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.

Evaluation of aquatic rehabilitation technologies for polluted urban rivers and the case study of the Foshan Channel

An index system for evaluation of technologies for urban river rehabilitation was proposed and discussed.The index system includes indicators of cost,resources,environmental improvement,and social effects.The calculation method for an objective value of each index based on its attributes and weights was presented.The Foshan Channel,which is a seriously polluted,black and malodorous urban river in Foshan City,China,was selected as a case study.The values of the attributes and the weights of the indices for the Foshan Channel were determined.The technologies for the rehabilitation of the Foshan Channel were evaluated based on this index system.Finally,a rehabilitation scheme for the Foshan Channel was proposed.

An approach to calculating allowable watershed pollutant loads

To improve the management of discharge pollutants loads in the reservoirs＇ watershed, an approach of the allowable pollutants loads calculation and its allocation, based on the water environment model, was proposed. Establishment of the approach framework was described at first. Under the guidance of this framework, two major steps were as follows： modeling and scenario analysis were involved and should be applied to support the decision of discharge loads management; Environ- mental Fluid Dynamic Code （EFDC） model was selected as the kernel model in this framework. In modeling step, spatial discretization for establishing cell map in model, data preprocessing, parameter calibration and uncertainty analysis （which is considered as the significantly relevant factor of the margin of safety （MOS））, were conducted. As a result of the research, the model-based approach presented as a combination of estimation and precise calculation, which contributed to scenario analysis step. Some integrated modules, such as scenario simulation, result analysis and plan optimization were implemented as cycles in the scenario analysis. Finally, allowable pollutant loads under various conditions were calculated. The Chaihe Reservoir in Liaoning Province, China was used as a case study for an application of the approach described above. Results of the Chaihe reservoir water quality simulation, show good agreement with field data and demonstrated that the approach used in the present study provide an efficient and appropriate methodology for pollutant load allocation.

Scenario analysis of water pollution control in the typical peri-urban river using a coupled hydrodynamic-water quality model

The water quality pollution and ecological deterioration in peri-urban rivers are usually serious under rapid urbanization and economic growth.In the study,a typical peri-urban river,Nansha River,was selected as a case study to discuss the scheme of peri-urban river rehabilitation.Located in the north part of the Beijing central region,the Nansha River watershed has been designated as an ecologically friendly garden-style area with high-tech industry parks and upscale residential zones.However,the Nansha River is currently seriously contaminated by urban and rural pollutants from both nonpoint sources(NPS)and point sources(PS).In this study,the pollutant loads from point sources and nonpoint sources in the Nansha River watershed were first assessed.A coupled model,derived from the Environmental Fluid Dynamics Code and Water Quality Analysis Simulation Program,was developed to simulate the hydrodynamics and water quality in the Nansha River.According to the characteristics of the typical peri-urban river,three different PS and NPS control scenarios were designed and examined by modeling analyses.Based on the results of the scenario analysis,a river rehabilitation scheme was recommended for implementation.

China＇s Sponge City construction： A discussion on technical approaches

Since 2014, China has been implementing the Sponge City Construction initiative, which represents an enormous and unprecedented effort by any government in the world for achieving urban sustainability. According to preliminary estimates, the total investment on the Sponge City Plan is roughly 100 to 150 million Yuan （RMB） （$15 to $22.5 million） average per square kilometer or 10 Trillion Yuan （RMB） （$1.5 Trillion） for the 657 cities nationwide. The Sponge City Plan （SCP） calls for the use of natural processes such as soil and vegetation as part of the urban runoff control strategy, which is similar to that of low impact development （LID） and green infrastructure （G1） practices being promoted in many parts of the world. The SCP includes as its goals not only effective urban flood control, but also rainwater harvest, water quality improvement and ecological restoration. So far, the SCP implementation has encountered-some barriers and challenges due to many factors. The present paper presents a review of those barriers and challenges, oftizrs discussions and recommendations on several technical aspects such as control goals and objectives; planning/design and construction of LID/GI practices; performance evaluation. Several key recommendations are proposed on Sponge City implementation strategy, Site-specific regulatory fi＇amework and technical gmdance, Product innovation and certification, LID/GI Project financing, LID/G1 profcssional training and certification, public outreach and education. It is expected that the successful implemen!atiun of the. SCP not only will bring about a sustainable, eco-friendly urbanization process in China, but also contribute enormously to the LID/Gl research and development with the vast amount of relevant data and experiences generated from the Sponge City construction projects.

SWMM-based methodology for block-scale LID-BMPs planning based on site-scale multi-objective optimization： a case study in Tianjin

Low impact development type of best management practices （LID-BMPs） aims to mitigate urban stormwater runoffand lessen pollutant loads in an economical and eco-friendly way and has become a global concern in modem urban stormwater management. A new methodology based on stormwater management model （SWMM） for block-scale LID-BMPs planning was developed. This method integrated LID-BMP chain layout optimization in site-scale parcels with scenario analysis in the entire block-scale urban area. Non-dominated sorting genetic algorithm （NSGA-II） was successfully coupled to SWMM through Python to complete the site-scale optimization process. Different LID scenarios of the research area were designed on the basis of the optimized LID-BMP chain layout. A multi-index evaluation that considered runoff quantity indices, pollutant loads, and construction costs simultaneously helped select the cost-effective scenario as the final planning scheme. A case study in Tianjin, China, was conducted to demonstrate the proposed methodology. Results showed that more than 75% control rate of total runoff volume, 22%-46% peak flow reduction efficiency, and more than 32% pollutant removal rate were achieved. The robustness analysis indicated that the selected final planning scheme was considerably robust with varied weight values.

Hydraulic model for multi-sources reclaimed water pipe network based on EPANET and its applications in Beijing, China

Water shortage is one of the major water related problems for many cities in the world.The planning for utilization of reclaimed water has been or would be drafted in these cities.For using the reclaimed water soundly,Beijing planned to build a large scale reclaimed water pipe networks with multi-sources.In order to support the plan,the integrated hydraulic model of planning pipe network was developed based on EPANET supported by geographic information system(GIS).The complicated pipe network was divided into four weak conjunction subzones according to the distribution of reclaimed water plants and the elevation.It could provide a better solution for the problem of overhigh pressure in several regions of the network.Through the scenarios analy-sis in different subzones,some of the initial diameter of pipes in the network was adjusted.At last the pipe network planning scheme of reclaimed water was proposed.The proposed planning scheme could reach the balances between reclaimed water requirements and reclaimed water supplies,and provided a scientific basis for the reclaimed water utilization in Beijing.Now the scheme had been adopted by Beijing municipal government.

Factors influencing water quality indices in a typical urban river originated with reclaimed water

The water quality in a typical urban river segment originated with reclaimed water in Beijing was monitored for two years to investigate the evolution of water quality along the rivcr, and statistical analysis was applied to determine factors influencing water quality of such river recharged by reclaimed water. It was found that no significant change in pollutant concentrations （including COD, NH4＋-N, TN and TP） was observed during this time, and their average values were close to those of the original reclaimed water. However, turbidity and algal contents fluctuated temporally in the direction of river flow. Statistical analysis showed that turbidity was strongly positively correlated with algal contents for flow rate 〈 0.1 m.s-1. whereas it was strongly positively correlated with both algalcontents and TOC for flow rate 〉 0. 1m. s-1. It was observed that diatom was the absolute predominant phyla with Melosira as the major species. In terms of algal bloom control, the specific growth rate of algae was strongly correlated to temperature, and was influenced by flow rate as well. Compared with two other rivers originated with reclaimed water and one originated with natural water, the Shannon Wiener index in the objective river was the lowest, with values between 0.7 and 1.6, indicating a high risk for algal bloom. Statistics showed that Shannon Wiener index was strongly negatively correlated to nutrient salts and cations.

Low Impact Development and Sponge City Construction for Urban Stormwater Management--Selected Papers from the 2016 International Low Impact Development Conference in Beijing, China

Low Impact Development and Sponge City Construction are new paradigm for Urban Stormwater Management. It has become a hot focus in urban water resources research and practices globally. In this context, in order to provide an international forum for stormwater management professionals to present the latest developments, technologies and case studies related to low impact development （LID） and green infrastructure （GI） technology, the 2016 International Low Impact Development Conference was organized and held. The Conference was jointly sponsored by the Water Industrial Society of the Chinese Society of Civil Engineers, the Water Environment Research Institute of the American Society of Civil Engineers and the Chinese Academy of Engineering. Organizers included Tsinghua University, Peking University and Beijing University of Civil Engineering and Architecture.

Urban watershed management under rapid urbanization

Recent years have witnessed a trend of rapid urban growth, accompanied by a significant impact on the environment, in many parts of the world. For example, in China, an extraordinary urbanization process has exerted enormous pressures on water resources and the urban environment as well as ecological systems. Protecting the water environment is now one of the most important and pressing issues that demand great attention. Urban watershed management is therefore critically important to the sustainable use of water resources and the protection of valuable eco-systems. The objective of the International Conference on Urban Watershed Management （ICUWM）, inaugurated in 1997 at the University of Virginia, is to provide a forum for international professionals to share research and experiences in watershed management practices.