Driftless Area Streams in Karstic Agricultural Watersheds: Best Management Practices, Biotic Integrity, and Environmental Stressors

To protect streams in agricultural watersheds, best management practices (BMPs) are implemented to reduce or prevent contaminated runoff from reaching surface waters. Over the course of three growing seasons (2000–2002), this study assessed physical, chemical, and biological indicators of water quality at 13 total stream sites in two agricultural watersheds (Garvin Brook, Whitewater River) in southeastern Minnesota USA, where BMPs have been used for over 50 years prior to the study period. Some sites in both watersheds exhibited impaired water quality due to high turbidities, high levels of total suspended solids (TSS) and fecal coliform bacteria, and low fish and benthic macroinvertebrate biotic integrities. Non-metric multi-dimensional scaling of water quality indicators and principal components analysis of fish and invertebrate communities highlighted varying degrees of differences between watersheds. On average, Garvin watershed sites exhibited better water quality during 2000–2002 than sites in the Whitewater watershed, likely because more headwater reaches were surveyed in Garvin Brook. A fish community index biotic integrity (IBI) was significantly negatively correlated with turbidities, TSS, and fecal coliform bacteria levels, but the benthic macroinvertebrate community IBI was not correlated to any water quality indicator or to the fish IBI. More recent studies in these watersheds and current impaired waters listings continue to indicate significant and ongoing water quality issues, so continued water quality monitoring is needed in these two watersheds to highlight and prioritize problematic subwatersheds for future conservation efforts to reduce or prevent agriculture-related runoff from reaching the stream networks.

Influence and Analysis of a Viscosity-Velocity Combined Prediction Model on the Dynamic Thermodynamic Performance of Shell-and-Tube Heat Exchangers in Offshore/Coastal Marine Energy Systems

To address the lack of dynamic prediction methods for heat exchangers operating under variable-viscosity and fluctuating-flow conditions in marine integrated energy systems, this study develops a dynamic wall-temperature prediction model for a shell-and-tube heat exchanger under combined viscosity-flow conditions. The model is established over flow velocities of 0.8–1.5 m/s and kinematic viscosities of 1.45 × 10⁻⁶–1.45 × 10⁻⁵ m²/s, representing fouling-prone operating conditions relevant to seawater/sewage-source heat pump applications. The main novelty of the study lies in linking viscosity-flow combined with wall-temperature dynamics in a unified prediction framework and in quantifying the nonlinear thermal response over a practically relevant operating range. The results show that a quartic polynomial relationship with flow velocity and viscosity can describe wall temperature. A distinct dynamic response pattern is observed: under low-viscosity conditions, wall temperature exhibits pronounced multi-peak fluctuations, whereas under high-viscosity conditions, it shifts to a more stable single-peak or gently declining trend. This behavior helps clarify the physical mechanism governing wall-temperature evolution under combined transport effects. In addition, the sewage-side heat transfer coefficient increases by up to 41.3%, while the overall heat transfer coefficient increases by 18.2–20.6% over the investigated range. These findings provide a dynamic prediction tool for heat exchanger performance in seawater-source heat pump systems integrated with intermittent marine renewable energy (such as offshore wind and wave power), and further indicate that the proposed model can offer useful mechanism-level insight into the dynamic thermal behavior of fouling-prone heat exchangers, thereby supporting the design and operation of seawater/sewage-source heat pump systems integrated with intermittent marine renewable energy sources such as offshore wind power.

Correction: Song et al. Metallic Iron, (Rain)Water, and the City: A Handout for Researchers and Policymakers

A Reproducible R–Fortran Toolkit for Groundwater Flow and Contaminant Transport Modeling in Watershed Applications

Uncertainty and calibration are major challenges in hydrologic and hydraulic analysis, especially in watershed applications involving groundwater flow and contaminant transport. This study presents an integrated modeling framework for comprehensive simulation of groundwater flow and contaminant transport, with automated calibration and sensitivity analysis capabilities. The framework extends traditional Fortran-based modeling by incorporating the statistical, numerical, and visualization strengths of the R environment. In the proposed approach, the Fortran code is executed within R, while the Fortran program employs a finite-volume time-splitting method to discretize the governing equations of groundwater flow and contaminant transport. Integration with R statistical packages improves model calibration, sensitivity evaluation, and visualization of groundwater contamination results. To illustrate the applicability of the framework, two test cases of groundwater flow and contaminant transport through porous media were conducted. Results demonstrate the accuracy, efficiency, and enhanced visualization capabilities of the integrated system. Ultimately, the framework is intended to support three-dimensional analysis of pollution plume evolution in heterogeneous media and to investigate interactions among multiple contaminant sources in watershed systems.

Daily Variability of Climatic Projection Extremes Indices of Precipitation and Temperature in the Koliba-Corubal Watershed (Guinea and Guinea-Bissau)

Climate change is exacerbating extreme weather events in West Africa, threatening water resources and livelihoods. The Koliba-Corubal transboundary basin (Guinea-Guinea-Bissau), located primarily outside the Sahel region, constitutes a major freshwater resource for the area. This study analyzes the future daily variability of extreme rainfall and temperatures in this basin using CMIP6 projections. Four climate models (GFDL-ESM4, MPI-ESM1-2-HR, UKESM1-0-LL, IPSL-CM6A-LR) under the SSP1-2.6 and SSP5-8.5 scenarios were used. Six extreme precipitation indices (R99p, Rx3day, Rx5day, SDII, CWD, R20mm) and four extreme temperature indices (TN90p, TNx, TX90p, TXx) were calculated for three time horizons (2021–2050, 2051–2080, 2071–2100) and compared to the reference period 1985–2014. Extreme precipitation decreases considerably in both scenarios (under SSP1-2.6, −45.4% for R99p and −42.0% for Rx3day compared to the reference period 1985–2014), with a marked downward trend at the beginning of the period followed by an increase around 2100 under SSP5-8.5 (R99p: −37.4%; Rx3day: −20.2%). Concurrently, extreme temperatures are increasing significantly, particularly under SSP5-8.5, where TN90p is projected to increase by 169.7% by 2071–2100. Mann-Kendall tests confirm significant trends for most indices under the highest emissions scenario. The spatial distribution shows marked heterogeneity, with higher values in the central mountain areas. These results underscore the urgent need to adapt water resource management strategies and agricultural policies in this transboundary basin in the face of the projected intensification of climate extremes by the end of the century.

Synthesis of Hydroxyapatite Porous Microspheres for Efficient Adsorption of Copper Ion from Water

Copper is a common heavy metal contamination source for water bodies, and achieving sustainable and cost-effective removal of Cu²⁺ from Cu-containing wastewater remains a challenge. In this study, an economical and eco-friendly adsorbent—hydroxyapatite (HA) porous microspheres—was synthesized via a simple one-step hydrothermal method. Adsorption experiments demonstrated that the maximum adsorption capacity of HA porous microspheres for Cu²⁺ is 116 mg/g, approximately 3.74 times that of reported HA nanosheet adsorbents. The adsorption process follows the pseudo-second-order kinetic model and the Sips isotherm model. The correlation coefficient R² = 0.9997. Linear fitting of the amounts of Cu²⁺ removed and Ca²⁺ leached at the same time revealed an R² value as high as 0.997, indicating that ion exchange is the dominant adsorption mechanism. Therefore, the excellent adsorption performance is attributed to the high specific surface area (207 m²/g) and mesoporous structure of the spherical HA adsorbent, which provides abundant active sites and promotes efficient ion diffusion. These structural advantages significantly enhanced the two primary adsorption mechanisms: ion exchange and surface complexation. Furthermore, the effects of adsorbent dosage, solution pH, reaction time, initial Cu²⁺ concentration, and temperature on adsorption performance were systematically investigated. Finally, the adsorption mechanism was investigated by characterizing the adsorbed material using XRD, FTIR, and XPS. It was determined that ion exchange, complexation, and electrostatic attraction are the main adsorption mechanisms. This study enhances the adsorption capacity of HA materials for Cu²⁺ by controlling morphology, offering new perspectives for developing high-performance, economical, eco-friendly, and sustainable adsorbents.

Br-Doped Nickel-Cobalt Phosphide Nanoarrays on Engineered Porous NF for High-Efficiency Water Oxidation

The rational design of cost-effective electrocatalysts for the oxygen evolution reaction (OER) is pivotal for advancing green hydrogen production. This study presents a substrate-engineered Br-doped nickel-cobalt phosphide (NiCoP) electrocatalyst fabricated through a stepwise synthesis protocol. A porous and roughened nickel foam (NF) is initially constructed to provide a 3D conductive scaffold, followed by the hydrothermal growth of vertically aligned NiCo-layered double hydroxide (LDH) nanosheets. Subsequent controlled pyrolysis in the presence of a bromine source yields Br-doped NiCoP nanoarrays securely anchored on the NF/Ni substrate. Comprehensive structural characterization confirms the successful Br incorporation, which induces lattice distortion and optimizes the electronic configuration of NiCoP, while the interconnected porous architecture enhances electrolyte infiltration and gas release. Electrochemical evaluations reveal exceptional OER performance, achieving an ultralow overpotential of 220 mV at 10 mA·cm⁻² and a Tafel slope of 61.2 mV·dec⁻¹ in 1 M KOH, surpassing most reported NiCo-based phosphides. In-situ Raman spectroscopy and post-OER characterization uncover dynamic surface reconstruction into Br-enriched (oxy)hydroxide active species, elucidating the dual role of Br as both an electronic modulator and a stabilizer for reactive intermediates. This work demonstrates a substrate-guided heteroatom doping strategy to engineer high-performance bimetallic phosphide electrocatalysts, offering insights into interface engineering for sustainable energy technologies.

Does the Public Approve of Massive Water Transfers and Construction Projects? Aqueducts, Fracking, and Pipelines in the High Plains

Groundwater availability has been a growing problem in the state of Kansas, where the High Plains aquifer (HPA) has been declining. Simultaneously, the Sunflower State is moving toward wind energy, investing in red meat production, and eyeing a proposal for the Kansas Aqueduct (a tremendous water transfer from eastern to semiarid western Kansas, a region with a distinct vulnerability to drought that overlies the HPA). What do Kansans think about these changes in their environment and infrastructure? Using a survey of the state’s residents (n = 864), we find that owning a private water well is a significant predictor of opposition to the colossal aqueduct, while living above the HPA predicts support for the water transfer. Well owners and women oppose the construction of coal-fired power plants, oil pipelines, hydraulic fracturing, and large corporate feedlots, while politically conservative ideologies predict support. Furthermore, well owners and women are nearly twice as likely to disapprove of fracking; conservatives have lower odds of fracking opposition. The Just Transition in Kansas is not only a question of how water, agribusiness, and wind and nuclear energy are developed, but also residents’ perceptions of these projects.

Metallic Iron, (Rain)Water, and the City: A Handout for Researchers and Policymakers

This study aims to promote residential rainwater harvesting everywhere rain falls. It recalls the history of urban rainwater (stormwater) management while insisting on the origin of the perception that rainwater is not a relevant source of potable water. It also argues that where rainwater is polluted, it can be easily treated using frugal technologies such as filtration on metallic iron-based filters. The study notes that stormwater is precipitation that is not harvested. Thus, harvesting rainwater prevents (quantitative) stormwater generation, and transforms stormwater from a threat (e.g., erosion, floods) to a resource (e.g., drinking water, food security) for human and environmental needs. The effective management of stormwater (i) enhances the quality of human life, (ii) sustains local biodiversity, and (iii) protects the whole environment. Thus, the failure to harvest rainwater should be considered irresponsible, if not unethical. This argument alone makes each conscientious citizen a changemaker. A number of local changemakers will organize to determine the best way to integrate overflow from individual residences to enhance the community’s liveability. This study provides a valuable consolidation of information that will facilitate the mainstreaming of rainwater harvesting as the pillar of holistic integrated water resource management.

The Future of Environmentally Powered Gliders: Emerging Prospects and Trends

To address the endurance limitations of traditional electrically driven underwater gliders, which are constrained by onboard battery energy density, harnessing marine renewable energy for propulsion or supplemental power has emerged as a critical approach to overcoming their operational endurance bottleneck. This paper systematically reviews the research progress on underwater gliders powered by environmental energy sources, such as thermal and solar. It provides an in-depth analysis of the utilization mechanisms, core technologies, and current challenges associated with each energy type, with a focused exploration of technical pathways for achieving energy synergy and enhancing system endurance through multi-energy integration and intelligent energy management. Furthermore, this study is the first to establish a comprehensive technical evaluation framework for environmentally powered gliders from three dimensions: energy coupling, system design, and mission adaptability, offering a systematic reference for subsequent research. The paper also explores the application potential of this technology in advanced scenarios, such as long-term ocean observation and dynamic environmental monitoring. Future efforts should prioritize efficient multi-energy hybridization, dynamic energy management, and mission-adaptive control to comprehensively enhance the endurance and operational reliability of gliders in complex marine environments.