Non-point Source Pollution Load Research Articles

Management optimization of nonpoint source pollution considering the risk of exceeding criteria under uncertainty

Management of nonpoint source (NPS) pollution is highly important in watershed water environmental and ecological security. However, the many complexities and uncertainties that exist in the processes of export and management of NPS pollution exert substantial influences on the reliability of multiple management practices. This study developed an inexact multiobjective possibilistic mean-variance mixed-integer programming (IMPMMP) model for NPS pollution management through optimization of watershed land use pattern and livestock production structure. By coupling interval parameter programming, mixed-integer programming, multiobjective programming, and an export coefficient model within a general possibilistic mean-variance model framework, the IMPMMP model deals effectively with system uncertainties and complexities. Moreover, the risk of exceeding criteria (REC) in NPS pollution management systems can be considered. The proposed IMPMMP model was applied to a real-world case study in the Xinfengjiang Reservoir watershed in South China. Results showed that the preference of decision makers regarding land use adjustment plays a decisive role in determining model feasibility. The area provided for each land use type that could be adjusted has to reach a certain threshold to achieve the goals of reduced pollution load and REC control. The NPS pollution loads after optimization would be exported primarily from different land uses and the human population. Compared with NPS nitrogen pollution management, it is more difficult to reduce the NPS phosphorus load and to manage the corresponding REC through adjustment of the land use pattern and livestock production structure. Moreover, it is difficult to simultaneously reduce the NPS nitrogen and phosphorus pollution loads and REC in each subbasin. The model, which can provide policy makers with a series of schemes for optimization of land use pattern and livestock production structure, has satisfactory applicability and could be used for watershed NPS pollution management.

Identifying feasible nonpoint source pollutant sampling intervals for watersheds with paddy field and urban land uses

Abstract Monitoring provides data and information necessary for water quality assessment, but often it is prohibitive, especially when frequent sampling is required. In this study, we explored feasible sampling intervals for improved efficiency of nonpoint source (NPS) pollution assessment. We compared NPS pollutant loads calculated with concentration samples collected at 1, 2, 3, 4, and 6-hour intervals for the first 24 hours of 13 storm events and investigated the effect of different sampling intervals on load estimation for three watersheds that have different land uses. When compared to load estimates made from concentrations sampled at the reference (1-hour) interval, differences in load estimates were less than 10% in the cases of the 2-hour and 3-hour intervals in the urbanized and agricultural watersheds, respectively, except in the case of suspended solids (SS). When it comes to the total load estimation, up to 3-hour interval sampling provided load estimates with acceptable accuracy, except for SS. Thus, the 3-hour sampling interval was considered feasible for long-term pollutant load assessment, while the 2-hour sampling interval was suggested for SS. Such findings are expected to facilitate NPS pollution assessment by providing information required to improve monitoring efficiency.

Analysis of nonpoint source pollution load in Ulansuhai Nur basin

The aim of this study is to explore the specific situation of nonpoint source pollution in Ulansuhai Nur basin, so as to provide reasonable and scientific pollution control and water area protection schemes. According to the socioeconomic statistics and water quality information of Ulansuhai Nur basin from 2008 to 2019, taking chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) as the control indicators, the sources of nonpoint source pollutants (urban domestic sewage, livestock breeding, rural domestic area pollution, rural agricultural production area pollution, and aquaculture pollution) are analyzed. And the amount of each pollution source into the lake is analyzed according to the discharge coefficient and inflow coefficient. The inflow amount and the changing trends of COD, TN, and TP discharged from each pollution source are compared and analyzed, and the main sources of pollution for each control indicator are explored. The causes of water pollution in Ulansuhai Nur basin in recent 10 years are analyzed so as to provide theoretical basis for water pollution control in Ulansuhai Nur basin. The results show that the COD and TN intake in the Ulansuhai Nur basin increase year by year between 2008 and 2019, the pollution load is serious, and it mainly comes from urban domestic sewage and rural agricultural production pollution; the TP intake shows a trend of increasing first and then gradually decreasing, and the inflow amount of pollutants is relatively small and is mainly from livestock breeding; which indicate that the load of nonpoint source pollution in Ulansuhai Nur basin has exceeded the capacity of the lake greatly, causing serious harm to water quality, so proper measures should be taken to control it.

Developing a Reliability Index of Low Impact Development for Urban Areas

A defining characteristic of the urbanization is the transformation of existing pervious areas into impervious areas during development. This leads to numerous hydrologic and environmental problems such as an increase in surface runoff due to excess rainfall, flooding, the deterioration of water quality, and an increase in nonpoint source pollution. Several studies propose supplementary measures on environmental change problems in development areas using the low impact development technique. This study investigated the reduction of nonpoint source pollutant loads and flooding in catchments through urban catchment rainfall–runoff management. For the quantitative assessment of flood disasters and water pollution problems, we propose a reliability evaluation technique. This technique refers to a series of analysis methods that determine the disaster prevention performance of the existing systems. As the two factors involve physical quantities of different dimensions, a reliability evaluation technique was developed using the distance measure method. Using the storm water management model, multiple scenarios based on synthetic rainfall in the catchment of the Daerim 2 rainwater pumping station in Seoul, South Korea, were examined. Our results indicate the need for efficient management of natural disaster risks that may occur in urban catchments. Moreover, this study can be used as a primary reference for setting a significant reduction target and facilitating accurate decision making concerning urban drainage system management.

Response of Non-point Source Pollution Loads to Land Use Change under Different Precipitation Scenarios from a Future Perspective

To optimize the management of non-point source (NPS) pollution in a changing environment, the cellular automata (CA) and Hydrological Simulation Program-Fortran (HSPF) models were used to study the response mechanism of NPS pollution loads to land use change and different precipitation scenarios. Taking the Dongjiang River Basin as a case study, the land use situation and its spatial distribution patterns in 2020, 2030 and 2050 were predicted by the logistic regression-based CA model. The trends of the NPS pollution loads under different land use and precipitation scenarios were quantitatively evaluated. The results show that the total accuracy of the land use change simulated by the CA model was 81%. Both the HSPF model and the CA model were highly applicable to this basin. Precipitation is proven to be the main driving force of NPS pollution. From 2020 to 2050, the annual load, average monthly load, maximum and minimum monthly load of the BOD and TP show an upward trend. TN shows a slight downward trend, which is related to the reduction in cultivated land area and the use of nitrogen fertilizer. In view of the future trend of NPS pollution, the basin should continue to control TN pollution and focus on strengthening BOD and TP control to achieve high-quality management of the water environment.

Spatiotemporal variation in nitrogen loads and their impacts on river water quality in the upper Yangtze River basin

Understanding the spatiotemporal distribution of nonpoint-source pollutant river loads from catchments and their influences on the water quality along river networks in a large river basin is important for land management and water quality protection. In this study, a geomorphology-based nonpoint-source pollution (GBNP) model was applied to the upper Yangtze River basin (YRB) to analyze the nitrogen loads into the river network, as well as its influences on river water quality. Based on the simulation, we analyzed the spatial and temporal distribution of nonpoint-source nitrogen loads into river networks and the nitrogen retention along the river network. The results illustrated that the annual total nitrogen (TN) loads from the fields/hillslopes into the rivers ranged from 55 × 104 t to 392 × 104 t on average during 1990–2012 in the upper YRB. The export coefficient (the ratio of river TN load to TN input of the same sub-catchment) over the upper YRB varied from 0.04 to 0.82 and had a mean value of 0.26. The spatial variability in the annual TN load (TN load intensity) significantly influenced the export coefficient magnitudes in different tributaries. The river nitrogen retention ratio varied from 3.84% to 85.50%, and Minjiang (MJ) had the highest value among all tributaries. The nitrogen retention ratio was higher in spring and winter than in summer and autumn in all tributaries. Both temperature and stream flow conditions (discharge and velocity) were the major factors that influenced river nitrogen retention. In general, a higher TN load from the catchment resulted in a higher river TN concentration due to the “lift-up and carry-away” functions of the catchment rainfall-runoff processes. However, when the net anthropogenic nitrogen input (NANI) was low, the TN load was also relatively low, and the high flow could dilute the river nitrogen concentration. When the TN load was adequately high, the river flow dilution could disappear, and the river TN concentration had the same pattern as the river discharge.

Integral Application of Chemical Mass Balance and Watershed Model to Estimate Point and Nonpoint Source Pollutant Loads in Data-Scarce Little Akaki River, Ethiopia

The quality of Little Akaki River in Addis Ababa (Ethiopia) is deteriorating significantly due to uncontrolled waste released from point and diffuse sources. In this study, pollution load from these sources was quantified by integrating chemical mass balance analysis (CMB) and the watershed model of pollution load (PLOAD) for chemical oxygen demand, biochemical oxygen demand, total dissolved solid, total nitrogen, nitrate, and phosphate. Water samples monitored bimonthly at 15 main channel monitoring stations and 11-point sources were used for estimation of pollutant load using FLUX32 software in which the flow from the soil and water assessment tool (SWAT) model calibration, measured instantaneous flow, and constituent concentration were used as input. The SWAT simulated the flow quite well with a coefficient of determination (R2) of 0.78 and 0.82 and Nash-Sutcliff (NSE) of 0.76 and 0.80 during calibration and validation, respectively. The uncharacterized nonpoint source load calculated by integrating CMB and PLOAD showed that the contribution of nonpoint source prevails at the middle and downstream segments of the river. Maximum chemical oxygen demand (COD) load from uncharacterized nonpoint sources was calculated at the monitoring station located below the confluence of two rivers (near German Square). On the other hand, high organic pollution load, biochemical oxygen demand (BOD) load, was calculated at a station upstream of Aba Samuel Lake, whereas annual maximum total dissolved solid (TDS), total nitrogen (TN), and phosphate load (PO4-P) from the nonpoint source in Little Akaki River (LAR) were found at a river section near Kality Bridge and maximum NOX load was calculated at station near German Square. The integration of the CMB and PLOAD model in this study revealed that the use of area-specific pollutant export coefficients would give relatively accurate results than the use of mean and median ECf values of each land use.

Determination of Non-point Pollution Critical Areas to Provide Sustainable River Basin Management, Gördes Dam Basin, Turkey

Non-point source (NPS) pollution is the main factor cause of various water quality problems across river basins in Turkey. The determination of critical source areas (CSAs) is necessary to control non-point source (NPS) pollution at a basin scale, especially when there are limited resources in the areas. The aim of this study is to determine the spatial and temporal distribution of NPS pollution loads in the Gördes dam basin, Turkey. CSAs were identified based on the Soil and Water Assessment Tool (SWAT). Fact and Fully Calibration Tool (FACT) were used to calibrate the model. The distribution of total nitrogen and phosphorus load in the basin was determined based on the subbasins level. The results based on the calibrated model showed that the sub-basins heavily and seriously polluted by agricultural and forest areas. Higher TN and TP loads occurred mainly in the downstream areas of the Gördes dam basin. Furthermore, the central zone of the Gördes dam basin was identified as the major source of TN and TP loads owing to the flow direction.

Quantitative assessment of non-point source pollution load of PN/PP based on RUSLE model: a case study in Beiluo River Basin in China.

The runoff-sediment relationship in the Yellow River Basin of China is still grim. People pay more and more attention to non-point source (NPS) pollution caused by surface pollutants migrating into the receiving water body with rainfall runoff. The particulate load of pollutants adsorbed in the soil and sediment by erosion and denudation and migration into water is also quite serious. It is necessary to deeply analyze the quantitative relationship between particulate nitrogen and phosphorus (PN/PP) load and soil loss. The soil erosion estimation of different administrative units in the study basin is obtained by the revised universal soil loss equation (RUSLE). The spatial distribution and the variation characteristics at different slopes and different land use of PN/PP load are discussed. An empirical equation of particulate organic load is used to calculate the PN/PP load. The results show that the multi-annual average erosion modulus of the basin is 358.33t/(km2∙a); the multi-annual average soil erosion reaches 9.62 million tons. The PN/PP load caused by soil loss reaches 11,107.1t and 7909.3t, and the export coefficients are 4.13kg/hm2 and 2.94kg/hm2, respectively. Spatial distribution of the PN/PP load is in step with the soil erosion distribution. Soil erosion is prone to occur in the region under the slope of 8 ~ 25°, the NPS load of PN/PP are relatively large, and the average export coefficients of PN/PP are 7.17kg/hm2 and 5.06kg/hm2. With the increase of the slope, the PN/PP load export coefficient increases first and then decreases. Agricultural land (AGRL), forest land (FRST), and pasture (PAST) are the land use types that contribute the most to the PN/PP load and soil erosion, and the average export coefficients of PN/PP are 4.54kg/hm2 and 3.23kg/hm2, respectively. The variability of natural elements, the unevenness and heterogeneity of spatial distribution, and the heavy involvement of human activities will have a conspicuous impact on the soil erosion and NPS pollution processes in the basin. The research on the influence of single factor and combined factors on NPS pollution process can be strengthen and provides scientific theoretical basis for formulating reasonable and efficient water and soil conservation measures and NPS pollution control scheme, so as to achieve effective control and scientific management of environment pollution.

Is the sponge city construction sufficiently adaptable for the future stormwater management under climate change?

Climate change increases the uncertainties associated with the future urban stormwater management. This study employed the Personal Computer Stormwater Management Model to evaluate the impact of climate change on problems associated with stormwater management at the city scale. These include urban flooding, non-point source (NPS) pollution, and combined sewer overflow (CSO) pollution. Multiple methods were adopted to overcome the difficulties when building credible modellings. Time partitioning and sectional difference were used during the calibration of hydrological and hydraulic parameters. The groundwater/river infiltration was assessed via extensive monitoring. The field rainfall simulator system was used to determine NPS parameters. Promising adaptions of sponge city construction in response to climate change were further evaluated. The adaption strategies were set in strict accordance with the “Sponge City Construction Systematization Program”. The results showed that future climate change will increase the urban flooding risk, both NPS and CSO pollution loads, and will worsen river water quality. Sponge city construction was demonstrated to be a no-regrets adaption strategy toward the reduction of the combined pressures induced by changing climate. However, the adaptability was insufficient and varies largely with regard to concentration pathways, rainfall intensities, and pollutants. In best case scenarios, the flooding risk as well as diffuse pollution loads can be decreased to or below their current level under future climate change. However, the current level needs to be considered, since the urban drainage function was far from sufficient and the water quality was very poor. The increased NPS pollution risk was noticed after sponge city construction. Especially, for chemical oxygen demand and suspended solids, the increased NPS loads could even offset the decreased CSO pollution loads. Thus, flexibility is suggested to be allowed in the design of storm-drainage and pollution-control measures in future urban stormwater management.

Assessment and analysis of agricultural non-point source pollution loads in China: 1978–2017

China's successful agriculture development has resulted in public concerned environmental problems. However, continuous and detailed data about Chinese agricultural non-point source pollution (ANPSP) loads are lacking. To assess and analyze Chinese ANPSP loads from 1978 to 2017, an inventory analysis was performed, and a socioeconomic and spatiotemporal analysis in the scale of provinces was conducted. The results showed that the pollution loads of chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) increased by 91.0%, 196.2% and 244.1%, respectively, and their variation underwent a free development stage, reform promotion stage, market regulation stage and policy incentive stage. The results of the pollution source analysis showed that over the past 40 years, the total percent contribution to COD by livestock and poultry breeding (LPB) and rural household waste (RHW) accounted for 83.1%–96.6%, the total percent contribution to TN by mineral fertilizers (MF) and LPB accounted for 72.3%–80.8%, and the total percent contribution to TP by LPB, RHW and MF accounted for 69.1%–88.6%. In addition, Shandong, Guangdong, Sichuan, and Henan were the top producers of ANPSP loads, and their COD, TN, and TP loads accounted for approximately 32%, 30%, and 35% of the national totals, respectively. The discharge intensity of COD, TN and TP decreased by 79.2%, 67.8%, and 62.6%, respectively. The discharge intensity exhibited a phasic feature that aligned with the national economic plan in the temporal scale and was closely related to the agricultural conditions in the spatial scale.

Selection of Priority Tributaries for Point and Non-Point Source Pollution Management

The Korean Ministry of Environment has established management policies for four major rivers; these policies include plans to restore ecosystems and manage hazardous materials and non-point source pollution in the watersheds. The purpose of this study was to select priority tributaries in the Nakdong River basin for immediate management under these plans by using water quality index (WQI), principal component analysis (PCA), and non-point source pollution modeling data. First, comprehensive water pollution was assessed for 22 sub-basins in the Nakdong River basin by using a WQI. Seasonal pollution was then categorized as either point or non-point source by using the PCA results based on observed water quality data, and lastly, a distributed model was developed to analyze non-point source pollutant loads. This allowed for an assessment of the degree of potential non-point source pollution from several land cover types and the selection of basins where such pollution should be managed on a priority basis. Four sub-basins (Nos. 12, 13, 19, and 21) were found to have high pollution levels, and sub-basin No. 12 had the highest non-point loading. As a result of this comprehensive basin assessment, the Geumho River was selected as the first priority tributary for management. The approach applied in this study should be useful for future efforts to develop effective strategies to improve water resources in river basins.

The Influence of Different Forest Characteristics on Non-point Source Pollution: A Case Study at Chaohu Basin, China.

Forestland is a key land use/land cover (LULC) type that affects nonpoint source (NPS) pollution, and has great impacts on the spatiotemporal features of watershed NPS pollution. In this study, the forestland characteristics of the Chaohu Basin, China, were quantitatively represented using forestland types (FLTs), watershed forest coverage (WFC) and forest distance from the river (DFR). To clarify the impact of forests on NPS pollution, the relationship between forestland characteristics and watershed nutrient outputs (TN and TP) was explored on a monthly scale using SWAT (Soil and Water Assessment Tool) and the period simulation was 2008–2016. The results showed that: (1) the TN and TP showed similar output characteristics and the rainy season was the peak period of nitrogen and phosphorus output. (2) Among the forestland characteristics of forestland types, watershed forest coverage and forest distance from the river, watershed forest coverage and forest distance from the river had greater effects than forestland types on the control of watershed nutrient outputs (TN and TP). (3) In different forestland types, the watershed nutrient outputs intensity remained at the lowest level when the FLTs was mixed forest, with a TN output of 1244.73kg/km2 and TP output of 341.39 kg/km2. (4) The watershed nutrient outputs and watershed forest coverage were negatively correlated, with the highest watershed forest coverage (over 75%) reducing the TN outputs by 56.69% and the TP outputs by 53.46% compared to the lowest watershed forest coverage (below 25%), it showed that in areas with high forest land coverage, the non-point source pollution load in the watershed is smaller than in other areas. (5) forest distance from the river had an uncertain effect on the TN and TP output of the basin, the forestland itself is a source of pollution, but it also has the function of intercepting pollution movement; the forest distance from the river in the range of 500–1000 m had the lowest NPS pollution. Considering the different forest characteristics and topographical factors, an optimal allocation mode of differentiated forest land was proposed, these suggestions will provide a scheme for surface source pollution prevention and control in the basin. This research gap is the basis of real forestland optimization. We may optimize the forestland layout for NPS pollution prevention and control by clarifying the internal mechanism.

Research of method for non-point source pollution load

With the increasingly prominent problem of non-point source pollution in river basin water environment, it has attracted people’s attention and become a hot field of international research. This paper summarizes the digital model of non-point source pollution, briefly sketches the simulation analysis method of non-point source pollution model, and introduces an increasingly sophisticated method-SWAT model combined with scenario analysis. The application of the author’s preliminary research in the Minjiang River Basin using the SWAT model and scenario analysis is described. Finally, the development prospect of non-point source pollution model is analyzed and predicted.

Water quality attribution and simulation of non-point source pollution load flux in the Hulan River basin

Surface water is the main source of irrigation and drinking water for rural communities by the Hulan River basin, an important grain-producing region in northeastern China. Understanding the spatial and temporal distribution of water quality and its driving forces is critical for sustainable development and the protection of water resources in the basin. Following sample collection and testing, the spatial distribution and driving forces of water quality were investigated using cluster analysis, hydrochemical feature partitioning, and Gibbs diagrams. The results demonstrated that the surface waters of the Hulan River Basin tend to be medium–weakly alkaline with a low degree of mineralization and water-rock interaction. Changes in topography and land use, confluence, application of pesticides and fertilizers, and the development of tourism were found to be important driving forces affecting the water quality of the basin. Non-point source pollution load fluxes of nitrogen (N) and phosphorus (P) were simulated using the Soil Water and Assessment Tool. The simulation demonstrated that the non-point source pollution loading is low upstream and increases downstream. The distributions of N and P loading varied throughout the basin. The findings of this study provide information regarding the spatial distribution of water quality in the region and present a scientific basis for future pollution control.

Analysis of the Characteristics of Nitrogen and Phosphorus Emissions from Agricultural Non-Point Sources Pollution and Pollution Risk in Tianjin City, China

In order to understand the current status of agricultural non-point source pollution in Tianjin and figure out the main pollution source and areas, the evaluation and spatial distribution of agricultural non-point source pollution were analyzed. The pollution discharge coefficient method was used to estimate the agricultural non-point source pollution in Tianjin. The spatial distribution pattern of agricultural non-point source pollution load was analyzed by ArcGIS software, the pollution evaluation and sources analysis were carried out by equivalent pollution load method. The results show that the pollution load of TN and TP in Tianjin in 2017 was 11760.7 and 871.86 tonnes per year respectively, and the equivalent pollution loads were 11760.70 and 8718.68 m3 separately. Among the districts, the Baodi District, Wuqing District and Jinghai District have higher pollution loads, which are the key control areas. The spatial analysis showed the similar distribution characteristics of pollution load and intensity, which was higher in the middle and lower in the north and south in Tianjin. It is necessary to separately develop targeted pollution prevention measures to strengthen management and control.

Analysis of Livestock Nonpoint Source Pollutant Load Ratio for Each Sub-watershed in Sancheong Watershed using HSPF Model

Analysis of Livestock Nonpoint Source Pollutant Load Ratio for Each Sub-watershed in Sancheong Watershed using HSPF Model

Assessment of the Soil Vulnerability Index and comparison with AnnAGNPS in two Lower Mississippi River Basin watersheds

There is an increasing need to quickly and accurately identify areas where agricultural conservation practices can provide the greatest reduction in nutrient and sediment runoff. Geographic information systems (GIS)-based tools and indices are promising for identifying critical areas that are significant contributors of nonpoint source pollution loads with limited data. One such tool, the Soil Vulnerability Index (SVI), is tested here in Beasley Lake and Goodwin Creek watersheds in Mississippi. The SVI runoff component results are compared against aerial images and long-term land use histories in the watershed to determine if a higher SVI score is related to visibly degraded land or land removed from cultivation. SVI results are also compared to sediment yield estimates generated with the Annualized Agricultural Non-Point Source pollution model (AnnAGNPS) to determine the degree of agreement. The SVI runoff score demonstrated agreement with imagery and land use histories in both watersheds. The SVI categories and corresponding AnnAGNPS-predicted sediment yield also had moderate agreement, with 45% and 68% of watershed area in agreement in Beasley Lake and Goodwin Creek watersheds, respectively. In general, the tool is a quick way to assess spatial areas potentially contributing to nonpoint source pollution, which can then be combined with field-based knowledge and/or imagery to provide valuable insight for placement of conservation practices.

Comparative analysis of the runoff peak and non-point source pollution load of the initial area and the residential community developed from the area in Wuhan

Urban water environment and water safety problems are growing increasingly severe along with the accelerating rate of urbanization. It is very important to study the influence of traditional development model on water quality and quantity. In this study, SWMM model was developed to simulate and analyse the peak flow and pollution load changes before and after development in Wuhan residential communities with the short duration rainfall lasting 2 hours. It was found that under the traditional development model, the impervious surface area increased greatly, the peak runoff of rainwater increased by 66%∼183% compared with that before development, and the relationship between peak flow increment and rainfall before and after development can be calculated with ΔR=-0.023 H2 +1.49H+160. The confluence speed of rainwater decreased by 6.82%∼20.19%. After the development, the amount of pollutants and the initial concentration of pollutants increased significantly, and the concentration of pollutants converged faster. The maximum concentration of COD, TN and TP increased to 2.09 times, 2.19 times and 2.16 times, respectively. The annual pollution load of COD, TN and TP increased by 52.31%, 45.27% and 43.54%, respectively.

Determination of spatiotemporal characteristics of agricultural non-point source pollution of river basins using the dynamic time warping distance

The aims of this study were to develop a method to determine the spatial and temporal characteristics of agricultural non-point source (ANPS) pollution loads at the basin scale, and to identify the dominant processes and factors responsible. Time series of water flow and NH4+-N, TN, and TP loads at sub-basin outlets in the Qujiang and Fujiang river basins were obtained using a model calibrated with field measured data. The dynamic time warping (DTW) distances of flow rate and ANPS pollution loads between a sub-basin outlet and the basin outlet were calculated using the time series at the sub-basin outlet and the basin outlet. The DTWs were divided into clusters to evaluate the differences in variation, information content, and similarity among ANPS pollution load time series at the various spatial scales. Results showed that the proposed method could successfully identify the critical spatial scale of the basin. In the sub-basins smaller than the critical spatial scale, ANPS pollution loads were primarily affected by the land surface hydrological processes. In the sub-basins larger than the critical spatial scale, ANPS pollution loads were affected mainly by the river hydrological processes. In the Qujiang river basin, the spatial DTW clusters of ANPS pollution loads were similar to those of the water flow. In the sub-basins smaller than the critical scale, distinguishing factors for the ANPS pollution loads clusters were (from most to least important) stream order (i.e., the spatial scale), land use, and soil nutrient content. In the Fujiang river basin, the spatial DTW clusters of the three pollutants were similar. Distinguishing factors for the ANPS pollution loads clusters were (from most to least important) slope, land use, and soil nutrient content. This method developed can be used as a practical technique to characterize spatial and temporal distributions of ANPS pollution in river basins.