A comparison of nutrient losses from two simulated pastureland management scenarios

Fecal deposits by grazing animals on pasturelands have the potential to leach nutrients to runoff during rainfall events. Unlike croplands, grazing systems such as pasturelands or rangelands have little opportunity to ameliorate nutrient runoff through in-field or edge-of-field management practices. Thus, we investigated the amounts and concentrations of nutrients in overland flow from simulated grazing lands. Two grazing management scenarios were simulated: continuous grazing represented by two sparsely vegetated (SV) plots and rotational grazing represented by two densely vegetated (DV) plots. In addition, there were two control plots. The plots were treated with standard cowpats and rainfall was simulated until overland flow at the edge of the plots reached steady-state. Higher runoff was observed from DV plots (9.97 mm) than SV plots (7.05 mm), but the average total suspended solids concentration in runoff from SV plots was approximately 17 times the concentration observed in runoff from the DV plots. The average total phosphorus (TP) concentrations were highest in plots simulating continuous grazing (5.91 mg L(-1)). In both DV and SV plots at least 83% of the TP was found to be in the dissolved form. The average total Kjeldhal nitrogen (TKN) and total nitrogen concentrations observed in runoff samples from SV plots were 1.25 and 1.46 mg L(-1), respectively. Organic nitrogen comprised 95% of the TKN observed in runoff samples from SV plots. The SV plots have relatively higher loads for those nutrients in the particle associated form compared to DV plots, whereas DV plots had higher loads for those nutrients in the dissolved form. Grazing lands without any additional manure applications were found to release nutrients in high levels and vegetation did not show any effect on removing dissolved nutrients from runoff. These results are useful to inform selection of appropriate management practices to reduce nutrient transport to surface waters in watersheds dominated by grazed lands.     

Estimation of Land Use Specific Runoff and Pollutant Concentration for Tapi River Basin in India

Non-point source (NPS) pollution is the result of various land use practices such as agriculture, sites of construction and waste disposal, urban development and so on. The control of NPS pollution is possible by regular monitoring and assessment on watershed basis to educate people for implementing well-known structural and non-structural measures. Recent trend is to use GIS based modelling tool for assessment of rainfall-runoff and non-point loading. The approach requires generation and analysis of basin wide data on various features of land and estimates of Event Mean Concentrations (EMCs) of pollutants in the runoff. In the present paper, basin wide data in different districts of Tapi basin has been analysed for land use distribution; fertilizer application; low, medium and high-density habitation; and annual rainfall. Coefficients of runoff have been estimated considering pervious and impervious area for different land use types, and compared with the reported values for Indian conditions. The estimated mean annual runoff flow indicated that two districts Jalgaon and Dhule contribute maximum runoff to the Tapi River. Estimates of EMCs for BOD and nutrients (N and P) in the runoff from various districts are useful in GIS-based modelling study for NPS pollution assessment.     

Storm runoff quality and pollutant loading from commercial, residential, and industrial catchments in the tropic

Information on the pollution level and the influence of hydrologic regime on the stormwater pollutant loading in tropical urban areas are still scarce. More local data are still required because rainfall and runoff generation processes in tropical environment are very different from the temperate regions. This study investigated the extent of urban runoff pollution in residential, commercial, and industrial catchments in the south of Peninsular Malaysia. Stormwater samples and flow rate data were collected from 51 storm events. Samples were analyzed for total suspended solids, 5-day biochemical oxygen demand, chemical oxygen demand, oil and grease (O&G), nitrate nitrogen (NO₃-N), nitrite nitrogen, ammonia nitrogen, soluble reactive phosphorus, total phosphorus (TP), and zinc (Zn). It was found that the event mean concentrations (EMCs) of pollutants varied greatly between storm characteristics and land uses. The results revealed that site EMCs for residential catchment were lower than the published data but higher for the commercial and industrial catchments. All rainfall variables were negatively correlated with EMCs of most pollutants except for antecedent dry days (ADD). This study reinforced the earlier findings on the importance of ADD for causing greater EMC values with exceptions for O&G, NO₃-N, TP, and Zn. In contrast, the pollutant loadings are influenced primarily by rainfall depth, mean intensity, and max 5-min intensity in all the three catchments. Overall, ADD is an important variable in multiple linear regression models for predicting the EMC values in the tropical urban catchments.     

北京市水环境非点源污染监测与负荷估算研究

文章对北京全市域范围开展水环境非点源污染监测以及污染负荷估算研究。监测结果表明,天然降雨氨氮、总氮污染程度高;城区典型下垫面降雨径流的有机污染十分严重,其中屋面降雨径流总氮和氨氮污染最严重,路面降雨径流COD和总磷污染最严重;下垫面降雨径流汇入城市排水管网后,由于冲洗下水道中的沉积物,使得水质污染进一步恶化。农业典型小流域面源污染对水质影响也很明显。城市非点源污染负荷估算选用SWMM暴雨径流模型,农业非点源污染负荷模型选用改进的输出系数模型,估算结果表明:城市非点源污染主要来自大气湿沉降、综合用地、路面和屋面等,农业非点源污染主要来自耕地和林地;全市污染物排放总量中,点源排放总量与非点源排放总量基本各占50％左右。为进一步挖掘污染减排空间,完善总量减排体系提供了依据。     

Modelling nutrient loads to Sydney estuary (Australia)

Sydney estuary (Australia) catchment is substantially urbanised (80%) and small (480 km²) with a large population (2.5 million) and is therefore highly sensitive to anthropogenic influence. The Model for Urban Stormwater Improvement Conceptualisation used to model nutrient export to the estuary determined an average annual load of 475 t total nitrogen, 63.5 t total phosphorus and 343,000 t total suspended solids. Model verification included intense, short-term water sampling and analysis undertaken in the current project and use of published data spanning 10 years. Under high-rainfall conditions (>50 mm day^???1), the estuary becomes stratified and nutrients are either removed from the estuary directly in a plume or indirectly by advective/dispersive remobilisation. The majority of the nutrient load is delivered during moderate rainfall (5–50 mm day^???1) conditions and accumulates close to discharge points and remains in the estuary. To significantly reduce nutrient load, management strategies should aim to minimise low and moderate rainfall pollutant loads.     

The influence of estuarine water quality on cover of barnacles and Enteromorpha spp.

The influence of ambient water quality on the settlement of barnacles and the green alga Enteromorpha spp. to an artificial substratum in the estuaries of Sydney, Australia, was investigated to test the efficacy of both groups of organisms as indicators of changes in water quality due to urban stormwater runoff and/or sewage overflows. Wooden settlement panels were immersed for 4 months on 17 occasions between 1996 and 2005 at 11 locations known to vary in water-quality parameters (conductivity, total uncombined ammonia, oxidised nitrogen, total nitrogen, filterable phosphorus, total phosphorus, faecal coliforms and chlorophyll-a) and ambient meteorological conditions (total rainfall, maximum rainfall). Water-quality data were collected during the time that the settlement panels were deployed. Cover of barnacles was highly variable among locations (range 1.2?C55.2%). Hierarchical partitioning found that chlorophyll-a, total phosphorus and total nitrogen had significant independent positive effects on barnacle cover. Together, these variables explained 26% of the variation in barnacle cover. Mean cover of Enteromorpha spp., however, did not vary significantly among locations suggesting that other potentially more important factors are influencing its settlement and growth. The results of this study suggest that barnacle cover is likely to be a useful indicator of some components of water quality.     

Modelling vegetation greenness responses to climate variability in a Mediterranean terrestrial ecosystem

Accurate knowledge of the quality and environmental impact of the highway runoff in Pear River Delta, South China is required to assess this important non-point pollution source. This paper presents the quality characterization and environmental impact assessment of rainfall runoff from highways in urban and rural area of Guangzhou, the largest city of Pear River Delta over 1 year’s investigation. Multiple regression and Pearson correlation analysis were used to determine influence of the rainfall characteristics on water quality and correlations among the constituents in highway runoff. The results and analysis indicates that the runoff water is nearly neutral with low biodegradability. Oil and grease (O&G), suspended solids (SS) and heavy metals are the dominant pollutants in contrast to the low level of nutrient constituents in runoff. Quality of highway runoff at rural site is better than that of at urban site for most constituents. Depth and antecedent dry period are the main rainfall factors influencing quality of highway runoff. The correlation patterns among constituents in highway runoff at urban site are consistent with their dominant phases in water. Strong correlations (r ≥ 0.80) are found among chemical oxygen demand (COD), total phosphorus, Cu and Zn as well as conductivity, nitrate nitrogen and total nitrogen. O&G, COD, SS and Pb in highway runoff at urban site substantially exceed their concentrations in receiving water of Pear River. The soil directly discharged by highway runoff at rural site has contaminated seriously by heavy metals in surface layer accompanying with pH conversion from original acidic to alkaline at present.     

Nonpoint Source Pollution Assessment of Wujiang RiverWatershed in Guizhou Province,SW China

The amount of pollution from nonpoint sources flowing in the streams of the Wujiang River watershed in Guizhou Province, SW China, is estimated by a geographic information system (GIS)-based method using rainfall, surface runoff and land use data. A grid of cells of 100 m in size is laid over the landscape. For each cell, mean annual surface runoff is estimated from rainfall and percent land use, and expected pollutant concentration is estimated from land use. The product of surface runoff and concentration gives expected pollutant loading from that cell. These loadings are accumulated going downstream to give the expected annual pollutant loadings in streams and rivers. By dividing these accumulated loadings by the similarly accumulated mean annual surface runoff, the expected pollutant concentration from nonpoint sources is determined for each location in a stream or river. Observed pollutant concentrations in the watershed are averaged at each sample point and compared to the expected concentrations at the same locations determined from the grid cell model. In general, annual nonpoint source nutrient loadings in the Wujiang River watershed are seen to be predominantly from the agricultural and meadow areas. The total annual loadings through the outlet of the watershed are 40,309 and 2,607 tons for total nitrogen (TN) and total phosphorus (TP), respectively.     

典型山地城市初期雨水径流特征研究

通过在典型山地城区重庆北碚区香溪美林区域选择屋面及道路、砖石、绿地3类不同下垫面进行降雨采样监测并结合现有资料,分析初期雨水径流特征。结果表明:2016—2017年重庆北碚区小雨占总降雨天数的80.4%,暴雨仅占1.3%,平均降雨量为9 mm,平均降雨强度为9.75 mm/h,降雨历时以中、短历时(1 h～6 h)为主,多为单峰降雨。降雨初期径流量变化较快,中后期变化平稳。降雨强度相同时,屋面及道路径流量最大,绿地最小。初次径流形成时间随屋面及道路、砖石、绿地依次递增,随降雨强度增强而缩短。     

城市河流重金属元素对降雨径流的动态响应

以海口市美舍河市区河段为研究对象,于2020年雨季分别采集降雨径流以及降雨径流汇入后的河流瞬时水样,测定并分析主要重金属元素的浓度及其变化规律,探讨其对降雨径流的动态响应。研究结果表明：降雨径流对河流可溶态污染元素质量浓度的贡献不突出,对可溶态锌（Zn）、砷（As）、镉（Cd）、硒（Se）具有一定稀释作用,排水口下游 3 m处是可溶态铬(Cr）、锰（Mn）、钴（Co）对降雨径流响应最显著区域;降雨径流对各悬浮态元素质量浓度贡献较大,排水口下游7 m处是绝大多数悬浮态元素对降〖JP〗雨径流响应最显著区域;Mn、Zn、Cr、镍（Ni）、As、Co、Cd 7种元素的总质量浓度对降雨径流的动态响应表现为先上升后下降。其中,排水口下游3 m处是Cr、As总质量浓度对降雨径流响应最显著区段,排水口下游7 m处是Mn、Co、Ni、Zn及Cd总质量浓度对降雨径流响应最显著区段。降雨径流对河流主要污染元素年输入总量估算结果表明,海口市建成区降雨径流向美舍河等受纳水体直接年输入量最大的是Mn和Zn,其次是Cr、As、Ni,Se与Cd的年输入量最小。     

Modeling of land use and reservoir effects on nonpoint source pollution in a highly agricultural basin

Nonpoint source (NPS) pollution is tightly linked to land use activities that determine the sources and magnitudes of pollutant loadings to stream water. The pollutant loads may also be alleviated within reservoirs because of the physical interception resulting from changed hydrological regimes and other biochemical processes. It is important but challenging to assess the NPS pollution processes with human effects due to the measurement limitations. The objective of this study is to evaluate the effects of human activities such as land uses and reservoir operation on the hydrological and NPS pollution processes in a highly agricultural area-the Iowa River Basin-using the Soil and Water Assessment Tool (SWAT). The evaluation of model performance at multiple sites reveals that SWAT can consistently simulate the daily streamflow, and monthly/annual sediment and nutrient loads (nitrate nitrogen and mineral phosphorus) in the basin. We also used the calibrated model to estimate the trap efficiencies of sediment (～78%) and nutrients (～30%) in the Coralville Reservoir within the basin. These non-negligible effects emphasize the significance of incorporating the sediment and nutrient removal mechanisms into watershed system studies. The spatial quantification of the critical NPS pollution loads can help identify hot-spot areas that are likely locations for the best management practices.     

Effect of spatial variability of storm on the optimal placement of best management practices (BMPs)

It is significant to design best management practices (BMPs) and determine the proper BMPs placement for the purpose that can not only satisfy the water quantity and water quality standard, but also lower the total cost of BMPs. The spatial rainfall variability can have much effect on its relative runoff and non-point source pollution (NPSP). Meantime, the optimal design and placement of BMPs would be different as well. The objective of this study was to discuss the relationship between the spatial variability of rainfall and the optimal BMPs placements. Three synthetic rainfall storms with varied spatial distributions, including uniform rainfall, downstream rainfall and upstream rainfall, were designed. WinVAST model was applied to predict runoff and NPSP. Additionally, detention pond and swale were selected for being structural BMPs. Scatter search was applied to find the optimal BMPs placement. The results show that mostly the total cost of BMPs is higher in downstream rainfall than in upstream rainfall or uniform rainfall. Moreover, the cost of detention pond is much higher than swale. Thus, even though detention pond has larger efficiency for lowering peak flow and pollutant exports, it is not always the determined set in each subbasin.     

Uncertainty in watershed response predictions induced by spatial variability of precipitation

Negligence to consider the spatial variability of rainfall could result in serious errors in model outputs. The objective of this study was to examine the uncertainty of both runoff and pollutant transport predictions due to the input errors of rainfall. This study used synthetic data to represent the “true” rainfall pattern, instead of interpolated precipitation. It was conducted on a synthetic case area having a total area of 20 km² with ten subbasins. Each subbasin has one rainfall gauge with synthetic precipitation records. Six rainfall storms with varied spatial distribution were generated. The average rainfall was obtained from all of the ten gauges by the arithmetic average method. The input errors of rainfall were induced by the difference between the actual rainfall pattern and estimated average rainfall. The results show that spatial variability of rainfall can cause uncertainty in modeling outputs of hydrologic, which would be transport to pollutant export predictions, when uniformity of rainfall is assumed. Since rainfall is essential information for predicting watershed responses, it is important to consider the properties of rainfall, particularly spatial rainfall variability, in the application of hydrologic and water quality models.     

Modeling Runoff Response to Land Cover and Rainfall Spatial Variability in Semi-Arid Watersheds

Hydrologic response is an integrated indicator of watershed condition, and significant changes in land cover may affect the overall health and function of a watershed. This paper describes a procedure for evaluating the effects of land cover change and rainfall spatial variability on watershed response. Two hydrologic models were applied on a small semi-arid watershed; one model is event-based with a one-minute time step (KINEROS), and the second is a continuous model with a daily time step (SWAT). The inputs to the models were derived from Geographic Information System (GIS) theme layers of USGS digital elevation models, the State Soil Geographic Database (STATSGO) and the Landsat-based North American Landscape Characterization classification (NALC) in conjunction with available literature and look up tables. Rainfall data from a network of 10 raingauges and historical stream flow data were used to calibrate runoff depth using the continuous hydrologic model from 1966 to 1974. No calibration was carried out for the event-based model, in which six storms from the same period were used in the calculation of runoff depth and peak runoff. The assumption on which much of this study is based is that land cover change and rainfall spatial variability affect the rainfall-runoff relationships on the watershed. To validate this assumption, simulations were carried out wherein the entire watershed was transformed from the 1972 NALC land cover, which consisted of a mixture of desertscrub and grassland, to a single uniform land cover type such as riparian, forest, oak woodland, mesquite woodland, desertscrub, grassland, urban, agriculture, and barren. This study demonstrates the feasibility of using widely available data sets for parameterizing hydrologic simulation models. The simulation results show that both models were able to characterize the runoff response of the watershed due to changes of land cover.     

太湖流域果园种植面源氮磷输出强度及其定量评估方法

以太湖流域上游地区无锡阳山地区果园种植典型区域为研究对象,通过现场试验,调查了果园种植面源氮磷输出动态变化过程,计算并分析了氮磷输出强度,构建了果园种植面源氮磷输出强度定量评估模型。结果表明:取样监测期间,果园种植径流及淋溶氮磷指标变化幅度均超过200%;果园种植面源氮磷径流输出强度与其淋溶输出的变化一致,径流总氮的输出强度最高(13.201 kg/hm~2),淋溶硝酸盐输出强度最大(4.077 kg/hm~2);所建立的评估方程能较好地反映降雨量等环境因素对果园种植面源氮磷径流及淋溶输出强度的影响情况,模拟方程的复相关系数均在0.9左右。     

Nutrient transfer by runoff from sewage sludge amended soil under simulated rainfall

Wastewater sludges are used in agriculture as soil amendment and fertilizer, with regard to their organic matter and nutrient content. However, availability of nitrogen and phosphorus from sludge-amended soils and their transfer in runoff may lead to eutrophication of downstream surface water. The aim of this study is to establish and compare the effect of two different sludges on these transfers: an anaerobically digested and thermically stabilised sludge (Seine-Aval treatment plant, sludge no. 1), and a limed sludge (Saint-Quentin treatment plant, sludge no. 2). Experiments were performed on 12 sloping micro-plots (1 m × 1 m) submitted to sludge spreading and controlled rainfall simulation. Runoff water was sampled and analysed for concentrations in nitrogen species and phosphorus. Results show that spreading of sludge no. 1 increased both ammonium nitrogen (mean of 1.1 mg L^–1 N-NH₄ vs. 0.2 mg L^–1 N-NH₄ for control micro-plots) and particulate phosphorus concentrations (mean of 2 mg L^–1 P vs. 1.1 mg L^–1 P for control micro-plots) in runoff water. On the other hand, sludge no. 2 did not induce any significant effect on nutrient concentrations in runoff. These results are related to chemical composition and physical treatment of sludges. This study underlines the existence of a short-term risk of nutrient mobilisation by runoff after sludge spreading on soil, and the need to check precisely the impact of this practice on water quality.     

Phosphate run-off in the Nevezis River (Lithuania)

The long-term (40 yr) observation results of phosphates–phosphorus concentration and its runoff in the Lithuanian fourth largest river Nevezis are analysed. Amounts and peculiarities of background runoff, agricultural runoff, andpoint source pollution from towns were studied for various periods. It has been determined that phosphates enter into the river Nevezis mainly from towns (76.5%), from agricultureonly up to 16%, and the background runoff for 7.5%.Considerable agricultural influence was observed in 1979–1991,when the phosphate runoff increased to 22 kg P km^-2 a^-1 and formed in 1984 33% of the entire runoff. A relation of the phosphates runoff from agriculture, for the entire study period, was obtained with the number of animals in the river's basin. Since 1990, when the number of animals started to decrease, the runoff of phosphates decreased too. Now the phosphatesrunoff from agriculture formed only 2% of the entire runoff. Water in the river Nevezis is heavily polluted with phosphate,according to the EU general classification of the water quality of rivers, although the Lithuanian pollution norms for effluentsdischarging to surface water are not exceeded. Norms for effluents discharging in the rivers from point-sources pollution should be made stricter and the highest permitted ratiobetween the phosphorus load in the river and its waterdischarge should be established.     

Load estimation and source apportionment of nonpoint source nitrogen and phosphorus based on integrated application of SLURP model, ECM, and RUSLE: a case study in the Jinjiang River, China

The nonpoint source (NPS) pollution is difficult to manage and control due to its complicated generation and formation. Load estimation and source apportionment are an important and necessary process for efficient NPS control. Here, an integrated application of semi-distributed land use-based runoff process (SLURP) model, export coefficients model (ECM), and revise universal soil loss equation (RUSLE) for the load estimation and source apportionment of nitrogen and phosphorus was proposed. The Jinjiang River (China) was chosen for the evaluation of the method proposed here. The chosen watershed was divided into 27 subbasins. After which, the SLURP model was used to calculate land use runoff and to estimate loads of dissolved nitrogen and phosphorus, and ECM was applied to estimate dissolved loads from livestock and rural domestic sewage. Next, the RUSLE was employed for load estimation of adsorbed nitrogen and phosphorus. The results showed that the 12,029.06 t?a^?1 pollution loads of total NPS nitrogen (TN) mainly originated from dissolved nitrogen (96.24 %). The major sources of TN were land use runoff, which accounted for 45.97 % of the total, followed by livestock (32.43 %) and rural domestic sewage (17.83 %). For total NPS phosphorous (TP), its pollution loads were 570.82 t?a^?1 and made up of dissolved and adsorbed phosphorous with 66.29 and 33.71 % respectively. Soil erosion, land use runoff, rural domestic sewage, and livestock were the main sources of phosphorus with contribution ratios of 33.71, 45.73, 14.32, and 6.24 % respectively. Therefore, land use runoff, livestock, and soil erosion were identified as the main pollution sources to influence loads of NPS nitrogen and phosphorus in the Jinjiang River and should be controlled first. The method developed here provided a helpful guideline for conducting NPS pollution management in similar watershed.     

Evaluation of Point and Diffuse Sources of Nutrients in a River Basin on Base of Monitoring Data

The methodology of materials accounting is presented and applied to developing nutrient balance (nitrogen and phosphorus) in a river basin. The method is based on the balance principle: inputs and outputs of each nitrogen and phosphorus related sub-systems were balanced. The application of the methodology strategies was illustrated by means of a case study of the Krka river, Slovenia. Different pathways of emission to surface waters were taken into account: WWTP discharges, direct discharges, erosion/runoff and baseflow. Total annual emission into the river Krka was estimated to be 362 tonnes N/year and 73.3 tonnes P/year. The main sources of nitrogen are diffuse sources, emitted via baseflow (52%). Other important sources are effluents from WWTP, which account for 36% of total emissions. Other sources like erosion and direct discharges to surface water (animal manure, industry, households) are of lower magnitude. Erosion is main source of phosphorus emission (55% of total emission), WWTP effluents account for 37% of total emission, while other sources are less important. Besides reduction of point sources by means of wastewater collection and implementation of nutrient removal technology, managing agricultural nitrogen and phosphorus to protect water quality should become a major challenge in the Krka river basin.