Research Articles (Earth Sciences)

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

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Water level identification through the trade-off between the standards of drought defense and flood control for a reservoir in flood season
(Elsevier B.V., 2026) Niu, Zhilin; Liu, Dedi; Ren, Jinqiu; Zhang, Lisheng; Rao, Guanghui
Study Region: Songhuaba Reservoir, Yunnan Province, China Study Focus: As extreme droughts become increasingly frequent and widespread, the inherent conflict between drought defense and flood control presents a critical challenge for reservoir management, particularly during the flood season. To determine an optimal water level that balances the conflict for a reservoir in its flood season, a trade-off framework is developed to quantify drought defense and flood control standards and then the Technique for Order Preference by Similarity to Ideal Solution (i.e., TOPSIS) is applied to select the optimal water level. New hydrological insights for the region: Taking Songhuaba Reservoir in Yunnan, China, as a case study, the framework reveals a pronounced nonlinear trade-off relationship between drought defense and flood control standards. The flood control standard exhibits a steeper gradient when the drought defense standard is more stringent, indicating higher sensitivity under severe drought conditions. The optimal water level is identified as 1970.0 m, corresponding to a drought defense standard of 6.39% and a flood control standard of 0.87%, and indicates a compromise between the flood control and drought defense two objectives in the flood season. A weight analysis further reveals that the optimal water level adjusts stepwise with the varying criterion weights. The proposed framework for identifying an optimal water level can balance the conflicting drought defense and flood control and will help reservoir management in flood season.
Performance evaluation of solar-powered groundwater pumping systems in rural communities of greater Giyani municipality, Limpopo, South Africa
(Multidisciplinary Digital Publishing Institute (MDPI), 2026) Jovanovic, Nebojsa; Shika, Seemole S.; Mashabatu, Munashe
Large portions of rural population in South Africa lack access to basic water and sanitation. This advocates for urgent interventions in support of water supply. This study assessed the performance of solar-powered groundwater pumping systems established at nine pilot sites in rural areas of Greater Giyani Municipality (Limpopo, South Africa). Performance assessment indicators, namely weather, groundwater abstraction, power supply, water supply, water quality, number of beneficiaries and farm productivity, were monitored (2023–2024). Increased groundwater abstraction reduced groundwater levels by 0.4–11 m, depending on the monitored borehole. This was replenished by above-average rainfall in 2023 (≈650 mm). Power supply and pump discharge rates were stable with generally low fluctuations at recommended pumping rates (0.5–2.0 L s−1). Groundwater quality was generally fit to marginal for irrigation and drinking. High levels of NO3− and total organic carbon, especially in the proximity of villages, mandated the installation of mini water treatment plants for drinking water. The implementation of solar-powered groundwater pumping schemes was generally successful, with more than 5000 villagers benefiting directly from the interventions, whilst smallholder farms turned into commercial and financially viable enterprises. Long-term monitoring of bio-physical and socio-economic drivers is essential to ensure long-term sustainability of the solar-powered groundwater pumping systems.
Provenance of the late Ediacaran minas de Corrales formation, Nico Pérez terrane, Uruguay: paleogeographic implications
(Frontiers Media SA, 2026) Frei, Dirk; Abre, Paulina; Blanco, Gonzalo
The Nico Pérez Terrane, located in the eastern margin of the Río de la Plata Craton, played a critical role in the assembly of SW Gondwana. The Isla Cristalina de Rivera basement klippe represents the northernmost exposures of the Nico Pérez Terrane in Uruguay, where the metavolcanic-sedimentary Minas de Corrales Formation represents the only preserved Ediacaran supracrustal cover. The provenance analyses of this key succession have unraveled the crustal signature and ages of its sources, providing constraints on the paleogeography and tectonic evolution of the Arachania subduction-related orogeny that developed along the eastern margin of the Río de la Plata Craton. We compare it to other coeval extensional basins in a back-arc position regarding Arachania linked to the opening of the Brazilides Ocean. Detrital mineral quantification and whole-rock geochemistry of the Minas de Corrales Formation indicate that the bulk of the detritus was rapidly sourced from basement rocks, with a composition similar to average unrecycled upper continental crust, with influences of a less differentiated component. Nd isotopes further suggest a Mesoproterozoic mantle extraction age for the juvenile component of the metavolcanic sandstones. Detrital zircon patterns of all studied samples point to diverse source rock ages: one metasandstone displays a dominance (95%) of Siderian–Rhyacian ages, whereas the other shows a concentration of Tonian to Cryogenian ages (89%); the metavolcanic sandstones yield main populations of Rhyacian, Calymmian, and Ectasian ages. All provenance indicators suggest that the Ediacaran Mina de Corrales Formation was fed from Paleoproterozoic and Neoproterozoic basement sources that likely comprised the rift-shoulders and nearby areas; these sources are traced to the Taquarembó, Tijucas, São Gabriel, and Nico Pérez Terranes. The Minas de Corrales Formation was deposited in an extensional basin emplaced on the eastern margin of the Río de la Plata Craton that developed during the opening of the Brazilides Ocean.
Columnanidus calitzdorpensis ichnogen. ichnosp. nov: a new middle pleistocene subterranean termite trace fossil from South Africa
(John Wiley and Sons Ltd, 2026) Abrahams, Miengah; Muir, Robert A; Genise, Jorge F; Almond, John E; Hadebe, Gcinamahlubi; Hellstrom, John C; Jacobs, Rabia; Harris, Chris
Termites are landscape geo-engineers whose nesting activities substantially modify the physical and chemical properties of soils. Fossilised termite nests commonly constitute the only identifiable evidence of ancient termite activity and represent valuable trace fossil archives for reconstructing past environments. Here, we describe a new ichnogenus and ichnospecies, Columnanidus calitzdorpensis ichnogen. ichnosp. nov., from Quaternary alluvial deposits near Calitzdorp, South Africa. The subterranean nests are subcylindrical structures, reaching ~1 m in height and ~65 cm in diameter, and are characterised by a ~12 cm wide, shelved nest wall surrounding an empty central cavity. Within the nest wall, the gallery and chamber morphology and abundance vary between the inner and outer zones. The nests are preserved as calcretised features, composed of inter-laminations of clastic sediment and pedogenic carbonate precipitate. U-series dating of the carbonate laminations yields robust age peaks at 401 ± 46 ka and 323 ± 12 ka, indicating a Middle Pleistocene minimum age for nest formation. These ages coincide with intervals favourable for pedogenic carbonate development under semi-arid to arid climatic conditions. Hardpan calcretes capping the nests suggest prolonged periods of semi-arid conditions and sustained pedogenic stability during the Middle Pleistocene in the Calitzdorp region.
1D basin modelling of upper jurassic to upper cretaceous source rocks in the Southern Pletmos Sub-Basin, Outeniqua Basin, offshore South Africa
(John Wiley and Sons Inc, 2026) Agbor, Fritz Ako; Mhlambi, Sanelisiwe; Donker, Jan van Bever
The Pletmos sub-basin in the Outeniqua Basin, offshore South Africa, is divided by the Superior, Pletmos and Plettenberg faults into northern and southern depocentres. In this study, geological and organic geochemical data together with 1D basin modelling were used to investigate the burial, thermal and maturation histories, and the timing of hydrocarbon generation and expulsion of clay-rich source rocks in the southern depocentre. The modelled source rocks were of Kimmeridgian, Valanginian, Hauterivian, Aptian and Turonian ages. Source rock burial histories at the Ga-A4, Ga-E1, Ga-E2, Ga-H1, Ga-Q1 and Ga-Q2 wells in the Ga-A gas field were reconstructed with subsequent modelling of source rock thermal and maturation histories. The models were calibrated using vitrinite reflectance data from six offshore wells and constrained by palaeotemperature, heat flow and kinetic parameters. The modelling results indicate three principal phases of hydrocarbon generation (132–89, 89–45 and 45 Ma to present day), with a critical moment occurring at approximately 23 Ma during the Oligocene. The deepest syn-rift Kimmeridgian and Valanginian source rocks reached late-mature to over-mature conditions and are interpreted as the principal contributors to hydrocarbon charge in the basin. These results indicate that the petroleum system in the southern Pletmos sub-basin is predominantly gas-prone to gas-dominant, reflecting the advanced maturity of the deeper syn-rift source intervals and highlighting the continued exploration potential of deeply buried petroleum systems in the Outeniqua Basin
Occupational health and safety hazards associated with informal solid waste scavenging at Richmond sanitary landfill, Bulawayo, Zimbabwe
(Springer International Publishing, 2026) Musasa, Tatenda; Muringaniza, Kudakwashe C. R.; Simakani, Ashley
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.
Spatiotemporal analysis and future projections of co and o3 concentrations in Gauteng province using sentinel-5p and cmip6 models
(Elsevier B.V., 2026) Maphanga, Thabang; Muneri, Aluwani Innocent; Madonsela, Benett Siyabonga
This study is among the first to integrate high-resolution Sentinel-5P TROPOMI observations, ground-based SAAQIS measurements, and CMIP6 climate model outputs to generate long-term air quality projections for Gauteng Province. Gauteng, South Africa's economic hub, continues to experience severe air quality pressures driven by rapid urbanization, industrial emissions, and traffic density. However, long-term, multi-source projections for key pollutants such as carbon monoxide (CO) and ozone (O3) remain limited for the region. The objectives of this research were to: (1) characterize the spatiotemporal distribution of CO and O3 across Gauteng during the 2019–2020 baseline period using Sentinel-5P data (2) evaluate and validate CMIP6 climate model outputs against both satellite observations and SAAQIS ground-based measurements and (3) develop deterministic decadal projections for CO and O3 for the year 2030 under the SSP2-4.5 scenario. Model validation showed that CMIP6 outputs systematically underestimated pollutant levels, with consistently negative mean bias errors for CO (≈−101 ppb) and O3 (≈−18 ppb). Despite these biases, spatial correlations with observed concentrations were moderate to strong (r > 0.6). Under the SSP2-4.5 pathway, projections indicate a substantial decrease and increase in pollutants by 2030, with CO showing an increase (+4 to +7) on the other ha nd O3 showing the most pronounced decline (−7 to −95), likely driven by reductions in precursor emissions and associated chemical feedback. Spatial patterns suggest that existing pollution hotspots will shift eastward, away from the Johannesburg–Pretoria urban core. Overall, the findings demonstrate the value of an integrated satellite-ground-modelling approach for regional air quality assessment. While the magnitude of projected changes should be interpreted with caution due to model resolution and inherent uncertainties, the study provides critical evidence to support future policy development and long-term air quality management in Gauteng Province
Fault seal analysis for geological carbon dioxide storage in the pletmos basin, offshore South Africa
(Taylor & Francis Group, 2025) Amponsah-Dacosta Maxwell; Opuwari Mimonitu; Titinchi Salam
Sedimentary basins are considered to be potential carbon sinks and could provide a significant solution to decarbonising the global economy. In the highly faulted Pletmos Basin located offshore South Africa, there is potential for CO2 storage that draws attention to analysing the behaviour of faults as seals or pathways for CO2 migration. Faults were examined based on 3D seismic imagery using shale volume (Vshale) logs from well data. We employed well juxtaposition analysis using triangle-type diagrams and Shale Gouge Ratio (SGR) algorithms to predict their sealing potential. The sealing classification was based on results from SGR calculations. SGR between 0 and 0.2 represented “not sealing,” 0.2–0.4 represented “moderately sealing” and 0.5–1.0 represented “highly sealing.” From the seal classification, faults F-2, F-3, F-7 and the Superior Fault were moderately sealing faults, and fault F-11’s SGR (0.5) with limited sand-sand juxtapositions was classified as highly sealing. The SGR for the respective faults exceeded the 0.2 threshold, indicating their potential to act as seals for CO2 migration. The findings are expected to provide valuable knowledge that could enhance the overall understanding of the feasibility of geological CO2 storage in South Africa.
Tracing Groundwater Recharge Sources and Controls on Groundwater Quality in a Delineated Aquifer to Support Groundwater Allocation, De Aar, Northern Cape, South Africa
(Multidisciplinary Digital Publishing Institute (MDPI), 2026) Baloyi, Lucky; Mqhayi, Sikelela; Kanyerere, Thokozani
Groundwater-dependent communities such as De Aar require a better understanding of groundwater systems to ensure sustainable allocation. This study aims to trace recharge sources in unconfined and confined aquifers and identify processes controlling groundwater quality using hydrogeochemistry and environmental tracers. It argues that aquifer delineation and hydraulic parameters alone cannot fully identify recharge sources or geochemical processes; integrating them with hydrogeochemistry and environmental tracers provides stronger evidence to support groundwater allocation. To validate the argument, the study integrated hydrogeochemical analysis, stable isotopes, tritium, radon-222, and statistical methods supported by depth-specific groundwater sampling. The results, interpreted using Piper and Gibbs diagrams, PHREEQC modelling, and scatter plots, show that groundwater evolution is mainly controlled by rock–water interaction, ion exchange, evaporation, and mixing processes. Ca–HCO3 water indicates recent recharge, while Na–Cl water reflects evaporation effects in both unconfined and confined aquifers, with halite dissolution contributing to Na and Cl enrichment. Isotope results indicate that unconfined aquifer water is isotopically enriched and linked to recent recharge, whereas confined aquifer and spring waters are depleted, suggesting recharge from higher elevations through fractured zones. Tritium dating reveals young (<30 years), intermediate (30–50 years), and old groundwater (60–109 years), while radon results indicate active groundwater flow path, particularly along fractures. These findings demonstrate that groundwater recharge is derived from both local meteoric sources and regional contributions, resulting in predominantly fresh groundwater; however, localized quality concerns should be considered for improved water allocation.
Assessing water resources service value through simulation of a water supply–hydropower generation–ecosystem photosynthesis nexus system
(Elsevier B.V., 2026) Liu, Dedi; Yue, Feng; Liang, Hanxu
Water resources generate service values through water supply (S), hydropower generation (H), and ecosystem photosynthesis (E), forming a SHE nexus system that supports sustainable water resource management under the impacts of both climate change and human activities. However, these service values are often assessed in isolation, overlooking the complex interactions within the SHE nexus system and hindering the water resource management. To address this issue, we have coupled an ecohydrological model, reservoir operation rules, and a value assessment model to simulate the intricate dynamic and quantify the service values within the SHE nexus. The couple model is applied to the Han River Basin (HRB), which serves as the critical source region for the Middle Route of the South-to-North Water Diversion Project (MRSNWDP) in China. The results reveal significant trade-offs among these service values: water supply is the most prominent in low-elevation croplands, hydropower dominates high-elevation grasslands, and ecosystem photosynthesis peaks in mid-elevation forests. The synchronous variations in these service values are primarily driven by climate factors (∼ 60%) in the upper HRB, whereas hydrological processes dominate in the middle and lower reaches. Increased precipitation promotes hydropower generation and photosynthesis capacity. Reservoir operations improve water resource service values via increased streamflow; however, the MRSNWDP suppresses these gains wet seasons by reducing available flow for power and ecosystems. Therefore, our proposed model quantifies water resource service values to support integrated land–water management and water diversion operations.
Analysis of synthetic oviabsorption associated with galaxy groups in simba and tng50 simulations
(American Astronomical Society, 2026) Singh, Tanmay; Borthakur, Sanchayeeta; Nelson, Dylan; Dav́e, Romeel; McCabe, Tyler J.
We compare O vi absorption in synthetic spectra from galaxy groups in the SIMBA and TNG50 cosmological hydrodynamic simulations against those observed from the Cosmic Origins Spectrograph (COS)-IGrM survey. We select 14 galaxy groups from each simulation with (Formula presented) 12.89≤log(Mhalo/M⊙)≤13.61, closely matching COS-IGrM, and create 90,000 synthetic spectra per group. We demonstrate the utility of synthetic absorption spectroscopy when comparing simulations with QSO absorption-based observations. We investigate absorber properties such as radial distributions and kinematics with respect to the group and nearest galaxy. The O vi covering fractions (fOVI) in TNG50 (20.62% ± 2.56%) and SIMBA (5.98% ± 0.82%) are both systematically lower than COS-IGrM (44% ± 5%). A kinematic analysis reveals that the vast majority (∼95%) of absorbers in both of the simulations are gravitationally bound. In TNG50, strong absorbers ( (Formula presented) logNOV I>15 ) are located near star-forming galaxies ( (Formula presented) logsSFR>−11 ) within ∼200 kpc, suggesting a physical connection to stellar feedback, whereas SIMBA shows no comparable trend. Furthermore, in TNG50, the occurrence of O vi absorbers at small impact parameters increases with the stellar mass of the nearest galaxy, but shows no dependence on the total stellar mass of the group. In contrast, SIMBA shows no clear correlation with the nearest galaxy’s stellar mass, although groups with higher total stellar mass exhibit a higher detection rate at larger impact parameters. Differences observed in simulations may arise from feedback models and resolution effects. Finally, we show absorber analysis methodology is an important factor when comparing simulations with absorption spectroscopy observations.
Spectral assessment of senescent sourveld and sweetveld grass quality using continuum-removed absorption features from EnMAP spaceborne imaging spectrometer
(Elsevier B.V, 2026) Masenyama, Anita; Mutanga, Onisimo; Dube, Timothy; Sibanda, Mbulisi
Sourveld and sweetveld grasses exhibit interesting nutritional quality dynamics at the senescent stage, which have not been investigated from a remote sensing perspective. This study presents the first spatially explicit method(s) for estimating biochemical constituents of senescent grass across sour and sweet veld types using the spaceborne Hyperspectral Imager (HSI) on board the Environmental Mapping and Analysis Programme (EnMAP). Specifically, this study assessed the effectiveness of applying continuum removal to absorption features in data acquired from the EnMAP HSI. We also identified the key wavelengths relevant for senescent grass quality estimation in the different velds. Grass quality was quantified using three foliar biochemical indicators: nitrogen (N), acid detergent fibre (ADF) and acid detergent lignin (ADL). Data analysis was conducted using the random forest (RF) model and five broad continuum-removed absorption features which have been found to relate to foliar biochemicals in dry vegetation spectra. The study first evaluated the performance of four metrics derived from continuum-removed spectra, namely the continuum-removed derivative reflectance (CRDR), band depth (BD), band depth ratios (BDR) and the normalized band depth index (NBDI). The CRDR combined with RF regression was then used to identify key wavelengths from the absorption features for predicting senescent grass canopy N, ADF, and ADL across both veld types. Using the testing datasets, the selected wavebands yielded strong predictive performance for senescent sourveld, with R2 values of 0.72, 0.71, and 0.69, RMSEs of 0.08, 6.96, and 3.68, and RMSE% (of mean) of 13.77, 12.64, and 16.38 for N, ADF, and ADL, respectively. Statistical agreement was highest in sweetveld grasses, yielding R2 values of 0.73, 0.78, 0.82, corresponding RMSEs of 0.13, 5.82, and 2.01 while the RMSE% (of mean) were 10.95, 11.81 and 11.26 for N, ADF, and ADL, respectively. Overall, the R550.69 – 741.83 absorption feature had the highest number of optimal wavelengths in estimating canopy N across both velds. Moreso, optimal wavebands for estimating fibre concentration of senescent grass were derived more from the SWIR with the R2224.58 – 2376.95 absorption feature, yielding higher estimation accuracies. CRDR exhibited promising results, as it identified wavelengths causally linked to N, ADF and ADL in senescent vegetation. This work underscores the potential of spaceborne hyperspectral data with continuum removal on known absorption features for regional estimation of senescent grass quality.
The analysis ready multispectral data and machine learning algorithms for mapping groundwater-dependent invasive alien plants in Heuningnes Catchment, South Africa
(Taylor and Francis Ltd., 2026) Moropane, Mmasechaba L.; Dube, Timothy; Shoko, Cletah; Masocha, Mhosisi
Field monitoring of groundwater-dependent invasive alien plants (GDIAPs), though accurate, is spatially limited and prone to misclassification bias. Satellite imagery and machine learning algorithms (MLAs) offer scalable alternatives, yet their effectiveness in mapping GDIAPs remains underexplored. This study assessed Sentinel-2 and Landsat-8 data using five MLAs with pixel- and object-based approaches to delineate GDIAPs within groundwater-dependent ecosystems (GDEs) of the Heuningnes Catchment. Pixel-based random forest (RF) achieved the highest overall accuracies (98% with Sentinel-2, 94% with Landsat-8), while object-based gradient tree boosting (GTB) using Sentinel-2 achieved 85%, outperforming RF (82%). The class-specific F1-scores for GDIAPs and native plants exceeded 90% when pixel-based RF classifications were used. The Sentinel-2 pixel-based RF results indicated that GDIAPs dominated 26.8 km² (60%) of GDEs in 2022, compared to 13.6 km² (31%) of GDEs occupied by native fynbos. These findings demonstrate the value of satellite-based machine learning for monitoring GDIAPs and supporting invasive species management, ecosystem protection, and water resource planning.
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.
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.
Sociotechnical analyses of households’ comprehension of land use and land cover change in the Eastern Cape province of South Africa
(Springer Nature, 2026) Ndhleve, Simbarashe; Kabiti, Hlekani Muchazotida; Ayisi, Kingsley Kwabena; Zhou, Leocadia; Nakin, Motebang Dominic Vincent; Dube, Timothy I.
Communal land systems are undergoing degradation, and this has implications for food and water security. This study examines land use and land cover changes in communal land system of Mthatha river catchment, South Africa, by using a juxtaposition of GIS and Remote Sensing imageries and ethnography aimed at understanding how custodians of this land system comprehend LULC changes in their localities. The article examines the extent of divergence and/or convergence of inhabitants’ perceived LULC changes and GIS and Remote Sensing imageries of their area. A semi structured questionnaire was used to collect perceptions data from 183 randomly selected households within the catchment. Mitigation and adaptation strategies were also identified in the paper. Findings revealed that most participants (90%) correctly perceived an increase in built up areas, decreases in cultivated land (77%), water bodies (56%), plantations (72%), grasslands (52%) and natural forests (59%). Bare lands were perceived to be decreasing (72%) in contrast to an observed 11% increase through satellite imagery. Lack of consensus between perceived changes and findings from satellite images indicates gaps in existing knowledge about LULC. These divergence and convergence of understanding between the technical outputs of GIS and Remote Sensing and local communities’ knowledge, perceptions and practical experiences can be useful in managing LULC changes in context specific ways. How individuals perceive the problem determines the level of commitment to solving it. The findings of this study are important for policymakers and scientific communities as they create the important base for dialogue with communities.
Trimester-specific exposure to multiple heat indicators and adverse birth outcomes across four European countries
(Academic Press Inc., 2026) Jackson, Debra; Bao, Mian; Nobile, Federica
The health of pregnant women and their fetuses is increasingly challenged by abnormal heat events. Few studies have disentangled the trimester-specific effects of heat exposure during pregnancy on perinatal outcomes and examined potential differences across multiple heat indicators. This study included singleton births from multiple national and region registries across Europe: Sweden (2014-2019), Belgium (2012-2022), Italy (Lazio Region) (2001-2019), and Greece (1999-2021). We obtained 2-m air temperature, Universal Thermal Climate Index (UTCI), Wet Bulb Globe Temperature (WBGT), and Heat Index data from the ERA5 reanalysis dataset. Our study outcomes were preterm birth (PTB), stillbirth (SB), small for gestational age (SGA), and large for gestational age (LGA). Cox proportional hazard models, with gestational age as the underlying time scale, were applied to evaluate trimester-specific associations between multiple heat indicators and adverse birth outcomes. Country-specific estimates were then combined through meta-analyses. In total, 4,924,422 mother-child pairs were included in the analysis. An increase in mean temperature from the 75th to the 99th percentile in the third trimester was associated with PTB (HR = 1.51, 95% CI: 1.34-1.71), SB (HR = 1.54, 95% CI: 1.44-1.65), SGA (HR = 1.16, 95% CI: 1.11-1.20), and LGA (HR = 1.12, 95% CI: 1.07-1.17). Comparable associations were observed across heat indicators and countries for each trimester. Our findings suggest that the third trimester is a critical exposure window of vulnerability for heat during pregnancy. The comparable effect estimates among heat indicators highlight the usefulness of mean air temperature in Europe.
Groundwater responses to decadal rainfall variability in semi-arid South Africa
(Elsevier B.V., 2026-04) Kanyerere, Thokozani; Bjerre, Elisa; Jessen, Søren
This study examines groundwater responses to climate trends and variability in semi-arid South Africa (SA). Groundwater is a vital water resource in the semi-arid regions of Africa, which are characterized by low, erratic rainfall and intermittent streamflow. In these regions, water scarcity is intensifying due to rising irrigation demands, urbanization, and climate change. Semi-arid SA experiences significant rainfall variability at inter-annual and decadal timescales. However, groundwater responses to SA’s climate remains underexplored, partly due to limited observational data. This study analyses long-term trends and variability in rainfall, temperature, and groundwater levels in the Hout/Sand River catchment from 1940 to 2022 using climate and groundwater indices. Groundwater response to rainfall variability is assessed through correlations between the Standardized Precipitation Index (SPI) and the Standardized Groundwater Index (SGI) across annual to decadal timescales. Results indicate no significant trends in total annual rainfall, but rainfall patterns intensified manifested as higher daily rainfall intensity, longer dry periods, and shorter wet periods. The highest SGI-SPI correlation occurs at 7- and 8-year accumulation periods (r = 0.80), which indicates a dependence of groundwater levels on antecedent rainfall consistent with the region’s decadal climate variability of dry and wet epochs. The study adds to our conceptual understanding of groundwater responses to large-scale climatic patterns, which is essential for assessing future water availability under climate change.
A multiple spatial scales water use simulation for capturing its spatial heterogeneity through cellular automata model
(Copernicus Publications, 2025) Zhang, Jiayu; Liu, Dedi; Wang, Jiaoyang; Yue, Feng; Liang, Hanxu; Peng, Zhengbo; Guan, Wei
Reliable water use simulation is essential for sustainable water resource planning, especially under intensifying pressures from climate change, population growth, and socio-economic transitions. While previous studies have extensively explored water availability as supply side modeling across multiple spatial scales for its spatial heterogeneity, the water demand side remains relatively underdeveloped – often constrained by fixed spatial scales and coarse statistical data that assume spatial homogeneity. This mismatch between supply side and demand side limits the ability of existing models to accurately represent spatial heterogeneity in water use and brings uncertainty into water resource allocation strategies. To address this mismatch, we propose a novel multi-scale water use simulation framework by integrating cellular automata (CA) model with Generalized Likelihood Uncertainty Estimation (GLUE). The CA model captures the spatial heterogeneity of water use through the grid-based update rules. Two update rules are adopted – probability rule (i.e., capturing stochastic transitions via distribution fitting) and linear rule (i.e., modeling neighborhood-weighted evolution). To evaluate the impacts of spatial scale on water use heterogeneity, simulations are conducted at three spatial scales: 1 km, appropriate scale, and prefecture scale across 341 prefectures in China. Results show that both the update rule and spatial scale significantly affect spatial heterogeneity and uncertainty of water use. The probability rule can capture the broader variability but results in higher Root Mean Squared Error (RMSE) and Relative Error (RE) while the linear rule brings more stable performance with lower errors. While the 1 km scale increases uncertainty due to sensitivity to local fluctuations, and the prefecture scale suppresses spatial details, the appropriate scale offers the best trade-off between stability and spatial heterogeneity. The uncertainty quantified by GLUE, expresses as confidence intervals, varies across prefectures and spatial scales. Overall, the proposed framework offers a flexible tool for multi-scale water use simulation and highlights the critical role of spatial heterogeneity, thereby supporting adaptive water resource planning and management.
Utilizing Aquifer Hydraulic Parameters to Assess Local and Regional Recharge Potentials for Enhancing Water Allocations in Groundwater-Dependent Areas in De Aar, Northern Cape, South Africa
(MDPI, 2025) Baloyi, Lucky; Kanyerere, Thokozani; Muchingami, Innocent; Pienaar, Harrison; Igwebuike, Ndubuisi; Mukhawana, Mxolisi B
The precise and accurate use of aquifer hydraulic parameters for assessing local and regional recharge potential for enhancing groundwater allocation planning is vital for many hydrogeological studies. The conventional approach for allocating groundwater presents a challenging scenario, as it remains uncertain whether the applied recharge estimate is local or regional recharge. The approach does not account for the extent of the aquifer recharge in terms of local and regional scale; instead, it assumes that recharge is distributed across the catchment. This study aimed to demonstrate the use of aquifer hydraulic parameters (transmissivity and storativity) to explain areas of potential recharge (local and regional) for enhancing groundwater allocation planning with a specific case study of De Aar, Northern Cape, South Africa. It argues that not integrating local and regional recharge potentials in planning for groundwater allocations can result in over- or under-allocation of groundwater resources to users. A constant discharge pumping test and recovery test matching the duration of pumping were conducted for data collection. The Flow Characteristics method was used as a diagnostic tool to understand the different aquifer flow regimes in the study area. To develop an integrated understanding of the groundwater system, a hydrogeological conceptual model was used to visualize areas with higher or lower recharge potential across local and regional scales. Results showed significant variability in transmissivity, ranging from 213 to 596 m2/d, and storativity, ranging from 0.0000297 to 0.000185. The transmissivity values suggest that groundwater moves faster; meanwhile, the storativity values suggest that the aquifer system has high water storage capacity. These results will assist water resource planners in making informed decisions on how to allocate groundwater to users. This study demonstrated that aquifer hydraulic parameters are a valuable tool for improving groundwater allocations, thereby highlighting the importance of considering areas for potential recharge, both local and regional, in planning groundwater allocation.

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