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1.
研究鄱阳湖入、出湖污染物通量是加强鄱阳湖及长江水功能区限制纳污红线管理的前提,是建立鄱阳湖水质预测模型的基础.基于2008-2012年鄱阳湖8条主要入湖河流、出湖口的逐月水量、水质同步监测资料,根据污染源特征优选算法,计算总磷(TP)、氨氮(NH3-N)、高锰酸盐指数(CODMn)的入、出湖污染物通量,并分析时空变化特征及影响因素.结果表明:(1)出湖口和乐安河入湖口断面的NH3-N、TP及昌江入湖口断面的TP,以点源污染为主,采用每月瞬时通量作为月平均通量的算法更准确;其余以非点源污染为主,采用瞬时污染物浓度与月平均流量之积来计算月平均通量更准确.(2)2008-2012年CODMn、NH3-N和TP年平均人湖通量分别为304398、53063和9175 t,年平均出湖通量分别为367436、45814和8452t.8条入湖河流每年的入湖水量、CODMn通量和个别年份的NH3-N、TP通量小于出湖,这主要是因为未计算区间产流及相应排污和采砂引起的内源污染.(3)入、出湖污染物通量在年际间主要受水量影响而呈现W型波动变化趋势,CODMn、NH3-N、TP入湖通量及CODMn出湖通量均集中在汛期,NH3-N、TP出湖通量则是冬季较多(低水位下湿地植被净化作用受限).入湖TP、NH3-N、CODMn通量主要来自赣江、信江、乐安河,而NH3-N、TP浓度最高的是乐安河、信江. 相似文献
2.
基于洱海水生态特征的流域最大日负荷总量控制 总被引：1，自引：1，他引：0
基于洱海水生态历史数据及现状资料,采用概率密度分布曲线法及水生生物基准相结合的方式计算洱海总氮(TN)、总磷(TP)、高锰酸盐指数(COD_(Mn))和氨氮(NH_3-N)的控制目标,目标值分别为0.36、0.026、4和0.28 mg/L.再根据该水质目标,得到洱海的最大日负荷(TMDL)总量.TMDL总量采用线性规划法计算,其中污染物响应系数矩阵通过MIKE 21二维水质模型计算所得.安全容余(MOS)则通过一阶误差分析法确定.经过一系列的计算,最终确定洱海的TMDL总量控制计划.计算结果表明,洱海TN、TP、COD_(Mn)和NH_3-N的TMDL总量分别为2005.989、149.671、19258.844和1348.119 kg/d,其MOS所占比例分别为6.152%、5.570%、4.380%和5.021%,表明洱海农业面源污染为该流域主要的污染形式,其允许最大排放量约占全部允许排放量的90%左右. 相似文献
3.
定量解析污染源对水质影响的贡献是水环境精细化管理的重要基础。目前多通过水质和土地利用类型的关系以解析水体污染源的研究,忽略了空间尺度的差异性,引发景观配置不合理的后果。为此,本研究依据考虑空间尺度效应的污染源解析方法,基于异龙湖流域3条主要入湖河流的入湖口监测断面对雨季和旱季的水质数据进行研究。同时利用绝对主成分—多元线性回归模型(APCS-MLR)和bioenv分析揭示河道不同尺度缓冲区的土地利用变化对水质的影响并解析河流主要污染源。研究结果表明:(1)异龙湖主要入湖河流水质表现出季节性差异,旱季期间3条主要入湖河流的浊度、化学需氧量(CODCr)、氨氮(NH3-N)、总磷(TP)和总氮(TN)浓度平均值相比于雨季减幅分别为39.53%、39.93%、94.48%、38.29%和1.72%。其中,入湖河流水体中的TN在旱季和雨季的超标率分别为58%和74%,成为首要污染物;(2)在旱季,20 m缓冲区尺度内河流水质受耕地和裸地占比影响较大,随着空间尺度的扩大,至50～300 m缓冲区尺度时建设用地、林地及水体占比对水质的影响增加;在雨季,C... 相似文献
4.
环太湖江苏段入湖河道污染物通量与湖区水质的响应关系 总被引：1，自引：1，他引：0
基于2008-2018年环太湖江苏段入湖河道污染物通量及湖区水质数据,从时空变化及相关关系两个方面探讨了入湖污染物通量与湖区水质的响应关系,并分析了污染物进入湖体影响水质的主要因子.结果表明:太湖污染减排已见成效,氨氮、总氮、高锰酸盐指数和化学需氧量入湖污染物通量整体呈下降趋势,年均下降率分别为8.0%、2.0%、1.6%和2.2%,湖体氨氮和总氮时间格局响应较好,年均下降率分别为2.1%和2.3%.湖体氨氮、总氮、总磷、高锰酸盐指数和化学需氧量与入湖污染物通量整体由西北部、西部湖区向东南部、东部湖区递减,空间格局上响应基本一致.全湖区年尺度总氮、氨氮浓度与入湖河道污染物通量分别呈显著正相关、极显著正相关关系;影响湖区总氮、氨氮的主要因子为入湖河道的总氮、氨氮浓度,其次为入湖河道浓度与原湖区水质差值,因此亟需加强入湖河道水质浓度的控制. 相似文献
5.
为进一步揭示阳澄湖入湖河道的污染物来源,提出相应的治理对策,以2017—2021年阳澄湖入湖河道水质监测数据为基础进行分析讨论。依据入湖水量选取10条主要入湖河道进行分析,其中位于阳澄湖东岸的白曲港在七浦塘拓浚工程建成之前主导流向为出湖,工程建成后,通过Pearson相关分析证实了其流向与七浦塘引水时的水力关系,因此白曲港被选为主要入湖河道。采用距平系数法、系统聚类法和物元分析法将阳澄湖主要入湖河道分为3个类别:第1类别包括白荡、蠡塘河、北河泾、永昌泾4条河道,第2类别包括渭泾塘、界泾和施家斗港3条河道,第3类别包括南消泾、七浦塘和白曲港3条河道。使用因子分析法进行因子分析,第1类别河道的因子为高锰酸盐指数(CODMn)、氨氮(NH3-N)、溶解氧(DO)和总磷(TP),第2类别河道的污染因子为NH3-N、总氮(TN)、pH、TP和DO,第3类别河道的污染因子为pH、TP、TN和DO。通过对上游河道水质情况分析、文件研究以及实地调查等方式得出第1类别河道区域的污染源主要为工业污染源和生活污染源,第2类别河道区域污染源主要为工业污染源与种植业污染源,第3类别河道污染源主要为陆地水产养殖污... 相似文献
6.
Non‐point source (NPS) pollution from agricultural land is increasing exponentially in many countries of the world, including India. A modified approach based on the conservation of mass and reaction kinetics has been derived to estimate the inflow of non‐point source pollutants from a river reach. Two water quality variables, namely, nitrate (NO3) and ortho‐phosphate (o‐PO4), which are main contributors as non‐point source pollution, were monitored at four locations of River Kali, western Uttar Pradesh, India, and used for calibration and validation of the model. Extensive water quality sampling was done with a total of 576 field data sets collected during the period from March 1999 to February 2000. Remote sensing and geographical information system (GIS) techniques were used to obtain land use/land cover of the region, digital elevation model (DEM), delineation of basin area contributing to non‐point source pollution at each sampling location and drainage map. The results obtained from a modified approach were compared with the existing mass‐balance equations and distributed modelling, and the performances of different equations were evaluated using error estimation viz. standard error, normal mean error, mean multiplicative error and correlation statistics. The developed model for the River Kali minimizes error estimates and improves correlation between observed and computed NPS loads. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
7.
为掌握滇池流域花卉大棚种植区的非点源污染特征,提高和改善滇池水环境质量,本研究选取呈贡县斗南村花卉大棚种植区作为研究对象,在实测降雨径流数据的基础上,通过建立Storm Water Management Model模型分别对全年连续降雨条件下和典型设计降雨条件下的降雨径流水质、水量进行了模拟.研究结果表明:1)模型的流量、化学需氧量(COD_(Cr))、悬浮物(SS)、总氮(TN)和总磷(TP)的Nash-Sutcliffe效率系数分别为0.858、0.835、0.803、0.712和0.752,能够较好地模拟研究区域的水质、水量变化.2)研究区域的平均径流系数为0.59,CODCr、SS、TN和TP的单位面积负荷率分别为118.34、82.90、54.64和5.46 kg/(hm~2·a),TN和TP是主要控制的污染物.3)各污染物浓度峰值的出现时间均早于流量峰值出现的时间,因此对滇池东岸花卉大棚种植区应进行污染物尤其是TP、TN浓度与流量错峰控制. 相似文献
8.
For efficient and targeted management, this study demonstrates a recently developed non-point source (NPS) pollution model for a year-long estimation in the Pingqiao River Basin (22.3 km2) in China. This simple but physically reasonable model estimates NPS export in terms of land use by reflecting spatial hydrological features and source runoff measurements under different land-use types. The NPS export was separately analysed by a distributed hydrological model, a spatial hydrograph-separation technique, and an empirical water quality sub-model. Simulation results suggest that 57 890 kg of total nitrogen (TN) and 1148 kg of total phosphorus (TP) were delivered. The results, validated with observed stream concentrations, show relative errors of 23.3% for TN and 47.4% for TP. Countermeasures for urban areas (5.3% of total area) were prioritized because of the high contribution rate to TN (14.1%) and TP (26.2%) which is caused by the high degree of runoff (8.5%) and pollution source. 相似文献
9.
为探究城市湖泊富营养化的污染负荷来源及其贡献率,选择长江流域中下游典型富营养化湖泊(武汉后官湖)为研究对象,结合实测法、平均浓度法与排污系数法,解析了后官湖的外部污染来源(包括点源和面源,面源又进一步划分为农村生活、农业种植、水产养殖、畜禽养殖和城市径流).结果表明:化学需氧量(COD)主要来源于点源,入湖贡献为54%;总磷主要来源于面源,入湖贡献为71%.进一步筛选面源中污染物的主要来源发现,总磷主要来自农业种植和水产养殖,入湖贡献分别为41%和30%;面源中COD、氨氮和总氮贡献最大的是城市径流,入湖贡献率分别为61%、53%和37%.行政区污染排放贡献率中,COD、氨氮、总氮和总磷排放贡献率最大的分别为沌口街办(25. 24%)、蔡甸街办(23.28%)、永丰街办(24.04%)和大集街办(26.15%).开展沌口街办和永丰街办的点源治理可有效消减入湖COD与氨氮负荷,而大集街办的农业面源污染防治则是后官湖流域总磷治理的重点. 相似文献
10.
新安江对千岛湖外源输入总量的贡献分析(2006-2016年) 总被引：2，自引：0，他引：2
运用新安江模型,计算了千岛湖25条主要入湖河流在2006-2016年间的入湖流量,结合同时期入湖河道的逐月水质监测数据,分析了最大入流新安江的营养盐——总氮(TN)、总磷(TP)、氨氮(NH3-N)和高锰酸盐指数(CODMn)总量输入在该时段内的年际变化和季节变化规律,研究了新安江营养盐输入总量变化与新安江水质水量、黄山市人口、GDP和土地利用的关系,探讨了影响新安江营养盐总量的关键影响因素及其对千岛湖水质的影响.结果表明,研究时段内新安江多年平均年入湖水量占千岛湖多年平均年入湖水量的51.4%,占25条主要河流年总入流量的67.3%,新安江CODMn、TP、TN、NH3-N多年平均的输入总量分别为11458.4、214.9、7649.2和756.5 t/a,分别占千岛湖年总负荷的50.7%、34.3%、63.7%和48.4%.各指标的年入湖总量在统计期间均呈上升趋势,且春、夏两季高于秋、冬两季.相关性分析表明,黄山市GDP与新安江CODMn、TN和TP入湖总量呈显著正相关关系,农业面源污染对新安江TN输入总量有显著影响.作为千岛湖最大的入湖河流,新安江营养盐(TP、TN、NH3-N)的输入能显著影响千岛湖的生态系统健康. 相似文献
11.
平原河网区降雨径流污染负荷测算——以太湖流域望虞河西岸为例 总被引：1，自引：0，他引：1
如何精细量化降雨径流污染负荷是流域尺度实现面源精准治污全过程控制的重要前提.本研究以水污染较为严重的望虞河西岸综合示范区为例,通过开展不同土地利用类型的降雨观测实验,修正SCS-CN模型中的初损率,并基于土地利用类型遥感解译和降雨径流污染物浓度测定,精细刻画降雨径流中总磷(TP)、总氮(TN)、氨氮(NH3-N)、化学需氧量(COD) 4类主要污染物的时空分布格局.结果表明:研究区绿地和农田、硬质地表的降雨初损率分别为0.3和0.9;径流深、污染负荷与降雨深之间存在显著的正相关性.随着降雨量逐年递减,研究区降雨径流中TP、TN、NH3-N、COD四类污染物的负荷量分别从2017年的190、1359、445和16041 t减少至2019年的118、949、314和11250 t;单位面积TN和COD负荷最高的用地类型是农村住宅用地,草地的四种污染物单位面积负荷均最低,林地次之.相关研究结果为望虞河流域水污染控制提供了基础数据,也为定量测算平原河网区面源污染负荷提供了方法参考. 相似文献
12.
Synoptic water sampling at a fixed site monitoring station provides only limited ‘snap‐shots’ of the complex water quality dynamics within a surface water system. However, water quality often changes rapidly in both spatial and temporal dimensions, especially in highly polluted urban rivers. In this study, we designed and applied a continuous longitudinal sampling technique to monitor the fine‐scale spatial changes of water quality conditions, assess water pollutant sources, and determine the assimilative capacity for biochemical oxygen demand (BOD) in an urban segment of the hypoxic Wen‐Rui Tang River in eastern China. The continuous longitudinal sampling was capable of collecting dissolved oxygen (DO) data every 5 s yielding a ~11 m sampling interval with a precision of ±0.1 mg L?1. The Streeter and Phelps BOD‐DO model was used to calculate: (1) the oxygen consumption coefficient (K1) required for calibration of water quality models, (2) BOD assimilative capacity, and (3) BOD source and load identification. In the 2014 m river segment sampled, the oxygen consumption coefficient (K1) was 0.428 d?1 (20°C), the total BOD discharge was 916 kg d?1, and the BOD assimilative capacity was 382 kg d?1 when the minimum DO level was set to 2 mg L?1. In addition, the longitudinal analysis identified eight major drainage outlets (BOD point sources), which were verified by field observations. This new approach provides a simple, cost‐effective method of evaluating BOD‐DO dynamics over large spatial areas with rapidly changing water quality conditions, such as urban environments. It represents a major breakthrough in the development and application of water quality sampling techniques to obtain spatially distributed DO and BOD in real time. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
13.
为探究“十三五”期间武汉市湖泊水质变化特征及规律,分析当前武汉市湖泊水环境的主要问题及成因,为武汉市水生态环境保护“十四五”规划提供科学支撑,以武汉市166个湖泊为研究对象,根据武汉市环境监测中心2015-2019年对各个湖泊的监测数据,采用水质综合污染指数、富营养化状态评价、动态度分析等方法,对武汉市湖泊水环境进行综合评价.结果表明：1）2015-2019年武汉市湖泊水质总体好转,2019年全市湖泊综合污染指数较2015年下降7.74%,多数湖泊营养状态呈现稳中向好趋势,但湖泊水质较难实现持续改善.2）武汉市湖泊主要超标污染物总磷、氨氮、化学需氧量和高锰酸盐指数平均质量浓度在2015-2019年间均呈下降趋势,但2019年有47%湖泊总磷浓度劣于Ⅳ类评价标准,磷元素是制约湖泊水质的主要因素.3）2015-2019年武汉市中心城区湖泊综合污染指数下降,湖泊富营养化状态好转,但青山北湖、南湖等湖泊综合污染指数较高,排口排污、底泥内源污染是影响中心城区湖泊水质的主要因素.新城区湖泊水质改善仍面临一定压力,东西湖水系重度富营养化湖泊数量增多,后湖水系湖泊综合污染指数上升,农业面源、工业生产对新城区湖泊水质影响较大,湖泊破碎化导致的自净能力降低也是影响湖泊水质的重要因素. 相似文献
14.
基于2011—2020年乌梁素海水质监测数据,将综合营养指数法、PCA排序法和ArcGIS克里金插值法有机结合,综合评价2011—2020年乌梁素海水体富营养化程度年际时空变化特征,厘清引起水体富营养化发生变化的关键性驱动因子。研究结果表明:(1)乌梁素海水体总磷和总氮的峰值出现在平水期,氨氮的峰值在枯水期,CODMn的峰值在丰水期,水质整体以地表Ⅲ类水为主。(2)2011—2020年湖体水质经历了由轻度富营养-中营养-轻度富营养-中营养的变化过程,综合营养状态指数在60～70(中度富营养)的湖区面积占比由21.49%逐渐消失,综合营养状态指数在30～50(中营养)的湖区面积占比由23.84%扩增到44.87%。(3)乌梁素海生态补水量与总氮、总磷、CODMn和综合营养状态指数呈负相关,是影响湖泊水体营养化的另一个关键性驱动因子。 相似文献
15.
洱海主要污染物允许排放总量的控制分配 总被引：1，自引：0，他引：1
基于环境流体动力学模型EFDC(Environmental Fluid Dynamic Code),建立了洱海湖泊及湖湾的三维水动力水质模型.利用洱海2001 2011年连续11年的水动力水质监测数据对模型进行了率定和验证,模拟结果与实测资料吻合度较好,表明水动力水质模型计算结果较为合理.在考虑水质环境背景浓度的前提下,通过水质模型量化各个入湖排污口对水质控制点的贡献率,并对各水质控制点和入湖排污口的浓度进行约束限制,最终利用单纯形法求解得到各入湖排污口的允许排污量.计算结果表明,北区三条河流弥苴河、永安江、罗时江本身流量相对较大,所以允许排放总量也较大,总氮、总磷和CODMn的允许排放总量分别占到整个洱海允许排放量的47%、53%和49%.洱海主要污染物允许排放总量的控制分配研究对于洱海流域的环境综合整治具有十分重要的意义. 相似文献
16.
Nonpoint source pollution and hydromodification are the leading causes of impairment to our nation's rivers and streams. Roadside ditch networks, ubiquitous in both rural and urban landscapes, intercept and shunt substantial quantities of overland runoff and shallow groundwater to stream systems. By altering natural flowpaths, road ditches contribute not only to hydromodification but also potentially to nonpoint‐source (NPS) pollution by acting as hydrological links between agricultural fields and natural streams. Unfortunately, the impacts of these alterations on watershed hydrology and water quality are not well understood. Through a series of field measurements, including field surveys and discharge monitoring, this study examined the effect of road ditch networks on basin morphometry, field‐ and watershed‐scale hydrology, and pollutant transport in a 38 km2 agricultural watershed in south‐central NY. Salient findings include the following: (i) 94% of road ditches discharged to natural streams, effectively doubling the drainage density; (ii) on average, road ditches increased peak and total event flows in their receiving streams by 78% and 57%, respectively, but displayed significant variation across ditches; and (iii) ditches intercepted large quantities of surface and subsurface runoff from agricultural fields and therefore represent efficient conduits for the transport of agricultural NPS pollutants to sensitive receiving waterbodies. Our results provide useful information for hydrologists who wish to further understand how artificial drainage may be affecting watershed hydrology and for managers and engineers tasked with designing appropriate flood and NPS pollution control measures. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
17.
To improve quantitative understanding of mixed‐land‐use impacts on nutrient yields, a nested‐scale experimental watershed study design (n = 5) was applied in a 303(d), clean water act impaired urbanizing watershed of the lower Missouri River Basin, USA. From 2010 to 2013, water samples (n = 858 sample days per site) were analysed for total inorganic nitrogen (TIN‐N), nitrite (NO2–N) nitrate (NO3–N), ammonia (NH3–N), and total phosphorus (TP‐P). Annual, seasonal, and monthly flow‐weighted concentrations (FWCs) and nutrient yields were estimated. Mean nutrient concentrations were highest where agricultural land use comprised 58% of the drainage area (NH3 = 0.111 mg/l; NO2 = 0.045 mg/l; NO3 = 0.684 mg/l, TIN = 0.840 mg/l; TP = 0.127 mg/l). Average TP‐P increased by 15% with 20% increased urban land use area. Highly variable annual precipitation was observed during the study with highest nutrient yields during 2010 (record setting wet year) and lowest nutrient yields during 2012 (extreme drought year). Annual TIN‐N and TP‐P yields exceeded 10.3 and 2.04 kg ha?1 yr?1 from the agricultural dominated headwaters. Mean annual NH3–N, NO2–N, NO3–N, TIN‐N, and TP‐P yields were 0.742, 0.400, 4.24, 5.38, and 0.979 kg ha?1 yr?1, respectively near the watershed outlet. Precipitation accounted for the majority of the explained variance in nutrient yields (R2 values from 0.68 to 0.85). Nutrient yields were also dependent on annual precipitation of the preceding year (R2 values from 0.87 to 0.91) thus enforcing the great complexity of variable mixed‐land‐use mediated source‐sink nutrient yield relationships. Study results better inform land managers and best management practices designed to mitigate nutrient pollution issues in mixed‐land‐use freshwater ecosystems. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
18.
In accordance with the natural, geographic, and ecological characteristics of the Taihu Lake Basin, and the relation between the water body of Taihu Lake and its surrounding environment, an area, which has tight relevance with the water environment of Taihu Lake, was token as the main investigation region. The area was named as the Taihu Lake Region. Some factors, such as TN, TP, CODCr that characterized the main environmental problem, the eutrophication were selected when conducted the pollution sources investigation on in Taihu Lake Region. The categories, distribution, pollution contribution to the Lake of dijferent pollution sources, as well as the routes of pollutants entering the Lake were basically made clear. Pollution sources that must be preferentially controlled and the direction of controlling those main pollutants, such as TN, TP, CODCr, were proposed. Base on the investigation, a series of eco-systematic approaches for controlling Taihu Lake eutrophication were put forward. They are ecosystem regulation, nutrient substances transferring along food chain, trophic masse degrading step by step along the route from a pollution source to the Lake, building ecological preventive zone of the Lake, as well as the ecological measures for point sources treatment and so on. 相似文献
19.
巢湖流域塘西河上游分流制系统降雨径流污染特征及初期冲刷效应 总被引：1，自引：1，他引：0
研究城市径流水质变化及初期冲刷效应对控制与治理城市径流污染具有重要指导意义.对塘西河上游6次降雨径流水质水量进行监测分析,计算次降雨径流平均浓度(EMC)和单位面积次降雨径流污染负荷(EPL),作M(V)曲线图研究初期冲刷现象.结果表明:降雨径流中悬浮物(SS)、化学需氧量(CODCr)和总磷(TP)的EMC值相对较大;SS的EMC值波动最为显著;总氮(TN)、TP、COD_(Cr)、SS间的EMC值均呈正相关;TN的EMC值与降雨量呈负相关性.各污染物EPL值与各降雨特征间均呈正相关性,经估算2015年研究区在6-8月共有10.38 tTN、2.29 tTP、1022.43 t SS、161.70 t CODCr和5.18 t NH_3-N随降雨径流排入巢湖;降雨量和雨前干期是城市径流污染的主要影响因素;以FF5050为初期冲刷效应判别依据,5种污染物均有初期冲刷效应出现,冲刷程度表现为SSCODCrTPTNNH_3-N;各水质指标的初期冲刷强度与降雨特征之间无相关性;雨型对初期冲刷现象影响较大;当降雨强度达1.36 mm/h即有径流汇集流出时开始截流,截流时间取440 min,截取的最大径流量取224319.14 m~3. 相似文献
20.
Preliminary study on assessment of nutrient transport in the Taihu Basin based on SWAT modeling 总被引：4，自引：0，他引：4
With the Taihu Basin as a study area, using the spatially distributed and mechanism-based SWAT model, preliminary simulations of nutrient transport in the Taihu Basin during the period of 1995-2002 has been carried out. The topography, soil, meteorology and land use with industrial point pollution discharge, the loss of agricultural fertilizers, urban sewerage, and livestock drainages were all considered in the boundary conditions of the simulations. The model was calibrated and validated against water quality monitoring data from 2001 to 2002. The results show that the annual total productions of nitrogen (TN) and phosphorus (TP) into Lake Taihu are 40000t and 2000t respectively. Nutrient from the Huxi Region is a major resource for Lake Taihu. The non-point source (surface source) pollution is the main form of catchment sources of nutrients into Lake Taihu, occupied TN 53% and TP 56% respectively. TN and TP nutrients from industrial point pollution discharge are 30% and 16%, and sewerage in both forms of point source and non-point source are TN 31 % and TP 47%. Both the loss of agricultural fertilizers and livestock drainages from the catchment should be paid more attention as an important nutrient source. The results also show that SWAT is an effective model for the simulation of temporally and spatially nutrient changes and for the assessment of the trends in a catchment scale. 相似文献