Spatiotemporal variations of water quality and their driving forces in the Yangtze River Basin, China, from 2008 to 2020 based on multi-statistical analyses

Nutrients and metal(loid)s in surface sediments of the Chishui River: A DGT-based assessment of the last natural tributary of the upper Yangtze River (China)

This study investigates the distribution and probabilistic ecotoxicological risk assessment of nutrients and metal(loid)s in the Chishui River, the last natural tributary of the upper Yangtze River, which plays a crucial role in maintaining regional biodiversity and water quality. Understanding the impact of contaminants in this ecologically significant river is essential for effective environmental management. Sediment samples were analyzed using diffusive gradients in thin films (DGT) to measure labile concentrations of nutrients and metal(loid)s, revealing significant spatial variability. Concentrations of PO4-P, NH4-N, NO3-N, and metal(loid)s such as Mn, Fe, Cu, and Zn varied notably across sampling sites. Risk quotient (RQ) analysis identified Mn as posing the highest ecological risk, followed by Cu and Fe. A combined probabilistic risk assessment using the SPI (Species Sensitivity Distribution-Probabilistic Risk Assessment-Inclusion-Exclusion Principle) model indicated a 32.46 % probability of toxic effects from nutrient and metal(loid) mixtures on aquatic organisms. This study underscores the effectiveness of DGT technology in assessing bioavailable contaminants and highlights the need for targeted risk management strategies to mitigate ecological impacts in the Chishui River.

Geographical Information System-driven intelligent surface water quality assessment for enhanced drinking and irrigation purposes in Brahmani River, Odisha (India)

River basins in Odisha suffer from serious anthropogenic interventions that degrade water quality, including runoff from agriculture, municipal wastewater, and industrial discharges. The Brahmani River, an essential source of water for industrial, agricultural, and drinking uses, is especially affected by overuse of fertilizer and pesticides. Ensuring health and cleanliness in cities and communities requires constant monitoring and management of drinking water sources. This study evaluates the river's water quality for drinking and agricultural applications and identifies key factors influencing its deterioration. Water samples were collected from 12 locations during pre-monsoon (PRM) and post-monsoon (POM) seasons (2017-2021) and analyzed for physicochemical parameters against World Health Organization (WHO) standards. For quality assessment, values of analyzed parameters of the surface water samples were compared with the WHO water quality standards. The findings show that the majority of the samples are fit for drinking and irrigation, with the main cations arranged as Ca2⁺ > Na⁺ > Mg2⁺ > K⁺ and anions as HCO₃⁻ > Cl⁻ > SO₄2⁻ > CO₃2⁻, respectively. The analytical results indicate slightly alkaline nature of the surface water in the study area. Strong correlations among ions (HCO₃⁻, Ca2⁺, Mg2⁺, Cl⁻, SO₄2⁻) suggest influences from natural processes (weathering, erosion) and anthropogenic activities. Seasonal variations assessed using Water Quality Index (WQI) and Canadian Council of Ministers of the Environment Water Quality Index (CCME-WQI) method indicate that water quality ranges from good to poor in PRM and good to marginal in POM seasons. The metrics and the criteria differ significantly, indicating that remedial action is necessary to enhance the quality of the water at these locations. Irrigation suitability indices (SAR, MH, %Na, PI, RSC, KI, ESP) further confirm the water's acceptability for agricultural use. The irrigation suitability of agriculture-dominated basin was assessed using Empirical Bayesian Kriging (EBK) modeling, achieving high accuracy with an RMSS error and an MS error. Spatial maps generated using Geographical Information System (GIS) software, along with Gibbs plots, Piper diagrams, and Wilcox diagrams, help delineate agricultural zones and highlight the dominant geochemical processes. The study concludes that both anthropogenic (sewage discharge, waste dumping) and geogenic (evaporation, mineral dissolution) factors significantly affect water quality. The findings highlight the effectiveness of EBK for sustainable irrigation and agriculture. To preserve this critical resource, measures such as reducing sewage outflows, managing stormwater discharge, and preventing solid waste disposal are essential. The purpose of this study is to pinpoint areas with low water quality and offer workable solutions to the nation's water resources management agency in order to enhance the drinking water supply or attain sustainable water resources. Findings revealed greater water stress in upstream areas compared to downstream regions, offering valuable insights for drinking, irrigation management, and drought-resistant crop planning.

Decoupling the effects of climate, topography, land use, revegetation, and dam construction on streamflow, sediment, total nitrogen and phosphorus in the Yangtze River Basin

Evaluating changes in streamflow, sediment, and nutrient fluxes, as well as quantifying their influencing factors, is crucial for regional water resource protection. While the relationships between major influencing factors and these indicators have been widely studied, the quantitative contributions of the separate and interactive effects of these influencing factors have not been fully explored. This study quantitatively evaluated the changing characteristics of streamflow, sediment discharge, total nitrogen (TN) and total phosphorus (TP), as well as the separate and interactive effects of various major influencing factors such as-rainfall, temperature, evapotranspiration (ET), revegetation, dam construction, and land use change-by applying the GeoDetector method to account for their spatial heterogeneity and contributions. Our findings reveal that the influence of these factors has gradually intensified over time, with dam construction and land use change emerging as the most significant contributors to changes in sediment discharge and TN, respectively. Notably, the interactive effects between dam capacity and vegetation cover on streamflow and sediment discharge was twice as strong as their separate impacts, highlighting the effectiveness of integrating dam construction with reforestation to control erosion and sediment transport. Similarly, the interaction of dam capacity and land use change had a 1.5 times greater impact on TN and TP than their separate effects, indicating that reducing fertilizer application at the source and in the meantime implementing direct interception measures are more effective ways to control water pollution. These findings provide a solid foundation for policymakers to develop integrated water management strategies targeting multiple factors simultaneously, that address both water quantity and quality concerns in the Yangtze River Basin and similar regions.

Climate change influences on the streamflow and sediment supply to the Chao Phraya River basin, Thailand

This study investigates the effects of climate change on the sediment loads of the Ping and Wang River basins and their contribution to the sediment dynamics of the lower Chao Phraya River basin in Thailand. The various climate models under different Representative Concentration Pathways (RCPs) scenarios are employed to project sediment loads in future. The findings indicate a significant increase in river flow approximately 20% in the Ping River (PR) and 35% in the Wang River (WR) by the mid-21st century and continuing into the distant future. Consequently, this is expected to result in sediment loads up to 0.33 × 106 t/y in the PR and 0.28 × 106 t/y in the WR. This escalation is particularly notable under the RCP 8.5 scenario, which assumes higher greenhouse gas emissions. Additionally, the research provides insights into the potential positive implications for the Chao Phraya Delta's coastal management. Without further damming in the Ping and Wang River basins, the anticipated rise in sediment supply could aid in mitigating the adverse effects of land subsidence and sea-level rise, which have historically caused extensive shoreline retreat in the delta region, particularly around Bangkok Metropolis. The paper concludes that proactive adaptation strategies are required to manage the expected changes in the hydrological and sediment regimes to protect vulnerable coastal zones and ensure the sustainable management of the Chao Phraya River Basin in the face of climate change.

A review of conservation status of freshwater fish diversity in China

China harbors a high species diversity of freshwater fishes not shared with any of its neighboring nations. Freshwater fish diversity in the country has been under severe threat from human activities over the past decades, thus conservation freshwater fishes and ecosystems is urgently needed. To accumulate baseline data for guiding protection actions, the third red list assessment of Chinese freshwater fishes was carried out. Among Chinese freshwater fishes assessed, there are 355 at-risk species (22.3% of the total), including 69 ranked as Critically Endangered, 97 as Endangered, and 189 as Vulnerable. Two species are classified as Extinct and one as Regionally Extinct. China's threat level seems to be lower than the known average level found in the IUCN's global assessment of freshwater fishes, but this is an artifact of a high rate of species classified as Data Deficient. Conservation of freshwater fishes is presently facing a grim situation in China. Imperilment of Chinese freshwater fishes is primarily attributed to habitat loss and degradation arising from human perturbations, particularly river damming. Despite the adoption of protected areas setting up, captive breeding and release, and a fishing moratorium, conservation efforts for freshwater fishes are compromised by disproportional attention in China's biodiversity conservation, baseline data deficiency, insufficiently designed protection networks, and inefficient or inadequate implementation of conservation strategies. To achieve the objectives of Chinese freshwater fish conservation, it is proposed to conduct a national-scale survey of fish diversity and reassess their at-risk status, develop systematic conservation planning of freshwater fish diversity and ecosystems, prioritize strategies for protected areas development, perform genetic-based captive breeding for releasing in concert with other protection actions, and implement flexible fishing moratorium strategies in different water bodies.