Combining CLUE-S and SWAT Models to Forecast Land Use Change and Non-point Source Pollution Impact at a Watershed Scale in Liaoning Province, China

Non-point source(NPS) pollution has become a major source of water pollution. A combination of models would provide the necessary direction and approaches designed to control NPS pollution through land use planning. In this study, NPS pollution load was simulated in urban planning, historic trends and ecological protection land use scenarios based on the Conversion of Land Use and its Effect at Small regional extent(CLUE-S) and Soil and Water Assessment Tool(SWAT) models applied to Hunhe-Taizi River Watershed, Liaoning Province, China. Total nitrogen(TN) and total phosphorus(TP) were chosen as NPS pollution indices. The results of models validation showed that CLUE-S and SWAT models were suitable in the study area. NPS pollution mainly came from dry farmland, paddy, rural and urban areas. The spatial distribution of TN and TP exhibited the same trend in 57 sub-catchments. The TN and TP had the highest NPS pollution load in the western and central plains, which concentrated the urban area and farm land. The NPS pollution load would increase in the urban planning and historic trends scenarios, and would be even higher in the urban planning scenario. However, the NPS pollution load decreased in the ecological protection scenario. The differences observed in the three scenarios indicated that land use had a degree of impact on NPS pollution, which showed that scientific and ecologically sound construction could effectively reduce the NPS pollution load in a watershed. This study provides a scientific method for conducting NPS pollution research at the watershed scale, a scientific basis for non-point source pollution control, and a reference for related policy making.

Analysis on the Status of Agricultural Non-point Source Pollution in Xinan River Basin

Taking Xinan River basin as research object,the status of agricultural non-point source pollution was analyzed based on field survey,as well as the effect of fertilizer and pesticide leaching and runoff,livestock and poultry breeding and rural domestic pollution on non-point source TN and TP.At last,some technical countermeasures of controlling non-point source pollution were put forward according to the characteristics of agricultural non-point source pollution in Xinan River basin.

Landscape Ecology Researches on the Regulation of Non-point Source Pollution in Agroforestry Watershed

Non-point source(NPS) water pollution generated by agricultural production has become a major environmental issue in agroforestry watersheds such as the Three Gorges. Landscape ecology emphasizes the regulation and effect of landscape pattern on material flow, energy flow in the ecological processes. This paper reviewed landscape ecological approaches of controlling non-point source pollution in agroforestry watershed of the Three Gorges from the patch level and landscape level. Stage I: landscape ecological investigation. The investigation is to fi gure out landscape pattern characteristics of the watershed, major causes and key sections of the non-point source pollution, "source" patches and ecological process of non-point source pollution, and the feedback relationship between landscape pattern and non-point source pollution. Stage II: landscape ecological planning. In the patch level, the best management procedures(BMPs) are selected to judge the application effect. In the landscape level, new landscape elements are introduced, "source" and "sink" landscape patch types adjusted, landscape level regulation effect assessed. Stage III: landscape ecological management. Small-watershed landscape ecological construction is carried out from patch level and landscape level, BMPs implemented gradually, landscape ecological planning and management integrated, landscape heterogeneity enhanced, intensity of non-point source pollution controlled effectively to achieve sustainable development of small watersheds.

Spatial and Temporal Distribution Characteristics of Agricultural Non-point Source Pollution in Xixi Watershed of Jinjiang Basin

The SWAT model was applied to analyze the temporal-spatial distribution patterns of non-point source pollution loads and the difference of pollution loads of different land use types in Xixi Watershed of Jinjiang Basin. The results showed that both yearly nitrogen and phosphorus pollution loads were evenly distributed during 1973 to 1979,the annual TN pollution from non-point source was 1530 t,or 6. 3 kg / ha,and the annual TP pollution from non-point source was 270 t,or 1. 1 kg / ha during 1973 to 1979 in the watershed. Considerable differences were identified on both monthly nitrogen and phosphorus pollution loads. The TN and TP pollution loads during the flood season( from April to September) accounted for 76. 2% and 75. 8% of the annual load respectively. There were great differences in both TN and TP pollution loads of different land use types in the study area,and the pollution load of both farmland and orchard was higher than that of the other land use types. TN and TP pollution loads of farmland accounted for 66% and 83% of total watershed. There was a great spatial difference in the nonpoint source pollution load of the study area. The critical source areas of non-point source pollution are mainly located at Guanqiao Town,Longmen Town,Changkeng Town,Shangqing Town and Dapu Town,where the efforts of controlling pollution should be made.

Simulation on the Time Progress of the Non-Point Source Pollution Load in Initial Stage Runoff for Small Watershed

Taking a reservoir in South China as an example, we use rainfall-runoff unit hydrograph method to analyze the time changing process of surface runoff inflow, which generated by typical design rainfall. On the basis of time series data of flow and water quality in control section of the main rivers in Xili Reservoir, we establish mathematical response relation between non-point source pollutants flux, such as flux of COD, flux of NH3-H, in catchment area of control section and runoff. Then we simulate the time dynamic change progress of non-point source pollution load which generate with the initial stage runoff that generated by design rainfall and flow into reservoir. It can provide technical parameters for the design of non-point source which generate from early runoff treatment project.

A distributed non-point source pollution model: calibration and validation in the Yellow River Basin

The applicability of a non-point source pollution model—SWAT(soil and water assessment tools) in a large river basin with high sediment runoff modulus(770 t/km2 in the Yellow River) was examined. The basic database, which includes DEM, soil and landuse map, weather data, and land management data, was established for the study area using GIS. A two-stage “Brute Force' optimization method was used to calibrate the parameters with the observed monthly flow and sediment data from 1992 to 1997. In the process of calibration automated digital filter technique was used to separate direct runoff and base flow. The direct runoff was firstly calibrated, and the base flow, then the total runoff was matched. The sediment yield was calibrated to match well. Keeping input parameters set during the calibration process unchanged, the model was validated with 1998—1999's observed monthly flow and sediment. The evaluation coefficients for simulated and observed flow and sediment showed that SWAT was successfully applied in the study area: relative error was within 20%, coefficient of determination and Nash-Suttcliffe simulation efficiency were all equal to or above 0.70 during calibration and validation period.

Method for calculating non-point source pollution distribution in plain rivers

The land area in a river network is divided into certain-scale square cells for the sake of precision, and, based on the physical mechanisms of rainfall-runoff processes and runoff pollution, the non-point source pollution from cells is estimated using the export coefficients of different land use types. The non-point source pollution from a land cell should all go into the closest fiver reach, so it is distributed according to the terrain of the plain river network area and the positions of land cells and river network reaches. A relationship between a single land cell and its pollution-receiving reach can be determined using this system. In view of the above, a spatial distribution model of the rainfall runoff and non-point source pollution in reaches of a plain river network area was established. This model can provide technological support for further research on the dynamic effects of non-point source pollution on water quality.

Research on the Influence of Land Use Changing on Non-point Source Pollution in Heihe River Basin

Based on the exploring of SWAT model suitability in Hei River Basin, this paper analyze quantitatively and compare non-point source pollution loads occurred under different land use scene. At last, the following conclusion can be attained： （1） Land use change exerts tremendous influence on non-point source pollution. Since forest land can save water and reduce soil loss, which decreases greatly the source of non-point source pollution; （2） Strengthening land management and promoting reasonable land use, especially the over 15 degree slope farmland, will be the effective measure to control non-point source pollution and protect the quality of water in the Hei River basin; （3） The best land use situation in Hei River basin should be like the following modes： complying with national water source protection policy, gradual evacuation of river basin population, returning all the sloping farmland which is above 15 degree to forest land, allowing the existence of few farming land below 15 slope degree on the premise that the drinking water quality standard is reached, no unused land, good vegetation covering situation. At then, total nitrogen load is 13.25 kg, total phosphate load is 3.29 kg, which means it will not contaminate

Application of SWAT Model to Non-point Source Pollution in Xincai River Basin

[Objective]The study aimed to simulate the production and transportation process of surface runoff,sediment and non-point source pollution in Xincai River basin based on SWAT model.[Method]On the basis of analyzing the principles of SWAT model,the correlative parameters of runoff,sediment and water quality were calibrated,then the spatial and temporal distribution of runoff,sediment and non-point source pollutants in Xincai River basin were studied by using SWAT model.[Result]The results of calibration and validation showed that SWAT model was reasonable and available,and it can be used to simulate the non-point source pollution of Xincai River basin.The simulation results revealed that the load of sediment and various pollutants was the highest in the rainy year,followed by the normal year,while it was the minimum in the dry year,indicating that the production of sediment and non-point source pollutants was closely related to annual runoff.[Conclusion]The research could provide scientific references for the prevention of non-point source pollution in a basin.

Control division of agricultural non-point source pollution at medium-sized watershed scale in Southeast China

This paper presents the study carried out for controlling agricultural non-point source pollution(NSP)in a medium-sized watershed covering 1.47×10^(4) km^(2) in Southeast China using quantitative analysis coupled with geographic information system(GIS),universal soil loss equation(USLE),soil conservation service-curve number(SCS-CN),nutrient loss equations,and annualized agricultural nonpoint source model(AnnAGNPS).Based on the quantitative results derived from GIS and environmental models,five control division units were generated for NSP control in Jiulong River watershed,namely,controlling unit for soil losses,controlling unit for livestock breeding and soil losses,controlling unit for excessive fertilizer use and livestock breeding,controlling unit for soil losses and fertilizer use,and controlling unit for excessive fertilizer use and soil losses.This study proved that integrating GIS with environmental models can be adopted to efficiently evaluate major sources and contributors of NSP,and identify the critical source areas of NSP,which enables adjusting measures to local conditions by further control division units developed through such study for control and management of water quality degradation induced by NSP in the Jiulong River watershed.

Contribution of baseflow nitrate export to non-point source pollution

As a common pollutant of nitrogen in groundwater, nitrate contamination has become a major concern worldwide. Baseflow, one of the dominant hydrological pathways for nitrate migration to streamflow, has been confirmed as a leading nitrate source for stream water where groundwater or subsurface flow contaminated heavily by nitrate. That is, sufficient improvements of water quality may not be attained without proper management for baseflow, even if non-point sources(NPS) pollutants discharged through surface runoff are being well managed. This article reviews the primary nitrate sources, the main factors affecting its transport, and the methodologies for baseflow nitrate estimation, to give some recommendations for future works, including:(1) giving sufficient consideration for the effects of climatological, morphological, and geological factors on baseflow recessions to obtain more reliable and accurate baseflow separation;(2) trying to solve calibration and validation problems for baseflow loads determining in storm flow period;(3) developing a simple and convenient algorithm with certain physics that can be used to separate baseflow NPS pollution from the total directly in different regions, for a reliable estimation of baseflow NPS pollution at larger scale(e.g., national scale);(4) improving groundwater quality simulation module of existing NPS pollution models to have a better simulation for biogeochemical processes in shallow aquifers;(5) taking integrated measures of "source control", "process interception" and "end remediation" to prevent and control NPS nitrate pollution effectively, not just only the strict control of nutrients loss from surface runoff.

Modeling agricultural non-point source pollution in a high-precipitation coastal area of China

Non-point source （NPS） pollution simulation in the high-precipitation coastal areas of China is difficult because varying annual typhoon incidence leads to highly contrasting rainfall patterns in dry years and wet years. An IMPULSE （Integrated Model of Non-point Sources Pollution Processes） based NPS model of the Changtan Reservoir watershed, which is a typical high-precipitation coastal area in China, was established based on the analysis of point and NPS pollution data, a digital elevation model, and data on land-use, soil, meteorology, economy, and agricultural management practice. Pre-processed pre-rain- fall soil moisture levels were introduced during the simulation to model the effects of typhoons on hydrology. Rainfall events were simulated sequentially through the year and the model was calibrated and verified using hydrological and water quality data. Accuracy of the simulated rainfall runoff and water quality in the Changtan watershed was found to be acceptable. The study showed that the NPS modeling system could be applied to the simulation and prediction ofNPS loadings in the Changtan Reservoir watershed.

Loss coefficient of nitrogenous non-point source pollution under various precipitation conditions

In this study,calibrations of non-point source(NPS)pollution models are performed based on Black River basin historical real-time runoff data,sedimentation record data,and NPS sources survey information.The concept of NPS loss coefficient for the watershed or the loss coefficients(LC)for simplicity is brought up by examining NPS build-up and migration processes along riverbanks in natural river systems.The historical data is used for determining the nitrogenous NPS loss coefficient for five land use types including farmland,urban land,grassland,shrub land,and forest under different precipitation conditions.The comparison of outputs from Soil and Water Assessment Tool(SWAT)model and coefficient export method showed that both methods could obtain reasonable LC.The high Pearson correlation coefficient(0.94722)between those two sets of calculation results justified the consistency of those two models.Another result in the study is that different combinations of precipitation condition and land use types could significantly affect the calculated loss coefficient.As for the adsorptive nitrogen,the order of impact on LC for different land use types can be sorted as:farm land.urban land.grassland.shrub land.forest while the order was farmland.grass land.shrub land.forest.urban land for soluble nitrogen.

九龙江流域丰枯水期表层水体氮污染特征及其来源解析

为探明九龙江流域表层水体氮污染分布特征及其污染来源,于2020年7月(丰水期)和2021年1月(枯水期)开展九龙江全流域表层水体多点多断面原位观测,利用正定矩阵因子分析模型(positive matrix factorization,PMF)对不同水期全流域表层水体氮污染来源及贡献率进行解析,耦合相关性统计分析方法研究不同水期流域表层水体氮污染的关键驱动因子。结果表明,九龙江流域表层水体氮污染存在明显的水期分异特征,ρ(TN)为0.72~13.14 mg·L^(-1),丰水期ρ(TN)为1.39~10.95 mg·L^(-1),枯水期为0.72~13.14 mg·L^(-1)。硝态氮(NO_(3)^(-)-N)、氨氮(NH_(4)^(+)-N)、亚硝态氮(NO_(2)^(-)-N)和溶解性有机氮(DON)浓度均表现为丰水期大于枯水期,但颗粒态氮(PN)浓度则表现为枯水期大于丰水期。丰水期氮污染以NO_(3)^(-)-N、NH_(4)^(+)-N和DON形态为主,枯水期则以NO_(3)^(-)-N、DON和PN形态为主。应用PMF模型对流域表层水体氮污染来源进行解析,结果表明,丰水期流域农业化肥施用引起的农业面源污染、生活污水及河流内动植物残体、微生物、矿物颗粒是流域水体氮污染的主要来源,而枯水期流域农业化肥污染、城市工业污水排放及河流中动植物残体等悬浮颗粒则是流域水体氮污染的主要来源。该结果强化了丰枯水期九龙江流域表层水体氮污染受流域农业生产活动和径流变化共同影响的认识,建议将流域农业、工业生产氮污染源头控制和氮污染的水期分异有效纳入流域水体氮污染综合管理。

平原河网地区生态清洁小流域综合治理模式研究

为解决平原河网地区河渠功能退化、农业面源污染、农村生活垃圾与污水等生态环境问题,以汉川市幸福渠小流域为例,研究总结平原河网地区生态清洁小流域建设模式。提出遵循以问题为导向的设计理念,将小流域划分为人居生态治理区、农田生态保护区、水系生态修复区,围绕“乡村振兴”发展战略,统筹推进多部门协同治理,因地制宜实施水系景观保护与修复、污水及垃圾处理、乡村绿化美化、面源污染防治、实用技术及生态产业推广等措施。结果表明:通过多部门协同治理,可推动平原河网地区小流域水土流失综合治理从减量降级向提质增效转变。研究成果可为同类型小流域治理提供参考。

笋溪河面源污染及其与河岸带土壤有机碳、氮、磷的关系

[目的]分析水体和河岸带土壤氮磷的空间异质性,探讨河岸带土壤有机碳、氮、磷含量对水体面源污染的影响程度,为明晰重庆笋溪河水体面源污染状况及其与河岸带土壤的关系提供理论依据。[方法]沿笋溪河采集水样44个、0—20与20—40 cm土层土样各44个,采用内梅罗指数评价了笋溪河水质污染状况,并运用方差分析和多重比较、独立样本t检验、相关性分析和冗余分析等方法研究了河岸带水体不同形态氮、磷,土壤有机碳与氮、磷总量和有效量的空间分布特征,以及水体氮、磷对土壤有机碳与各形态氮、磷及化学计量比的响应。[结果](1)笋溪河水体严重污染,且下游污染较上、中游严重;(2)笋溪河下游水体总氮、总磷和可溶性磷酸盐极显著高于上、中游,下游硝酸盐氮极显著高于中游(p<0.01);(3)下游20—40 cm土层土壤有机碳含量显著高于中游,两个土层土壤有效磷和20—40 cm全磷在各河段间差异显著,而20—40 cm C/P和0—40 cm N/P在上游均显著高于中、下游(p<0.05);0—20 cm土壤有机碳、全氮、硝态氮、全磷和有效磷含量均显著高于20—40 cm(p<0.05),表聚现象明显;(4)相关性分析显示水体各形态氮和总磷与土壤全磷和有效磷呈显著正相关(p<0.05),冗余分析表明土壤有机碳与各形态氮、磷及化学计量比对水体各形态氮、磷的总解释率达64.15%,土壤全磷和有效磷是影响水体面源污染的主导因子。[结论]笋溪河面源污染严重,土壤全磷和有效磷可显著影响水体污染状况,面源污染治理应重点关注河岸带生态系统。

基于冗余分析与受体模型的岷江水质特征与流域污染源解析

基于岷江眉山段地表水水质数据与土地利用指标,利用冗余分析(RDA)阐明水质对土地利用的响应机制,并将此作为辅助信息来优化正定矩阵因子分解(PMF)模型中的污染源解析过程,为污染源判定提供科学依据。结果表明,研究区以氮磷和有机污染为主,各水质指标间存在不同程度关联性;土地利用指标对水质指标的影响方式和强度不同,耕地、建设用地、人口密度、化肥施用量和单位面积工业GDP表现为对水质不利的因素,林地和草地为对水质保护有利的因素;污染源贡献依次为企业点源污染排放(23.13%)>农业面源污染(18.71%)>季节因素(16.67%)>生活污水排放(15.56%)>城市面源污染(15.26%)>自然源(10.67%)。

东辽河流域土地利用变化对非点源污染的影响研究

采用国际前沿的SWAT模型及CLUE-S模型,基于3S技术和统计分析方法,分析了吉林省东辽河流域土地利用2000-2005年的土地利用动态变化,并借助于Logistic回归结果探讨了2000-2005年土地利用变化的驱动力空间特征;运用2000年和2005年土地利用数据,结合CLUE-S模型,模拟不同预测方案下东辽河流域未来20a土地利用变化情况.在此基础上,应用SWAT模型分别对研究区2025年2种情景下非点源污染负荷进行模拟.结果表明:不同的土地利用条件下,情景2比情景1的多年平均径流减少了12.26mm、泥沙减少了8.4×103t、溶解态氮减少了8.29kg、有机氮减少了9.49kg、总氮减少了8.4kg、溶解态磷减少了8.61kg、有机磷减少了7.18kg、总磷减少了7.18kg,情景2比情景1更能有效的控制非点源污染.

小清河流域抗生素污染分布特征与生态风险评估

利用固相萃取、高效液相色谱-串联质谱法(HPLC-MS/MS)检测小清河流域地表水中4类抗生素的残留水平,分析其分布特征,结合土地利用类型探讨其可能的污染源,并通过计算风险商(RQs)来进行生态风险评估。结果表明:小清河流域地表水有13种抗生素检出,其中大环内酯类抗生素和甲氧苄啶的检出率为100%;20个采样点的大环内酯类、喹诺酮类、磺胺类和磺胺增效类的质量浓度范围分别是2.18~84.9、nd^1600、nd^845、1.88~3900 ng·L-1。高浓度的大环内酯类和喹诺酮类抗生素主要集中在人口密集区下游,在水产养殖密集的下游区域检测到较高浓度的磺胺类和磺胺增效药甲氧苄啶,表明生活污水和水产养殖废水仍是小清河流域抗生素污染的主要来源。生态风险评估结果显示,13种抗生素中处于高风险等级、中等风险等级、无风险等级的比例分别是38.5%、23.1%、38.5%,表明小清河流域部分水体抗生素污染具有较高的生态风险。

汉江中下游农业面源污染动态监测信息系统的建立与初步应用

根据汉江中下游农业面源污染治理决策的需求 ,应用遥感与GIS一体化的方法 ,研究设计了汉江中下游农业面源污染动态监测信息系统的结构、功能及数据库的组成 ,并建立了可运行的汉江中下游农业面源污染动态监测信息系统 ,在系统支持下可有效地实现汉江中下游农业面源污染动态监测、最佳管理措施的选择以及区域农业面源污染综合治理规划。系统可以为地方政府相关部门决策提供依据 ,对有效的保护汉江流域水资源环境 ,控制汉江流域水污染有着重要意义。