外来水入流入渗是影响排水系统运行的负面因素之一。由于地下水位高、降雨丰富等原因，我国平原河网地区排水管网的外来水入流入渗现象尤为突出。但如何在明晰入流入渗特征的基础上有效提升管网输水能力和污水厂减排能力，目前仍缺乏相应的评估分析方法与工具。为此，针对入流入渗危害防控与系统运行效能改善需求，本研究构建基于入流入渗规律识别的排水管网运行效能评估方法，实现在定量解析和预测入流入渗的基础上评判排水管网输送能力及其对污水厂运行的影响，为制定有针对性的排水系统管理方案提供支撑。本研究选择苏州市中心城区为案例区域验证方法的可行性与有效性。本研究提出采用三角分析法与水质特征因子法相结合来实现不同时空尺度上的排水管网入流入渗解析要求：前者用于排水系统较大服务片区内年度或季度水平的解析；后者则用于地块范围内日或小时精度的解析，在实际应用中通过比选TN、电导率和18O、2H确定最优水质因子（案例区比选后采用18O）。本研究通过在SWMM软件平台上扩展开发入流入渗模块实现入流入渗预测及其对排水系统潜在影响的计算，其中入渗预测采用节点等比例常量模式，入流预测采用分布式幂函数形式。在此基础上，从水力性能、环境性能、协调性能3个维度出发构建排水管网运行效能评估指标体系，包含外来水量指数、管道空间指数、漫溢水量指数、漫溢水质指数、污水厂进水水量指数和污水厂进水水质指数6项指标。定义分钟或小时尺度的计算方法并利用模型实现单指标评估；定义指标时间平均计算方法和多指标集成方法，实现排水管网运行效能的多尺度整体评估。对案例区开展入流入渗解析和分流制污水管网运行效能评估。结果表明，2014-2017年管网输送水量中约30%为入流入渗外来水，其中旱天入渗占22%，雨天入流入渗占40%以上；不同地块旱天入渗量占比的时变化系数在[2, 3]区间内，时均值在8%-27%之间不等，雨天外来水量占比均在45%以上。2018年8-10月期间，福星片区污水管网效能均值为0.86，取值范围[0.28, 0.96]，旱天均值比雨天高约10%，运行效能受降雨期入流影响显著。水力性能、环境性能、协调性能均值为0.93、0.91、0.72，评估期降雨条件下入流入渗的负面效应以冲击污水厂运行为主、输水能力挤占和漫溢风险加剧为辅。管网运行效能存在空间差异，6个片区得分标准差为0.03，需重点控制城西片区和厂前片区外来水量、改善金门泵站和城西泵站服务片区管网输水能力和管道利用空间。

Sewer inflow and infiltration in urban drainage system are one of the negative factors affecting the operation of the system. Due to the high groundwater level and abundant rainfall, the problem of inflow and infiltration in the plain river network area of China is particularly prominent. However, there is still a lack of assessment methods and analysis tools for improvement of the pipeline capacity and the emission reduction capacity of the wastewater treatment plant based on the quantification of the inflow and infiltration. In order to meet the requirements of inflow and infiltration control and system operational performance improvement, this study constructs an assessment method for the operation efficiency of the drainage system based on the quantification of inflow and infiltration, and assesses the operational performance of the pipeline and the wastewater treatment plant, to provide support for the development of targeted drainage system management solutions. The feasibility and effectiveness of the method is verified by taking the downtown area of Suzhou as the case area.This study proposes the use of triangle method combined with the water markers method to achieve the analysis of the inflow and infiltration for different time and space scales: the former is used for the analysis of the annual or quarterly level in the larger area, and the latter is used for the analysis of daily or hour level within the plots. In the actual application, the optimal water marker is determined by comparison between TN, conductivity and 18O, 2H (18O after case comparison). In this study, the inflow and infiltration prediction and its potential impact on the drainage system are realized by expanding the inflow and infiltration module on the SWMM software platform. The infiltration prediction adopts the node proportional constant mode, and the inflow prediction adopts the distributed power function form. On this basis, the performance assessment index system is constructed with three dimensions of hydraulic performance, environmental performance and coordination performance, including the external inflows index (EI), the pipe space index (PS), the overflow volume index (OV), the overflow concentration index (OC), the influent flow and concentration of the wastewater treatment plant index (IF & IC). The calculation methods using the model simulation results of every index at the different time scale and the integration methods of indices are defined, so as to assess the operational performance at multi-scale.The method is applied in the case area. The results show that about 30% of the water transported by the pipe network in 2014-2017 is inflow and infiltration water. The proportion of the infiltration in total flow collected is about 22% on average during dry days, and the amount of inflow and infiltration during the rainy days accounts for more than 40%. The infiltration in dry days is different in different plots: the time-varying coefficient is in the range of [2, 3], and the mean value varies from 8% to 27%. The proportion of external water in rainy days is above 45%. During the period from August to October of 2018, the average operational performance of the drainage system in Fuxing area is 0.86, and the value range is [0.28, 0.96]. The average in dry days is about 10% higher than that in rainy days, indicating that the operational performance is significantly affected by the inflow of rainfall. The average hydraulic performance, environmental performance and coordination performance are 0.93, 0.91 and 0.72 respectively. The negative effects of the inflow and infiltration in the rainfall conditions during the assessment period mainly reflects on the operation of the wastewater treatment plant, supplemented with the pipeline capacity and the risk of overflow. The operational performance has spatial difference, and the standard deviation of the scores of the six zones is 0.03. The service area of Chengxi Pump Station is the key area for the inflow and infiltration control, and the upstream of Jinmen Pump Station and the downstream of Chengxi Pump Station are the key areas for the improvement of the pipeline water delivery capacity and the pipeline utilization space.