Search Results (105)

Rainfall-driven non-point source (NPS) pollution has become a critical issue for water environment management in urban watershed systems. However, single-model use is limited to fully represent the intricate processes of rainfall-correlated NPS pollution generation and dispersion for effective decision-making. This study develops a novel cross-scale, multi-factor coupled model framework to characterize hydrologic and NPS pollution responses to different rainfall events in Shenzhen, China, a representative worldwide metropolis facing challenges from rapid urbanization. The calibrated and validated coupled model achieved remarkable agreements with observed hydrologic (Nash–Sutcliffe efficiency, NSE > 0.81) and water quality (NSE > 0.85) data in different rainfall events and demonstrated high-resolution dynamic changes in flow and pollutant transfer within the studied watershed. In an individual rainfall event, heterogeneous spatial distributions of discharge and pollutant loads were found, highly correlated with land use types. The temporal change pattern and risk of flooding and NPS pollution differed significantly with rainfall intensity, and the increase in the pollutants (mean 322% and 596%, respectively) was much larger than the discharge (207% and 302%, respectively) under intense rainfall conditions. Based on these findings, a decision-support framework was established, featuring land-use-driven spatial prioritization of industrial hotspots, rainfall-intensity-stratified management protocols with event-triggered operational rules, and integrated source-pathway-receiving end intervention strategies. The validated model framework provides quantitative guidance for optimizing infrastructure design parameters, establishing performance-based regulatory standards, and enabling real-time operational decision-making in urban watershed management. Full article

Non-point source pollution (NPS) from agriculture is a primary driver of water eutrophication, necessitating effective control for regional water ecological security and sustainable agricultural development. This study focuses on the Chenzhuang village watershed, a typical green agricultural demonstration area in Jiangsu Province, using the HYPE model to analyze hydrological processes and Total Nitrogen (TN) and Total Phosphorus (TP) migration patterns. The model achieved robust performance, with Nash–Sutcliffe Efficiency (NSE) values exceeding 0.7 for daily runoff and 0.35 for monthly TN and TP simulations, ensuring reliable predictions. A multi-scenario simulation framework evaluated the synergistic control effectiveness of Best Management Practices (BMPs), including agricultural production management, nutrient management, and landscape configuration, on TN and TP pollution. The results showed that crop rotation reduced annual average TN and TP concentrations by 11.8% and 13.6%, respectively, by shortening the fallow period. Substituting 50% of chemical fertilizers with organic fertilizers decreased TN by 50.5% (from 1.92 mg/L to 0.95 mg/L) and TP by 68.2% (from 0.22 mg/L to 0.07 mg/L). Converting 3% of farmland to forest enhanced pollutant interception, reducing TN by 4.14% and TP by 2.78%. The integrated BMP scenario (S13), combining these measures, achieved TN and TP concentrations of 0.63 mg/L and 0.046 mg/L, respectively, meeting Class II surface water standards since 2020. Economic analysis revealed an annual net income increase of approximately 15,000 CNY for a 50-acre plot. This was achieved through cost savings, increased crop value, and policy compensation. These findings validate a “source reduction–process interception” approach, providing a scalable management solution for NPS control in small rural watersheds while balancing environmental and economic benefits. Full article

Nonpoint Source (NPS) pollution refers to water pollution that does not originate from a single identifiable source. In this study, we conducted water-quality monitoring during the snowmelt period from February to March of 2024 and 2025 in Jaun, a highland agricultural area. We analyzed changes in nonpoint source pollutant concentration and evaluated Best Management Practice (BMPs) effectiveness. A year-to-year comparison showed that in 2024, a single intense snowmelt event led to a sharp increase in particulate pollutants, such as TP and SS. In 2025, repeated and gradual thawing resulted in the accumulation and release of dissolved pollutants, including TN and TOC. BMPs such as straw mulching were partially effective in reducing pollutant concentrations. However, in 2025, a lack of proper maintenance led to increased concentration at certain sites. The water quality during the snowmelt period was comparable to that during the summer monsoon season, indicating that snowmelt has a similar potential for generating nonpoint source pollution. The findings provide area-based insights into snowmelt-induced nonpoint source pollution and can form a foundation for developing seasonal water quality management policies. Full article

The U.S. Environmental Protection Agency (EPA) developed the concept of Water Quality Volume (WQv) as a Best Management Practice (BMP) to treat the first 25.4 mm of rainfall in urban areas, aiming to capture approximately 90% of annual runoff. However, applying this urban-based standard—designed for areas with over 50% imperviousness—to rural regions with higher infiltration and pervious surfaces may result in overestimated facility capacities. In Korea, a uniform WQv criterion of 5 mm is applied nationwide, regardless of land use or hydrological conditions. This study examines the suitability of this 5 mm standard in rural catchments using the Hydrological Simulation Program–Fortran (HSPF). Eight sub-watersheds in the target area were simulated under varying cumulative runoff depths (1–10 mm) to assess pollutant loads and runoff characteristics. First-flush effects were most evident below 5 mm, with variation depending on land cover. Nature-based treatment systems for constructed wetlands were modeled for each sub-watershed, and their effectiveness was evaluated using Flow Duration Curves (FDCs) and Load Duration Curves (LDCs). The findings suggest that the uniform 5 mm WQv criterion may result in overdesign in rural watersheds and highlight the need for region-specific standards that consider local land-use and hydrological variability. Full article

Non-point source (NPS) pollution continues to pose threats to ecosystems and NPS pollution control represents a significant global challenge. This study presents a bibliometric analysis of 1328 studies on the assessment of NPS pollution control, collected from the Web of Science (WOS) Core Collection database for the period between January 1993 and April 2025. The analysis encompassed multiple dimensions, including annual publication volume, most prolific authors and journals, top funding organizations, and keyword co-occurrence. Results reveal a consistently accelerating publication trend, with China and the United States emerging as the most prominent contributors. The findings highlight a distinct evolution in research focus—from early efforts centered on pollutant source tracing and model-based simulations of best management practices (BMPs), such as SWAT and AnnAGNPS, to more holistic, multidimensional assessments that integrate economic, environmental, ecological, and social dimensions to support multi-objective optimization. Future directions are expected to emphasize non-structural measures and promote the development of globally standardized evaluation frameworks for NPS control strategies, thereby enhancing cross-regional comparability and aligning with the United Nations Sustainable Development Goals (UNSDGs). Full article

Understanding the impact of climate change on agricultural nonpoint source (NPS) pollution is crucial for developing effective adaptation strategies and reducing vulnerabilities where such challenges exist. This study evaluated the impact of precipitation and temperature variations on Total Inorganic Nitrogen (TIN), Total Inorganic Phosphorus (TIP), and sediment loads in the Sand River Catchment (SRC) using the Soil and Water Assessment Tool plus (SWAT+). One-way analysis of variance (ANOVA) was used to determine the significance (p < 0.05) of the relationships (R²) between precipitation and temperature on sediment, TIN, and TIP loads in the SRC. SWAT+ calibration and validation demonstrated that the statistical indices (NSE and R² ≥ 0.72; −17.30 ≤ PBIAS ≤ 14.74) fell within an acceptable range. Results indicated a significant influence of average monthly precipitation (p < 0.0001) and temperature (p ≤ 0.004) on sediment, TIN, and TIP loads. In addition, a decrease in average annual precipitation led to a decline in sediment, TIN, and TIP loads (R² ≥ 0.55), with the average annual temperature increasing in the same period (R² ≤ 0.23). This study confirms that climate change contributes to agricultural NPS pollution in the SRC and highlights the need to employ suitable adaptation strategies for pollution control in the catchment. Full article

Is it possible to control NPS (non-point source) pollution whose sources, sizes, and origins are difficult to identify? This study provides a positive answer in a non-cooperative n-firm oligopoly model in which the firms determine levels of differentiated goods and abatement technologies. It first derives a Cournot–Nash equilibrium in which the firms maximize their profit and emit pollution under the ambient charge scheme, combining rewards from the total NPS concentration less than a given standard with the penalties above. The effect of the ambient charge is then analytically shown in homogeneous and heterogeneous duopoly and triopoly. Further, possible controllability is numerically examined in the case of $n\ge 4$. Full article

Non-point source (NPS) pollution from agriculture accounts for more than 20% of the total pollution load in the Republic of Korea, with the highest nutrient balance among OECD countries. Rice paddy fields are among the most important NPSs because of their large area, intensive fertilizer use, intensive use of irrigation water, and subsequent drainage. Therefore, the use of controlled drainage in paddy fields (Test) was evaluated for reduction in the discharged volumes and pollutant loads in drainage and stormwater runoff in comparison to plots using traditional drainages (Control). The results show that the loads were highly variable and that the reductions in the annual load of biochemical oxygen demand (BOD), suspended solid (SS), total nitrogen (T-N), total phosphorus (T-P), and total organic carbon (TOC) in the Test compared to that of the Control were 31.0 ± 28.9%, 83.5 ± 11.8%, 65.4 ± 12.2%, 69.1 ± 21.7%, and 64.9 ± 12.9%, respectively. It was shown that discharge in the post-harrowing and transplanting drainage (HD) was predominantly responsible for the total loads; therefore, the load reduction in HD was evaluated further at additional sites. The reduction at all studied sites was highly variable and as follows: 30.0 ± 33.6%, 70.9 ± 24.6%, 32.2 ± 45.5%, 45.7 ± 37.0%, and 27.0 ± 71.5%, for BOD, SS, T-N, T-P, and TOC, respectively. It was also demonstrated that controlled drainage contributed significantly to reducing the loads and volume of stormwater runoff from paddy fields. Correlations between paddy field conditions and multiple regression showed that the loads were significantly related to paddy water quality. The results of this study strongly suggest that controlled drainage is an excellent alternative for reducing the discharge of NPS pollutants from paddy fields. It is also suggested that the best discharge control would be achieved by combinations of various discharge mitigation alternatives, such as the management of irrigation, drainage, and fertilization, as well as drainage treatment, supported by more field tests, identification of the fates of pollutants, effects of rainfall, and climate changes. Full article

Extreme precipitation events are one of the common hazards in eastern Texas, generating a large amount of storm water. Water running off urban areas may carry non-point source (NPS) pollution to natural resources such as rivers and lakes. Urbanization exacerbates this issue by increasing impervious surfaces that prevent natural infiltration. This study evaluated the efficacy of rain gardens, a nature-based best management practice (BMP), in mitigating NPS pollution from urban stormwater runoff. Stormwater samples were collected at inflow and outflow points of three rain gardens and analyzed for various water quality parameters, including pH, electrical conductivity, fluoride, chloride, nitrate, nitrite, phosphate, sulfate, salts, carbonates, bicarbonates, sodium, potassium, aluminum, boron, calcium, mercury, arsenic, copper iron lead magnesium, manganese and zinc. Removal efficiencies for nitrate, phosphate, and zinc exceeded 70%, while heavy metals such as lead achieved reductions up to 80%. However, certain parameters, such as calcium, magnesium and conductivity, showed increased outflow concentrations, attributed to substrate leaching. These increases resulted in a higher outflow pH. Overall, the pollutants were removed with an efficiency exceeding 50%. These findings demonstrate that rain gardens are an effective and sustainable solution for managing urban stormwater runoff and mitigating NPS pollution in eastern Texas, particularly in regions vulnerable to extreme precipitation events. Full article

With the acceleration of urbanization, the diffusion mechanism of urban non-point source (NPS) pollution caused by extreme rainfall is not clear, which leads to high cost and difficulty in water environment treatment. In view of the shortcomings of dynamic diffusion simulations of mesoscale pollution, this paper proposes a simulation framework based on cellular automata, GIS geographic technology, and a two-dimensional shallow water model. Taking the 500 m × 500 m grid as the unit, we explore the migration laws of nitrogen and phosphorus pollutants and the response relationship between pollutant diffusion and land use under extreme rainfall scenarios. The results show that (i) the pollution risk increases significantly with diffusion, with the maximum pollution load in high-risk areas increasing by 181%, and the diffusion rate is positively correlated with the rate of change in rainfall intensity; (ii) forest land has the highest grid pollution load loss rate, whereas the water grid has the highest accumulation rate; (iii) this method can accurately identify the hot spots of pollution diffusion, providing a basis for the precise control of high-risk areas. This study can support the targeted governance of pollution sources and land planning optimization in urban storm and flood management, and help reduce environmental health risks in extreme climates. Full article

Non-point source (NPS) pollution in agricultural land continues to rise despite urbanization in South Korea. NPS pollution management in rural areas has been conducted using Best Management Practices (BMPs) to reduce NPS pollution in rural areas. Among them, nature-based facilities are commonly used to reduce runoff NPS pollution. To design such facilities, it is necessary to determine the Water Quality Volume (WQv), which serves as a key indicator for evaluating the performance of pollution reduction facilities, as well as the estimation of the design rainfall intensity. These are critical factors for the design of the delineation of catchment areas and NPS pollution reduction. However, conventional methods for capacity estimation often rely on total area rather than considering the specific land use distribution, leading to lower pollution reduction efficiency and excessive project costs. Therefore, this study uses actual monitoring data from existing nature-based facilities, and an analysis was performed to establish a method for determining their optimal capacity while accounting for land use characteristics. A regression analysis was conducted based on the land use area ratio, and the results demonstrated that the proposed method yields similar or improved outcomes in terms of water quality improvement and economic feasibility compared to conventional capacity estimation methods. These findings highlight the importance of incorporating diverse land use distributions into capacity estimation for improving NPS pollution management efficiency by enhancing water quality and reducing project costs. Full article

Agricultural activities such as fertilization and cultivation constitute a substantial source of non-point source (NPS) nitrogen (N) in aquatic ecosystems. Precise quantification of fluxes across diverse land uses and identification of critical source areas are essential for effectively mitigating nitrogen loads. In this study, the Soil Water Assessment Tool (SWAT) was employed to accurately model the watershed hydrology and total nitrogen (TN) transport in the Zhongtian River Basin, i.e., an agricultural watershed characterized by low mountainous terrain. The simulation results indicated that the average TN load intensity within the watershed was 21.34 kg ha⁻¹ yr⁻¹, and that TN load intensities for paddy fields and tea plantation were 34.96 and 33.04 kg ha⁻¹ yr⁻¹, respectively. Agricultural land, which covered 32.06% of the area, disproportionately contributed 52.88% of the N output in the watershed. Pearson and redundancy analysis (RDA) underscored land use as the primary driver of nitrogen emissions, with a contribution exceeding 50%. Building on a high-precision simulation analysis, a suite of best management practices (BMPs) was established. These findings highlight the superior performance of engineered BMPs over agricultural BMPs, with TN load reduction rates of 12.23 and 27.07% for filter strips and grassed waterways, respectively. Among three agricultural BMPs, the effect of fertilizer reduction was the most pronounced, achieving reductions of 6.44% for TN and 21.26% for nitrate. These results suggest that optimizing fertilizer management and implementing engineered BMPs could significantly reduce nitrogen pollution in agricultural watersheds, providing valuable insights for sustainable agricultural practices and water quality management. Full article

Numerical models are commonly used to support the management of diffuse pollution sources in large agricultural landscapes. This paper investigates the suitability of a three-dimensional groundwater streamline-based nonpoint source (NPS) assessment tool for agricultural aquifers. The streamline approach is built on the assumption of steady-state groundwater flow and neglects the effect of transverse dispersion but offers considerable computational efficiency. To test the practical applicability of these assumptions, two groundwater transport models were developed using the standard three-dimensional advection–dispersion equation (ADE): one with steady-state flow and the other with transient flow conditions. The streamline approach was compared with both ADE models, under various nitrate management practice scenarios. The results show that the streamline approach predictions are comparable to the steady-state ADE, but both steady-state methods tend to overestimate the concentrations across wells by up to 10% compared to the transient ADE. The prediction of long-term attenuation of nitrate under alternative land management scenarios is identical between the streamline and the transient ADE results. Full article

Urban non-point source (NPS) pollution is an important risk factor that leads to the deterioration of urban water quality, affects human health, and destroys the ecological balance of the water environment. Reasonable risk prevention and control of urban NPS pollution are conducive to reducing the cost of pollution management. Therefore, based on the theory of “source–sink” in landscape ecology, combined with the minimum cumulative resistance (MCR) model, this study considered the influence of geographic-environment factors in Shenyang’s built-up area on pollutants in the process of entering the water body under the action of surface runoff, and evaluated its risk. The results indicated that the highest pollution loads are generated by road surfaces. High-density residential zones and industrial zones are the main sources of urban NPS pollution. Impervious surface ratios and patch density were the dominant environmental factors affecting pollutant transport, with contributions of 56% and 40%, respectively. The minimum cumulative resistance to urban NPS pollution transport is significantly and positively correlated with the distance from water bodies and roads. Higher risk areas are mainly concentrated in the center of built-up areas and roads near the Hun River. Green spaces, business zones, public service zones, development zones, and educational zones demonstrate the highest average risk index values, exceeding 29. In contrast, preservation zones showed the lowest risk index (7.3). Compared with the traditional risk index method, the method proposed in this study could accurately estimate the risk of urban NPS pollution and provide a new reference for risk assessments of urban NPS pollution. Full article

The alterations in runoff resulting from changes in land use and land cover (LULC) were the primary influencing factors contributing to non-point source pollution (NPS). In order to evaluate the long-term hydrological consequences of LULC for the purposes of land use optimization in the Hulan River Basin, Northeast China, the validated Long-term Hydrological Impact Assessment (L-THIA) model was employed to simulate the spatiotemporal distribution of total nitrogen (TN) and total phosphorus (TP) non-point source (NPS) loads from 2000 to 2020. Additionally, the load per unit area index (LPUAI) method was utilized to identify critical source areas. The findings indicated that the regions with elevated pollution levels were predominantly situated in areas designated for agricultural and construction activities. The greatest contributor to nitrogen and phosphorus loads was agricultural land. There were clear increases in both TN and TP during the study period, with increases of 51.73% and 55.56%, respectively. As a consequence of the process of urbanization in the basin, the area of land devoted to construction activities increased, reaching a coverage of 5.02%. Nevertheless, the contribution of construction land to the total basin NPS load exceeded 10% in 2020. This was the primary factor contributing to the observed increase in pollution loads despite a reduction in agricultural land area over the past two decades. TN and TP loads were markedly higher during the flood season than the non-flood season, accounting for over 80% of the NPS load. The sub-watersheds in the southwest and northeast have been identified as significant sources of nitrogen and phosphorus loss, contributing to the overall burden of NPS pollution. Implementing measures such as fertilizer reduction and conversion of farmlands to forests and grasslands can effectively mitigate NPS pollution, particularly TN pollution. This study proposes that the integration of L-THIA with GIS can serve as a valuable tool for local planners to consider potential pollution risks during future planning and development activities. Full article