How uncertain is model-based prediction of copper loads in stormwater runoff?

In this paper, we conduct a systematic analysis of the uncertainty related with estimating the total load of pollution (copper) from a separate stormwater drainage system, conditioned on a specific combination of input data, a dynamic conceptual pollutant accumulation-washout model and measurements (runoff volumes and pollutant masses). We use the generalized likelihood uncertainty estimation (GLUE) methodology and generate posterior parameter distributions that result in model outputs encompassing a significant number of the highly variable measurements. Given the applied pollution accumulation-washout model and a total of 57 measurements during one month, the total predicted copper masses can be predicted within a range of +/-50% of the median value. The message is that this relatively large uncertainty should be acknowledged in connection with posting statements about micropollutant loads as estimated from dynamic models, even when calibrated with on-site concentration data.     

基于GLUE的新安江模型参数不确定性分析及应用

结合新安江模型在东洋河流域的应用,提出了基于GLUE方法的新安江模型参数不确定性分析。采用GLUE算法抽样结果对东洋河流域进行不确定性预报,选用水文模拟中常用的确定性系数作为似然判据,通过设定0.7为阀值,得到的90%置信区间的流量过程,实例研究表明,以该结果进行不确定预报是可行的。     

基于GLUE 方法的饱和多孔介质中溶质运移模型参数不确定性分析

模型参数的不确定性分析是模型不确定性研究的重要内容之一。本文以示踪剂Br和反应性溶质Cu在石英砂中的运移为例,采用GLUE方法探讨了多孔介质中溶质运移模型参数的不确定性。研究结果表明,仅对水力学参数θs和λ进行识别时,θs和λ的可识别性较强。对耦合Freundlich等温吸附的模型参数进行识别时,由于参数间的相互作用,θs和λ的可识别性降低;吸附特性参数kF的后验分布基本呈均匀分布,可识别性较差,吸附特性参数β、ω、f的取值区间则相对收敛,可识别性较强。K-S检验结果表明,参数区域敏感度由高到底的排序为f、ω、β、kF、λ、θs,主要是因为石英砂对Cu的吸附以动力学反应为主,而f和ω是与动力学吸附反应相关的两个参数。上述结论有助于加深对溶质运移模型参数的理解和提高模型预测的可靠性。     

Air-water mass transfer and tracer gases in stormwater systems.

Reaeration is a central quality parameter for the performance of environmental systems such as ponds receiving urban and road runoff. Tracer gases can be used to measure reaeration rates in these systems. The methods comprise injection of a volatile tracer into an environmental system and subsequently measurement of the emission of the volatile tracer. The physical basis of such methods is the existence of a constant ratio between the air-water mass transfer coefficient for oxygen and the corresponding mass transfer coefficient for the volatile tracer gas. This constant ratio is often not clearly defined in the literature due to difficulties in both experimental procedures and handling of data. In this study such methods are evaluated and an experimental procedure and a corresponding data processing procedure for a general and reliable determination of mass transfer rates are presented. Propane is selected as an example of an appropriate tracer gas and the ratio between the mass transfer coefficients of oxygen and propane is determined.     

Hydrological analysis of single and dual storage systems for stormwater harvesting

As stormwater flows are intermittent, the requirement to store urban runoff is important to the design of a stormwater re-use scheme. In many urban areas, the space available to provide storage is limited and thus the need to optimise the storage volume becomes critical. This paper will highlight the advantages and disadvantages of two different approaches of providing storage: 1) a single shallow storage (0.5 m depth) in which stormwater capture and a balanced release to supply users is provided by the one unit; and 2) a dual system in which the functions of stormwater capture and supply release are provided by two separate deeper storage units (2 m depth). The comparison between the two strategies is supported by water balance modelling assessing the supply reliability and storage volume requirements for both options. Above a critical volumetric capacity, the supply yield of a dual storage system is higher than that from a single storage of equal volume mainly because of a smaller assumed footprint. The single storage exhibited greater evaporation loss and is more susceptible to algae blooms due to long water residence times. Results of the comparison provide guidance to the design of more efficient storages associated with stormwater harvesting systems.     

Retention of heavy metals by stormwater filtration systems: breakthrough analysis

Biofiltration systems are widely used to mitigate the impacts of stormwater on receiving waters, however their long-term capacity to retain heavy metals has not previously been assessed. Accelerated-dosing laboratory experiments were used to assess the likelihood of breakthrough occurring for three different types of soil-based filter media that are commonly used in stormwater biofilters. In all cases, breakthrough of zinc (Zn) was observed, but not of cadmium (Cd), copper (Cu) and lead (Pb). If biofiltration systems are sized so that they are large relative to their catchment (at least 2-3% of its area) or have a deep filter layer (at least 0.5 m deep), then breakthrough will not occur for at least ten years and probably longer. However, after the equivalent of 12-15 years of operation, Cd, Cu and Zn had accumulated in the filter media to levels that exceeded human health and/or ecological guidelines. Further, depending on the design, it is possible that spent filter media may be classified as contaminated soil and thus require special disposal.     

Statistical analysis of pollution in stormwater infiltration basins.

In order to characterize soil pollution in stormwater infiltration basins, four basins of the Lyon area were selected and sampled. Altogether, 66 soil samples were collected. Each sample was analyzed for pH, cationic exchange capacity, particle size distribution, total organic carbon, total nitrogen, total phosphorus, metals, total hydrocarbons and polycyclic aromatic hydrocarbons (PAHs). Data was explored in a classic way (soil profiles) and using multivariate analysis techniques. Two methods were applied: Principal Component Analysis (PCA) and Cluster Analysis (CA). Main results are presented in this paper. Pollutant concentrations decrease rapidly with depth while pH and grain size increase. Sustainable concentrations are reached at a 50-cm depth, even after 21 years of operation. Multivariate analysis shows how pollution affects each sampling depth.     

Correlation analysis among highway stormwater pollutants and characteristics.

Stormwater runoff from highway land use is a common non-point source of pollutants. A large quantity of highway stormwater runoff characteristics were collected in California during the past three years. Correlations among various water quality parameters and constituents were performed using data sets collected over the 2000-2001, 2001-2002, and 2002-2003 wet seasons for 18, 21 and 23 storm events at three highway sites in west Los Angeles, California. In addition, statistical and graphical correlation analysis of the mass first flush ratio (MFF) with storm characteristics was made to determine if the first flush is related to site or storm characteristics. The results and analyses performed indicate that (1) TSS correlates well with most particulate-bound metals. However, TSS was poorly correlated with most other pollutants. (2) Strong correlations were also observed among dissolved and total metals; DOC, COD, TKN and oil and grease; conductivity and Cl. (3) Total metals, COD and DOC were generally well correlated with mass first flush, suggesting that BMPs that treat the early portion of runoff have an opportunity to remove high concentrations of these pollutants.     

GLUE法分析水文模型参数不确定性的研究

应用新安江模型,采用普适似然不确定估计(GLUE)方法,对梁辉水库洪水预报中参数的不确定性问题进行研究并对预报误差进行分析,结果发现,模型参数中存在大量的"异参同效"参数组,即存在许多可接受的似然估计值的参数值组合.据此,将参数分为敏感性参数和不敏感性参数两大类.深入了解新安江模型参数的意义及其敏感性问题为今后流域水文模拟提供参考,以助于新安江模型参数的率定和模型的推广应用.     

Evaluation of street sweeping effectiveness as a stormwater management practice using statistical power analysis.

Although street sweeping is commonly regarded as a cost-effective stormwater best management practice, there is little quantitative evidence that street sweeping directly improves runoff water quality. In this paper, several previous street sweeping studies were re-evaluated using statistical power analysis. Two-group, independent-sample one-sided t-test power analyses were performed using log-transformed event mean concentrations (EMCs) of total suspended solids, suspended sediment concentration or chemical oxygen demand. The effect size between the two groups was estimated using the sweepers' pick-up efficiency, which showed that the failure to detect the difference between mean EMCs of the two sample groups (i.e., unswept and swept groups) is likely due to limited sample numbers. Too few samples, which also resulted in a high coefficient of variation, were analysed to detect the likely difference between swept and unswept observations. In addition, the temporal gap between street sweeping and subsequent storm events was not controlled to improve statistical power.     

灰绿耦合雨洪系统多目标优化建模与应用

以中山市某开发区为例,以灰绿基础设施总成本、径流系数和节点总溢流量为目标函数,以子汇水区内涝风险等级作为罚函数构建灰绿耦合排水系统多目标优化模型,基于NSGA-Ⅱ算法,编写SWMM接口程序,调用SWMM进行雨洪模型计算及方案寻优,对24h设计暴雨条件下的灰色调蓄设施和绿色LID设施的规模进行多目标优化设计及综合评估。结果表明:绿色LID设施径流系数和节点总溢流量削减量均随其成本的增加呈近似线性下降的趋势,并随重现期增加而加快;灰色调蓄设施容积与节点总溢流量曲线存在明显拐点,拐点后规模增大的边际效益趋0;提出的灰绿耦合基础设施优化模型及求解程序对初始种群设置技术要求低,且能稳定收敛,可为城市雨洪管理方案的制定提供支持和依据。     

Prediction of stormwater particle loads from impervious urban surfaces based on a rainfall detachment index.

This paper makes use of Non-Coarse Particle (NCP) data collected from three different impervious surfaces in Toowoomba, Australia. NCP is defined as suspended solids less than 500 microm in size. NCP loads (in mg/m(2)) were derived for 24 storms from a galvanized iron roof, a concrete car park and a bitumen road pavement. A scatter plot analysis was used to identify potential correlations between NCP loads and basic rainfall parameters such as rainfall depth and intensity. An exponential-type trend, consistent with many washoff models, was evident between load and average rainfall intensity for all surfaces. However, load data for some storms did not fit this general trend. Various indices, comprising different combinations of basic rainfall parameters, were evaluated as an alternative to rainfall intensity. A composite index, referred to as the Rainfall Detachment Index, was found to be better than average rainfall intensity in explaining a relationship between NCP load and storm rainfall characteristics. The selected rainfall index utilizes 6-minute rainfall intensities and is a variant of the well known Rainfall Erosivity Index (EI30) used for soil erosion estimation.     

火焰原子吸收法测定地表水中铜的不确定度

随着化学分析方法的发展。管理层和客户对分析数据的质量要求越来越高,而分析数据的质量以其准确性、可靠性和实用性来表现,也就是由计算结果的不确定度来表示。     

The influence of temperature on nutrient treatment efficiency in stormwater biofilter systems.

Nutrients can cause eutrophication of natural water bodies. Thus, urban stormwater which is an important nutrient source in urbanised areas has to be treated in order to reduce its nutrient loads. Biofilters which use soil filter media, biofilms and plants, are a good treatment option for nutrients. This paper presents the results of a biofilter column study in cold temperatures (+2 degrees C, +8 degrees C, control at +20 degrees C) which may cause special problems regarding biofilter performance. It was shown that particle-bound pollutants as TSS and a high fraction of phosphorus were reduced well without being negatively influenced by cold temperatures. Nitrogen, however, was not reduced; especially NO(x) was produced in the columns. This behaviour can be explained with both insufficient denitrification and high leaching from the columns.     

Sampling for representative micropollutant loads in sewer systems.

Most commercially available auto-sampling devices do not support a continuous flow-proportional sampling mode, which would conceptually be the best for collecting representative composite samples. Instead different discrete sampling modes are available. Household chemicals can show considerable random short-term variations. With the anticorrosive benzotriazole, relating to a middle-frequent household activity, we show that, besides an accurate flow meter, mainly three factors are decisive for the representativeness of a substance's average load: the substance's load pattern, the sampling frequency and the length of the composite sample. When the sampling intervals are 10 minutes or longer, errors in the order of +/-40% (standard deviation) or more have to be accepted, if the substance of interest is contained in a low number of wastewater pulses (i.e., the level of household activity). This particularly holds true for specific pharmaceuticals e.g. carbamazepine. Ammonium would be less critical, because it relates to a larger number of sources in the same catchment.     

中韩水文测验及管理体制对比分析

为与韩国水文在测验和管理体制上相互借鉴,运用历史研究和比较研究的方法,对中韩两国的水文站网、测验管理、测验技术、水文资料和信息服务等方面进行了发展脉络梳理和对比评价分析。通过研究发现,中韩两国水文测验的发展历史十分相似,沿革的深层动因也比较接近,但由于自然与国情的各自特点,两国在管理体制、测验技术和信息服务的选择又殊为不同,并最终形成了目前各自的技术、方法和管理体系。韩国水文的一些做法和经验,可为我国水文监测技术进步和水文测验管理体系改革提供有益借鉴。     

An inventory analysis of rural pollution loads in China.

Rural pollution has attracted increasing attention over the past decade for its important consequences on surface and groundwater quality. This is particularly so in China due to the wide and effective control of industrial and municipal wastewater discharges over the past decade. Based on the discussion of rural activities in China, this paper develops a new method of inventory analysis through the definition of elementary unit (EU). This inventory analysis approach is then applied to estimate the total rural pollution loads of COD, TN and TP, as well as their spatial distributions in China. Further analysis is also conducted to investigate the correlations between rural pollution loads and agricultural production outputs, as well as population. It is found that China's agriculture is developing largely at the cost of environment quality, and a high population, as well as the increasing demand for agricultural products, is one of the dominant driving forces. The constructed EKC, which describes the relationship between rural pollution loads and agricultural income, also reveals that current agricultural development in China is mostly far from de-locked from the environmental problem.     

苏州河沿岸排水系统雨水调蓄池设计方案探讨

探讨了通过式雨水调蓄池长期平均运行效率的评价方法,对影响调蓄池类型选择与运行效率的主要因素--雨天出流的初期效应及悬浮物沉降性能进行了分析.针对上海市苏州河沿岸排水系统雨天出流的特性,提出了调蓄池形式优化选择的策略:对于存在一定初期效应且沉降性能差的合流制系统采用存储池;而对于基本无初期效应、出流中污染物沉降性能好的分流制系统采用存储-沉淀池.     

Performance comparison between infiltration and non-infiltration type of structural stormwater treatment systems

The study was constructed to monitor representative inflow and outflow from infiltration and non-infiltration type best management practice (BMP) sites developed at a university campus, allowing the determination of overall performance efficiency in terms of runoff reduction and pollutant removal. Based on the monitored storm events, the runoff and discharged volume and flow rates exhibited high positive correlations with total rainfall depth (p<0.001). Findings revealed that as the total rainfall increases, the amount of volume reduction and pollutant removal decreases for both types of BMP. Infiltration BMP showed a higher ability in treatment performance especially during small storm events than non-infiltration type; however, the differences were not significant. Pollutant removal rates of infiltration type were in the range of 70-90% while between 35 and 80% for the non-infiltration type for storm events with less than 10 mm rainfall depth. Average volume reductions were 71 ± 33% and 32 ± 32% for the infiltration and non-infiltration type, respectively. The ratio of the discharge volume was significantly greater than the ratio of discharge pollutant load indicating a high potential for water quality improvement. Design recommendations were provided considering sizing and cost for on-site application of similar BMP designs in the future.     

Application of uncertainty and sensitivity analysis in river basin management.

Considering uncertainty in the decision-making process in river basin management is important because uncertainty is regarded as one of the main obstacles to sound decision-making. In case of high uncertainty, the risks of making a wrong decision could be quite high, which may have severe consequences. This paper applies a screening sensitivity analysis method, the Morris method, to investigate the propagation of uncertainty from factors in a flood damage model into the model outputs and explores the importance of factors based on the sensitivity analysis. Uncertainty reduction in the most influential factors identified by the Morris method is proposed as a means to reduce the uncertainty in model outputs. In this way the risks of making a wrong decision could be reduced. The results in this paper show that the Morris method is an efficient approach to help reduce the uncertainty in model outputs.