Modeling and Management of Urban Stormwater Runoff Quality: A Review

Nonpoint source (NPS) pollution from urban runoff has been established as a major cause of receiving water degradation. In an effort to control this problem, new regulations have been passed in the U.S.A. and federal, state, and local agencies are devising urban runoff management programs. This paper reviews recent regulations and studies related to urban stormwater runoff control and planning in the U.S.A.; discusses fundamentals of urban NPS pollution including transport processes and types and sources of pollutants; reviews current hydrologic and water quality mathematical models used in the U.S.A.; presents case studies in both modeling and management; and describes fundamentals of Best Management Practices (BMPs) in urban runoff control. Finally, it summarizes future research needs.     

基于自然循环雨水径流流量优化调控方法

通过分析现有雨水径流流量调节方法在应用过程中存在的优缺点和发展趋势,介绍了基于雨水自然循环的雨水分流管理方法。该方法将雨水径流分为蒸发、渗滤和排放3部分,通过调节这3部分的比例来模拟区域开发前雨水自然循环过程。分流方法认为：蒸发是降低地面径流量的主要途径之一,蒸发量受当地气象条件的制约,一般为固定值,小的降雨事件以蒸发为主,中等降雨事件以蒸发和渗滤为主。大的降雨事件以排放为主。通过实例分析,详细描述了雨水分流技术的实际应用方法和效果。结果表明．雨水分流技术对于降低雨水径流量和峰流速率,实现雨水的自然循环,保护开发区域的生态环境具有重要实际意义。     

作物覆盖与径流能量的关系

黄土高原的土壤侵蚀往往是由几场大的暴雨形成的，因此研究植被覆盖与径流的能量关系具有积极的现实意义。在整理分析了黄土高原西峰、绥德、天水、淳化4个水土保持试验站降雨、径流及泥沙资料的基础上，探讨了作物覆盖与径流能量的关系。结果表明：①作物覆盖对径流能量具有消减作用，其削减率平均值为72．4％；②作物覆盖与平均径流能量削减率之间呈直线关系；③作物覆盖的削减能量作用受降雨动能的影响，随降雨动能的增大，植被对径流能量的削减作用减小。     

邯郸市区不同下垫面降雨径流水质变化特征研究

为缓解邯郸市城区水资源供需矛盾,合理利用雨洪资源,在对生活区屋面、城区道路、公园绿地降雨径流水质进行检测的基础上,分析了雨水径流中主要污染物的变化过程,探讨降雨径流水质受环境条件影响情况。通过研究得出城区初期雨水径流污染最为严重,随降雨历时的延长,污染物浓度逐渐下降并趋于稳定。不同城区下垫面雨水径流污染物含量差异明显,城区主干道路降雨径流水质最差。     

Effectiveness of Rainwater Harvesting in Runoff Volume Reduction in a Planned Industrial Park,China

It is urgent to effectively mitigate flood disasters in humid mountainous areas in southeastern China for the increasing flood risk under urbanization and industrialization. In this study, a rural district with an area of 13.39 km² that planning to build an industrial park covering an area of 7.98 km² in Changting was selected to estimate the potential of collectable rainwater and the extent to which runoff volume can potentially be mitigated by rainwater harvesting. In addition, the optimum cistern capacity of a rainwater harvesting system in the planned industrial park was evaluated using daily water balance simulation and cost-efficiency analysis. The results showed that rainwater harvesting in the planned industrial park has great potential. The annually collectable rainwater is approximately 9.8?×?10⁶ m³ and the optimum cistern capacity is determined to be 0.9?×?10⁶ m³. With the optimum cistern capacity, the annual rainwater usage rate is 0.99, showing neither financial savings nor deficits. Rainwater harvesting can reduce 100 % of runoff volume in the cases of critical rainfall storm (50 mm) and annual average maximum daily rainfall (111.2 mm), and 58 % of runoff volume in the case of maximum daily rainfall (233.6 mm), respectively. All surface runoff can be collected and stored in the cisterns when rainfall amount is less than 135.5 mm in a rainstorm event.     

Development and investigation of a pollution control pit for treatment of stormwater from metal roofs and traffic areas.

Source control by on-site retention and infiltration of stormwater is a sustainable and proven alternative to classical drainage methods. Unfortunately, sedimentary particles and pollutants from drained surfaces cause clogging and endanger soil and groundwater during long-term operation of infiltration devices. German water authorities recommend the use of infiltration devices, such as swales or swale-trench-systems. Direct infiltration by underground facilities, such as pipes, trenches or sinks, without pretreatment of runoff is generally not permitted. Problems occur with runoff from metal roofs, traffic areas and industrial sites. However, due to site limitations, underground systems are often the only feasible option. To overcome this situation, a pollution control pit was developed with a hydrodynamic separator and a multistage filter made of coated porous concrete. The system treats runoff at source and protects soil, groundwater and receiving waterways. Typically, more than 90% of the pollutants such as sedimentary particles, hydrocarbons and heavy metals can be removed. Filters have been developed to treat even higher polluted stormwater loads from metal roofs and industrial sites. The treatment process is based on sedimentation, filtration, adsorption and chemical precipitation. Sediments are trapped in a special chamber within the pit and can be removed easily. Other pollutants are captured in the concrete filter upstream of the sediment separator chamber. Filters can be easily replaced.     

Field Study of Catch Basin Inserts for the Removal of Pollutants from Urban Runoff

Non-point source (NPS) pollution, unlike point source pollution from domestic and industrial wastewater treatment plants, comes from many diffuse sources. It is caused by the movement of rainfall or snowmelt that picks up and carries pollutants to receiving waters. NPS pollution represents the main cause of contamination of many rivers, streams and other water bodies of many developed countries. Best management practices (BMPs) are intended to reduce NPS pollutants, particularly those from highway runoff, e.g., oil and grit separators, grassed swales, vegetated filter strips, retention ponds, and catch basin inserts. A catch basin insert (CBIs) is a device that reduces stormwater pollution from runoff, without requiring any land use because it is typically mounted within a catch basin. In this study, six commercially-available CBIs were installed and monitored at sites along highways in Westchester County that are under the jurisdiction of the New York State Department of Transportation. The study focused on the CBI installation characteristics, durability and maintenance of the catch basin inserts, as well as whether the inserts can be conveniently, safely, and economically installed and maintained. The CBIs were the Ultra-Urban® Filter, StreamGuard $_{\mbox{{\texttrademark}}}$ Passive Skimmer, StreamGuard $_{\mbox{{\texttrademark}}}$ Catch Basin Insert, FloGard Filter $_{\mbox{{\texttrademark}}}$ , Hydro-Kleen $_{\mbox{{\texttrademark}}}$ Filtration System, Silt Sack®.     

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.     

Runoff characteristics of highway pollutants based on a long-term survey through a year.

Highway pollutants generated mainly from traffics are repeating accumulation, raise, drift and move on the highways. Some of them are removed by road cleanings done regularly, the others are flushed by stormwater into receiving water. The objectives of this study are to survey characteristics of the highway pollutants, and to quantify their behavior on the highways. The study area is a part of Meishin Expressway running through the main island of Japan. Surveys on pollutant runoff from the highway were done for all storm events through one year from December 2004 to November 2005. For the surveys, samples were collected by continuous water sampling during storm events. And chemical substances in each sample such as SS, TOC, TN, TP, heavy metals and polycyclic aromatic hydrocarbons (PAHs) for each class of particle size were measured. Using the results of the survey, characteristics of pollutant runoff during storm events were examined. And it cleared the basic unit loads for the highway pollutants throughout a year. As a result, some significant knowledge for the environmental management of highway pollution has been obtained.     

Assessments of Impacts of Climate Change and Human Activities on Runoff with SWAT for the Huifa River Basin,Northeast China

The impacts of climate change and human activates on the runoff for Huifa River Basin, Northeast China, have been investigated with the soil and water assessment tool (SWAT), which is calibrated and verified for the baseline period 1956–1964, and then used to reconstruct the natural runoff from 1965 to 2005. The results indicate that both climate change and human activities are responsible for the decrease of observed runoff in Huifa River. The climate change could result in a decrease or increase of runoff depending on precipitation, temperature, radiation variation, as well as land cover changes. Its impacts on annual runoff are -36.7, -59.5, +36.9 and -45.2 mm/a for 1965–1975, 1976–1985, 1986–1995 and 1996–2005, respectively, compared with the baseline period 1956–1964. Human activities, on the other hand, generally lead to a decrease of runoff and a relatively larger magnitude than climate change after 1985. It has decreased the annual runoff by -32.9, -46.8, -67.8 and -54.9 mm/a for 1965–1975, 1976–1985, 1986–1995 and 1996–2005, respectively. Human activities contributed more to runoff decrease in wet years due to regulation and storage of the water projects. The results of this study could be a reference for regional water resources management since there are quite a number of reservoirs in the Huifa River basin.