Citation: Shah, D.N., Tachamo Shah, R.D., Mishra, K. et al. (2026). Seasonal dynamics of spring water quality and quantity in urban cities of Kathmandu Valley, Central Nepal. Environmental Earth Sciences, 85, 182. https://doi.org/10.1007/s12665-026-12915-3.

Abstract: Springs are important sources of water in the mid-hills of Nepal, yet they are rapidly depleting. This study was carried out in the Kathmandu Valley, Central Nepal, to map natural spring locations, assess their water quality and quantity for drinking, irrigation, and aquatic life, and evaluate overall spring ecosystem health. A total of 150 spring sources were mapped. Water quality parameters were analyzed for 146 springs in the post-monsoon season (November 2023) and 142 springs in the pre-monsoon season (March 2024). Discharge measurements were recorded for 104 and 98 springs during field visits in post-monsoon and pre-monsoon seasons, respectively, where six springs were found to be dry in the pre-monsoon season. Compared to the post-monsoon season, more than 90% of springs exhibited reduced discharge in the pre-monsoon season, indicating high vulnerability during the dry season. Significant seasonal variations in discharge were recorded for low-discharge springs (< 5 lpm, p < 0.001 and 5–10 lpm, p < 0.03), reflecting their sensitivity to enhanced monsoonal recharge. All measured water quality parameters except phosphate, were within the threshold limits of the WHO, the National Drinking Water Quality Standards of Nepal, and Indian and Chinese guidelines for aquatic animal protection. The Weighted Arithmetic Water Quality Index (WAWQI) showed that in the post-monsoon season, 26.69% of springs were classified as good, 48.97% as poor, 12.41% as very poor, and 17.93% as unsuitable for drinking. In the pre-monsoon season, 22.54% of springs were classified as good, 33.80% as poor, 10.56% as very poor, and 33.10% as unsuitable for human consumption. Piper plot showed a predominance of the Ca-HCO₃ facies in both post-monsoon (90.41%) and pre-monsoon (80.27%) seasons, indicating that carbonate weathering is the dominant process. Factor analysis identified geology and anthropogenic activities as the primary factors influencing spring water chemistry. The Wilcox diagram revealed that the sodium adsorption ratio (SAR) values of springs in both seasons were suitable for irrigation. Overall, this study provides valuable insights into the seasonal variability, hydrochemistry, and sustainability of springs in the Kathmandu Valley and underscores the urgent need for management interventions to ensure their long-term yield and conservation.

Citation: Farooq, M., Wen, Z., Shah, D. N., Tachamo-Shah, R. D., Mondal, D. K., Guili, L., ... & Cai, Q. (2026). Multidimensional riverine biodiversity reveals decadal and sub-decadal effects of hydrological and water-quality changes. Environmental Research, 124000. https://doi.org/10.1016/j.envres.2026.124000.

Abstract: Freshwater biodiversity is increasingly affected by compounded anthropogenic pressures and climatic variability. However, the current understanding of how multiple environmental stressors reorganize biodiversity across taxonomic, functional, and phylogenetic dimensions at different temporal scales remains poorly understood. It is particularly evident in highly climatic and hydrologically dynamic systems, such as in the Mediterranean climate and monsoonal areas. Using two decades of macroinvertebrate data from three contrasting Mediterranean watersheds, we examine how multidimensional biodiversity patterns vary across decadal and sub-decadal scales in response to hydrological variability and environmental stressors. This multi-scale design provides a robust, regionally representative dataset for testing scale-dependent biodiversity dynamics. We partitioned the 20-year dataset into decadal (10-year) and sub-decadal (5-year) periods to assess scale-dependent variability. We found a scale-dependent hierarchy: at the decadal scale, taxonomic richness showed no net change while functional and phylogenetic diversity declined; at sub-decadal scales, phylogenetic diversity exhibited detectable variability and environmental filtering, whereas functional assembly remained predominantly random. Hydrological variables and organic nutrients were among the key correlates of this scale-dependent variability. Our work reveals a mixed assembly framework where random processes dominated (60–80% of communities), but within the non-random subset, phylogenetic clustering varied across time periods, indicating that scale-dependent environmental filtering operates alongside strong stochasticity. This demonstrates that different biodiversity dimensions respond to environmental change at distinct temporal grains, with even coarse phylogenetic proxies revealing detectable filtering at fine resolutions, necessitating scale-aware, phylogeny- and trait-based conservation strategies to accurately assess resilience under escalating global change.

Citation: Sitaula, S., Basnet, N., Bhattarai, S. et al. (2026). Chemical characterization and spatial distribution of microplastics in the surface water of the Arun River Basin, Central Himalaya, Nepal. Water, Air, & Soil Pollution, 237, 549. https://doi.org/10.1007/s11270-026-09239-0.

Abstract: Glacier-fed Himalayan Rivers are vital lifelines for South Asia, sustaining ecosystems, agriculture, and millions of people across national boundaries. Although microplastic pollution is reported in several water systems, the transboundary rivers in the central Himalayas remain critically understudied. This research investigates the chemical characteristics and spatial distribution of microplastics in the surface water of the Arun River, a major transboundary tributary of the Ganges system, spanning China, Nepal, and India. Surface water samples (n = 28) were collected in duplicate from 14 sites across the Arun River Basin, Koshi Province, Nepal, selected based on land use and land cover, spatial distribution, and anthropogenic activities. Microplastics were detected in all samples, with an average concentration of 30 ± 3.2 particles per liter (range: 23–35 particles/L). Microplastic concentrations were notably elevated in proximity to cropland and built-up zones, with peak levels recorded at sites influenced by construction activities and agricultural runoff. Intriguingly, comparable concentrations were also detected at relatively undisturbed locations, indicating the potential for long-distance transport mechanisms. Most particles were black (78%), fragment-shaped (69%), and small-sized (32–100 μm; 95%). Dominant polymers included polyethylene, polyethylene terephthalate, polypropylene, and polystyrene. Multivariate analysis and land use mapping indicated higher microplastic loads in urbanized and construction-impacted zones, while tributary inflows contributed to dilution. Unlike global patterns of downstream accumulation, microplastic concentrations in the Arun River peaked in its middle reaches, reflecting localized land use dynamics. These findings highlight the influence of human activities and call for targeted interventions to reduce plastic pollution in transboundary Himalayan River Systems.

Citation: Pant, R.R., Pathak, G., Wang, G. et al. (2026). Spatiotemporal dynamics of trace elements and associated health risks in Phewa Lake, Nepal. Environmental Monitoring and Assessment, 198, 313. https://doi.org/10.1007/s10661-026-15169-5.

Abstract: Freshwater lakes are critical sources of drinking water worldwide, yet contamination by trace elements (TEs) presents significant health risks. Phewa Lake, Nepal, a Ramsar-listed wetland supporting many people, irrigation, fisheries, and tourism, was selected as a case study due to its socio-economic and ecological value. This study investigates the spatiotemporal distribution and health risks of 10 TEs across pre-monsoon and monsoon seasons. 50 lake water samples were collected, split evenly between pre-monsoon and monsoon. Results showed elevated concentrations of arsenic (As), chromium (Cr), copper (Cu), manganese (Mn), nickel (Ni), lead (Pb), and zinc (Zn) during the pre-monsoon, with values declining by approximately half during the monsoon due to rainfall dilution. Spatially, higher concentrations were observed near urban settlements and drainage points. Subsequent statistical analyses identified geogenic sources as predominant, with minor anthropogenic influence mapped to urban shorelines. Water quality was assessed using the Water Quality Index (WQI) and Metal Index (MI): scores were 9.66 and 0.09 pre-monsoon, and 2.86 and 0.03 during monsoon, all well within the World Health Organization (WHO) guideline limits. Hazard Index (HI) values for all TEs were below unity, with As posing the highest non-carcinogenic risk (HI_children = 0.115, HI_adults = 0.076). Cancer risk was low to medium for Pb, Cr, and As. Although water quality was generally acceptable with low risks, proactive measures, such as routine monitoring, regulated runoff, and improved wastewater treatment in alignment with Sustainable Development Goals (SDGs) 6, 13, and 15, are recommended. These findings can inform sustainable urban lake management in the Himalayas and comparable regions globally.

Citation: Upadhaya, M., Adhikari, D., Thapa, L.B. et al. (2026). Assessment of drinking water quality and irrigation suitability in the Marsyangdi River Basin, Nepal: Implications for SDG 6 and ecosystem sustainability. Environmental Earth Sciences, 85, 130. https://doi.org/10.1007/s12665-025-12782-4.

Abstract: The Marsyangdi River Basin (MRB) in central Nepal is a crucial source of drinking water, irrigation, and hydropower; however, it is increasingly threatened by agricultural intensification, urban expansion, and climate change. This study evaluated the suitability of river water for drinking and irrigation in relation to Sustainable Development Goal 6 (Clean Water and Sanitation). A total of 84 water samples (42 per season) were collected during pre-monsoon and monsoon periods from the main river and its tributaries. Physicochemical and microbial parameters were analyzed following standard protocols, and water quality was evaluated using the Weighted Arithmetic Water Quality Index (WQI) and irrigation indices including sodium percentage (Na%), sodium adsorption ratio (SAR), magnesium adsorption rate (MAR), Kelly’s ratio (KR), permeability index (PI), and the cation ratio of soil structural stability (CROSS). Results showed that overall water quality for drinking was excellent (mean WQI < 50 across both seasons). However, Escherichia coli contamination was detected in more than 60% of samples, underscoring health risks and the need for treatment before consumption. Irrigation water was generally suitable (C1–S1 and C2–S1 classes on the Wilcox diagram), with spatial variation reflecting geology and land-use patterns: lower sodium but higher magnesium in leeward Manang, and higher sodium hazards in the intensively farmed districts of Lamjung and Tanahun. These findings highlight the dual challenge of ensuring safe drinking water and sustaining irrigation under changing hydro-climatic conditions. Continuous monitoring and localized water management strategies are essential to safeguard human health, agricultural productivity, and ecosystem resilience in Himalayan River basins.

Citation: Reshmi, N., Awasthi, M.P., Bohara, R. et al. (2026). Hydrochemical dynamics and pollution regimes in Satyawati Lake, Nepal: implications for water quality and sustainable management. International Journal of Energy and Water Resources, 10, 10. https://doi.org/10.1007/s42108-025-00442-z.

Abstract: Globally, freshwater lakes are increasingly threatened by climate change, urbanization, and agricultural runoff, leading to water quality degradation, biodiversity loss, and ecosystem imbalance. In the Nepal Himalayas, these challenges are compounded by rapid land-use changes and pollution, impacting critical aquatic ecosystems. This study focuses on Satyawati Lake, a mid-hill lake in Nepal, to assess seasonal hydrochemical variations and their implications for water quality. In post- and pre-monsoon periods, water samples were obtained from thirty sites and analyzed for critical parameters, including total dissolved solids (TDS), electrical conductivity (EC), dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), potential of hydrogen (pH). Most parameters, like EC, TDS, and pH, were within WHO limits, although DO was relatively low (3.11 mg/L) and COD (26.1 mg/L) levels were elevated in the post-monsoon period, signaling organic pollution. Hierarchical cluster analysis (HCA) identified clear spatial and seasonal pollution patterns, with higher mineral content in the pre-monsoon and increased organic load in the post-monsoon period. These findings posed challenges to achieving sustainable development goals (SDGs) that are relevant to life on land, climate action, and clean water. Moreover, climate variability has exacerbated water quality deterioration, and future efforts should address these issues through improved pollution control, sustainable agriculture, and climate-resilient water management. The study emphasized long-term monitoring and sustainable management strategies to preserve Satyawati Lake’s ecological, economic, and aesthetic values, contributing to the broader conservation of Himalayan Lake ecosystems.

Citation: Maharjan, N., Lamichhane, G. P., Timalsina, N., Paudel, S. P., & Sapkota, R. P. (2026). Long-range transport, regional forest fire events and meteorological influences on PM2.5 in western Nepal. Geographical Journal of Nepal, 19(1), 1–22. https://doi.org/10.3126/gjn.v19i1.92139.

Abstract: PM_2.5 pollution is a major global environmental concern, upsetting human as well as ecosystem health. This study examines the long-range transport and effects of meteorological factors on PM_2.5 concentration, utilizing data from a real-time air quality monitoring station established in the Rara National Park in 2020 and satellite data. Similarly, the influence of forest fire events on PM_2.5 levels were also assessed. PM_2.5 concentration at the Rara Station showed bimodal pattern, higher during early morning and late night, with peak levels in March and April, particularly due to forest fires in regional geographical extent. The correlation between PM_2.5 and meteorological factors showed a moderate negative relationship with humidity, and weak negative and positive correlation with temperature and wind speed, respectively. Wind direction analysis indicated that southern and southwestern air masses significantly contributed to elevated PM_2.5 levels, suggesting regional and transboundary transport of pollutants. The strong correlation between fire frequency and PM_2.5 concentration was observed around 100-200 km at 2-day time lag emphasizing the long-range transport of pollutants. Linear regression model indicated that forest fires had a significant impact on air quality, explaining about 74% of the variance in PM_2.5 levels. Linear regression analysis further indicated that forest fire frequency explained a substantial portion of PM_2.5 variability, with each additional fire within 100 km increasing PM_2.5 by 0.4 μg m^-3. The findings highlight regional approach and transboundary cooperation for research and policy interventions to mitigate regional forest fire events and improve regional and local air quality.

Citation: Sharma, G. P., Sapkota, R. P., Gurung, T., Puppala, S. P., & Maskey Byanju, R. (2026). Perceptions of farmers and government officials towards the effects of air pollution on honey bees in Bhutan. Nepal Journal of Environmental Science, 14(1), 21–30. https://doi.org/10.3126/njes.v14i1.84217.

Abstract: Bees interact with the environment, mainly the atmosphere, during foraging, and collect a wide range of airborne suspended particulate matter. Integrating beekeeping into farming operations is an important initiative for improving livelihoods, but little is known about the perceived impacts of air pollution on honey bees in Bhutan. This study aims to examine the perspectives of Bhutanese farmers and Department of Livestock (DOL) officials on the effects of air pollution on honey bees. PM_2.5 concentrations of Thimphu from 2018 to 2024, collected by the National Environment Commission (NEC) and made available by the National Statistical Bureau (NSB) were utilised for the data analysis. Questionnaire survey was undertaken from 85 farmers and 85 DOL officials to acquire information on air pollution and its impact on bees. Between 2018 and 2024, PM_2.5 concentrations revealed a twofold rise, with levels above the WHO 2021 Air Quality Guidelines (AQG) of 5 µg/m³, indicating a continual worsening in the quality of the air in Thimphu as well as in Bhutan.  Almost 55% of farmers and DOL officials reported an increase in air pollution, while 48% indicated a decline in Bhutan's bee populations over time. It was found that 77% of the respondents felt that bees and bee products are negatively impacted by air pollution. Similarly, 61% believe that apiculture will reduce rural-urban migration in Bhutan. Re-enforcing current laws and regulations is necessary to reduce air pollution and its impacts on honey bees in Bhutan.

Citation: Shrestha, H., Karna, A., De Foy, B., Bhave, P. V., Sapkota, R. P., Byanju, R. M., Bergin, M. H., & McAdoo, B. (2026). Investigation of the cross-border movement of PM_2.5 in the Terai belt of Nepal using a low-cost sensor network. Atmospheric Pollution Research, 102920. https://doi.org/10.1016/j.apr.2026.102920.

Abstract: Transboundary air pollution is a critical environmental and public health issue across South Asia. Nepal experiences high exposure due to its geographic location near major emission regions. A network of calibrated low-cost PM_2.5 sensors across the Terai belt and two Mid-land valleys recorded a sharp rise in PM_2.5 levels from December 28 to 30, 2022. Monitoring sites across the country showed elevated concentration during this period. Meteorological and atmospheric data, including aerosol optical depth, air parcel trajectories, boundary layer height, ventilation coefficients, and fire events, were used to describe the regional dynamics. The Potential Source Contribution Function model was implemented to trace air masses transporting pollutants into Nepal. Our analysis shows that south-easterly winds in the east and south-westerly winds in the west carried emissions from the Indo-Gangetic Plain toward the valleys. Fire activity in the region remained low, suggesting limited influence from biomass burning. The study confirmed the viability of low-cost sensors for identifying both local and transported pollution. The findings highlight the urgent need for regional cooperation and targeted policy measures in the southern Terai to reduce cross-border and domestic emissions.

Citation: Budha, P.B., Bhattarai, D.R., Sapkota, R.P., Dhital, N.B., Pokhrel, C.P., Khadka, U.R., & Rijal, K. (2026). Spatial and temporal distribution of wildfires in Nepal Himalayas. Journal of Tropical Forest Science, 38(1), 48-64. https://www.jstor.org/stable/48857182.

Abstract: Wildfires are common in Nepal during the pre-monsoon period (March to May), causing significant damage to forests and wildlife. Understanding their occurrence and distribution is crucial for effective forest management. This study analyses wildfire data from 2012 to 2021, obtained from the Visible Infrared Imaging Radiometer Suite (VIIRS). The active fire product of VIIRS was filtered to identify wildfires in forests, grasslands, and other wooded areas, and these incidents were geospatially analysed across Gandaki Province in the Nepal Himalaya. Wildfire locations were overlaid with environmental and topographic variables, including aspect, elevation, slope, land use and land cover, moisture, soil type, road proximity, and stream density. Nepal recorded 230,077 wildfire occurrences over the decade, with 16,860 in Gandaki Province. Nearly 75% of these fires occurred in March (21%) and April (54%). About 80% of incidents took place below 2000 m elevation, 55% on south to southeast-facing slopes, and 71% on slopes between 10° and 50°. Additionally, 73% of fires were within 500 m of a road, and 77% occurred in areas with drainage densities between 1 km/km² and 2 km/km². Wildfire frequency reached up to 4 events per km² in areas with population densities above 500 people per km², which is nearly four times higher than in sparsely populated regions. This study presents the first comprehensive spatiotemporal analysis of wildfire patterns in Gandaki Province using a decade of satellite data integrated with topographic, ecological, and human factors. The findings provide critical insight into wildfire risk areas and influencing factors, offering a data-driven foundation for risk assessment and targeted forest management. The results have direct implications for developing region-specific wildfire prevention and mitigation strategies, particularly in the vulnerable mid-hill landscapes of the Nepal Himalaya.

Citation: Thakuri, S., Shrestha, S., Palikhe, R., & Chauhan, R. (2026). GHG emission from diesel-powered irrigation pumps and mitigation potentials in agriculture sector of Nepal. Environmental Science and Pollution Research, 33, 3266–3280 (2026). https://doi.org/10.1007/s11356-026-37494-5.

Abstract: Emissions from diesel-powered irrigation pumps (DIPs) in Nepal’s agriculture sector contribute to climate change and local air pollution. This study presents the emission estimation using emission factors (EFs) for energy use in DIPs and estimates the contribution of DIPs to the GHGs emission in Nepal using both the bottom-up and top-down approaches. It involves analyzing data on the number of DIPs, the amount of fuel used for irrigation, hours of operations, and efficiency of the pumps. The various EFs for the DIPs were collected from the previous research reports and articles. The activity data for the bottom-up approach was collected from a telephone survey, field sampling, and review of the existing documents. The country-specific EFs for energy use in DIPs developed in Nepal by previous studies using sample measurements were used in this study. The estimated number of DIPs for 2024 is about 51,137 (1.5 to 9 hp; average 5 hp DIPs), operating an average of 192 h per year in Nepal. The DIPs consume 5891 m³ (kL) of fuel per year and emit 14,674 tons of CO₂, 20.9 tons of CH₄, 0.18 tons of N₂O, 71.3 tons of NO_x, 52.2 tons of non-methane volatile organic carbon (NMVOC), 332.0 tons of CO, 54.4 tons of PM_2.5, 40.30 tons of organic carbon (OC), 17.8 tons of black carbon (BC), and 0.6 tons of SO₂ each year. The number of solar-powered irrigation pumps (SIPs) is 3129, which is about 2% of total irrigation pumps in Nepal. Farmers are providing encouraging feedback on the use of SIPs in their small-sized farms. The study shows that the number of electricity-powered pumps has increased rapidly by replacing the DIPs after the mid-2010s due to increased access to the grid electricity. The assessment is expected to support identifying opportunities to reduce emissions through improvements in technology, management practices, and other strategies.

Citation: Chhinal, L., Thakuri, S., Mathema, A. B., Dulal, B., & Khanal, S. N. (2026). Flood Hazard Mapping and Risk Evaluation in the Lower Karnali River Basin of Nepal. Geographical Journal of Nepal, 19(1), 23–43. https://doi.org/10.3126/gjn.v19i1.92144.

Abstract: This study presents flood hazard mapping and risk assessment using a hydrodynamic simulation in HEC-RAS tool, focusing on a 38 km stretch of the river from Chisapani to the Nepal-India border in the Lower Karnali River Basin (KRB). A time series of daily mean discharge records from the Chisapani gauging station was used for model simulations. Flood magnitudes of 10-, 20-, 50-, and 100- year return periods (YRPs) were estimated using Gumbel’s distribution, with the 100-YRP daily discharge of 20,343 m³/s. Field surveys were conducted in flood-prone areas of Rajapur Municipality using the Vulnerability and Risk Assessment (VRA) framework. Results show that parts of Rajapur Municipality, Wards #1, #3, #4, and #7 are susceptible to inundation, even during normal flood events, with water depths reaching upto 10 m posing significant risk to the communities inhabiting in these areas. Agricultural land is particularly exposed, posing serious risks to food security and livelihoods. Moreover, even after a five-year return period, the 2014 flood simulations (equal to a 100-YRP) indicate that these wards remains highly vulnerable. This findings emphasizes the urgent need for improved settlement planning and the development of effective flood control measures in Rajpur Municipality.

Citation: Xiao, X., Zhang, X., Zhong, Q., Wang, Y., Yu, Z., Liu, K., & Pant, R. R. (2026). River water hydrochemical characteristics and weathering fluxes of a subtropical monsoon basin, south‐central China. Hydrological Processes, 40(1), e70397. https://doi.org/10.1002/hyp.70397

Abstract: Quantifying weathering-driven carbon sinks in human-impacted subtropical basins remains a critical gap. In the carbonate-dominated, densely populated Xiangjiang River Basin, this study tracked hydrochemistry through two hydrological years to partition solute sources and constrain CO₂ consumption at high resolution. Findings revealed precipitation total dissolved solids (TDSs) spanning 1.7–201.4 mg/L, where Ca²⁺, K⁺, SO₄²⁻ and NO₃⁻ constituted the principal ionic constituents and the values for Xiangjiang River water were 25.8–183.1 mg/L, with Ca²⁺ and HCO₃⁻ as the dominant ions. The chemical weathering contributions from carbonate rock (62.2%) and silicate rock (14.5%) were estimated using a forward model, indicating that carbonate rock weathering is the primary source of the Xiangjiang River solutes. The average annual weathering fluxes of carbonate and silicate rocks in the Xiangjiang River were 21.6 and 3.4 t/km²/year, respectively, with corresponding CO₂ consumption rates of 293.1 × 10³ and 81.0 × 10³ mol/km²/year. This study provides the first high-resolution quantification confirming that the subtropical monsoon climate of the Xiangjiang River Basin generates intermediate weathering-driven CO₂ consumption rates, positioning its carbon sink capacity between that of arid/plateau regions and tropical zones. The findings establish hydrochemical baselines for the Xiangjiang and offer quantitative benchmarks for regional water-resource management and carbon-cycle modelling under intensifying anthropogenic pressures.

Citation: Pokhrel, S., Thakuri, S., Subedi, C. K., Kunwar, R. M., Sharma, K. P., Chaudhary, R. P., & Ghimire, S. K. (2026). Spatiotemporal impacts of forest fires on mountain vegetation: A case study from Langtang National Park, Nepal Himalaya. Ecology and Evolution, 16(1), e72758. https://doi.org/10.1002/ece3.72758

Abstract: Forest fires in the Himalayan region are increasing under climate change, yet their interactions with vegetation dynamics and anthropogenic drivers in protected areas remain poorly understood. This study presents a two decade (2000–2020) spatiotemporal assessment of these interactions in Langtang National Park, Nepal. We integrated MODIS-derived active-fire and burned-area data with vegetation indices, including the Normalized Difference Vegetation Index (NDVI) and Vegetation Condition Index (VCI), along with climatic variables (CHIRPS precipitation and land surface temperature, LST). Trends and drivers were validated through field ecological surveys and stakeholder interviews. Our analysis revealed a significant long-term greening trend (increasing max NDVI; Z = 2.2044, p = 0.0275) alongside a stable fire regime. Fire activity showed strong land-cover specificity, disproportionately affecting grasslands and needle-leaf forests, whereas closed broadleaf forests exhibited high resilience. Maximum temperature was the primary climatic driver of burned-area extent (r = 0.62, p < 0.01), and VCI was the strongest predictor of overall vegetation health (β = 0.6285, p < 0.001). Field evidence confirmed fire-mediated ecological succession and highlighted intentional burning as a key anthropogenic ignition source. These findings advance understanding of Himalayan fire ecology, demonstrating that climatic warming and land cover interact to shape fire risk even in a greening landscape. We propose a stratified management framework targeting high-risk zones, leveraging resistant forests as natural firebreaks, carrying out controlled burning in areas where artificial firebreaks can be created, conducting early season burns in key sensitive zones, and incorporating VCI into early warning systems to enhance the resilience of Himalayan-protected areas.

Citation: Pant, R. R., Zeng, C., Wang, G., Qaiser, F. U. R., Awasthi, M. P., Bishwakarma, K., Zhang, Q., & Saqr, A. (2026). Hydrogeochemistry and water quality of the transboundary Koshi River Basin in the Central Himalayas. Journal of Mountain Science, 23, 559-582. https://doi.org/10.1007/s11629-025-9919-2

Abstract: Rivers are essential for water supply, agriculture, hydropower, and biodiversity, yet they face increasing threats from climate change and pollution globally. The Koshi River Basin, spanning China, Nepal, and India, is a transboundary basin that includes glacier-fed headwaters and densely populated downstream regions. This study investigates the hydrogeochemistry and water quality dynamics of the basin, focusing on seasonal and spatial variations and their implications for drinking and irrigation suitability. A total of 117 water samples from different segments of the basin were analyzed across premonsoon, monsoon, and post-monsoon seasons using in-situ, laboratory tests, and multivariate statistical methods. The results indicated that carbonate and silicate weathering were the dominant sources of solutes in the study region, with Ca²⁺ and HNO₃ being the major ionic constituents. Seasonal variations revealed higher ionic concentrations in pre- and post-monsoon periods due to increased mineralization, while monsoonal dilution significantly reduced solute loads. Spatially, the higher hydrogeochemistry index in the upstream and lower values in downstream tributaries indicate intensive weathering in the headwaters but are further diluted by melting water and precipitation downstream. Inversely, higher pollution risks only appeared in downstream areas, where NO₃ suggested agricultural runoff and wastewater intrusion. Water quality index < 50 classified most river segments as suitable for drinking, while sodium adsorption ratio < 1 confirmed irrigation suitability, except in some segments of the downstream zones with higher anthropogenic influence based on major ions. This study also supports Sustainable Development Goal 6 (clean water and sanitation), 13 (climate action), and 15 (life on land) by providing critical insights into water quality dynamics and informing sustainable water management strategies applicable to other glacier-fed river basins worldwide.

Citation: Baral, S. K., Shrestha, K., & Parajuli, I. (2026). Foodborne bacterial pathogens and contamination level in retail meat samples from Kathmandu, Nepal. American Journal of Laboratory Medicine, 11(1), 16-23. https://doi.org/10.11648/j.ajlm.20261101.13

Abstract: 

Foodborne pathogens contaminating meat products represent a significant public health concern, particularly in regions with suboptimal hygiene standards. Multidrug-resistant (MDR) bacteria further complicate treatment options and increase morbidity and mortality. Therefore, the aim of this study was to determine the distribution of foodborne bacterial pathogens, their antibiotic susceptibility patterns, and contamination levels in retail meat samples from Kathmandu, Nepal. A laboratory-based cross-sectional study was conducted over six months (October 2023–March 2024) at the Department of Laboratory Medicine, Manmohan Memorial Institute of Health Sciences. A total of 80 raw meat samples (40 chicken and 40 buffalo) were collected from retail shops in Kathmandu. Bacterial isolation and identification were performed using standard microbiological techniques. Antibiotic susceptibility testing was conducted using the Kirby-Bauer disc diffusion method according to CLSI guidelines. Phenotypic detection of β-lactamase (ESBL, MBL, AmpC) and MRSA was performed. Total viable count (TVC) was determined using the pour plate method. Out of 204 bacterial isolates, Escherichia coli (59, 28.92%) was the predominant isolate, followed by Klebsiella spp. (28, 13.74%), Proteus spp. (26, 12.75%), Citrobacter spp. (19, 9.31%), and Salmonella spp. (16, 7.84%). Among gram-positive bacteria, Staphylococcus aureus was found in 16 (7.84%) isolates and coagulase-negative staphylococci in 7 (3.43%) isolates. The distribution of MDR isolates was 136 (66.7%). Among gram-negative bacteria (n=181), ESBL producers comprised 5 (2.76%), MBL producers 47 (25.96%), and AmpC producers 36 (19.88%) of isolates. Methicillin-resistant Staphylococcus aureus (MRSA) was detected in 10 (62.5%) of the 16 S. aureus isolates. Mean total viable count was higher in chicken (5.66 log₁₀ CFU/g) compared to buffalo meat (5.64 log₁₀ CFU/g). This study demonstrates a high prevalence of MDR, MBL, and AmpC β-lactamase-producing bacteria in retail meat samples, though ESBL producers were relatively uncommon. These findings underscore the urgent need for stringent hygiene standards and sanitation practices in meat handling and retail environments to ensure consumer safety.

Citation: Adhikari, A., Sharma, R., & Sharma, C.M. (2026). Phytoplankton and fish diet as bioindicators of river health in the Narayani and East Rapti rivers, Nepal. Aquatic Ecology, 60, 14. https://doi.org/10.1007/s10452-025-10254-2

Abstract:

Biological indicators, such as phytoplankton, are crucial in monitoring changes in freshwater ecosystems as these are directly affected by nutrient concentration which helps to regulate their growth and development. Phytoplankton can serve as a biomonitoring tool because the phytoplanktonic species present in the diet can be used as bioindicator. This study aims to evaluate the use of phytoplankton and fish diet as bioindicators of river health in two important rivers, Narayani and East Rapti, of Nepal. The impact of water quality on phytoplankton, both in habitat and in the fish diet, was also assessed. Phytoplankton, fish gut and water samples were collected from 27 sites including the main river and its major tributaries. The correlational analysis and multiple linear regression determined the relationship between physico-chemical parameters and phytoplanktonic species in habitat. Twenty-one phytoplanktonic species were recorded from different habitats and 25 species from the fish diet. Spirogyra sp. was the dominant taxa in both habitat and the fish diet. Whereas Ulothrix sp. was the second most preferred food item for fish. Varied food items were recorded in Channa punctata, Pethia conchonius, Opsarius bendelisis and Acanthocobitis botia and limited food items were recorded in Chitala chitala, Garra annandalei, Puntius terio, Cabdio jaya, Tor mosal, Pseudambassis baculis, Botia lohachata, Botia histrionica, Salmostoma acinaces, Bangana dero, Botia geto, Aorichthys seenghala, and Anabas cobojius. Phytoplankton in habitat was positively related with temperature, EC, TDS, chloride, alkalinity, total hardness, calcium hardness, magnesium hardness, free CO_2, NO₃⁻, K⁺, Ca²⁺, Mg²⁺, and Na⁺ had negative relationship with DO, pH, PO₄³⁻, and NH₃. Sites with dense settlement and industrialized areas had more pollutant tolerant phytoplanktonic species both in habitat and fish diet which indicates an influence of pollution in aquatic biota. Temporal monitoring of aquatic biota is recommended to track changes in river health of both Narayani and East Rapti rivers.