Multiple linear regression models of urban runoff pollutant load and event mean concentration considering rainfall variables

Rainfall is an important factor in estimating the event mean concentration （EMC） which is used to quantify the washed-off pollutant concentrations from non-point sources （NPSs）. Pollutant loads could also be calculated using rainfall, catchment area and runoff coefficient. In this study, runoff quantity and quality data gathered from a 28-month monitoring conducted on the road and parking lot sites in Korea were evaluated using multiple linear regression （MLR） to develop equations for estimating pollutant loads and EMCs as a function of rainfall variables. The results revealed that total event rainfall and average rainfall intensity are possible predictors of pollutant loads. Overall, the models are indicators of the high uncertainties of NPSs; perhaps estimation of EMCs and loads could be accurately obtained by means of water quality sampling or a long term monitoring is needed to gather more data that can be used for the development of estimation models.

Distributions of typical contaminant species in urban short-term storm runoff and their fates during rain events:A case of Xiamen City

The pollutants in urban storm runoff, which lead to an non-point source contamination of water environment around cities, are of great concems. The distributions of typical contaminants and the variations of their species in short term storm runoff from different land surfaces in Xiamen City were investigated. The concentrations of various contaminants, including organic matter, nutrients （i.e., N and P） and heavy metals, were significantly higher in parking lot and road runoff than those in roof and lawn runoff. The early runoff samples from traffic road and parking lot contained much high total nitrogen （TN 6-19 mg/L） and total phosphorus （TP 1-3 mg/L）. A large proportion （around 60%） of TN existed as total dissolved nitrogen （TDN） species in most runoff. The percentage of TDN and the percentage of total dissolved phosphorus remained relatively stable during the rain events and did not decrease as dramatically as TN and TP. In addition, only parking lot and road runoff were contaminated by heavy metals, and both Pb （25-120 μg/L） and Zn （0.1-1.2 mg/L） were major heavy metals contaminating both runoff. Soluble Pb and Zn were predominantly existed as labile complex species （50%-99%）, which may be adsorbed onto the surfaces of suspended particles and could be easily released out when pH decreased. This would have the great impact to the environment.

Advances in LID BMPs research and practice for urban runoff control in China

China is at present experiencing a very rapid urbanization process, which has brought a number of adverse impacts upon the water environment. In particular, urban runoff quantity and quality control have emerged as one of the key concerns for municipal officials. One of the strategies being considered is the use of a Low Impact Development type of Best Management Practices （LID BMPs） for urban storm water runoff quantity and quality control. In this paper, the situation surrounding urban runoff control in China is reviewed first. Then the conventional strategy and technologies for the construction and management of urban drainage systems are discussed, while exploring their inherent dilemmas. The LID BMPs are then introduced to control urban runoff in the context of urban sustainable water systems. After the comprehensive analysis of the various LID BMPs, the advances in LID BMPs research and practice for urban runoff control in China are investigated and summarized. At last, the difficulties of implementing LID BMPs in China are discussed, and a direction for the future is proposed.

Environmental Factors, Constraints and Risks of Rainwater Runoff in Commune II of Maradi (Republic of Niger)

The Urban Commune of Maradi in Niger experienced increasingly frequent flooding following rainy episodes generating volumes and water flows that are difficult to control in recent years. This study aims to determine the impacts of runoff water in Commune II of Maradi City and to assess the role of urban planning in runoff management, as well as the strengths and weaknesses of urban sanitation in Maradi. The methodological approach used consisted of: 1) an interpretation of documentary data, 2) gathering information on runoff at several sites in the study area, and 3) interviews and questionnaires with local communities. This approach made it possible to understand the degree of vulnerability of the populations to flooding and then to propose sustainable solutions to reduce the vulnerability of the affected populations, through the implementation of effective urban rainwater management practices (USWMP). The results show that the impacts of runoff are mainly related to the lack of adequate storm water drainage networks in the area, but also to the nature of the habitats. Geomorphological factors such as the nature of the soil, the slope of the terrain and the altitude increase the degree of risk. In addition, the inadequacy and dilapidation of the drainage systems of the canals and above all the anarchic occupation of the land linked to accelerated urbanization are the cause of flooding by stagnation of rainwater. A phenomenon now linked to numerous deteriorations of urban equipment, the runoff of rainwater in the city of Maradi carries so many pollutants that municipalities, businesses and individuals should put in place pollution prevention measures.

Revealing the characteristics of dissolved organic matter in urban runoff at three typical regions via optical indices and molecular composition

Dissolved organic matter(DOM)plays a major role in ecological systems and influences the fate and transportation of many pollutants.Despite the significance of DOM,understanding of how environmental and anthropogenic factors influence its composition and characteristics is limited,especially in urban stormwater runoff.In this article,the chemical properties(pollutant loads,molecular weight,aromaticity,sources,and molecular composition)of DOM in stormwater extracted from three typical end-members(traffic,residential,and campus regions)were characterized by UV–visible(UV–vis)spectroscopy,excitationemission matrix spectroscopy combined with parallel factor analysis(EEM-PARAFAC),and ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry(UPLC-Q-TOF-MS).There are three findings:(1)The basic properties of DOM in stormwater runoff varied obviously from three urban fields,and the effect of initial flush was also apparent.(2)The DOM in residential areas mainly came from autochthonous sources,while allochthonous sources primarily contributed to the DOM in traffic and campus areas.However,it was mainly composed of terrestrial humic-like components with CHO and CHON element composition and HULO and aliphatic formulas.(3)The parameters characterizing DOM were primarily related to terrestrial source and aromaticity,but their correlations varied.Through the combination of optical methods and UPLC-Q-TOF spectrometry,the optical and molecular characteristics of rainwater are effectively revealed,which may provide a solid foundation for the classification management of stormwater runoff in different urban regions.

First flush of storm runoff pollution from an urban catchment in China

Storm runoff pollution process was investigated in an urban catchment with an area of 1.3 km^2 in Wuhan City of China. The results indicate that the pollutant concentration peaks preceded the flow peaks in all of 8 monitored storm events. The intervals between pollution peak and flow peak were shorter in the rain events with higher intensity in the initial period than those with lower intensity. The fractions of pollution load transported by the first 30% of runoff volume （FF30） were 52.2%-72.1% for total suspended solids （TSS）, 53.0%-65.3% for chemical oxygen demand （COD）, 40.4%-50.6% for total nitrogen （TN）, and 45.8%-63.2% for total phosphorus （TP）, respectively. Runoff pollution was positively related to non-raining days before the rainfall. Intercepting the first 30% of runoff volume can remove 62.4% of TSS load, 59.4% of COD load, 46.8% of TN load, and 54.1% of TP load, respectively, according to all the storm events. It is suggested that controlling the first flush is a critical measure in reduction of urban stormwater pollution.

Study on Management and Control of Nonpoint Source Pollution from Urban Surface Runoff

Urbanization is the dominant form of land-use change in terms of impacts on water quality, hydrology, physical proper- ties of watersheds and their nonpoint source (NPS) pollution po- tential at present. Urbanization has changed the source, process and sink of urban NPS pollution, especially raised the pollution load of urban runoff NPS in receiving water. Urban runoff pollu- tion is a hot spot of research on NPS. This paper analyzed type, source and harm of the NPS pollutants of urban runoff and its influence on the receiving water. Through estimating NPS pollu- tion load of urban runoff and summarizing the law and character- istics of urban runoff NPS systemically, study on management and control of urban runoff NPS pollution was focused on the applica- tion of BMPs (best management practices). It is a fresh method- ology that management and control on NPS pollution from urban surface runoff was analyzed by methods of landscape ecology, environmental economics and environmental management. The paper provided a scientific reference for mitigating urban water environment pressure and an effective method for management and control of NPS pollution from urban surface runoff..

Determination of urban runoff coefficient using time series inverse modeling

Runoff coefficient is an important parameter for the decision support of urban stormwater management. However, factors like comprehensive land-use type, variable spatial elevation, dynamic rainfall and groundwater elevation, make the direct estimation of runoff coefficient difficult. This paper presented a novel method to estimate the urban runoff coefficient using the inverse method, where observed time-series catchment outfall flow volume was employed as input for the water balance model and runoff coefficients of different catchments were treated as unknown parameters. A developed constrained minimization objective function was combined to solve the model and minimized error between observed and modeled outfall flow is satisfactory for the presenting of a set of runoff coefficients. Estimated runoff coefficients for the urban catchments in Shanghai downtown area demonstrated that practice of low impact design could play an important role in reducing the urban runoff.

Pollutant loads of surface runoff in Wuhan City Zoo, an urban tourist area

The pollutant loads of surface runoff in an urban tourist area have been investigated for two years in the Wuhan City Zoo, China. Eight sampling sites, including two woodlands, three animal yards, two roofs and one road, were selected for sampling and study. The results indicate that pollutants ranked in a predictable order of decreasing load （e.g. animal yard〉roof〉woodland〉road）, with animal yards acting as the key pollution source in the zoo. Pollutants were transported mainly by particulate form in runoff. Particulate nitrogen and particulate phosphorous accounted on average for 61%, 78% of total pollutant, respectively, over 13 monitored rainfall events. These results indicate the treatment practices should be implemented to improve particulate nutrient removal. Analysis of the M（V） curve indicate that no first flush effect existed in the surface runoff from pervious areas （e.g. woodland, animal ground yard）, whereas a first flush effect was evident in runoff from impervious surfaces （e.g. animal cement yard, roof, road）.

Modeling Urban Hydrology: A Comparison of New Urbanist and Traditional Neighborhood Design Surface Runoff

Urban development generally leads to an increase in impervious cover resulting in a greater volume of surface runoff following storm activity. However, the type of urban development in place strongly controls the degree of impervious cover generated. Traditional neighborhood designs focus on a medium-to-low urban density spread over larger areas, while new urbanist neighborhood designs incorporate more diversity by increasing urban density across smaller areas. The purpose of this study is to model and compare the potential surface runoff for two urban neighborhoods in Austin, Texas-Circle C Ranch, a traditional neighborhood design, and Mueller, a new urbanist development for a 10-year 24-hour storm scenario. Potential surface runoff was calculated by layering various geospatial datasets representing the physical characteristics of both study sites within the Watershed Modeling System (WMS) to configure the HEC-HMS runoff model. Results initially imply that the higher density new urbanist neighborhood significantly increases total and peak storm runoff compared to the traditional neighborhood. However, a greater number of residential units are available at Mueller over the same area as Circle C Ranch. When taking this into account the increased potential surface runoff is negated at the new urbanist site. Although new urbanist neighborhoods will usually contain more residential units than traditional developments when compared at the same scale, the higher urban density associated with these neighborhoods demand the development of more effective stormwater retention systems to cope with a potential increase in surface runoff.

Effects of urban grass coverage on rainfall-induced runoff in Xi'an loess region in China

In this study, laboratory rainfall simulation experiments were conducted to investigate the regulatory effects of grass coverage on rainfallrunoff processes. A total of 80 grass blocks planted with well-grown manilagrass, together with their root systems, were sampled from an eastern suburban area of Xi'an City in the northwest arid area of China and sent to a laboratory for rainfall simulation experiments. The runoff and infiltration processes of a slope with different grass coverage ratios and vegetation patterns were analyzed. The results show that the runoff coefficient decreases with the increase of the grass coverage ratio, and the influence of grass coverage on the reduction of runoff shows a high degree of spatial variation. At a constant grass coverage ratio, as the area of grass coverage moves downward, the runoff coefficient, total runoff,and flood peak discharge gradually decrease, and the flood peak occurs later. With the increase of the grass coverage ratio, the flood peak discharge gradually decreases, and the flood peak occurs later as well. In conclusion, a high grass coverage ratio with the area of grass coverage located at the lower part of the slope will lead to satisfactory regulatory effects on rainfall-induced runoff.

城市地表径流内涝关系与排洪道优化设计研究——以兰州市为例

为探究暴雨后地表径流与城市内涝关系,以兰州市为例,利用ArcGIS软件对其数字高程模型进行水文分析,获得了兰州市地表径流空间分布。根据地表径流空间分布规律,从城市全局视角分析了兰州市城市内涝问题,并对兰州市现有排洪道进行了优化。结果表明:易涝路段与径流路径具有高度相关性,地表径流流经大部分内涝路段,导致内涝发生,且径流路径的密集程度与内涝的严重程度相关,其中城关区最为严重,七里河区与西固区次之,安宁区相对轻微,符合兰州市现实情况,说明了该模型方法的正确性;内涝点集中分布在建筑用地、裸地(水泥地面等)区域,表明城市下垫面的高不透水率是造成道路积水的原因之一;优化后的排洪道使易涝区域的雨水就近排入洪道,减少了薄弱地区洪水冲入城市街道的可能性,减轻了地下排水设施的排水压力,在一定程度上能够解决城市内涝问题;将山地原始沟渠巩固、加宽、延长为新建排洪道,减少了发生山洪的风险。因该研究区域黄河穿城而过,地表径流最终通过排洪道汇入黄河,故该方法可为我国后续整个黄河流域、长江流域“一河一盘棋”的整体防洪研究提供参考。

Review on the Impact of Climate Change on Great Lakes Region’s Agriculture and Water Resources

This study investigates the multifaceted impacts of climate change on the Midwest region of the United States, particularly the rising temperatures and precipitation brought about by hot weather activities and technological advances since the 19th century. From 1900 to 2010, temperatures in the Midwest rose by an average of 1.5 degrees Fahrenheit, which would also lead to an increase in greenhouse gas emissions. Precipitation is also expected to increase due to increased storm activity and changes in regional weather patterns. This paper explores the impact of these changes on urban and agricultural areas. In urban areas such as the city of Chicago, runoff from the increasing impervious surface areas poses challenges to the drainage system, and agriculture areas are challenged by soil erosion, nutrient loss, and fewer planting days due to excessive rainfall. Sustainable solutions such as no-till agriculture and the creation of grassland zones are discussed. Using historical data, recent climate studies and projections, the paper Outlines ways to enhance the Midwest’s ecology and resilience to climate change.

降雨径流过程对不透水面空间分布的响应解析

【目的】城市化导致城市下垫面空间特征复杂化,其中显著特征是不透水面与透水面之间形成复杂的空间关系,对城市地表径流过程产生一定影响。进一步探索降雨径流过程对不透水面空间分布的响应机理,有利于深化城市水文效应科学认知。【方法】开展了降雨径流试验,基于试验数据对二维水动力模型参数进行了率定和验证,并基于所得参数构建了区域大小为1 km×1 km的降雨径流模型,开展了3场真实降雨情景和4类(不透水面上、中、下游和随机分布)城市不透水面空间分布情景下的地表径流过程模拟,对不同情景下的地表径流过程和径流特征进行了分析。【结果】结果表明:在降雨情景A(降雨量10.0 mm)和20%不透水率情景下,上游分布和随机分布之间的径流系数差值占比最大,可达59.9%;在降雨情景B下(降雨量51.8 mm),最大径流流量差值占比为67%。【结论】在同一不透水率下,不透水面空间分布对地表径流过程和径流特征值有一定影响,其影响程度通常随着降雨强度的增加而减小;在同一降雨和不透水率下,在设置的4类不透水面空间分布情景中,不透水面随机分布对径流过程的影响相对其他分布较大。研究结果可为城市径流管控与洪涝防治提供一定参考。

小区尺度雨洪过程模拟及径流分配特性研究

为了研究小区尺度地表径流各组分占比随不同重现期降雨的变化规律,以西咸新区天福和园小区为研究对象,采用GAST-SWMM耦合模型,以模拟时长及地形边界条件为变量进行研究分析。研究表明:经两场实测降雨过程验证,模型确定性系数分别为0.83和0.82,表明构建的一二维耦合模型精度较高;在本文设置的两种工况下,小区地表径流外排率和管网排水率均随降雨重现期增大而以渐进曲线形式增大,土壤下渗占比和地表填洼率随降雨重现期增大而减小;小区地表径流外排和管网排水主要发生在降雨期间,分别占各自排水总量的94.88%和94.36%;小区地形边界条件对径流过程模拟的影响不容忽视,在有围墙及无围墙工况下平均地表径流外排率分别为9.42%、22.55%。本研究可为地势相对四周较低区域的排水防涝设计提供参考。

成都市主城区道路冲洗径流污染研究

为评估城市道路冲洗径流污染程度,于2022年3—8月在成都市主城区内选取交通性路段、商业性路段、生活性路段和餐饮性路段进行冲洗水径流采样,通过对采样结果进行差异显著性分析,探究道路类型、降雨冲刷和较高气温(>30℃)对冲洗径流污染负荷的影响,综合考虑这3个因素推导道路冲洗径流年污染排放量估算公式。结果表明:不同类型道路冲洗径流污染程度存在差异,其中,餐饮性路段严重,生活性路段和商业性路段次之,交通性路段最轻;通过相关性分析推测,路两侧餐饮经营活动的污染排放是导致不同类型道路冲洗径流污染负荷值存在差异的主要原因;此外,较高气温(>30℃)会导致道路冲洗经流污染负荷升高,而降雨则反之;以成都市为例进行估算,2022年主城区道路冲洗径流中化学需氧量(chemical oxygen demand,COD)、总氮(total nitrogen,TN)、总磷(total phosphorus,TP)、悬浮物(suspended solids,SS)和氨氮(ammonia nitrogen,NH3-N)的排放量分别为3 506、167.56、30.32、1 441、55.687 kg。

城市不同下垫面降雨径流水质监测及特征研究

城市面源污染是仅次于农业面源污染的第二大非点源污染,也是影响城市水生态系统健康的重要原因。随着城市化的快速发展,下垫面改变导致城市河流洪峰增大,河流污染加剧。基于沥青屋面、砖砌路面、油毡屋面和绿地四种典型城市下垫面的5场降雨径流监测试验资料,分析了不同下垫面条件下的降雨径流污染水平、径流水质变化特征和初始冲刷效应。结果表明:(1)4种下垫面的降雨径流总氮质量浓度均属于劣Ⅴ类水;四种下垫面的总磷污染程度相对较轻,沥青屋面、砖砌路面、油毡屋面和绿地的降雨径流总磷质量浓度优于Ⅳ类水的频率分别为80%、16%、88.46%和5.56%;沥青屋面、砖砌路面、油毡屋面和绿地的降雨径流总悬浮物质量浓度分布范围分别是7~798、15~569、10~871和44~378 mg/L。(2)总氮和总磷的径流污染水平排序为:砖砌路面>绿地>沥青屋面>油毡屋面;总悬浮物的径流污染水平排序为:绿地>砖砌路面>油毡屋面>沥青屋面。(3)中雨情景下各下垫面不同污染指标变化趋势差异较大,而小雨情景下受人为活动影响较大的下垫面的各污染指标浓度较高。(4)各下垫面污染物的初始冲刷强度排序均为:总悬浮物>总磷>总氮;各下垫面的初始冲刷强度排序为:沥青屋面>油毡屋面>砖砌路面>绿地。(5)沥青屋面和油毡屋面降雨径流中的总悬浮物和总磷具有较好的同源性,而砖砌路面降雨径流中的总磷与总氮和总悬浮物都具有较好的同源性。综合而言,各下垫面总氮和总悬浮物的场次降雨径流平均浓度远超于地表水Ⅴ类水质标准,会对城市水体造成污染,可根据不同下垫面的特点采取相应措施来降低污染物浓度。

产流模式空间分布对城市雨洪过程模拟的影响

通过耦合网格产流计算模型(GRGM)和暴雨洪水管理模型(SWMM)汇流计算模块构建了GRGM-SWMM模型。以贾鲁河中牟水文站控制流域(包括郑州市中心城区)为研究区,基于18场实测暴雨洪水资料探究了产流模式空间分布对洪水过程模拟精度的影响。结果表明:研究区超渗产流模式空间分布面积占比高达72%,城市下垫面仍以超渗产流模式为主;相较于仅考虑超渗产流计算的SWMM,考虑超渗、蓄满和混合等不同产流模式空间分布的GRGM-SWMM模型场次洪水产流量、流量过程模拟精度明显提高,产流量模拟相对误差平均降低33.26%、决定系数平均提高0.089,流量过程模拟均方根误差平均降低5.13 m^(3)/s、纳什效率系数和决定系数分别平均提高0.227、0.207。

动态径流系数法和基于城市功能区的SWMM参数率定方法研究

城市雨洪模型是研究城市内涝形成规律及演进过程的重要手段,但在我国城市化进程加速、雨水内涝监测能力不足的背景下,模型参数率定和应用面临挑战。为解决缺乏实测雨洪数据条件下城市雨洪模型参数校准的难题,本文提出了根据地理和气候特征计算雨水径流量的动态径流系数法和基于城市功能区的Storm Water Management Model(SWMM)参数率定方法。在福建省三明市的应用表明:动态径流系数法与规范和经验公式结果一致,与传统方法相比则能反映降雨产流随雨强、下渗等因素变化的规律,更符合城市降雨产流的实际过程。基于城市功能区的参数率定方法结果与研究区城市化水平和下垫面特征相符。率定后雨水径流过程NSE值达到0.80,雨水总径流量误差处于6%以内,洪峰时间误差小于3分钟。本文提出的方法可为缺乏实测雨洪数据地区的城市雨洪模拟提供参考。