnitude and hydrograph of the inflow into the downmost reservoir. © 2026 American Water Resources Association.
Assessing the variations of the available flood storage capacity in a flood retention basin due to the changing environment
(Academic Press, 2026) Liu Dedi; Zhang Yuling; Wang Zhenyu
Flood retention basin (FRB) is an important measure for the flood control. As the available flood storage capacity of FRB reflects the maximum amount of flood that can be stored, it is often varied due to the changing environment, which impacts on the its flood control function. Based on the principle of allowing only specific areas to be inundated for flood control, a systematic framework is proposed to quantify the variations of the available flood storage capacity of an FRB due to the combined effects of human activities and climate change. The Variable Infiltration Capacity hydrological model is a tool of simulation of flood flow in the framework. A Geodetector model is applied to figure out the contributions of human activities and climate change. Applying the framework to 42 FRBs in the middle reaches of the Changjiang River Basin, the results show a significant 9.6% decrease in total available flood storage capacity from 2000 to 2020, with human activities contributing more than climate change. The decrease of available flood storage capacities in the FRBs bring the increases of frequencies (i.e., the decrease of the standard of flood control) of the flood inflows that represents the maximum preventing flood for FRBs from 0.111%, 0.167%, 0.100% to 0.143%, 0.250% and 0.167%, respectively. Our study will not only help assess variations of the available flood storage capacity, but also contribute to the protection of the FRBs.
Synergistic use of sentinel-1 and sentinel-2 data for fall armyworm infestation detection and mapping in maize croplands
(Taylor and Francis Ltd, 2025) Dzurume, Tatenda; Dube, Timothy; Darvishzadeh, Roshanak
Fall Armyworm (FAW) is a widespread invasive pest in maize crops. This study aimed at detecting and mapping FAW infestations in maize fields across Bangladesh, using freely available Sentinel-1 and Sentinel-2 data. Field observations were conducted during the 2019–2020 maize growing season in 579 maize fields across six administrative divisions of Bangladesh. The study covered both infested and non-infested sites across four crop growth phases, namely vegetative phases 9 (V9) and 12 (V12), as well as the silking and maturing phases. Synthetic Aperture Radar backscatter values, spectral reflectance profiles, and eight vegetation indices were extracted from the Sentinel data and analysed using non-parametric statistical tests to identify differences between infested and non-infested fields. Machine learning models, specifically Random Forest - and Support Vector Machine, were then used to classify infestation severity based on five model input data combinations: (i) Sentinel-1, (ii) Sentinel-2, (iii) Sentinel-2 with vegetation indices, (iv) Sentinel-1 and Sentinel-2, and (v) Sentinel-1, Sentinel-2, and vegetation indices. The results indicated that infested maize fields exhibited reduced near-infrared reflectance and distinct backscatter patterns in σVHo, with notable variations at silking and maturity phases. The red edge (740 nm), near-infrared (865 nm) and shortwave infrared (1610–2190 nm) bands were particularly effective in distinguishing infestation levels across all growing phases. Among the studied vegetation indices, the Normalized Difference Vegetation Index, Modified Chlorophyll Absorption in Reflectance Index, Red Edge Simple Ratio, and Modified Simple Ratio - were identified as the most significant indicators for discriminating between non-infested and infested maize classes at all growing phases. RF achieved 94–96% accuracy (96% in V9) versus SVM’s 78–80% using only Sentinel‐1 data. Multi‐source (Sentinel-1, Sentinel-2 and Vegetation Indices) integration improved both models in most cases.

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