Shallow wells are common source of drinking water in low-resource countries; however, they are highly vulnerable to fecal contamination. Here, we assessed the microbial quality and antibiotic susceptibility patterns of enteric bacteria recovered from shallow wells situated near sanitation facilities in four security-challenged areas of Katsina State, Nigeria. A total of 45 water samples were collected from 15 wells. Bacterial isolation and identification were performed using standard microbiological procedures and the analytical profile index (API) 20E kit. Antibiotic susceptibility testing was performed using the disk diffusion method, and Pearson’s correlation was performed to determine associations between risk factors and microbial contamination. Total coliform counts exceeded the World Health Organization-recommended limits. Klebsiella pneumoniae (25.0%) was the most frequently isolated species, followed by Salmonella species (20.83%) and Escherichia coli (16.67%). Notably, 86.5% of isolates exhibited multidrug-resistant phenotypes. Well distance relative to sanitation structures did not establish a causal relationship between sanitary risk scores and total coliform counts (r = 0.32, p = 0.47). Improved sanitation, regular water disinfection, and routine surveillance of groundwater is recommended to protect vulnerable communities in these security-challenged areas. A limitation of this study is its relatively small sample size and reliance on phenotypic methods, which may limit the comprehensiveness of the analyses.

Water quality in semi-arid reservoirs is vulnerable to drought, yet impacts remain poorly quantified. This study assesses meteorological drought effects on Boukerdane Dam, Tipaza, Algeria, from 2019 to 2023 using high-resolution weekly physicochemical sampling and daily volume records. Drought severity was measured using Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI). Water quality was evaluated via the Water Quality Index (WQI) and irrigation indices Sodium Adsorption Ratio, Residual Sodium Carbonate, Magnesium Ratio, and Magnesium Hazard. Results revealed strong negative correlations between drought indices and key parameters: drought increased conductivity, nitrate, and turbidity, while decreasing dissolved oxygen and volume. SPEI showed marginally stronger correlations than SPI for physicochemical parameters, highlighting evaporation’s role. Trend analysis confirmed a significant drying trend coupled with declining water quality. A stepwise degradation pattern was identified, where post-drought recoveries were incomplete. Principal Component Analysis retained six components explaining 72.3% variance, identifying salinity and temperature as primary drivers. Although WQI remained stable, irrigation indices indicated rising sodium hazards. The study concludes that drought degraded water quality, heightening risks of salinization and nutrient pollution. Parameter-specific monitoring is recommended over aggregate indices for effective management under climate change.

This study assessed the relative contributions of selected nitrogen sources to nori cultivation in Mikawa Bay using nitrogen stable isotope ratios (δ¹⁵N) and a Bayesian isotope mixing model (MixSIAR). The analysis considered three potential nitrogen sources: Yahagi River water, sewage effluent, and offshore subsurface oceanic nitrate. Water samples were collected between November 2024 and February 2025, and dried nori produced across eight districts in the bay were also sampled during this period. The δ¹⁵N–NO₃⁻ values in sewage effluent (15.6–21.3‰, n = 6) were substantially higher than those in Yahagi River water (7.1–9.2‰, n = 6) and offshore water (5.6–7.3‰, n = 4). By comparing these isotopic signatures with the δ¹⁵N values of dried nori (12.8 ± 1.8‰, n = 48), we evaluated the relative importance of nitrogen sources using MixSIAR. The results suggest that wastewater-derived nitrogen may account for a relatively large proportion of the nitrogen in cultivated nori, particularly near the sewage treatment facility, with a detectable influence extending to the bay mouth (16 km from the river mouth). Given the limitations of single-tracer isotope mixing models, these results should be interpreted as semi-quantitative estimates under the assumptions of the present study.

We developed a novel modeling framework that forecasts nutrient load inputs to coastal waters at site-specific resolution by integrating demographic change, industrial activity, and operational conditions at sewage treatment plants. This framework quantifies the controllable range of nutrient inflows achievable through anthropogenic interventions and supports evaluation of management strategies addressing both eutrophication and oligotrophication. In the model, the coastal zone is divided into subregions, and chemical oxygen demand, total nitrogen, and total phosphorus loads originating from sewage are predicted using explanatory variables including resident population, numbers of manufacturing employees, and manufactured-goods shipment values. Predicted loads showed strong agreement with observations (r > 0.9), confirming model validity. By incorporating variable nutrient removal efficiencies at treatment plants, the model enables scenario-based estimation of discharged nutrient loads under alternative management and socioeconomic conditions. Application of the model to two adjacent but contrasting systems—eutrophic Osaka Bay and increasingly oligotrophic Harima-nada—demonstrated its ability to resolve region-specific load dynamics and future trajectories. This integrated framework provides essential input information for decision support in adaptive and region-specific nutrient management by quantifying feasible ranges of nutrient inflow adjustments; when coupled with hydrodynamic–ecosystem models, it can support the evaluation of restoration, aquaculture, and water-quality improvement strategies.